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Welcome to the world of birds.

Imagine, if you will, a hypothetical world much like our own, but populated only by a very small sampling of creatures, which were then allowed to evolve entirely on their own for hundreds of millions of years until their ancestors resembled them barely at all.
-Introduction
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Serina: A Natural History of the World of Birds is a Web Original Speculative Biology project written and illustrated by Dylan Bajda. It follows the evolution of life on a fictional moon, terraformed to Earth-like conditions, over 250 million years. All of said life descends from a sampling of small Earth species. The largest plants are bamboo and sunflowers. There are insects, but none that pollinate. The only vertebrate species can all be found in a pet store and none are bigger than a human hand. Six species of small, live-bearing fish populate the waters, and the only tetrapod is the moon's and project's namesake: Serinus canaria, the domestic canary. As generations pass and natural selection takes hold, these humble colonists spiral into a myriad of forms familiar and alien.

The project was put on hiatus by the creator due to lack of interest from June to November 2020, though updates are present again as of this writing.

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Compare Snaiad, Spec World, Amphiterra, and Hamster's Paradise, the latter of which was directly inspired by this project.


Serina contains examples of:

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    Tropes A-M 
  • Aerith and Bob: Some names are fairly simple and descriptive, such as "boarbirds", "hoppers" or "eelsnakes", but some are completely bizarre, such as mucks, shimmersnoots, poultrypuses or tweezles.
  • Alien Kudzu:
    • Spikeleaf waterweed, a Tempuscene freshwater grass, evolves rapid growth and sharp silica-edged leaves to deter herbivorous fish and becomes an aquatic equivalent. If not regularly fed on by the giant gemnus, it can reduce entire waterways to choked marshes.
    • Assassin grass is similarly tough and fast-growing, with the additional aid of carrying poisons in its leaf edges to kill neighboring plants. Unsurprisingly, this makes it unpalatable to grazing animals, enabling it to comprise 99% of plant biomass in some places until the gluetrap tree evolves resistance to the grass and shades it out.
  • Alien Sea: Downplayed. The moon's oceans are largely similar to Earth's, but a vast amount of phytoplankton in the water gives it a greenish tint. Compared to Earth, more of Serina's oceans consist of shallow seas, which allows a greater abundance of aquatic plant life and by extension, a more diverse array of animal life.
  • Alien Sky: Being a moon as opposed to a planet, Serina orbits a large blue gas giant that illuminates its night sky more than Earth's moon does, so Serinan night is no darker than Earth twilight unless clouds obscure the planet. The intelligent babbling-jays come to regard it in their oral tradition as the source of all rain.
  • All Animals Are Dogs: Inverted with the canitheres: despite their dog-like appearance, their behavior is scarcely canine, instead being more behaviorally akin to more primitive mammals like opossums due to their less-developed brains.
  • All of the Other Reindeer: Brighteye and his brother Whitecrown are pariahs amongst their fellow bluetails, Brighteye because of his sapience and Whitecrown because of his albinism.
  • Amazing Technicolor Wildlife: While most of the mammal-analogue tribbetheres are of subdued shades of brown, black and gray, similar to actual mammals, some species have taken more unusual colorations, such as the green moose-like antlears, or the vibropterans, hummingbird-like tribbats that come in vivid neon shades. There are also aquatic molodonts who take on parrotfish-like colors.
  • Animal Eyes: Even highly derived members of the tribbet lineage tend to have eyes with horizontal or cross-shaped pupils, like a frog's. The main exception are the woodcrafters who've evolved round pupils for better vision.
  • Animal Jingoism:
    • The gravediggers and the woodcrafters end up in an evolutionary arms race toward intelligence due to the gravediggers learning to construct increasingly complex traps to catch their prey, and the woodcrafters learning to better escape and avoid their traps. This culminates in the two species becoming true sapients and waging war, with the woodcrafters emerging the victors and driving the gravediggers out of their forests. Ultimately subverted when an adolescent woodcrafter takes pity upon an orphaned gravedigger and raises him among them, causing him to imprint upon the antlears and mostly lack the asociality associated with their species. After another orphaned gravedigger is taken in by the antlears and is taught their language, her descendants end up changing gravedigger society by making them more amenable to sociality, and they enter a mutualistic relationship with their former antlear foes in which they kill off pests, and, with permission, eat the woodcrafter dead. The gravedigger art even ends up becoming the basis for the written language of the antlears.
    • Another example is between an herbivorous and a carnivorous species of dolfinch, which ends with the fisher daydreamers making friends with the semi-sapient luddies, and the pastoralist daydreamers breeding the sapience out of the porplets to turn them into the living meat packages known as nops.
    • The pelagan daydreamers and tortorncas (in particular the sea rex) have a rivalry going back to even before the seastrikers achieved sapience, as the latter specifically evolved to hunt dolfinches. It's settled by the former driving the latter extinct by targeting their more vulnerable young, and by the Late Ocean Age the daydreamers have managed to drive the large predator burdles completely extinct.
    • The snowscrougers and glacier ravens are highly intelligent vicious rivals native to Serina's south pole, with the latter raiding the former's larders for food, which they need to survive the sixth month winter. The snowscrounger can plan for days and weeks to kill the latter, while the glacier raven has the assistance of larger numbers. It's for this reason that one has not managed to extinct the other.
    • The wooly wumpo has a strong dislike of predators (or biters as they call them) for hunting them and they are also suspicious of chatteravens (or harbingers) due to the latter sometimes deliberately leading predators to them. However, its stated that all wumpos have a very strong hatred for thorngrazers (razers) thanks to them allowing the spread of cactaigas, which between that and their constant feeding has greatly diminished the wumpo's feeding grounds and has been killing them off in a way that the biters never came close to.
  • Animal Religion:
    • Downplayed in the fork-tailed babbling jays' culture. They have a simple Creation Myth that the world was nothing but barren desert until all life was born from an intense rainstorm. The closest thing they have to a deity is the "Sky Sea", the planet that Serina orbits, which they believe to be the source of all rain. However, they have no concept of an afterlife.
    • The bluetailed chatteravens are highly superstitious, and do rituals such as spinning in place and making talismans from the tailfeathers of slain rivals that they carry while foraging or fighting for good luck and protection from death. The narration posits that these may be the beginnings of a rudimentary religion, and attributes it to their pattern-seeking brains.
    • The daydreamers believe that they were once part of a singular creator deity, that made the sky, earth and sea. This god grew curious so split apart into three: the "wings", the legs and the swimmers (the daydreamers themselves). Notably, the practical aspect of real world religious is emphasised: different daydreamer populations have different variations and use their beliefs to justify things, with the warmongers seeing themselves as the sole inherittors of this divinity and justifying their genocidal ways.
    • While reapers lack an organized religion, they do have a belief in life after death and a pantheistic belief in a shared life essence between all beings.
  • Animal Wrongs Group: Pastoralist daydreamers view their fisher cousins as terrorists for sabotaging the nop farms they use to survive, which the second group views as immoral due to almost all porplets being nearly as intelligent as they are. However, it's mentioned that the original founding fishers didn't have much of a problem with the eating of nops since they recognized that they lacked the intelligence of their wild counterparts, what they took issue with was the hunting of wild dolfinches which were intelligent. Modern fishers would end up scapegoating the nops due to the information becoming distorted over time as modern pastoralists feed almost exclusively on their livestock, they also conflated the pastoralists with the whalers who do hunt intelligent dolfinches but lost contact with them several thousand years ago due to the similarities between the two. However, after the war with the warmongers, the fishers come to the conclusion that the pastoralists actually have the most ethical way of feeding out of all the daydreamers as they are only eating creatures that lack the ability to physically or mentally suffer thanks to generations of domestication while leaving the intelligent wild ones untouched. They even insist that they teach the warmongers how to farm the nops.
  • Ant Assault: Ants were among the handful of Earth creatures placed on the titular moon. Most of the species are fairly harmless but a few manage to become very dangerous.
    • The first are the empire ants, which evolve in the early days of Serina's history to be large in both individual size and numbers in the absence of competition and predators. They devour the giant snails and flightless birds present at the time but become reliant on these animals for food; when they eat them all, they began to starve and eventually die off when a species of labybird with parasitic larvae starts eating their colonies from the inside out.
    • The next arrive over two hundred million years later in the form of the billion-stingers. They have much smaller colonies than the empire ants, but can still overwhelm and skeletonize large animals in minutes.
    • The descendants of the billion-stingers, the sea shoggoths, are one of the most dangerous predators of the Late Ultimocene oceans, capable of killing even warmongers by eating them from the inside out. The sea stewards manage to placate them by allowing them to feed on their refuses, but this has only made them smarter, and when the contract is inadvertently broken by their departure, they revert back to their wild instincts within three months and thrive in the post-Ocean Age seas.
  • Anthropomorphic Shift: Downplayed with thalassic gravediggers, which have adopted more towards bipedal locomotion than their ancestors. This makes them the most humanoid of Serina's sapients simply by virtue of having two arms and two legs.
  • Antlion Monster: The females of some metamorph species are neotenic and mature as sessile predators who remain buried for most of their live, catching prey with wings modified into jaw-like traps.
  • Ape Shall Never Kill Ape: The SPS (small-prey) subtype of the daydreamers diverged from the Large-prey subtype about 300,000 years before their article's present because they considered eating other dolfinches, their ancestral prey from the time of the seastrikers, to be immoral. Over hundreds of millennia this change in ideology was even reflected in their biology, as their beaks became smaller and their bodies more agile in order to catch fish. However, despite changes in outward appearance, they're still genetically close enough to their cousins to not count as a different subspecies, let alone their own species.
  • Apocalypse How:
    • The Thermocene-Pangeacene mass extinction is a strong Class 4, wiping out 99% of all life on Serina via runaway global warming and ocean deoxygenation. Only a small sampling of the moon's biodiversity survives near the south pole. For comparison, the worst mass extinction in Earth's history wiped out 83% of genera.
    • The Late Ocean Age ends with a massive coal seam fire sparked by Whitecrown that kills off most life on Serinarcta, save for those who managed to reach wetter spots where the fires couldn't spread, and acidifies the oceans, leading to the end of the sea steward's civilization, though the sophonts themselves are taken by the watcher to a new home and are spared the fate of actual death. By the end of the thawing period, 95% of Serina's endemic ocean life goes extinct.
    • The final extinction, a Class 6 at the end of the Ultimocene, is much more gradual, simply being an ice age that eventually grows too severe for any life to survive as Serina's core cools and tectonics stop.
  • Arc Words: "I love you, Bird."
  • Armless Biped: All members of the tentacle bird family lack wings of any kind due to their common ancestor losing their wings to become better swimmers, which is part of the reason they developed prehensile facial appendages.
  • Art Evolution: Noticeable, as the project has been going since 2015. Specifically, a greater tendency toward brighter colors and less prominent outlines.
  • Artifact Name: The ancestral gravedigger species is so named because of its distinctive habit of killing prey through spiked pit traps. None of its three descendant species alive during the Ocean Age retains this habit — thalassic gravediggers and icefishers both hunt sealife using implements such as fishing lines, nets and harpoons, while savage gravediggers lack both the resources and intelligence for any kind of tool use — but retain the collective moniker used for their ancestors.
  • Artifact Title: Serina is no longer only the "World of Birds" past the Pangaeacene, when tribbetheres attain large-scale success and even displace avians from some niches.
  • Artistic Licence – Biology: The author takes pains to be as accurate as possible, but given the sheer scale of the project, instances of this were inevitable. Most of them, however, have at least some sort of in-universe explanation and are things only a seasoned biologist would catch.
  • Artistic Licence - Space: Serina is described as the tidally-locked moon of a gas giant, but behaves more like a regular planet and does not have to deal with long days and nights, passing through radiation belts, and having tectonics driven by tidal forces. These, however, are minutae beyond the biological focus of the project with conditions set by Serina's creator. The gas giant at least does reflect light unto the moon, at times even creating twilight conditions, and the tectonics of Serina are not elaborated upon but seem to be prone to extensive volcanism.
  • Ascended to Carnivorism:
    • Only 10,000 years after establishment, some canaries have begun to eat insects and the eggs of other birds, and they're just the beginning...
    • The falconary is the first true megafaunal apex predator of Serina, and quickly drives to extinction many species who had evolved without fear of predators.
    • While most serezelles are antelope-like grazers, one group, the spearrunners, while retaining their running quadrupedal deer-like build, become predators that hunt insects, tribbets and small molodonts in a manner similar to a heron.
    • An independent example are the carnivorous circuagodonts. Their unique slicing jaw parts prove to be just as good at cutting through flesh and bone as they are through grass, which allows some species to become predators with few modifications. Thanks to this, their higher intelligence and social hunting, they completely displace the more traditionally predatory dogbeasts by the time of the Ultimocene, with the added bonus of looking enough like their prey that they can sneak into herds of herbivores and ambush them from within.
    • Many of the grazing tentacle birds secondarily become carnivorous in the Ultimocene, such as the grisly carnackle.
    • Downplayed in that the scorplears are omnivores that feed on carrion rather than obligate carnivores, but they are the last descendants of the otherwise obligate herbivore antlear lineage, using the jaws that their ancestor the burrowing antlear used for woody plants to easily slice through bones. They still have the fermenting stomach of their herbivore ancestors, however.
    • The woolly wumpos, descended from the herbivorous mammoth trunko and desert wump, downplay this by being opportunistically omnivorous, though they refrain from eating the corpses of predators or "biters" due to the belief that consuming the meat of a biter will make a wumpo become a biter. This narrative posits that this may be the garbled cultural memory of wumpos eating the meat of the omnivorous and cannibalistic thorngrazers and getting infected by a prion disease that managed to jump species, causing them to go mad and attack other members of their species. Their opportunistic omnivory is shared by their island wumpo cousins.
  • Attack Its Weak Point: Razorbacks are noted to have soft underbellies, which are protected by the fact that their stubby limbs make them hard to flip over.
  • Bad Ol' Badger: Bumblebadgers are an avian version of this trope and certainly live up to the ferocity and tenacity of their namesakes. One species, the gravedigger, eventually becomes sapient, and learns how to kill much larger prey using pitfall traps lined with spears.
  • Bait-and-Switch: We are told that a sapient species has evolved on the savannas of the late Pangaeacene. The bizarre bludgebird (right) is set up as such: it certainly looks like an alien, yet also has certain similarities to early humans: it walks upright, stands about five feet tall, has a mostly naked body, is an endurance-pursuit predator, and kills its prey with a club. However, they are only as intelligent as apes. After a pair of bludgebirds makes its kill, they are attacked and driven off the carcass by a flock of the small colorful birds who were watching them, now wielding tiny stone knives.
  • Bat Out of Hell:
    • The nightbiters are parasitic tribbats that are basically flying cookiecutter sharks, gnawing chunks of flesh off from giant herbivores. They are in turn preyed upon by the even more horrific-looking flapsnapper, who in a bit of a subversion is actually beneficial to the nightbiters' victims as it keeps the pest populations down.
    • The aeracuda is a large, diurnal forest predator that uses its extensible mouth to snap up prey both on the ground and the air and can also take on much larger quarry.
  • Bears Are Bad News: The largest of the bumblebadgers are called bumblebears and are dangerous and bad-tempered ground predators found on Serina's plains. Special mention however goes to two particular species of the Middle Ultimocene:
    • A relatively small species, the bramblebreaker, is described as "an animal nobody wants to meet". They're highly muscular, dangerous predators and extremely foul-tempered even by bumblebear standards, but provide a useful service for other animals through their ability to open paths through the dense cactaiga by simply chewing their way through the dense growths of spiny plants.
    • The truculent bumblebear, at eight feet in height and nine hundred pounds in weight, is one of the largest bumblebear species and the apex predator of its era. They're extremely powerful and dangerous predators, equally happy killing and eating literally any creature they encounter as they are chasing off other predators from their kills. They have no natural enemies, and their most common cause of death is being killed by a conspecific in a conflict over territory. This species eventually gives rise to the dire bumblebear of the Late Ocean Age, which is even bigger and even more vicious due to having adapted to hunt the hulking, ill-tempered, hyperomnivorous thorngrazers.
  • Became Their Own Antithesis: The woodcrafters started out as prey who eventually became powerful enough to drive away the gravediggers and had grown to view predators as monsters. Once they did drove them out, however, they started to become bolder and began venturing out of their territories in order to kill predators that were no threat to them for sport and took sick amusement in their suffering, becoming even more monstrous than their perception of the gravediggers, who only kill for survival and had long since avoided hunting the woodcrafters.
  • Beneath Notice:
    • Gravediggers will hang around their prey for quite some time, learning how they think and therefore how best to trap them as they don't associate the gravedigger with their traps. They got good enough at it over the millennia that the ancestral gravedigger drove at least one non-sapient antlear species to extinction.
    • According to Blaze's telling of the first encounters between the coastian thalassic gravediggers and woolly wumpos, the latter didn't pay the former much mind since they were seemingly too small to pose a threat to them, until they started using fire and their intelligence to hunt them.
    • Brighteye is able to spy on thalassic gravedigger camps without anyone noticing something different about him because of the fact that outwardly he seems no different from any other bluetail despite his intelligence. As such, it comes as a huge shock to them when he starts speaking to them in a way that goes beyond simple mimicry.
  • Bestiality Is Depraved:
    • Inverted in the case of some of the nonsapient savage gravediggers who forcibly mated with female southern gravediggers instead of just killing and eating them as was the norm. It's stated that this has mainly affected the resultant icefisher population more in terms of size and coloration than cognition or behavior as they've kept their sapience and are far less violent than either of their ancestors.
    • The sapient woolly wumpos have a taboo against mating with their closely related but only near-sophont island wumpo cousins, though some have done so anywaynote , with the sapient hybrids being passed off as regular woolies by the herd leaders until their differences become obvious.
    • Reaper aukvultures refuse to breed with their nonsapient relatives, who they refer to as "the untamed", which prevents their sapience from being subsumed by the greater aukvulture population, but also leaves them susceptible to inbreeding depression, making it so that 500 years later only one, Eve, is left.
  • Beware the Nice Ones:
    • The social gravediggers are known for their empathy and connection to the living things in their ecosystem, but, when the second battle against the warmongers occurs, they arm their daydreamer allies with armor and poisoned spears that quickly turns the tide in their favor. Unlike the daydreamers who are horrified by the gruesome deaths suffered by the paralyzed warmongers, the gravediggers prove themselves to be quite ruthless and pragmatic when the chips are down, feeling very little sympathy for their hated enemies, and even celebrating the news of their victory.
    • The aukvultures are known for their gentle temperaments despite their formidable appearance, but they are still a fairly large animal with a beak designed to crush bone. When they are forced to start raiding the sea stewards abandoned food supplies when they don’t return, some greedy sea ravens keep attempting to steal their food until a combination of starvation and anger causes one aukvulture to snap and break the neck of one of them and force the rest to back off. The aukvulture itself is briefly horrified at what it had just done until its hunger forces it to forget and focus on finding food.
  • Big Creepy-Crawlies: There are many examples, throughout the ages:
    • As early as ten million years PE, crickets have reached the size of rabbits thanks to the lack of predators early on and lower gravity.
    • The Serinian bullworm is a giant earthworm living one million years post-establishment and can grow to lengths of up to thirty feet as the largest invertebrate of its time. Around the same time are sea slugs the size of cars.
    • In an inversion, some of the Verminfans and Osteopulma clades of metamorph birds, such as the varicolored bumblebird and the zebra tweezle, become very tiny, being possibly the tiniest a vertebrate could be at about insect-size.
  • Bittersweet Ending: The Ocean Age/Middle Ultimocene ends this way. The release of the trapped carbon thanks to the underground coal fire warms the moon and prolongs the end of its habitable stage, allowing life to last longer than it would have, but it also causes a mass extinction that kills many of the more specialized creatures currently living. In addition, the sea stewards are whisked away to a copy of their old world that will steadily improve to save them from this extinction, but not before the woolly wumpos are all burned to death and Brighteye dies alone knowing his role in their demise. Also, the disappearance of the sea stewards will make the subsequent mass extinction worse as the ecosystem had become dependent on them to function.
  • Bizarre Alien Biology: Thorngrazers not only have three stomachs, but as an adaptation for their Extreme Omnivory have built-in bypasses so that food that needs less digesting like meat will go straight to the intestines instead of their fermenting stomach. Uniquely for a vertebrate, through horizontal gene transfer with long extinct stomach bateria, they have acquired the gene for producing cellulase, which allows them to easily break down wood and leaves and gain nutrients without having to share. This is what allows them to live like both obligate herbivores and carnivores depending on what's around.
  • Bizarre Alien Limbs:
    • The tribbets are tripedal terrestrial descendants of guppies that modified their tails and pectoral fins into three walking limbs. Beyond that, the various tribbet lineages develop a number of very unusual limb arrangements:
      • One lineage, the mammal-like tribbetheres, develop erect forearms with seven digits on each forepaw. One canithere species, the thylacine-like painted repandor, develops its single hind leg into having a backwards-bending knee joint and a downward-curved back that turn the hind leg into a spring to help launch the creature forward when running. Merwals, a type of aquatic canithere, have a tail fluke derived from its single hind leg, and thus still possesses an ankle and knee joint, almost resembling a person wearing a mermaid tail.
      • The antlears are a group of circuagodonts that have developed mobile, jointed antler-like limbs on their ears that they use to pull branches down to their mouths. The explanation for this is that the ears of tribbetheres have a bony matrix in them due to being derived from the gill plates of their fish ancestors, unlike the cartilaginous ears of Earth mammals. This gave them much better mobility and the ability to grip. Burrowing antlears and their scorplear descendants take this to an entirely new level, having adapted to use their ears as an additional set of legs.
      • Another group of tribbets, the handfishes, shorten their forearms but lengthen their fingers instead, eventually turning their individual fingers into separate limbs themselves (becoming hexapedal with the former wrist becoming a double-shoulder joint).
      • The siphontooth is a species of gliding molodont which becomes the first-ever quadrupedal tribbet, despite the basic tribbet body plan having only three legs, by hypertrophying the fingers of its hindleg until the two lateral ones become grasshopper-like legs, while the middle one remains as a balancing organ.
    • The snuffalo is a large grazing relative of the softbill birds that uses its huge thick beak as a third limb due to its short legs and massive heavy head.
    • The bumblets use their clawed wings as spades for burrowing, which resulted in them becoming extremely rigid by having their wrist bones hypertrophy all the way to their socket. This means that they, and their descendants like the bumblebears and gravediggers, have no elbows. This becomes a challenge for the marine social gravedigger due to their reliance on tool use but they get around their lack of dexterity by working cooperatively.
  • Bizarre Alien Locomotion:
    • The varicolored bumblebird, as a larva, modifies its front limbs into grabbing "jaws". While most metamorph bird larvae use their forelimbs to crawl about, the bumblebird larva's forelimbs are too specialized to aid in locomotion and it instead moves by wiggling along using its abdominal muscles. This extends to the flighted adult bumblebird: having retained the stiff forelimbs it had as a larva, it can't flap its wings like a normal bird would and instead uses its specialized abdominal muscles to fly more like an insect.
    • Snuffalos walk tripedally, using their huge bills as a third leg, and their neck provides much of their propulsion. They rest its blunt tip on the ground when at rest in order to support their massive heads, and when walking they press it down in front of themselves and then use their huge neck muscles to pull themselves towards the spot where it's planted.
    • The antlears' most distinctive traits are their pronged, keratinized ears, first used to grasp tree branches. These become jointed and enlarged in later species, and the burrowing antlears eventually develop them into a full set of walking limbs. These ear legs start out mainly as a supplementary support in the first burrowing antlear species, but become much more well-developed in their scorplear descendants.
    • Cartwheels are a species of simiagibs — tribbets adapted for monkey-like arboreal lifestyles — that use their clade's distinctive "fractal" limbs and tail, formed by fingers fused into two sub-limbs each before separating again at the tips, to move through the trees by rolling underneath branches. They do this by grasping a branch with their right pair of hands, swinging their tail hands up to grasp it as well, let go of their hands' hold and allow themselves to hang upside down, and swing their left hands up to grasp back at the branch before righting themselves and repeating the cycle. They can move extremely quickly in this manner, using gravity to speed up further when fleeing from predators, and on the ground use a variant of their arboreal gait where they essentially roll along like living wheels.
  • Bizarre Alien Psychology:
    • The gravediggers are subject to this given they are solitary sophont species. Since they aren't social, they don't need to interact with others of their own kind for emotional fulfillment unlike humans and don't seem to experience boredom when it comes to performing long menial tasks like digging trenches and develop strict, almost ritualistic daily routines. They use art scratched on the trees located on their territorial boundaries as a form of long-distance communication and may even experience sorrow if another gravedigger they shared art with for years dies but will become violently aggressive if they were to ever meet in person.
    • The daydreamers have evolved to be able to remain conscious with only half their brain active so that they can rest it while still also preventing drowning and this results in the being able to see their dreams while awake, which they interpret as visions.
    • The woolly wumpo are fully sapient by most standards as they have a language, religious beliefs and even an understanding of abstract concepts like art but most of them suffer from Creative Sterility that makes it very difficult for them to innovate and which leaves them stagnant. However, a rare few members of their species are born with a form of neurodivergence known as wide-mindedness that gives them at same innovation as the other sophontic species and these individuals typically become figures of great importance in their species' society.
  • Bizarre Alien Reproduction:
    • Changelings evolve a reproductive cycle more like that of a fly than a bird. The mother lays tiny, delicate eggs within a carcass or a larder of meat and promptly abandons them. These hatch into tiny, near-embryonic offspring like newborn marsupials. The "larvae" eat and grow continuously until they secrete a mucous chrysalis, emerging as a normal fledgling. Their descendants, the ornimorphs, take this Up to Eleven, passing through all the stock Evolutionary Levels of vertebrate evolution as part of one individual's life cycle. Another lineage of changelings develop placental live birth like mammals by retaining their larvae within their bodies instead.
    • Bloons and birdwhales are fully marine birds descended from pelican-like seabirds that have adapted to carry their eggs in their throat pouch. After millions of years of evolution this pouch has fully separated from the digestive system and become highly vascularized in order to provide heat and oxygen for the egg, effectively becoming a pseudo uterus.
    • The bumblets evolve the ability to give live birth by retaining their egg internally and oxygenating it by... flatulence.
    • The neckbeards developed a patch of highly vascularized skin on their neck which allow then to carry their eggs with them. The trunkos, their decendents, have expanded on this and have developed muscules in this pouch that hold the egg in place which makes them the closet thing a bird has gotten to a marsupial.
  • Bizarre Sexual Dimorphism:
    • The polymorph birds are a species of softbill bird that have different morphs of male similar to the ruff bird and side-blotched lizard, each with their own distinct appearances and behaviors.
      • The Ardor is only slightly larger than the female and is a monogamous breeder who will assist his mate in rearing their offspring.
      • The Keeper is twice the size of the female, is very aggressively territorial, and keeps harems of females.
      • The Tramp is very similar to the female in size and appearance and will use this to sneak into the territories of Keepers, mate with their harems, and take off.
      • The rarest morph is the Bachelor, which is nearly as large as the Keeper and much less aggressive. Their most unusual trait is that they form mostly homosexual pair bonds with either other Bachelors or Ardors and will either steal or adopt the eggs of other Polymorph Birds to raise as their own.
    • Male firetail changelings need lots of easily processed energy for finding and mating with as many females as possible, and so have long thin bills for consuming nectar. Females need more protein in their diets to produce eggs and therefore have shorter beaks for catching small prey. This arrangement was likely based on mosquitoes, the sexes of which have similar dietary differences for the same reason.
  • Blade Below the Shoulder:
    • The gigantic serestriders keep foldable hand-derived blades folded against their bodies to defend themselves from tyrant serins.
    • The mucks have a single large claw at the ends of their wings. The original arboreal species simply used them to climb through tree branches while the later terrestrial species would use them to fight off predators.
  • Blood Knight: The grisly carnackle is said to relish fighting against strong opponents, be they members of its own kind over food and territory or predators that try to make a meal of it, and are even willing to fight to the death.
  • Body Horror: The nops have been getting farmed for so long that their bodies are now grotesquely bloated with a disproportionately tiny head and flippers.
  • Bookends:
    • The woodcrafters first developed sapience due to being killed by the gravedigger's pit-traps. After Ember, the last woodcrafter, dies her body is placed in a pit made by the gravediggers, but this time, as an actual grave.
    • The story of Brighteye, which begins with him comforting his albino brother with "I love you, bird", concludes with a (non-sapient) chatterraven uttering the phrase to an albino gravedigger.
    • At the start of Serina, snails were the dominant megafauna. At the late Ultimocene, their descendants, the snarks, become dominant animals once more.
  • Boring, but Practical:
    • Egg-eating, rodent-like molodonts have diminished bird populations by the time of the Ultimocene. While several groups of birds managed to avoid this thanks to more exotic ways of breeding such as live-birth or laying their eggs in water, what do the sparrowgulls and mittens do? Carry their eggs to a safer place, and they're arguably some of the more successful birds of this era for it, to the point that the tentacle birds are the only remaining avian megafauna that still lay hard-shelled eggs.
    • Small perching birds very similar to the original canary stock persist all the way to the late Ultimocene, while more exotic clades rise and fall throughout the ages. It's compared by the author to the success and adaptability of lizards, closely akin to the earliest reptiles, and opossums, which are nearly identical to the ancestor of all mammals.
    • The thorngrazers aren't very numerous in terms of species because their Extreme Omnivory means that they don't really suffer any pressures to speciate and as such have singular lines of descent, with the nimicorn directly descending from the crabheaded thorngrazer and the razorback from the sextacorn thorngrazer.
    • The trunkos all possess a highly generalized, omnivorous diet rather than specializing into a particular one, this has allowed them to survive and thrive in the middle Ultimocene while many other species have diminished or died out entirely.
    • The duckbilled sealumps are far less fantastic than their more massive fully aquatic relatives, but they survive the end of the Ocean Age by virtue of being able to step on land and graze on food there, which their water-restricted relatives, stuck in the dying oceans, cannot do.
    • The main floral survivors 1,000 years post-Late Ocean Age include the relatively evolutionarily conservative descendants of clovers and dandelions.
    • From the Late Ocean Age into the early Hothouse Age, some species are so successful that the only noticeable physical change between them and their ancestors is one of coloration, with the steppestalker being just a lighter-colored Pallete Swap of its shadowstalker ancestor, and the Late Ocean Age surfscoters being darker than their starkly black and white Early Ocean Age ancestors.
    • The early Late Ultimocene sea's fish population is mostly comprised of mollyminnows, evolutionarily conservative guppy descendants who spread out as the Meridians sunk with the rising sea levels.
  • Born Under the Sail: The social gravediggers of the oceanic age have become a nomadic seafaring people that use things like plant fibers to make canoes and nets as well as animal parts to make their tools. It's also stated that they typically don't destroy the island ecosystems they come across like ancient humans due to them not settling on the islands and actually living on the ocean itself. After making peace with the daydreamers, they strike out with them from the Icebox Seaway to explore the open ocean, and find so much success there that they last for a million years and evolve into a genetically distinct species.
  • Brother–Sister Incest: A female mitten will sometimes take two mates. All three birds in the triad will mate with each other. The two males in these cases are almost always brothers.
  • Cats Hate Water: Described to be the case with a primitive cat-like predatory tribbethere who falls into a shallow stream while retreating from an attempt to hunt a muck. The author points out the irony that being a guppy descendant, the tribbethere is technically still a fishnote ... that hates water.
  • Call a Smeerp a "Rabbit":
    • Many of Serina's birds are named after other types of Earth birds, such as porporants, squorks and sparrowgulls. They aren't cormorants, storks, or gulls, of course, being canary descendants that through convergent evolution came to resemble these birds.
    • A notable example are the "waterfowl", which as with everything refer to aquatic canaries. At least two such lineages exist (one derived from the dougals and resembling ducks and the others from the galliwats and resembling rails) and the text often doesn't make it clear which one is being alluded to.
    • Some of the smaller, hare-like circuagodonts are literally called smeerps.
    • The woolly wumpos refer to the tiny seed-eating molodonts they eat to supplement their diets as "mice".
  • Cannibal Clan: The warmonger daydreamers are a distinct cultural group that hunt and eat other daydreamers even though they are all still the same species despite their physical differences. They started first with other whalers not part of their group as their normal prey dwindled due to climate change, and after the pelagans banded together to kick them out of their open sea territory roughly 20 years before the fishers made contact with the gravediggers, they started preying upon the fishers and pastoralists instead.
  • Carnivore Confusion: This is basically the warmongers' schtick, since they will happily prey on closely related species or even their own kind, and despite being sapient they have no moral qualms whatsoever about doing so.
  • Carry a Big Stick: The bludgebirds wield clubs using their beak tentacles, swinging them at small prey such as circuagodonts to break their vulnerable hind leg.
  • Caught Up in the Rapture: As Serinarcta burns due to the observer's meddling, it feels guilty for dooming the sea stewards to extinction and places them all in a copy of Serina where the fire never happened and the observer never revealed itself. To the sophonts, it was as if a Cosmic Retcon occurred. To the rest of Serina, the sea stewards just vanished.
  • Celibate Hero: Seeker the greenskeeper is noted to have no interest in mating with anyone regardless of gender, compared to his gravedigger friend Pebble who is implied to be a lesbian.
  • Cessation of Existence: While little of the various sophonts' beliefs in the afterlife is revealed and there is a fleeting moment where the dying dream that they are restored to health in a vision of a better world, descriptions state that there is nothing to experience and no one to experience after their brain shuts down.
  • Changeling Tale: Referenced not with the birds actually called changelings, but a primitive tribbet called the nest goblin. It has evolved to observe and mimic the appearance, calls, and movements of baby birds to a superstimulating degree to get free meals from their parents. The birds put all their time and energy into feeding the goblin while their chicks either learn to feed themselves or starve.
  • Character Development: Word of God states that the observer has undergone this. It started out as an unfeeling entity that simply charted down the life on the world as it went on, which is reflected in how the entries are regularly spaced out by millions of years and focused on species and environments as a whole. By the Mid-Ultimocene, however, it has been around long enough to develop more of a personality as well as develop attachments, which is shown by more of the entries from this period being closer together and focusing on individuals. It has also changed enough to actively interfere with the project to prolong its life as well as save the sea stewards after experiencing guilt for Brighteye's death due to its meddling.
  • Chekhov's Gunman: The fireslime lumpus, a tribbet with a potent batrachotoxin, is first mentioned in the Cactaiga entry as almost an aside. Said toxin is used by the gravediggers to help the fisher and pastoralist daydreamers turn the tide against their warmonger foes by gifting them with poisoned spears. The lumpus was also seen even earlier being bitten by a spiny sniffler.
  • Child Eater: The seastriker hunts baby porplets in particular, as the adults will just breed more.
  • A Child Shall Lead Them:
    • Since seers are that much smarter than the other seastrikers, even adolescent seers hold a place of leadership over seasoned adults.
    • Wideminds are seen as more flexible in thought by the woolly wumpos, and so young ones are venerated by elders due to their ability to change how things are done in ways that only they can.
  • Combat Pragmatist: The social gravediggers are smaller, weaker, and less adapted to an aquatic environment than the warmongers, so they armor the fishers and pastoralists with shells and bone and give them poisoned weapons to fight in their stead.
  • Commonality Connection: Apart from her intelligence, Brighteye feels kinship with Blaze because her heterochromia marks her as unique in the same way as Brighteye's intelligence and Whitecrown's albinism.
  • Continuity Creep: The South Serinarctan Forest Refugia and Daydreamer Saga arcs are much more of a coherent narrative than previous eras, which obviously followed the evolution of life on Serina, but in an episodic manner of describing one species or group, habitat, etc.
  • Continuity Nod: In "The Domain of Demons", taking place during the Late Ocean Age as the gravediggers start mining in order to collect enough coal to stop the ocean from freezing over, one thing they find is the fossilized skull of a tyrant serin, a group that went extinct hundreds of millions of years before.
  • Crafted From Animals: Gravediggers normally use animal sinews to create snares, while their later seagoing descendants use fish teeth and bones to create fishhooks and their tendons for fishing lines, and the sea-living social gravediggers before them make boats and sails from animal skins and bone, along with bone oars. Since they primarily use animal fats as fuel for fire, the peat and coal mined with bone shovels are referred to as "earthfats".
  • Creative Sterility:
    • The woolly wumpos are, as a species, uninnovative and neophobic — while they're very emotionally well-developed and have a strong understanding of abstract concepts, they're not good at learning new things, inventing new solutions or tools or improving on old ones, or facing unfamiliar problems, and for the most part rely on well-established traditions. The exception to this are very rare, neurodivergent individuals called wideminds, who are more innovative, less fearful, and better at coming up with new things. Wideminds are highly respected in wumpo society, and historically have been responsible for creating most new tools, solutions or practices, which afterwards spread through the species and became established as part of tradition.
    • The chatteravens are capable of innovation to a degree and learn fast but they have little in the way of abstract thought which hampers their creativity and their skills at making new tools or behaviors. Brighteye, being the only fully sapient chatteraven, is the exception as his strong grasp of abstract concepts and natural learning ability allows him to outperform wumpo wideminds when it comes to making new tools and discoveries.
  • Creepy Crows: Woolly wumpos refer to the raven-like bluetailed chatteravens as "harbingers" due to their tendency to signify the presence of the predators that they can summon.
  • Crippling Overspecialization: Plenty of cases:
    • The serezelles die out due to being unable to graze on the unpalatable razorgrass, the merwals become specialized to eating shellfish and could not adapt to a different diet when the marine molodonts become more efficient clam eaters, and the specialized burrowing birds of the Kyran Islands had no defense against an influx of predatory tribbetheres when the islands collided with the mainland. This is Truth in Television — many animals respond to selective pressures by specializing, but specialist niches are far more fragile than generalists.
    • This is what spells the end of the woodcrafters. They became so specialized for feeding from a specific type of broadleaf tree that was already on the decline when they evolved that, when it becomes too cold for those trees to survive, they begin to die out from malnutrition, while the carnivorous gravediggers can subsist on any source of meat, on top of being more flexible in mindset in general. It's eventually discovered that seaweed can actually sustain the woodcrafters, though its softness means their jaws grow longer, but by then it was already too late as the surviving woodcrafters were all well past child-bearing age (only males keep their fertility past their thirties, and woodcrafters as a whole rarely live past fifty years), on top of their population being too small to prevent a genetic bottleneck even if they weren't too old to have children.
    • The colossal quadclaw, a fully terrestrial crustacean descended from hermit crabs endemic to the Meridian Islands, goes extinct due to being outcompeted by the newly arrived, warm-blooded grazing birds that can eat grass at any time of day, as opposed to the quadclaws only being able to forage during the day due to being susceptible to the nighttime chill.
    • There was once a larger species of skystrike (sparrowgulls that attack their prey in groups) roughly the size of a golden eagle that was adapted to hunt the gigantic archangels of the Early and Early Middle Ultimocene such as the stormsonor, but went extinct once its prey died out and the other archangels were too small to sustain it.
    • The whaler subtype of daydreamer, specialized to hunt open-ocean prey, is on the decline due to the warming ocean lowering the numbers of their filter-feeding prey, most notably the banded maw, the largest animal on Serina during the Ultimocene. By the time of the Ocean Age, only the pelagans and warmongers are left, and millennia after the latter's war with the other daydreamers, the last of the former die out, but not before reuniting with their fellow daydreamers and passing on their history as the woodcrafters did before them.
    • The circuagodogs, who once outcompeted their avian and other tribbethere competition, die out not only when their fellow circuagodonts start going extinct themselves, but the trunkos who served as their other prey source grow smart enough to start preemptively targeting their predators by killing their babies and breaking apart their packs. The last circuagodog, a scissortooth, dies starving to death before getting beaten to death by one of the very trunkos its kind used to hunt as a Mercy Kill.
    • The icefishers go extinct when the thawing of the ice they need to survive puts them in the crosshairs of their savage gravedigger relatives, who outcompete them into extinction.
    • Save for the duckbilled sealump, the rest of the group dies out during the Great Thaw because unlike their cousins who can go on land when necessary, they're trapped in the dying oceans.
    • The cactaiga plant was very prolific during the Mid-Ultimocene as it was adapted for cold and arid conditions, but was unable to handle the increased rainfall of the Late Ultimocene and went extinct.
  • Crusading Widow: The warmonger matriarch is completely blinded when the grieving mate of one of the soldiers she sent into battle stalks her after she fled the angry mob and stabs her in her good eye with a broken shaft from one of the gravedigger's spears.
  • Cthulhumanoid: An avian variant. The various "softbill" birds sport facial tentacles derived from soft tissue that covered their ancestors' beaks and have unusually upright stances for birds, making them a rare example of a Cthulavian.
  • Cuteness Proximity: The luddy porplets have this effect on the fisher daydreamers due to their chubby appearance and child-like behavior. It doesn't work on the pastoral daydreamers, who are taught from childhood to only view porplets as food. The luddy's descendant, the greengrazer, are also considered cute by novan daydreamers.
  • Death by Irony:
    • Merwals are marine canitheres that used their tail derived hind leg to swim, much like how their fish ancestors used their tails to swim. However, because it has long since been used for walking, its joints and rigidity now made it very poorly suited for aquatic locomotion, so, when the aquatic molodonts arrive who use their front legs for swimming, the merwals are swiftly outcompeted and go extinct.
    • The wombler is the first megafaunal canary in Serina's history, evolving ten million years post-establishment in a predator-free Sugar Bowl, into a seven-foot, slow-moving flightless herbivore. Due to this peaceful environment, however, the womblers evolved to be less than peaceful: never having learned how to fear for their own survival, they become very fearless and aggressive, often killing each other in fights over territory and mates, because they never learned to back down and flee. This eventually proves to be their undoing when the first true predators, the falconaries, begin evolving; the womblers quickly go extinct and leave no descendants.
    • The fork-tailed babbling jays have a quasi-religious reverence for rainfall, believing that plants and animals are created by it, and that the gas giant Serina orbits is a "sky sea" that blesses them with it. Ultimately, it's rain that leads to their extinction, as it eventually causes the fork-tails' desert habitat to turn into a humid forest ridden with diseases they have no resistance to.
    • The warmonger matriarch was the ruler of some of the most deadly apex predators to swim Serina's oceans, but is eaten by a sea shoggoth, which is made of the tiniest carnivores in the sea.
    • The circauagodogs outcompete the canitheres by being smarter than them, only to reach an intelligence bottleneck that does them in when both their prey and predator competition gets smarter than them.
    • Cactaiga plants are able to thrive in harsh, barren conditions that most other flora can't survive but are done in by warm temperatures and increased rainfall, something typically beneficial for plant life.
  • Deus ex Machina: Near literally how the Late Ocean Age is resolved. The god-like intelligence observing Serina takes pity on the sea stewards for inadvertently destroying their world due to interfering to keep the project running, so it clones them and puts them in a copy of Serina, saving them while the original keeps burning.
  • Disaster Dominoes: The Thermocene/Pangaeacene mass extinction. A gradual increase in volcanism sets these off that leads to the entire moon becoming an irradiated Hailfire Peaks and the extinction of 99% of all life.
  • The Discovery of Fire: The gravediggers discovered how to create fire at the beginning of the Ocean Age, but learning to control it only becomes relevant as Brighteye seeks to learn their secret in order to help the wumpos hold back the thorngrazers and the cactaiga.
  • Distracted by the Sexy: In this story, a young male gmu enters his first mating season and becomes obsessed with pursuing the scent and calls of a receptive female to a fatal degree, as he fails to detect the greater grappler stalking him until it swiftly and brutally kills him.
  • A Dog Named "Dog": Ember's pet bird is named, well, Bird.
  • The Dreaded:
    • In an ironic twist, the woodcrafters became this to their former predators the gravediggers. Their tendency to retaliate if one of them was killed or injured caused the gravediggers to view them as a jinx and their systematic hunting at their hands made them a danger to be steered clear of. The gravediggers that lived in the refugia would not create any tree art for fear of drawing their attention and when the woodcrafters began hunting the ones outside their territory, they start depicting them as deadly monsters in their artwork.
    • The savage gravedigggers, or "wildwalkers" in the tongue of the thalassic gravediggers, are feared by them due to their not quite sapient level but still high intelligence combined with their viciousness.
    • The woolly wumpos fear the thalassic gravediggers for being smart enough to hunt them, referring to them as "demons" for driving them to the far north where it was much tougher for them to survive. For their part, the coastian thalassic gravedigger seem to fear the wumpos back as ever since Retally drove them off, they never made any permanent settlements along the shoreline, only come to shore to mine peat and coal, and both species try to give each other a wide berth whenever possible.
  • Driven to Suicide: Implied with Retally the woolly wumpo. After his lack of mastery over fire creates a blaze that kills nearly all of his clan, Retally is consumed with grief and regret. He heads to the inhospitable north and is never seen again.
  • Dumb Muscle:
    • Savage gravediggers are the largest and strongest of the three gravedigger species of the Late Ocean Age, but are only about as smart as a chimp due to losing the higher intelligence exhibited by their tundra gravedigger ancestors.
    • The thorngrazers of the middle Ultimocene are among the strongest of the remaining land animals but have greatly lost their intelligence, not only stupid by Serinian standards, but even by the standards of Earth mammals. They survive due to a combination of their strength, sheer aggression, and ability to eat practically anything. However, this means that they are also covered in parasites that gradually weaken them since their stupidity means that they can't form real social attachment and engage in social grooming to get rid of them.
  • Dying Alone: Brighteye dies of smoke inhalation on the beach with only the watcher as company.
  • Dying Dream:
    • As the last woodcrafter dies, she receives a dream from something restoring her health and people, reassuring her that she did well and pulling back the curtain to show the world from its perspective, millions of lifetimes and species far beyond her comprehension, all starting from a little fish and a little bird.
    • The warmonger matriarch receives a vision of her people prosperous and at peace as she is eaten alive by a sea shoggoth. No matter how hard she swims towards them, they only get further away until she can only feel the indifferent presence of something beside her, and then nothing at all.
    • Brighteye gets a vision of the watcher in his last moments where it reveals to him its part in bringing he and Blaze together in the first place, which eventually leads to the death of the family thanks to the massive coal fire sparked by Whitecrown and his clan's carelessness with fire. Brighteye's last words in response to their apology and statement that this was not the end of the world, but merely another chapter in its history, are a Dying Curse towards them for their interference before expiring.
  • Dying Race: Quite a few, as Serina's biodiversity continues to decline over the Middle and Late Ultimocene:
    • The mourners-in-the-mist are the last relic population of boomsingers, having survived the loss of their environment and competition from better-adapted grazers by holding out on a single island devoid of competitors or predators. However, they're still ultimately doomed — in addition to being poorly adapted to its niche and only enduring because there's nothing to contest it from them, their small island can only support a hundred and fifty or so of them at any given time, making them very vulnerable to sudden disastrous events. Inbreeding is also taking a heavy toll of them, and most of their calves are stillborn; those that survive usually have significant problems with their immune systems, digestion, and organs. While they'll still endure for thousands of years, they're slowly but surely going extinct, and have by the Late Ocean Age.
    • The woolly wumpos have been on a slow decline thanks to the shrinking of habitable land and competition with thorngrazers and now only number around a few hundred individuals compared to around 300,000 beforehand. Conflict with the thalassic gravediggers forcing them further north to more inhospitable territory has also caused their numbers to dwindle. As a result, aberrant traits such as heterochromia and albinism are very common. The Late Ocean Age ends with them dying in the Serinarctan coal seam fire.
    • The dire bumblebears were already a fairly rare species due to their high food requirements, but after the great Serinarctan coal seam fire their population is reduced to a below sustainable number.
    • Due to the sea stewards' disappearance, the defenseless floating bloats' numbers are drastically cut by the sea shoggoths and other predators predating them due to lack of food, with the last dying of starvation around 250 years after the coal seam fire and falling to rest at the bottom of the ocean away from most creatures capable of eating it completely.
    • Due to inbreeding amongst themselves from their very inception 10,000 years post-coal seam fire, the reapers have poor reproductive success, with nineteen out of twenty pupal sacs failing to mature, and even fewer managing to reach their first year. As a result, from an initial population of less than 2,000 scattered across the world they continue to dwindle until only a single female, Eve, is left 500 years later.
  • Eaten Alive:
    • After the blinded, weakened warmonger matriarch gets caught in thick vegetation her struggles catch the attention of a sea shoggoth, which swarms over her and takes her apart while she's powerless to resist.
    • Blaze considers getting killed by a dire bumblebear preferable to getting killed by thorngrazers, because at least the former would kill her quickly, instead of the latter's inefficiency at predation meaning that they'd just start taking bites out of her slowly long before she actually died.
    • Once the sea stewards are no longer around to feed them and there's no more carrion to consume, the sea shoggoths start eating the floating bloats while they’re helpless to do anything about it. A lucky few die quickly when the attacking ants end up suffocating them, but the others die slowly from being eaten from the outside in over the course of days or even weeks.
  • Eldritch Ocean Abyss: From the perspective of the woolly wumpos, the ocean is the realm of demons, as it's where the thalassic gravediggers who hunted them came from. Before first contact between the two peoples, however, the ocean was revered as a source of highly nutritious seaweed. Even after Retally managed to drive the gravediggers from the shoreline by turning fire against them, the wumpos still have a major taboo against making their homes along the shoreline.
  • The Empire: The warmonger daydreamers have a supremacist culture and believe it is their right to conquer the ocean and destroy the other daydreamers. Unlike the fishers and pastoralists who have fairly loose clan structures, the warmongers have a large, united society with central leadership determined by monarchy which gives them an edge over both.
  • End of an Age:
    • The death of the last woodcrafter informally marks the end of the early Middle Ultimocene, and the beginning of the Ocean Age.
    • The end of the Ocean Age and the Middle Ultimocene with it is marked by the Serinarctan coal seam fire, the death of Brighteye and the woolly wumpos, and the sea stewards being transported to a new world. The sea steward's departure, combined with the extinction of the icefishers due to their ice refuge melting, also marks the end of the age of sapient life on Serina, with most surviving lifeforms focusing more on being tough than on their intelligence.
    • Following the Serinarctan coal seam fire, anoxic events and lack of food due to rising sea levels kills off most vertebrate life in the oceans, leaving the molluscs and sea shoggoths to take over the seas.
  • Enemy Mine: The fisher and pastoralist daydreamers have been in a cold war for centuries, but with the gravediggers serving as the bridge, they unite in order to face off against the warmongers who wish to kill them all.
  • Everyone Has Standards:
    • The pastoralist daydreamers farm the non-sapient descendants of their close relatives, the nops, for food but they draw the line at eating them alive and will Mercy Kill them first, even though the nops aren't able to feel pain anymore due to millions of years of domestication.
    • The social gravediggers are noted to be highly empathetic to other species, but even they come to see the warmongers as evil before officially fighting them due to the fact that they are willingly eating other people (daydreamers) despite the current abundance of alternative food in the shallows they are currently invading.
    • The shallow water daydreamers may view the warmongers as evil monsters for their actions, but they're still horrified when they see the poisoned warmongers drown in their second battle.
    • While Brighteye detests the thorngrazers just as much as everyone else who happens to be aware of them, even he thinks them getting burned to death is too horrible a fate to suffer.
  • Everything's Better with Dinosaurs: Aside from the Velociraptor-like banshee, you have pseudornithopods, tyrant serins (which even live 65 million years hence), and the blue-throated boomsinger, which is essentially a tailless sauropod. There are also birds that resemble other non-dinosaur Mesozoic reptiles, such as the marine predatory penguipleurodon that resembles an avian mosasaur, and the quadrupedal Giant Flyer archangels that bring to mind Quetzalcoatlus. And, of course, all birds are technically dinosaurs, so this trope really applies to every bird on Serina.
  • Everything's Better with Penguins: Pretenguins are a group of flightless, mostly aquatic sparrowgulls that have convergently evolved with penguins. They are noted as being playful, docile, and intelligent creatures, and one species, the penpal, has been domesticated by the gravedigger-daydreamer-greenskeeper civilization. Unfortunately, they end up being among the casualties of the Great Thaw when the oceans become too toxic for them to survive. However, "The Visitor: Part 3" reveals that the freshwater pygmy pretenguin managed to survive and is now living in the marshes of Serinarcta.
  • Evil Is Bigger: Warmongers are on average about 20% larger than their fisher and pastoral cousins, and they believe in whaler supremacy over other dolfinches.
  • Evil Old Folks: The warmongers are led by an elderly matriarch, and it's her idea to try genociding the gravediggers in order to preserve warmonger beliefs.
  • Exactly What It Says on the Tin: Many creatures are named very descriptively after their primary physical features or habits — for example, falconaries are falcon-like canary descendants, boomsingers communicate through loud, echoing calls, gravediggers dig spiked pits to kill their prey, thorngrazers eat spiky plants, and so on.
  • Exotic Equipment: Not mentioned within the story proper, but tribbetheres, much like the guppies they're descended from, have prehensile penises.
  • Expy: Some creatures may have been inspired by other works of Speculative Biology.
    • Molebirds and bumblets are similar to spinks.
    • The archangels are also similar to the great blue windrunner (being large crane-like birds with additional wing feathers on their legs), and the banshees are reminiscent of the carakiller (predatory flightless birds whose wings sport dinosaur-like claws). Vibropterans bear some resemblance to the forest flish, and boomsingers are rather reminiscent of toratons, being beaked, tailless sauropod analogues, despite being of avian origin while the latter is a tortoise. The lumberbeest fills the same niche in deep forests and looks less like a sauropod but more like an actual giant tortoise.
    • Porporants are flightless, predatory seabirds that fill the niches of dolphins and seals, much like the porpin and gannetwhale. The former has an analogue to baleen whales as a relative, and Serina also has birdwhales.
    • The simiagibs, brightly-colored monkey-like tree-dwellers with two pairs of partly-joined arms, bear an uncanny resemblance to the Prolemuris from Avatar.
  • Extra Digits: Tribbets have seven digits on each forelimb. The more derived spiderfrogs have only four, but their fingers are long enough to function as arms in their own right and have developed tiny fingers of their own. While most advanced tribbetheres have seven digits per forepaw, the primitive Nest Goblin has more than eight.
  • Extreme Omnivore: The omniphages are a group of large molodonts that are adapted to eat pretty much anything they come across, including rotten wood, thorns, and bones. They can even extract nutrients from dirt by digesting organic bits in it. One desert-dwelling species, the thorngrazer, adapted to feed on spine-covered cactus analogs, and its ice age descendants fill a unique niche as their environment's primary grazers and scavengers alike. This has a noticeable effect on their evolution. Unlike most other grazers who have populations separate into different species when they specialize into feeding of different plants, the thorngrazers' ability to eat pretty much anything means they don't have to specialize. There are only two species of throrngrazer during the Late Ocean Age as a result, the longer legged nimicorns who are somewhat better suited for browsing and active hunting, and the squat, armored razorbacks who are better built for grazing and scavenging.
  • Face Death with Dignity:
    • The woodcrafter culture typically doesn't become worried about things that can't be resolved. As such, when it becomes clear that their species is going to die out, they simply decide to use their remaining time to help the gravediggers and impart their final lessons on them.
    • This is attempted by the exiled warmonger matriarch after she's rendered blind as she tries to swim back out to the open ocean where she likely would have been put to death by the pelagans, which she saw as a more dignified way to go out. However, she ends up getting turned around and went back into the shallows, where she gets tangled up in seaweed and devoured by a sea shoggoth.
  • Fantastic Arousal: Female snarks have certain spots on their bodies that the males pierce with their love darts when they mate. This gives the females a rush of endorphins rather than pain. Even touching the spots is pleasurable to them; they're said to rub against objects in their environment for self-stimulation.
  • Fantasy Counterpart Culture: For the most part averted, since the sophonts are genuinely inhuman. However, the sea steward society combines elements of Inuit and other Arctic peoples (reliance on the sea, use of bones and pelts to make boats) and Aboriginal Australian cultures (maintaining a sustained, garden-like environment). Surreal/symbolic art draws heavy inspiration from Pacific Northwest cultures.
  • Fantastic Fauna Counterpart: As the colonists diversify to occupy various niches, they take on many forms resembling Earth life:
    • Mucks are avian iguanas, serezelles are bird antelopes, and the canaribou is the canary version of reindeer and elk.
    • Primitive serestriders are giant ostrich-like birds that fill a niche similar to sauropods, while some later strains develop dermal armor and stouter bodies similar to ankylosaurs. These birds are all preyed upon by the immense, flightless and heavy-beaked tyrant serins, which resemble tyrannosaurs. As a result, the plains of the later Thermocene end up decidedly resembling those of the Mesozoic.
    • The tribbetheres, which arise later in the Ultimocene also become convergent with mammals, with canitheres being like hyenas, circuagodonts becoming like deer and hares, or the molodonts coming to resemble rodents.
    • Water snuffles are basically platypuses if they were actually birds.
    • Some of the grazing circuagodonts evolve into predatory forms, somewhat evoking the mesonychids and entelodonts, prehistoric ungulates that became hoofed meat-eaters.
    • The canitheres of the Ultimocene have occupied some new niches to avoid competition with the predator wheeljaws. The brushbounder is similar to a honey badger or wolverine, the big-eared foxtrotter is blatantly similar to a fennec fox, and the repandors are speedy grassland hunters similar to jackals and dingos.
    • Snarks are the Serinan equivalents to octopi and squids as surprisingly intelligent, free-swimming predatory mollusks. Later, sea mittens converge upon larger, cold-water cephalopods.
    • The tribbats also take on some unusual niches, such as the owl-like moonbeast and its descendant the snowspirit that more particularly takes after a snowy owl, the vibropterans, colorful nectar-eaters similar to hummingbirds, or the night biter, basically a flying cookiecutter shark.
    • Some of the handfish tribbets take on hexapedal, arboreal monkey-like forms, such as the tarsier-like gibbets, which later give rise to the ape-like simiagibs.
    • Many of the larger molodonts in the Ultimocene take on aquatic niches, becoming analogues of walruses, manatees, and cetaceans.
    • The saber-toothed circuagodog and the mammoth neckbeard are Serina's expies of, well, machairodontine cats and mammoths as the shaggy, trunked, social, ice-age megafauna and its pack-hunting, sabertoothed predator.
    • The jackal carnackle acts similarly to an arctic fox, following around large predators such as bumblebears to share their kills.
    • Seastrikers are very similar to orcas due to being large, highly intelligent aquatic predators that live in matrilineal social groups and play with their prey before killing it. Their descendants, the daydreamers, take this resemblance further by living in cultural groups distinguished by choice of diet, with the fishers, pastoralists, and whalers roughly corresponding to the resident, transient, and offshore orca populations of western North America respectively, while the warmonger whalers' habit of tipping ice floes to prey on molodonts resting on them is based on a common hunting tactic used by polar orcas. The fishers learning to speak the gravedigger language may also be based on some orcas attempting to mimic human speech.
    • Archangels and lanks are essentially Serina's azhdarchid pterosaurs, though the former are more herbivorous.
    • The snowscrounger comes off as a flightless equivalent of the snowy sheathbill, Antarctica's sole terrestrial bird species that also acts as a scavenger and opportunistic predator of young animals. Their rivals, the glacier ravens, are also roughly equivalent to skuas.
    • The gupgops of the Meridian Islands are slugs that have taken the niche of toads.
    • Predatory burdles, such as the sea rexes, are the Serinan answer to a pliosaur.
    • The bluetails are extremely similar to chimpanzees despite being raven-like: they are highly-intelligent semi-sophonts who are aggressive and violent, are prone to gang wars and hostile takeovers of territories, and reject albinos and often harass and kill them, as chimpanzees are known to do.
    • Pretenguins are mostly analogous to penguins as per their name, but the ptarmenguin takes mostly after a giant flightless goose crossed with a moose, the pygmy pretenguin a duck, and the penpals are very similar to flightless cormorants in both body plan and niche, while being the thalassic gravediggers' rough equivalent of a hunting dog.
    • Savage gravediggers are a combination of honey badger and polar bear. They can also be seen as analogous to chimpanzees as they are nonsapient but intelligent and vicious relatives to a species of sapient, bipedal tool users.
  • Fantastic Livestock:
    • The farmerjays are a species of songbird that feed and raise fattened, domesticated snails in tree hollows. Notably, the farmerjays themselves are intelligent but aren't actually sapient as they farm their snail livestock through a combination of instinct and behaviors passed down from the adults.
    • The social gravediggers end up domesticating a species of smeerp (A rabbit-like tribbethere) for food, which allows their population to no longer be tied to the amount of wild prey in their environment. As a result, the population skyrockets in virtually no time.
    • The daydreamers are sapient, orca-like marine birds that farm a herbivorous marine bird known as a ring-necked porplet as livestock, over millions of years these porplets become fatter and dumber, eventually developing into the bloated, barley intelligent nops. One thing of note is that the porplets and their nop descendants are actually related to the daydreamers (making it somewhat analogous to humans farming monkeys for meat) and this relation causes some daydreamers to view the eating of nops as morally repugnant and they start feeding exclusively on creatures like fish.
    • Five million years later, the novan daydreamers and their terrestrial gravedigger allies have replaced the nops with the floating bloat, a massive sauropod-like animal that can reach lengths of 140 feet and feeds on the plants growing on the ocean floor. The only reason these birds can even grow so large is because the daydreamers, gravediggers, and greenskeepers (sapient descendants of the nops' still-wild relatives) have been actively maintaining the shallow seas for millions of years and have made them more biologically productive.
  • Fantastic Racism:
    • Some fisher daydreamers will discriminate against pastoralists who choose to join their communities, while pastoralist insularity can give way to plain xenophobia.
    • Warmongers view all other beings as lesser, including the other daydreamers, making no distinction between either the fishers, or the pastoralists who happen to be their closest cousins. As far as they're concerned, their cousins are both little more than meat.
  • Fantastic Slurs: Warmongers refer to daydreamers born with the species' typical yellow markings as "bile-bathers", as to them they look like they're covered in vomit.
  • Fat Idiot: Nops are bred to be much fatter and dumber than their thinner luddy cousins.
  • Fearless Fool: Womblers, the very first megafaunal canaries to evolve, inhabit a serene grassland world virtually without predators or indeed any creature larger than themselves. As a result, they are not the brightest of birds and have virtually no sense of fear. However, this actually makes them very dangerous animals because they don't know any better than to fight to the death over territorial and mating disputes.
  • Feather Fingers: In an unusual take on this trope, the farmerjay evolves a crude grasping mechanism from the alula and a fleshy pad on the wrist of its wing, allowing it to handle its offspring and the snails it instinctively farms for food. This is a trait common to all sparrowgulls.
  • Feathered Fiend: Every avian apex predator, naturally. Also, some of the herbivores can be quite deadly in self-defense, such as the blade-winged serestriders, or the Mammoth Neckbeard (even shown impaling a carnivorous circuagodont through the head with its toe claw.)
  • Feel No Pain: Nops have had the ability to feel pain almost entirely bred out of them, so it's possible for one to get Eaten Alive by predators (save for their daydreamer shepherds, who opt for a Mercy Kill when it comes time to harvest them) and just keep grazing until their bodies are too broken to graze anymore.
  • Foil:
    • The porplets and the seastrikers are being set up as this to the woodcrafters and gravediggers:
      • The porplets and woodcrafters are both highly social intelligent herbivores being hunted by an intelligent predator, but the woodcrafters are highly empathetic to their herdmates and will try to help or avenge them when one is attacked, while the porplets will leave their herdmates to die if it means the survival of the whole group.
      • The gravediggers and seastrikers are likewise both highly intelligent hunters, but the gravediggers are solitary predators that mostly rely on traps to dispatch their prey but take no pleasure in the act of killing, while the seastrikers are very social and hunt their food directly and also have a tendency to play with their food.
      • There's also the relationships the predators have with their prey species. The gravediggers would kill their woodcrafter prey as much as they could with no regard to long-term consequences, which led to them becoming more intelligent and becoming a threat to the gravediggers before they eventually made peace. The porplets are completely at the mercy of the seastrikers, who now only kill them in a way that benefits themselves in the long run.
    • Later on, the daydreamers become a foil to the marine social gravediggers: they are both the sapient, carnivorous, ocean living descendants of bumblets with fully realized cultures but differ in some key ways. The gravediggers are united in their empathy to one another and the creatures in their environment and rely heavily on tool use to live on and feed from the ocean, but have no desire to advance beyond that point. The daydreamers on the other hand, are divided by ideological differences that lead to violent conflicts with each other and are perfectly designed to live in their aquatic habitat, which leaves them unable to make or use tools, yet they think very deeply about the future and how they can affect it despite that.
    • The luddy and nop, the two descendants of the ring-necked porplet. Luddies are relatively thin, semi-sapient, look more or less the same, are highly communicative, and are treated as pets by the fisher daydreamers. Nops are fat, incredibly unintelligent, have numerous color variations due to domestication, are completely incapable of speech, and are protected by the pastoralist daydreamers as food. Their ultimate fates are also different. The luddy evolves into the fully sapient greenskeeper, while the nops go extinct due to the floating bloat serving as a better food source.
    • The pelagan daydreamers and the sea rex, the two apex predators of the open seas. While both are aardgeese, the pelgans descend from the bumblet vivas, while the sea rexes are burdles descended from the muck serestriders. The pelagans are sapient, social, and live in a collectivist society, whereas the sea rex is nonsapient, solitary, and only come together to mate. Both end up going extinct, but while the last surviving pelagans make contact with the daydreamer-gravedigger civilization and survive through their lore, the last sea rex dies alone and unmourned as solely a feast for scavengers.
    • In the southernmost ice-free peninsula of Serinarcta, the thorngrazers and their main predator, the sawjaws. Thorngrazers are incredibly unintelligent, by both Ultimocene Serina and Earth standards, rely mainly on their bulk and sheer aggression to survive, and only live in groups because it lessens their own chances of getting eaten. The sawjaws are very intelligent and work together to survive out of altruism. While thorngrazers are Social Darwinists who leave the injured to die at the beaks of the sawjaws, sawjaws will take care of even those who can't take care of themselves.
    • The woolly wumpos have quite a few foils:
      • The woolly wumpos and the bluetailed chatteravens. The wumpos are descendants of a near-sapient species that became sapient, whereas the bluetails are the (Mostly) non-sapient descendants of a sapient species. Wumpos treat their entire species as one big family, while the bluetails are highly territorial and think nothing of harming those outside of their family. Wumpos are very emotionally mature even if they tend to be neophobic, bluetails are quick learners but possess a species wide Hair-Trigger Temper. The wumpos revere the neurodivergent wideminders and have no issue with physical differences, whereas the bluetails have treated Brighteye as a pariah his whole life for his intelligence and despise albinos like Whitecrown for his physical aberration.
      • In "Allies", the woolly wumpos and thorngrazer groups are contrasted with each other. The thorngrazers are only together to avoid predation, and even trample their own while retreating from Brighteye and the wumpo family coming to assist the injured Blaze. The wumpos by contrast are altruistic enough to help one another no matter how dangerous the foe is.
      • The woolly wumpos and their closest cousins, the island wumpos who they've begun to interact with as the encroachment of the glaciers has created a land bridge between the latter's home islands and the Serinarcta mainland. Woolly wumpos are very large and cold adapted, whereas island wumpos are about a quarter of their size on average and live in a temperate environment. While both are highly social species, woollies stick closely with their families whenever possible, taking after the mammoth trunko who serves as their primary ancestors, whereas islanders take after their desert wump primary ancestors by having no issue only being in pairs or completely alone for days at a time. The woollies are true sophonts and highly rational but neophobic, whereas the islanders are near-sophonts who tend to be more emotional and are very curious as a result of their island tameness. Woolies tend to be virtually plain-colored, whereas islanders have brightly colored faces that make them closely resemble the ancestral trunko species they descend from. While both have tiny populations, the woollies have many aberrant traits such as albinism and piebaldness, whereas the gauntlet the island wumpo's ancestors had to beat to reach their islands has left them highly resistant to inbreeding depression despite the fact that their population is 95% homogenous, if more prone to erythrism and feathers growing on their feet. While the woollies have been driven to the brink of extinction due to their thorngrazers eating their food, the islanders are small and quick enough that the thorngrazers don't pay them much mind, allowing them to eat the plants of the cactaiga that the woolies aren't able to access due to their size, and hunt the small animals the thorngrazers inadvertently flush out and even form a mutually beneficial relationship with them after the great coal fire. Ultimately, the woolly wumpos are among the casualties of the Late Ocean Age catastrophe, while the island wumpos survive into the Late Ultimocene.
    • The pretenguins contrast the other extant sparrowgulls of the Late Ocean Age, in particular the sea- and chatteravens, by being openly friendly towards strangers, while their cousins are highly aggressive to anything that isn't one of them.
  • A Form You Are Comfortable With: The watcher appears to Seeker as the overlayed outlines of a daydreamer, greenskeeper, gravedigger, and Brighteye sharing a single glowing eye in the way that visions appear to daydreamers.
  • Formerly Sapient Species:
    • Downplayed in that the ring-necked porplets were more accurately semi-sapient, but millions of years of farming by the seastrikers and later Large-Prey Ecotype daydreamers turned the ones farmed by the pastoralists into the far less intelligent nop. Fatter than their porplet ancestors, millennia of selective breeding for docility and edibility have made them so dumb that they're utterly defenseless without their daydreamer shepherds to protect them.
    • When the folk-tailed babbling jays went extinct, the last surviving member of their species took a mate with a closely related but non-sapient bird and had hybrid offspring that lacked his intelligence (save for a grandchild who was killed by a predatory bird when they got distracted due to their high intellect before they got the chance to breed). By the time of the middle Ultimocene, these hybrids still live on in their descendants the chatterers, who aren't sapient themselves but are still highly intelligent and able to mimic spoken language. By the time of the Late Ocean Age, one bluetail chatteraven known as Brighteye is fully sapient, but the rest are merely about as intelligent as a chimp.
    • Savage gravediggers are descendants of the tundra gravediggers forced towards the southern coast during the Ultimocene glaciation. The extremely harsh environments where they evolved and now live produced a strong selection against higher intelligence, as the lack of useful building materials following the extinction of forest environments provided little benefit for tool use and the scarcity of food made big, energy-hungry brains a liability. As a result, they're only about as bright as a chimp and have lost all forms of tool use and culture.
    • In the vision the watcher gives Seeker of what will happen if the sea stewards choose to die with their world, he sees that the generalist thalassic gravediggers have managed to survive, being less attached to the ocean than the others, but at the cost of their sapience, and they feast upon the corpses of their former brethren, the daydreamers and greenskeepers.
  • From Nobody to Nightmare:
    • The tribbetheres certainly count, at least from the birds' perspective. Starting out as small, rat-sized hoppers in the Thermocene, the Thermocene-Pangaeacene extinction changes the climate to better suit the early tribbetheres, especially in the isolated Kyran islands that have now collided with the mainland. The defenseless island natives quickly fall to an onslaught of tribbethere predators, which grow up to thirty times their original size as they fill new apex-predator niches. The bigger tribbetheres then spread outward from the Kyran peninsula back into the mainland, having now evolved into new forms that are capable of preying on or competing with birds, in ways that their original tiny ancestors could not. The tribbetheres then spread around the globe, with new herbivorous species outcompeting the grazing avians to extinction, and egg-eating rodent-like molodonts leading to the decline or extinction of many ground-nesting birds that lay hard-shelled eggs.
    • The thorngrazers evolved from small molodonts closely related to the seedsnatcher, but become Extreme Omnivores so efficient at their jobs that between them and the cold they've shrunken non-cactaiga environments immensely, and are the most numerous large terrestrial species on Serina by the Late Ocean Age. It takes the Serinarctan coal seam fire to extinct the razorbacks, who are too slow to escape the flames, but the faster nimicorns manage to survive into the Late Ultimocene.
  • Genre Shift: Serina starts off as a speculative evolution project, but the Middle to Late Ultimocene section shifts into pure Xenofiction with a Low Fantasy vibe, due to the increasing focus on individuals within sapient species and their perspectives and later into Magical Realism with the fulfillment of a prophecy and the intervention of something that could effectively be called god.
  • Gentle Giant:
    • Averted with the wombler, a seven-foot moa-like canary that evolves early on, 10 million years post-establishment. The first of the large avian megafauna to evolve, they adapted in a world without predators and thus, like the dodo, evolved to have no sense of fear. Ironically, this caused them to be unnaturally aggressive, compared by the author to domestic dogs without bite inhibition, and are very prone to fighting and killing their own species, especially the males. Unsurprisingly, the Womblers become extinct very quickly once the Falconaries, Serina's first birds of prey, evolve.
    • Played straight with the aquatic bloon, growing up to thirty feet in length and being a peaceful herbivore.
    • Chubbirds are a group of flightless canaries native to the Kyran Islands that are mostly friendly, due to their sheer size preventing other animals from preying on them once they're fully grown. The exception is if you're a crab trying to attack their chicks, which will make them stomp you to death.
    • Boomsingers are giant sauropod-like herbivores descended from the serezelles, and spend most of their time browsing placidly in the treetops.
    • The mammoth trunko is a large elephantine tentacle bird that are very peaceful animals with a strong sense of empathy. They'll even adopt the orphan chicks of other mammoth trunko and their snow snoot relatives. It's for this reason that the Woodcrafters revere them as a kind of spiritual teacher that is worthy of emulation.
    • The archangels are Giant Flyers resembling swans that grow to the size of Quetzalcoatlus, but are peaceful grazers.
    • The floating bloat is a descendant of the sea-sweeper that is more than 140 feet long and just over 210 tons, making them the largest animal ever known on both Serina and on Earth. As a result of being selectively bred for millions of years and their sheer size, they are completely docile, making them an excellent food source. It's also noted that large oceanic animals in general are tame during the Late Ocean Age due to the gravediggers and daydreamers preventing the evolution of anything big enough to hunt them.
    • The aukvultures stand nearly as tall as a man (making them significantly larger than the diminutive thalassic gravediggers) and possess a 20ft wingspan yet they are known for their quiet and docile personalities when waiting for scavenging scraps, something that they actually enforce as a form of culture. In fact, the sea stewards will deliberately keep them around as their size serves as a deterrent for the smaller but much more aggressive sea ravens who will even sometimes attack their children. Their scientific name even means "learning gentle-giant". By the early Late Ultimocene it's played with, as, while the reapers descended from the aukvultures remain about as gentle as ever, the rest of the species has reverted to its aggressive instincts.
  • Giant Flyer:
    • Ornimorphs and the four-winged archangels reach wingspans of 25 to 50note  feet.
    • Even before then, there were falconaries with wingspans of 20 feet thanks to the moon's lower gravity.
    • The aukvultures have a 20ft wingspan, making them the largest living seraph of the Ocean Age. In the early Late Ultimocene, they've gotten slightly larger with a more than 23 ft wingspan in order to fend off terrestrial scavengers, and remain the largest fliers on Serina.
  • Gigantic Adults, Tiny Babies:
    • The changeling birds are the same size as most typical songbirds, but lay tiny, soft-shelled eggs the size of grains of rice, which hatch into larval offspring barely a few millimeters long at birth.
    • Shadowskimmers, a type of ornimorph, hatch as fish-like larvae a few inches long, metamorphose into a flying juvenile about the size of a pigeon, and eventually reach an adult size of up to a twenty-foot wingspan.
    • The giant gemnus is a thirty-foot-long freshwater fishnote  that gives birth to over 100,000 centimeter-long fry at a time.
    • Inverted with the Tufted Frogjar, whose newt-like juvenile form is actually bigger than the adult and shrinks considerably upon metamorphosis, akin to the real-life Paradoxical Frog.
    • A fully grown sea rex is a 50ft predator that is virtually unbeatable but they don't take care of their young. Instead, a female will journey to the edge of the shallows to give birth to a litter of small, fast-swimming fish eaters who spend their earliest days in these waters and filling different niches depending on age before reaching daydreamer size and returning to the open ocean. The pelagians use this to their advantage by hunting down these smaller, more vulnerable juveniles to slowly wipe them out.
  • Glacial Apocalypse: The last geologic period in Serina's history, the Ultimocene, is marked by drastic global cooling caused by the halting of volcanic activity (and thus of the main means by which carbon in the deep crust is released into the atmosphere) and by the locking of large quantities of carbon dioxide into the soil by earlier eras' flourishing plant life. This loss of natural greenhouse gases leads to the onset of runaway ice age conditions, as glaciers creep down from the poles and winters grow harsher and harsher. The tropical biomes are the first to collapse under the strain of cooling weather and refugee species fleeing from the temperate areas, the southern continent becomes entirely encased in ice, and a catastrophic loss of biodiversity generally ensues. Life manages to survive and thrive despite these conditions, for a time — a holdout of the temperate forests endures for a long time on the northern continent's southern coast, and numerous plant and animal species adapt to thrive in the bitter tundra further north — but as the glaciation continues, the temperate refugium is eventually snuffed out and even the cold-adapted species slowly go extinct, as the world slowly becomes too cold and barren for any kind of life to survive.
  • Goal-Oriented Evolution:
    • The series offers an interesting take on this trope. It argues that animal life has a tendency to evolve greater intelligence as they become more complex. By the time of the Ultimocene, biodiversity has reached a point where high intelligence has become the norm rather than the exception.
    • Averted with some notable cases of evolution seemingly going back and forth with no definite direction, such as metamorph birds evolving to become r-strategists and producing lots of larval young, only for some metamorphs to re-evolve parental care. There are also the tribbetheres, whose first early forms were dog-like carnivores, which gave rise to rodent-like seed eaters, which in turn gave rise to ungulate-like grazers, some of which in turn became predatory again.
    • Also, the merwals and marine molodonts, being fish that evolved to live on land, gained many terrestrial adaptations, and then returned to the water to become fully-aquatic once again.
    • Ultimately averted with the babbling jays and the woodcrafters, who are as subjected to the forces of natural selection as any non-sapient animal, and ultimately each last only a few thousand years.
  • God Guise: The fisher daydreamers come to believe that the gravediggers are one of the missing fragments of their creator deity, while the gravediggers themselves were completely oblivious to the daydreamers' sapience until some of them began speaking to them. While by the time of the Late Ocean Age most of the sea stewards consider it just a story, Brighteye the sapient bluetail manages to rekindle the belief amongst large sections of the community.
  • Godzilla Threshold: The watcher's job on Serina is simply to observe, even if the moon becomes an iceball, because that's simply the natural way of things. However, the gravediggers managing to discover coal, and the subsequent continent-wide coal fire caused by Whitecrown and his clan of bluetails, forces them to directly interfere to stop the project's destruction, revealing themselves to and removing the sea stewards to save them from their otherwise inevitable extinction, and creating a clone Serina for them to live on as a new project.
  • Golden Age:
    • The Early Ultimocene, 250 million years PE, is this for life on Serina. Biodiversity is at its absolute peak, and the complexity of life has advanced to the point that the average animal is as smart as a corvid or a monkey. However, it is brought to an end by the onset of the final ice age that will gradually grow harsher and harsher until no life can remain.
    • After the conclusion of the war, the daydreamers and their allies the gravediggers enter one for their joined civilization, exploring the open ocean together for over a million years. By the Late Ocean Age they alongside the greenskeepers, the fully sapient descendants of the luddy, have turned their ocean home into a garden paradise. This age is ultimately brought to an end by Whitecrown and his flock managing to cause a coal seam fire that heralds Serina's penultimate mass extinction event.
    • For the animals who manage to survive the Great Thaw, their numbers increase by thousands due to the abundance in food caused by the melting of the glaciers. On Serinaustra in particular, the local predators and new arrivals gorge themselves on the corpses of animals washed up from the toxic seas to the point that they're nonaggressive towards one another simply because there's so much to eat, a state that remains for centuries.
  • Gray-and-Grey Morality: This the crux of the conflict between the fishers and the pastoralists. The fishers refuse to eat other intelligent creatures, and are very welcoming and outgoing to others, but they can also be overbearing, judgmental, and will sometimes sabotage pastoralist farms despite the nops not even being able to fend for themselves. The pastoralists on the other hand, eat the mentally degraded descendants of their close relatives, are highly xenophobic, and are generally distrustful of change, but they also prefer to keep to themselves and feed only on their livestock while leaving the wild dolfinches alone. Some fishers have started to become more introspective on this conflict and question if they are truly superior to their rivals.
  • Grayscale of Evil: The warmongers are black and white in color and attempt genocide on the gravediggers and their fellow daydreamers.
  • Green Hill Zone: The Hypostecene Era, the first five million years after establishment, serves as this for life on Serina. All land on the moon is warm sunny grassland, and the complexity and danger levels are quite low compared to what is to come.
  • Grim Up North:
    • The Great Tundra Ring of the Ultimocene is a harsh environment stretching from its borders with the steppes and towertree taiga to the south, to the southernmost extent of the ice sheets to the north, with winters that last for eight months and generally poor conditions. The tundra gravediggers, a subspecies of the gravedigger adapted to the harsher conditions, are far more aggressive and much more willing to personally dispatch their prey instead of relying on traps. The harshness of their environment also means they generally live only half as long as their southern cousins.
    • By the Late Ocean Age Serinarcta as a whole has become this for the thalassic gravediggers, due to its cold and dangerous predators such as the savage gravedigger, which they refer to as wildwalkers.
  • Had to Be Sharp:
    • The tundra gravedigger are larger, more aggressive, and more willing to personally kill their prey when compared to the southern gravediggers thanks to the extremely harsh and barren lands they live in. It's also mentioned that they aren't less intelligent than their southern relatives, but they rarely create tree art, and their thinking is generally geared more towards animalistic survival. However, they are also expert trappers and problem-solvers due to the more unpredictable nature of the animals migrating through the tundra.
    • The Late Ocean Age sea shoggoths are much smarter than their predecessors, as the overly aggressive and indiscriminate colonies were eliminated by the gravediggers taking advantage of their weaknesses to water and fire to burn and drown them.
  • Handy Mouth: The social gravediggers are able to use their mouth in crafting and using tools as a way of compensating for their stiff arms. Later on, they are able to teach the daydreamers how to craft tools of their own using their mouths and group coordination.
  • Has Two Daddies: The bachelor males of the polymorph bird form pair bonds with other male Bachelors and are known to steal and adopt the eggs of other polymorphs and raise them. Curiously, this is actually beneficial to the species, as the pairs whose eggs were "stolen" by bachelors lay replacement eggs, thus increasing the fecundity of the population. Also, since bachelor males are larger than tramps or ardors, a pair of bachelors has greater success protecting their young than an ardor and a female.
  • Hailfire Peaks: During the three-million-year mass extinction event between the Thermocene and Pangeacene, the entire moon of Serina is divided between completely frozen temperate and polar regions and a scalding hot equatorial region with extreme volcanism. Both temperature zones are too extreme to support life, except for a small region on the south shore of the new supercontinent. Even there, seasonal temperatures fluctuate between 110 F summers and subzero winters.
  • He Who Fights Monsters: The woodcrafters become far crueler than their predators, which only kill to survive, when they start going out of their way to exterminate them and bring back their heads and hides as trophies.
  • The Hedge of Thorns: The cactaiga consists of a dense growth of cactus-like sunflower descendants that covers a good quarter or so of Serinarcta in the Ultimocene glaciation. They endure the powerful winds of their environment, which can snap trees like toothpicks, by growing in an interlocking mass of plants all mutually supporting each other. This makes the cactaiga very difficult to live in, as the whole thing consists of a solid mass of spines and thorns with virtually no open space between individual plants. Most of the area's megafauna goes extinct once the cactaiga forms, as it literally squeezes out both edible plants and animal populations; this only changes with the arrival of the thorngrazers, who can chew their way through the plants using their massive tooth plates and keratinized spikes that defend their faces from the thorns, and which literally eat their way through the mass to create open spaces and paths that allow other plants and animals to find shelter from the ice age storms within the resulting maze of thorn-walled pocket environments.
  • Hell Is That Noise:
    • The calling of a pair of lanks (which are scary enough, being twenty-foot-tall, predatory "demon storks") is explicitly described as haunting, rising and falling like a broken tornado siren.
    • The cry of the dire bumblebear, the even more dangerous descendant of the truculent bumblebear, is described as sounding like neither a squawk or a roar, but somehow sounding worse than both.
    • The ants of the sea shoggoth colonies communicate with each other in what are described as metallic clicking.
  • Herbivores Are Friendly:
    • The woodcrafters have this view and certainly see themselves as such due to starting out as a prey species and thus generally try to avoid harming other prey animals. However, they end up becoming Hypocrites when they both drive off browsing herbivores that might damage their trees and especially when they start going out to cruelly slaughter carnivores outside their territory that weren't a threat to them.
    • Zig-zagged with the porplets. These marine herbivores are described as highly social and playful thanks to the abundance of food, but they will abandon their own kind (including their own babies) when being attacked by predators without a second thought.
    • The floating bloat, a gigantic descendant of the sea-sweeper dolfinches, is completely docile due to a combination of sheer size and lack of natural predators apart from the novan daydreamers and thalassic gravediggers that farm them.
  • Heritage Disconnect: Bridge, the first socialized gravedigger, was taken in by the woodcrafters at such a young age that when Lucky, the second, appears in Bridge's village, he can't understand a word of the gravedigger tongue and she only knows just enough woodcrafter to introduce herself. It's not until she achieves fluency in the woodcrafter language that they can hold a conversation. Years before, he leaves the village and tries living "amongst" his fellow gravediggers, but his lack of territoriality thanks to being raised amongst the woodcrafters and inability to speak the gravedigger tongue leads to problems, and beaten and bruised he returns to his village and stays for the rest of his days.
  • History Repeats:
    • The banshee greatly resembles its distant ancestors, the raptors, in appearance and hunting style; it leaps onto its prey and flaps its wings for balance.
    • The rise of the tribbetheres mirrors the rise of mammals on earth. Originally evolving from fish which evolve into amphibian- and later reptile-like creatures, they become furry warm-blooded animals which end up forcing many of the bird species off of the ground. Then, similarly to cetaceans, the merwals and certain molodonts return to the sea and become fully aquatic animals once again.
    • Later on, during the peak of the glaciation, the marine social gravediggers have developed into a keystone species that actively maintain the health and balance of the oceans and islands they call home, much like how the woodcrafters would care for the well-being of the forests they once lived in.
    • By the Middle Ultimocene, squaves — ornimorphs that reach adulthood in the "reptile" phase of their life cycle — have evolved into squotters, which have traits of primitive mammals, such as live birth and fur-like plumage.
    • The gravediggers of the Ocean Age are once again met by another sapient species who wishes to genocide them, although, unlike the woodcrafters they evolved alongside, warmonger culture outright encourages such behavior. Also, while the woodcrafters attempted to kill off the gravediggers out of the belief that they were rebelling against the tyranny of predators, the warmongers only see them as a threat to their superiority.
    • The last pelagans are met by the combined gravedigger-daydreamer civilization when they're all long past childbearing age, dooming their group to extinction, but do all they can to impart pelagan lore onto them before dying comfortably much like the woodcrafters millennia before. This is not lost on the gravediggers.
    • The daydreamers first became sapient when some individuals were born fully sapient from near-sapient families. Millions of years later, one bluetail (a descendant of the babbling jays no less) is born fully sapient amongst an otherwise near-sapient species.
    • The woolly wumpos, descendants of the mammoth trunkos that the woodcrafters revered, end up also exterminating their main predators from their territories by being smarter than them.
    • The coastian thalassic gravediggers, much like their southern gravedigger ancestors with the woodcrafters, end up being driven from their hunting areas due to a war with their sapient prey, in this case the woolly wumpos.
    • Retally killed off nearly his entire clan due to his inability to control fire. Whitecrown's inability to control fire causes a blaze that spreads throughout Serinarcta and kills off his clan, his brother, the wumpos who adopted them, and countless other creatures.
    • The dominant lifeforms of Serina's early days were the snails and ants before they eventually were relegated to small, background organisms. By the late Ultimocene, snails and ants manage to rise to the status of dominant animal again through the snarks and sea shoggoths, albeit in the oceans rather than on land.
    • The muck survived the mass extinction event that killed off the other serestriders by living on islands. Its descendant, the burrowing burdle, ends up surviving both the daydreamers purposely eliminating their aquatic relatives and the Great Thaw making the oceans anoxic by being a terrestrial island dweller.
    • About 10,000 years after the great coal seam fire, the oceans have become mostly devoid of large life aside from things like small fish and water snails, much like the oceans at the beginning of Serina's habitable stage and the early Thermocene.
  • Hoist by His Own Petard:
    • The empire ants from Serina's early years suffer this twofold. They grow massive in both size and numbers by devouring the giant snails and first wave of flightless birds but they eventually wipe them out and by then they are too big to climb after the smaller snails and flying birds. At this point their immense supercolonies quickly begin to starve, forcing them to start raiding the other ant species, but this would end up spelling their doom. As it turns out, these other ants colonies were being parasitized by the larvae of ladybird beetles that mimicked their pheromones and allowed them to eat the ant's larvae. When the empire ants began to raid the nests these beetle larvae quickly adapted and started feeding on the starving empire's offspring, this becomes so severe that the supercolonies collapse and the empire ants are driven to extinction.
    • The aquatic molodonts, whose powerful crushing jaws were used to eat shellfish, were victims of their own success. Being incredibly efficient at eating clams and snails, they outcompeted the merwals into extinction... but themselves eventually almost died out when they wiped out their mollusk prey and starved en masse. Fortunately, a few species that fed on smaller, faster-breeding snails were able to survive, while the ones that relied on slower-growing molluscs died out.
    • The gravediggers became highly successful predators of antlears due to their complex trapmaking skills, but in doing this, they would usually end up killing the more naïve antlears while the more observant and intelligent members of the species would live to pass on their skills at avoiding and sabotaging the traps. This would end up starting an evolutionary Lensman Arms Race of increasingly more elaborate traps and more savvy antlears that would ultimately result in both species becoming sapient and elevate the antlears from prey to mortal enemies.
    • When the warmongers learn of the gravediggers, their matriarch realizes what their existence could mean for their cultural beliefs, and impulsively orders their extermination before they have the chance to understand their targets. This leads to both the gravediggers avoiding the warmonger's attacks thanks to their ability to move on land, and the general population learning about the gravediggers when the soldiers carrying out her orders tell about what they have seen. In addition, it causes the gravediggers to pull out the stops in their next fight, leading many of the soldiers to a horrible demise, including her most fanatical supporters, and leads their grieving families to chase the matriarch out of the pod.
    • The thalassic gravediggers used fire to scare the woolly wumpos into either their traps on land or off seaside cliffs where they could be then butchered en masse. Retally, a widemind of the Tidelands Herd, managed to drive them from the shoreline for generations by figuring out how to make fire himself from observing them, but due to his lack of control over it also managed to be an example of the trope himself, as he ended up killing most of his own herd by accident as well.
    • Whitecrown and his clan die when one of the trunkos they're hunting is set alight and runs into one of the gravediggers' old coal mines, setting off an explosion that kills them instantly.
  • Hollywood Evolution: Played with by the ornimorphs, who essentially reenact the evolutionary history of vertebrate life and its Evolutionary Levels within the life cycle of a single individual, starting out as a small fish-like larva, growing legs and becoming an amphibian-like stage, becoming fully terrestrial and coming to resemble a reptile, then climbing into the treetops to become an arboreal glider resembling a scansoriopterygid dinosaur, and finally sprouting feathers upon maturity and becoming a fully-flighted, adult bird.
  • Homefield Advantage: During the war against the warmongers:
    • The warmongers initially think the destruction of the gravediggers will be easy due to how helpless they are in the water once knocked out of their boats, but in their haste to wipe them out fail to realize that the gravediggers can simply retreat to the shore, a place where a daydreamer is utterly incapable of following them.
    • The fishers and the pastoralists are also able to use their greater knowledge of the shallow regions in their first battle against the warmongers to help make up for their lack of experience in actual combat.
  • Homeworld Evacuation: To save the sea stewards from the extinction caused by the coal fires, the observer moves them off of Serina and to a planet that's been terraformed to resemble their old home but not before altering their memories so that they believe they always lived there. Notably, this only extends to the sea stewards — the moon's other sapient natives, the woolly wumpos and the icefishers, are left behind.
  • Honey Trap: Female truculent bumblebears will sometimes pretend that they're receptive to mating, only to kill the male once they're in a compromising position. This is believed to be either in order to protect their children from infanticide, as this is most often observed in bumblebears that are close to giving birth, or simply to rid themselves of a competitor and get a free meal in the process.
  • Honor Before Reason: The woodcrafters won't harm other prey creatures, but even when the smerps and molodonts living in their territory reach plague numbers and start devastating their food supply due to a lack of predators, they still refuse to kill them.
  • Honorable Elephant: The mammoth trunko of the Middle Ultimocene is, as its name implies, as close as a bird can get to a mammoth, and like the elephant is a peaceful, near-sapient beast with lifelong close family bonds that will even adopt chicks of other trunko species. Woodcrafters revere them as a spiritual ideal, and the two species will aid each other, as humans have been known to do with elephants.
  • Hufflepuff House:
    • It's mentioned that there are three major social groups of thalassic gravedigger, the meadow dwellers of the open seas, the central islanders of the Meridian Islands who live the most terrestrial lifestyle, and the coastians who live close to the shores of Serinarcta. The viewpoint thalassic gravediggers Patch and Pebble come from the meadow population, the coastians play a major role in the leadup to the Great Thaw through their knowledge of coal, but the islanders of the Meridians aren't really gone over in detail.
    • Of all the sophonts of the Late Ocean Age, the icefishers have little in the way of characterization compared to the sea stewards, Brighteye, and the woolly wumpos, by virtue of being the most isolated of all of them, living on the north edge of the Seaway far from the Refugial Peninsula where Brighteye's story takes place, and compared to the other sophonts whose ultimate fate is gone into in detail, their extinction due to the Great Thaw and competition with the savage gravediggers is treated as a footnote.
  • Humans Are the Real Monsters: Or civilized sapient beings are, anyway, since humans are surely long gone 260 million years into the future. The woodcrafter, a sapient antlear descended from the standing antlear, actively hunts and kills the carnivorous, and equally sapient, gravediggers, seeing them as nothing more than vicious monsters, even though the gravediggers have already decided to leave them alone, having realized their own sapience ages ago, and even achieving sapience first. That changes when an antlear discovers evidence of gravedigger art... and realizes the creatures they were killing were also sapient beings.
  • Humans Are Survivors: According to the author, trying to render tool-making, innovative sophonts extinct naturally would require killing all terrestrial life along with them. As a small, adaptable generalist despite its seagoing habits, the thalassic gravedigger would have the best chance of surviving the apocalyptic events that would have killed off the other components of the sea stewards, but at the cost of losing the culture that kept their worst instincts at bay. However, assuming that they don't lose their sapience, the surviving gravediggers would have a high chance of managing to kill off Serina anyway through either stripping it of its natural resources via industrialization, or killing everything though a nuclear holocaust like how the bluetails managed to destroy their world with the coal seam fire.
  • Hope Spot: The sea stewards manage to stave off their icy fate by breaking the glacier threatening to stop the currents using the power of coal... but leaving their mines unattended leads to the end of the Late Ocean Age anyway when Whitecrown and his clan create a coal seam fire that sets Serinarcta ablaze.
  • Humanoid Aliens: The gravediggers are effectively this to the daydreamers as they basically look like a tiny daydreamer with hands and feet instead of flippers.
  • The Hunter Becomes the Hunted: During the Late Ocean Age the circuagadogs, already on the brink due to loss of prey and failure to adapt, are finally brought to extinction by the trunkos they once hunted deciding to start hunting them in turn by killing their young and breaking up their packs.
  • Hulk Speak: The gravediggers' language is said to be very simple, as could be expected of a solitary species, and is entirely lacking in pronouns. They prefer to communicate through art scratched into tree trunks.
  • I Surrender, Suckers: Brighteye gets the better of Tyr-reet, a rival bluetail trying to kill Whitecrown, by pretending to submit before taking the opportunity to stab them through the eye with a knife and fleeing with his brother while Tyr-reet's brothers are stuck watching in horror as he does his death throes.
  • Inbred and Evil:
    • The warmongers, an extremist subset of the whaler daydreamers, purposely inbred themselves over thousands of years to give themselves darker coatings and eliminate their yellow pigmentation, and wish to genocide all other daydreamers.
    • The is completely inverted by the reapers, a sapient offshoot of the aukvultures with a culture that values empathy and understanding. They are also highly inbred due to their entire species being only a few hundred years old and descended from two siblings and compounded by their refusal to mate with their non-sapient relatives. Their low genetic diversity results in most of their babies dying in the pupal sack and makes them cherish the ones that do survive even more.
  • Incompatible Orientation: The homosexual Bachelor morph of the Polymorph bird is attracted to male plumage and so will sometimes attempt unsuccessfully to court Keepers (alpha males that mate with a harem of females) due to the Keepers being naturally aggressive towards other males.
  • Intelligence Equals Isolation:
    • The first daydreamers arose from seastrikers who by a genetic fluke were every so often born with the capacity for sapience and the ability to see past their immediate survival, but for most of their existence the so-called "seers", while not shunned by the non-sapient seastriker population, lived mostly lonely lives due to their intelligence making them unable to fully relate to their brethren or vice versa. Since sapience was a recessive trait for most of their history, seastrikers only rarely birthed new seers, with only one appearing every few centuries for hundreds of millennia on average.
    • Brighteye, a bluetail (one of the descendants of the chatterer sparrowgulls), is sapient while every other bluetail, including his albino brother, is near-sapient at best. As a result, he's a pariah amongst his fellow bluetails, especially after he and his brother are forced to leave their home after a rival bluetail group murders their parents and he kills one of their leaders in return to save his brother before fleeing to avoid reprisal. Even beforehand, he refused to take a mate because the intelligence gap meant in his eyes that he'd be mating with a child. The narration detailing the bluetailed chatteravens makes a point of describing him as both the first and last bluetail person.
    • This is explicitly averted with the woolly wumpo. Most are highly uncreative despite their intelligence, but some are born with a much higher level of innovation. Unlike the seers or Brighteye these individuals don't feel isolated from their kin thanks to the high emotional maturity the species possess. In fact, they are celebrated by their kind due to their creativity often greatly benefiting them as a collective.
  • Interspecies Adoption:
    • In rare cases, a carnivorous circuagodont will misfire its parenting instincts onto a herbivorous circuagodont species and adopt what normally would be its prey. This usually doesn't end well for the youngster, as it ends up imprinting and associating with the carnivorous species, and thus loses its natural fear of its main predator, which has disastrous consequences when it approaches other packs of carnivorous circuagodonts that don't recognize its scent and simply see it as prey and devour it.
    • Sometimes trunkos will adopt snow snoots that have been separated from their herds as detailed in "Little Moments". It usually turns out better than the above example due to both species having similar behaviors.
    • As shown in Stronger Together, a young gravedigger is adopted by the regretful woodcrafters after they killed his mother. At first many of them feared him but he eventually becomes a beloved member of the village and is given the name Bridge for being a link between their two people. They taught him their language and made him more social while he kept the number of smerps down and introduced the concept of drawing to them. He briefly left when he reached adulthood due to his instincts but eventually came back and he drew in more curious young gravediggers which led to the two species to become more integrated with even the art Bridge taught the woodcrafters becoming the foundation for their first written language. It also shows a rarely considered consequence of such an event. Due to being raised by antlears at such a young age Bridge imprints on them, but not other gravediggers, and doesn't have any interest in breeding with them as a result. He never has offspring of his own. However, he does become the adoptive father of Lucky, and thanks to her being raised by another gravedigger, she does have children to which Bridge becomes their Honorary Uncle.
  • Interspecies Friendship:
    • The tundra gravedigger has developed a mutually beneficial relationship with the jackal carnackle, the carnackles will distract large prey animals that they wouldn't be able to take down themselves and drive them towards the gravedigger's traps while the gravedigger digs out molodonts that the carnackles wouldn't be able to reach but are able to catch them once above ground while the gravedigger is too slow and they all share in the meals. They are also said to enjoy each other's company and while even play and do tricks for one another.
    • The fisher daydreamers form friendships with the luddy porplets and other intelligent dolfinches, although they do tend to take a paternalistic role in these relationships.
    • Brighteye and Whitecrown, bluetail chatterravens, begin accompanying Blaze, a woolly wumpo several hundred times their size with Brighteye in particular developing a strong relationship with her.
  • Interspecies Romance: The last of the fork-tailed babbling jays take on mates from other species in a lonely search for company. However, while the babbling jays are intelligent, their impromptu mates are non-sapient.
  • In the Future, Humans Will Be One Race: A nonhuman example. After the exile of the warmonger matriarch, the surviving warmongers begin to interact more with the fishers and the pastoralists who would also communicate more often with each other thanks to the gravediggers. Over time, the relationships between the different daydreamer cultures shrink until none remain. Five million years later, the only group of daydreamer is the novan daydreamers, who have traits of all three cultures, which is most noticeable with their coloring and beak shape.
  • Introduced Species Calamity:
    • When the Kyran Islands connected to the mainland, the carnivorous tribbetheres living there were able to cross over and follow the Kyran snuffles into their burrows and eventually hunt them into extinction.
    • A variation occurs in the woodcrafter villages. The smerps and molodonts there are native to the region, but after the woodcrafters removed the small predators keeping them in check, they exploded in number and began to do severe damage to the antlears' trees and crops, making them functionally similar to an outbreak of an invasive species.
  • Invading Refugees: The warmongers were driven to the shallows after a failed attempt to conquer and destroy the pelagans resulted in the latter driving them out of both the open oceans and their original southern territories. They see the shallows as a chance to both heal their wounded pride and build up their numbers by devouring the smaller, less organized daydreamers living there.
  • Ironic Name: Eve in the Bible is the first woman, whereas Eve the reaper is the last of the reapers.
  • Irony:
    • In a world with little violence in the Hypostecene, the wombler dies out... because of intraspecies violence. Never having learned how to flee from conflict, the womblers fought each other to the death, and recklessly faced the first few predators that did evolve.
    • The page of the ninth-year canary talks about how it's the [last of the changeling birds and how it will likely go extinct, but when a mass-extinction rivaling the Great Dying occurs at the end of the Thermocene, it ends up being among the relatively few creatures that survive and its descendants become one of the dominant groups of the Ultimocene.
    • The efts are a group of aquatic metamorph birds that remain in their gilled larval stage their whole lives and come to be identical to fish, while the tribbets are fish that evolve to become land animals, with a flying group, the tribbats, eventually becoming colorful bird-like forms.
    • It's stated that the merwals and aquatic molodonts are a bit of an irony, given that they're technically still fish, but ones that had specialized to live on land... and then returned to the water yet again.
    • The seaborne thalassic gravediggers and the terrestrial woolly wumpos both fear one another and refer to each other's domains as the realm of demons.
  • It's All About Me: What little we see of thorngrazer thoughts paints them as very selfish and callous towards anything not themselves, including other thorngrazers. For instance, their herding together is only because it lessens the chance of any individual torngrazer alone getting eaten, and they don't form any social bonds past mothers and their children, and even then if they're injured the mother will leave them without remorse.
  • It Can Think:
    • The vibropteran tribbats are surprisingly intelligent, figuring out tool use and problem-solving tactics. They are known to gnaw through flowers to access nectar instead of specializing in only one type of flower that matches its mouth, allowing it to feed on a wider range of food sources.
    • Snarks are also said to be very intelligent, especially considering they're descended from snails.
    • Gigadons are extremely intelligent for fish, with high domed skulls to accommodate large brains. While not fully social, they organize into packs to bring down large prey and communicate by flashing their brilliant patterns.
    • While nonsapient, the savage gravediggers are still smart enough to probe for weaknesses in the fortresses of their thalassic gravedigger kin.
  • I've Come Too Far: The warmonger matriarch continues her genocidal actions despite her own internal doubts because it would mean the end of everything she's worked for.
  • The Juggernaut: Once fully grown, a sea rex is virtually invincible, its armor allowing it to shrug off even the bites of pelagic daydreamers while crushing their skulls in a single bite. It's for this reason that the pelagans target the young burdles instead of the adults when they decide to eliminate them, as they're only daydreamer-sized when they start to leave the inaccessible to daydreamer shallows, and as such are helpless against them in a pack.
  • Killer Rabbit:
    • The aptly named butcherraptor is the size of a chicken yet they're capable of bringing down the bison sized snuffalo through the use of numbers and ruthless tactics.
    • The spitfire sniffler looks cute but carries the potent batrachotoxin created by the fireslime lumpus in its quills, which makes it not only painful to the touch, but deadly to any predator that attacks it. As a result, they've been known to boldly walk up to predators and take bites out of their kills with impunity due to their confidence in their poisonous defense.
    • The scorplear of the Late Ocean Age (Coincidentally also happening to look like a rabbit) is about the size of a small dog but can use its jaws and hindlimb claws to horrifically maim anything that threatens it. It's not unusual to see predators with a missing or severely damaged eye from when a scorplear drove their claws through its socket.
  • Kill It with Fire: The end of the Late Ocean Age is heralded by Whitecrown's flock managing to spark a massive coal fire that burns throughout Serinarcta, killing the flock and basically everything else unable to escape the flames. Among the notable casualities are the woolly wumpos and the razorback thorngrazers.
  • Kill It with Ice: The inevitable fate of Serina by the end of the Ultimocene, losing heat and volcanic activity which will throw the world into a permanent ice age. A few adaptive lineages will continue to soldier on for a few million years, but ultimately all life on Serina becomes extinct.
  • Killed to Uphold the Masquerade: The warmongers believe that they are only descendants of their god, so, when they learn of the gravediggers whose very existence threatens this notion, their leaders decide to wipe them out to preserve this belief among their kind. Sure enough, after soldiers sent to battle the daydreamer-gravedigger coalition return and tell of what they have seen, this causes some of them to start questioning their beliefs.
  • Know When to Fold Them: When a glacier raven meets a glacial foxtrotter for the first time while the latter is attempting to steal the former's carcass, the glacier raven decides to let them have it despite the fact that it's bigger and stronger because it 1) has no knowledge of the unknown animal's capabilities and 2) there's still plenty of young to go around, so there's no reason to get into a potentially lethal fight over it.
  • Lack of Empathy:
    • As a result of the loss of their higher intellect and of all social habits, the savage gravediggers have almost no capacity for empathy. Females will raise their own offspring for up to two years, but in all other cases their response to meeting another living thing is violence — even mating is a vicious and violent affair, and they're quite happy to cannibalize each other if the opportunity presents itself.
    • The thorngrazers are intensely selfish as a species, having no issue leaving the weak to be picked off by predators without remorse.
    • Zigzagged with the bluetailed chatteravens, who are capable of feeling empathy, but only for those they consider part of their immediate family group. Anything or anyone else they'll treat brutally if they anger them in any way.
  • Land, Sea, Sky: The centerpiece of daydreamer religion is their creator deity splitting themselves into aquatic, terrestrial, and airborne essences. The daydreamers believe they are the aquatic, the gravediggers represent the land, and are still waiting for the sky.
  • Language Barrier:
    • The first attempts by the fisher daydreamers to communicate with the gravediggers were unsuccessful due to them not being able to understand each other's languages, with the gravedigger language being slow and guttural, and the daydreamer's language being so rapid and high-pitched that the gravediggers couldn't even recognize it as a language. Some fishers dedicated years of their lives to studying the Gravedigger language but it wasn't these individuals who made the first successful contact with them, but teenagers who had been listening to the gravediggers from a young age when it was still easier for them to learn new languages.
    • The warmonger tongue is much slower and deeper than that of the other daydreamers, making them even harder to understand than gravediggers.
    • Brighteye and Blaze have difficulty communicating at first as the chatteraven language is very different from the wumpo infrasonic language, leaving them physically incapable of understanding one another and having to make do with touching and simple gestures. They eventually get around this when they discover that they can both understand drawings and use pictures to communicate with each other, eventually streamlining the process until they create a hieroglyphic-like written language.
    • The wumpos can't communicate with the gravediggers because the latter simply cannot hear the former's infrasonic language, until Brighteye talks to them and some of the gravediggers manage to learn his and Blaze's glyph-based language over the years.
  • Last of His Kind: This turns up several times in the setting, as the dwindling and extinction of species and lineages is a recurring theme, particularly in the swan song of Serina's habitable stage that is the Ultimocene:
    • One of the entries detailing the beginning of the closing stages of the Ultimocene describes the last stormsonor, the last living specimen of a species of immense birds that slowly went extinct as the growing ice age covered their feeding grounds in ice and caused their egg-like pupal sacs to freeze to death before they could hatch. The last one was born in a freak warm year, from a clutch deposited by an ancient hen who died after laying and was the only one to hatch successfully. She never met another member of her kind, and instead imprinted on a flock of a much smaller related species with which she spent the rest of her long life.
    • One entry aptly titled The Last Woodcrafter goes over the extinction of the woodcrafter people. When the moon becomes too cold for the trees the woodcrafters depended on to survive, they become malnourished and are unable to reproduce as a result. The socialized gravediggers they lived with are eventually forced to migrate to the coast to stay alive while some woodcrafters chose to stay and die in their old forest home while others chose to leave with the gravediggers, these ones discover that they can feed on the coastal seaweed and return to health but there were far too few of them at that point and they were all past their reproductive age so they decide to spend their last days helping and guiding the gravediggers. The last woodcrafter is an elderly female named Ember who peacefully passes on surrounded by the gravediggers her kind came to view as their children.
    • Rivals ends with a description of the last living sea rex, a massive marine predator, after his species was gradually whittled down by the collapse of the open-ocean food chains and a bitter conflict with the pelagan daydreamers over what little prey remained in the shrinking ice age seas. Ultimately, the last great leviathan is left to wander the oceans for nearly a century after the death of the last female specimen and for forty years after the death of the second-last male, his mind just complex enough to be puzzled at why his mating calls are never answered, but not enough to understand his species' fate.
    • The pelagic daydreamers are gradually done in when the shrinking oceans kill off all the animals that could sustain them. The last members of their species were too old to reproduce and believed themselves to be the very last of the daydreamers until the mixed gravedigger-daydreamer civilization from the shallows find them, allowing their people to symbolically live on the stories and histories they tell them.
    • The burrowing burdle is the last of the burdles during the Late Ocean Age into the early Late Ultimocene, as their aquatic relatives were killed off by the daydreamers.
    • The scorplear is the last of the antlear lineage by the Late Ocean Age, with the ice age having killed off the trees their more specialist relatives needed to survive. It's survived by becoming omnivorous but is far less intelligent than the antlears that came before it.
    • The scissortooth is the last of the circuagodogs in the Late Ocean Age, the others having been outcompeted by other, smarter predators such as the sawjaws who are better adapted to prey on the thorngrazers that have become Serina's most common terrestrial herbivore, and their prey either going extinct or becoming too smart to hunt. The solitary nature of most circuagodog species also serves to work against them. Eventually, the woolly wumpos, a sapient trunko species, get the idea to start systematically exterminating their predators, with the circuagodogs being too unintelligent to mount an effective enough defense, and the remainder either starve to death or meet their end at the clubs of the wumpos. Circuagodog Gone describes the last moments of the very last circuagodog, half-dead from starvation, as it calmly accepts its death at the hands — well, trunk — of a creature its kind once hunted.
    • Blaze is the last of the widemind woolly wumpos when she's introduced, and when she dies no others are born because the species is among the first casualties of the coal seam fire soon afterwards, either burning to death or dying from smoke inhalation or toxic fumes.
    • The Late Ultimocene has several families reduced to a single surviving species. The nimicorns are the only thorngrazers to survive into the era after their razorback cousins perish in the coal fire. Afterwards the savage gravediggers are the only remaining gravediggers after their thalassic cousins are transported away and the icefishers die when the sea ice they depended on melts. Finally, the duckbilled sealumps are the only members of the sealumps to survive since they were the only species that could still walk on land and escape the dying oceans, eventually settling on Serinaustra.
    • The hiddenwood is the last species of ant tree left by the early Late Ultimocene after the ice age due to most of the plant growing underground. With the increased warmth and wetness of the Late Ultimocene and the extinction of the more destructive razorback thorngrazer, it has seen a major resurgence. It's also the last of the sunflower tree lineage, with its cactaiga cousin being among the victims of the increased temperatures.
    • The rambleroot is the last survivor of a lineage of smaller understory trees descended from clovers in the early Late Ultimocene, having survived by mostly growing underground like the hiddenwood has. Following the warming caused by the coal seam fire and the disappearance of the cold winds that would blow smaller plants down, they start growing to knee height, flower and fruit, and spread to Serinaustra via bird dropppings.
    • "As Worlds Break Apart and Join Together" details the story of the last steppestalker, the direct descendant of the shadowstalker (differentiated only by its lighter coloration compared to its ancestor), and the largest of the tribbats on Serina 1,500 years post-coal seam fire. Having made it to a small island when the rampant global warming and subsequent glacier melting during the aftermath of the Serinarctan coal seam fire caused most of the Meridian Islands to sink beneath the waves, he manages to adapt to hunting fish in the shallows and serves as apex predator over the other species marooned there with him for over twenty-one years. However, eventually the refuge shrinks down to just some rocks as the remaining prey either rafts away or dies, until finally, weakened by drinking seawater as the waves batter him, one manages to knock him into the sea and he drowns.
    • Eve is the last of the reapers, a subspecies of the aukvulture that managed to achieve sapience, but went extinct due to inbreeding.
    • The pgymy pretenguin is the only pretenguin to surive the Great Thaw, having moved to Serinarcta with the sinking of the Meridian Islands.
    • The surfscoter survives the Great Thaw that extincts the other dolfinches by being a semi-aquatic species that can access the Serinarctan marshes where the larger species cannot go as the ocean food chain collapses.
  • Lean and Mean: Lanks are twenty-foot-tall apex predators with very long slender necks, beaks, and legs.
  • Lightworlder: Serina has a much lower gravity than Earth, allowing for much bigger fliers such as the archangels. Even the insects become Big Creepy-Crawlies due to the lesser gravity, with some cricket species growing to the size of rabbits.
  • Light Is Not Good: Whitecrown is basically the final boss of the Late Ocean Age, an albino bluetail leading a huge flock burning everything indiscriminately.
  • Legend Fades to Myth: The teachings of the last woodcrafter over the next three million years turns into a myth shared amongst the numerous marine social gravedigger religions, the exact details being lost to time but being subject to numerous but not contradictory interpretations.
  • Life Will Kill You: Blaze eventually dies from old age, surrounded by her family, save for Brighteye who happened to be away and only comes back once she's already been buried.
  • Logical Weakness:
    • The circuagodonts, being tripedal, have only a single hind leg, making it an obvious target for predators to easily cripple them.
    • The canitheres are significantly less intelligent than the predator wheeljaws, having disorganized packs attacking with only Zerg Rush tactics and prone to infighting once the prey is downed. This proves to be a disadvantage against the smarter wheeljaws, who share food amicably and hunt with coordination, with the canitheres quickly being pushed aside to scavenger and small-game hunter niches.
  • Long-Lived:
    • Stormsonors, the largest of the archangels, can live up to 135 years.
    • Daydreamers have a maximum lifespan between 130 and 140 years.
    • Reapers have an average lifespan of 80 to 90 years.
  • Loophole Abuse: The woodcrafters have a major taboo regarding killing other herbivores, even if they happen to be pests to the trees they need to eat. Once enough socialized gravediggers are around, however, they have them take care of their pest problem to keep their own hands clean.
  • Make Me Wanna Shout: The sea rexes have a mating call so powerful that it vibrates the water around them and can injure or even kill smaller animals that get too close.
  • Meaningful Name:
    • Tribbets are tripodal and froglike. Their descendants include reptile-analogues called tribtiles and mammal-analogues called tribbetheres.
    • Vivas are viviparous. Their descendants the ornitheres ("bird-beasts") are even more mammal-like.
    • The mitten and its descendant the glove. Guess what the soft tissue on their faces looks like and is used for.
    • Babbling jays have a true language, and their name brings the Tower of Babel to mind.
    • Snarks (snail-sharks) are active marine predators descended from gastropods.
    • The antlears have evolved their ears into limbs that resemble antlers.
    • Bridge, the first socialized gravedigger, was given that name by his adoptive antlear family to serve as a bridge between both species.
    • Ember, the last woodcrafter, passes on phrases of her language to the descendants of the babbling jays, which persist as the flame of sapience reignites in them.
    • The thalassic gravediggers are adapted to near-completely seaborne existence and have even evolved the ability to drink saltwater.
    • The daydreamers can dream even while awake by only using one hemisphere of their brain at a time.
    • Greenskeepers help maintain the plant life of the Ultimocene ocean.
    • Brighteye, the only bluetail capable of higher understanding, gave himself his purposely symbolic name.
    • While at first it's an Ironic Name since she's just as afraid of fire as every other woolly wumpo, thanks to Brighteye Blaze takes to the use of fire very well.
  • Meaningful Rename: Brighteye gave himself and his flockmates symbolic names instead of random sounds that hold no meaning, even if he is the only one capable of understanding them.
  • Medieval Stasis: The gravedigger-daydreamer-greenskeeper civilization is so productive and stable that it does not progress beyond a stone-age level of technology for over a million years while also having a written language and innate understanding of ecosystem dynamics. A lack of mineral resources and a lack of ecological or cultural pressure to innovate contributes to this.
  • Men Are the Expendable Gender: Male nimicorns live on the margins of their social groups so they're disproportinately preyed upon, but this serves to protect the more reproductively important females and juveniles.
  • Mercy Kill:
    • The pastoralist daydreamers will kill their nops before eating them rather than just eating them alive like their seastriker ancestors would've, despite the fact that they barely feel pain.
    • Blaze, a woolly wumpo, chooses to put the last scissortooth out of its misery quickly rather than just leave it to starve to death over hours due to developing empathy for "biters" through all her years hunting them, and despite the fact that it was her idea to systematically exterminate "biters" for the sake of the family in the first place.
    • The reapers are culturally opposed to killing for survival; the main exception to this is killing the already dying to ease suffering.
  • Metaphorically True: The daydreamer religion positing that daydreamers and gravediggers have an origin in common is actually sort of true, because dolfinches and bumblebadgers both descend from the bumblet.
  • Mighty Glacier: Razorback thorngrazers are strong and durable thanks to being covered in tooth-like armor, but very slow as they have very short legs and are incapable of running, simply hunkering down when threatened to protect their soft underbellies. This works against them when dealing with fire since they can easily be overtaken by the flames, leaving the nimicorns as the only surviving thorngrazer species following the Serinarctan coal seam fire.
  • Mirroring Factions:
    • The gravediggers and antlear people may be natural enemies, but they both have an artistic streak that they express using trees. It's this similarity that causes some of the woodcrafters to realize that they were murdering sapient beings.
    • The fishers and the pastoralists have the same fundamental creation story despite their cultural differences which led to some fishers becoming more introspective and questioning if their way of life is truly more moral than theirs.
    • Despite the disdain fishers have for daydreamers who feed on dolfinches, their lifestyle is more similar to the whalers than it is to the farming pastoralists they share their terrioties with, as both of them hunt for their food which leaves them more downtime. The differences being what they chose to hunt. This comes to a head in the aftermath of the war with the warmongers, the warmonger children searching for food display the exact same curiosity as the fishers did towards the gravediggers and learn to speak their language, allowing them to cut a mutually beneficial deal with them.
  • Mix-and-Match Critters:
    • Falconaries, the first hypercarnivorous birds to arise on Serina.
    • The tundra-dwelling, herd-forming, pseudo-viviparous canaribou and its omnivorous relative the boarbird.
    • Cervanser cervanser, the "deer-goose" viva.
    • Florgusts are descendants of crickets that greatly resemble butterflies through convergent evolution.
    • The water snuffle is essentially an avian platypus.
    • Archangels look and eat like swans with the quadrupedal posture and size of Quetzalcoatlus.
    • The king trawler is a giant sea slug with traits of baleen whales and manta rays.
    • Burdles and birdwhales strongly converge upon, well... sea turtles and baleen whales.
    • Serestriders are moa-like birds big enough, and with long enough necks, to hold the niche of sauropods.
    • The serezelles resemble a cross between an ostrich and a gazelle, and the boomsingers, giant serezelles that evolved to avoid competing with circuagodonts, are in essence beaked, tailless sauropods.
    • The Lumberbeest is essential a mix between a large tortoise and a sauropod.
    • The porporant family as a whole resemble seabirds formed into cetaceans and seals, and includes the dolfinch, croconary, and penguipleurodon.
    • Repandors resemble Tasmanian tigers crossed with cheetahs, but with jaws like a goblin shark.
    • Moonbeasts resemble a cross between a bat and an owl. Its descendant the snowspirit lessens the bat aspect but adds a cat aspect while increasing the owl similarities.
    • The night biter is essentially a mix of vampire bat and cookiecutter shark.
    • Vibropterans can be described as "fish-hummingbird-bats."
    • Aquatic molodonts in the Ultimocene fill a fair amount of marine mammal niches, such as the walrus-like Clamcracker and the manatee-like Rakewhale.
    • The bloons look like beaked plesiosaurs but are herbivorous like manatees.
    • The skuorc resembles a cross between an otter and a lizard with a bird's head.
    • The candescent flagbearer resembles a cross between a bat, a rabbit, and a bird of paradise.
  • Mook Horror Show: The second battle between the shallow water daydreamers and the warmongers starts off from the warmonger's perspective as it describes the armor of the daydreamers making them look like skeletons that had come back from the dead as they emerge from the shadows and then attacking them with weapons that they can't comprehend and have no way of countering.
  • More Teeth than the Osmond Family:
    • The repandors are a group of canitheres with a mouthful of sharp fangs (as well as a set of slicing teeth in the back of their mouths) and jaws than extend outwards like that of a goblin shark. The bushbounders have a similar set of teeth but theirs don't extend outwards so that they have a stronger bite.
    • The muckodiles' inner mouth and throat is full of tooth-like spines that make it harder for prey to escape their grasp, much like real-world penguins.
  • Mouthy Bird: The Vivas are a group of live-bearing birds whose herbivorous members have developed fleshy lips and snouts over their beaks. Though entirely unrelatednote , the tentacle birds are even more so.
  • Multicultural Alien Planet: By the middle and late Ultimocene, a general trend towards increasing intelligence means that multiple sophont species arise, often sharing the moon with each other, and most also tend to fragment into various subspecies and cultures.
    • Three sapient species evolve on the moon during the middle Ultimocene, two of which possess a number of distinct internal groups:
      • The social, herbivorous woodcrafters are natives of the southern coastal forests and build complex villages out of trees. Due to their small range, their culture is very homogeneous.
      • The gravediggers are a solitary, carnivorous species who communicate with art carved on trees on territorial boundaries and hunt by making elaborate traps. Gravediggers are divided into two subspecies, the primary forest-dwelling one and the tundra gravedigger, which is even more solitary, aggressive, and nomadic than their southern cousins. One population of southern gravediggers is later taken in by the woodcrafters and grows more social as a result, becoming its own distinct species after the woodcrafters die out. Eventually, as Serina's glaciation grows more severe, the social gravediggers adopt a marine culture while the tundra and southern gravediggers are pushed into a small strip of habitable land and cease to exist as two distinct populations.
      • Daydreamers are sapient marine predators who have been living alongside the other two groups for about three million years, over time splitting into different cultures that are even reflected by their phenotypes: a small-beaked ecotype that hunts fish, and a large-beaked ecotype that preys on other dolfinches.
      • The large-beaked predators, the ancestral group, eventually split further into the pastoralists, who live in reclusive communities in shallow waters and herd dim-witted domesticated dolfinches, and the large, heavily built whalers, who live in the deep ocean and prey on larger animals. The whalers further diversify into many clades and cultures, but the dieoff of large deep-ocean wildlife caused by shrinking seas eventually causes most to die off and only leaves two, the widespread and highly collectivist pelagans and the heavily-built, xenophobic warmongers.
      • There are also bands of daydreamers comprised of mixed ecotypes who live on the periphery of the other groups' territories and raid them for food, as it's often difficult to find a suitable food source for a group containing so many disparate beak shapes.
    • During the Late Ocean Age:
      • After a first-contact war between the shallow-water daydreamers and the warmongers, the shallow-water populations, warmongers, and eventually the last survivors of the collapsing pelagan society merge into a single population, which joins with the social gravediggers to form a single society. Over a period of five million years, they eventually evolve into new species, the novan daydreamers and thalassic gravediggers, while the luddies gradually reach sapience, becoming a new species known as the greenskeepers, and join them into a single multi-species marine civilization known as the sea stewards. They have a deal with the sea shoggoths, who are implied to have achieved sapience or are on the very cusp of it, in which they don't hunt the sea stewards or anything else in return for regular deliveries of food waste and dead bodies, who would clog up the ocean otherwise as their populations grow.
      • Within the thalassic gravediggers, the inhabitants of the meadows are contrasted with the central islanders of the Meridians, who live the most terrestrial lifestyle of the three main groups, and the highly independent coastians that live near Serinarcta's shores but only go on land to collect peat and coal due to the hostility of the local wildlife, in particular their conflicts with the woolly wumpos.
      • Two other gravedigger societies exist during this time, descended from the continental gravediggers; the savage gravediggers, a Formerly Sapient Species descended mainly from the tundra subspecies with some hybridization with the southern, and the icefishers, descended from southern gravediggers with some savage admixture displaced by the savage northern kind and adapted to life on the sea ice.
      • The descendants of the mammoth trunkos and desert wumps have also achieved sapience in the form of the woolly wumpos, although most remain fairly unimaginative, live in family groups, and even have a rudimentary religion based around the dusk and dawn.
      • There are also the bluetails, a near-sapient descendant of the babbling jays with a rudimentary language and culture who accidentally produce a single individual with full sapience.
  • Mundane Made Awesome: The fisher daydreamers come to believe that the gravediggers are the hands of their creator thanks to their ability to make and use tools like nets, fishing lines and boats. Something the daydreamers themselves are incapable of. The warmongers even go so far as to attribute the deaths of their soldiers by gravedigger weapons as an act of divine retribution.
  • My God, What Have I Done?:
    • After Retally managed to get nearly his entire herd killed due to his lack of mastery over fire, he was so ashamed that he decided to go north and was never heard from again, effectively committing suicide.
    • In the early days of the Late Ultimocene, an aukvulture, normally a gentle scavenger, kills a sea raven out of starvation-induced annoyance and feels shame before hunger makes it forget.
  • My Instincts Are Showing:
    • The original gravediggers felt no hatred but also no remorse for gruesomely killing animals in their traps, while their social descendants have become much more empathetic towards other lifeforms thanks to the influence of the woodcrafters. However, the warmongers attacking and killing them unprovoked causes this old callousness to resurface, and they feel no guilt for using poison to subject them to a slow, horrid death.
    • When Seeker, a greenskeeper descended from the ring-necked porplet, meets Whirl, a novan daydreamer descended from the seastrikers who used to be their primary predator, he briefly feels a primal fear when she opens her mouth to show him her teeth.
    • The sawjaws are wolf-sized but evolved from much smaller predators in a relatively short amount of time, so they still have the instincts and behaviors of much smaller animals despite the fact that they have no predators that hunt them.
  • My Species Doth Protest Too Much: Brighteye dislikes the other, nonsapient bluetails for their violent ways, and near the end of his life thinks of himself as more one of the woolly wumpos than his own species.
  • Mythology Gag: When Seeker is shown what happens if sea steward society collapses due to the coal seam fire, he sees that the gravediggers have survived but turned feral, a similar fate to what Sheather had planned for them when the woodcrafters went extinct in the original draft of the Ultimocene.

    Tropes N-Z 
  • Names to Run Away from Really Fast:
    • Tyrant serins, swordwhales, billion-stinger ants, razortooth circuagodogs, gravediggers, and sea shoggoths.
    • The apex predators of the Kyran Islands during the Thermocene are the taakarewera, whose name is Maori for "demon storks."
    • Subverted with the moonbeast, which despite its powerful-sounding name is no larger or more dangerous than an owl.
    • The warmonger is a daydreamer subtype that has no issue eating other sapients due to perceiving them as lesser and plans on taking over the ocean by ridding themselves of the competition.
    • Apart from the dire bumblebear's name already having "dire" in it, in the tongue of the woolly wumpos they're known as "slayers".
  • Nature Versus Nurture: While the gravediggers are inherently introverted as a rule, their tendencies for killing off all but the strongest newborns, and particularly amongst males, self-serving tendencies and opportunistic cannibalism are more the result of culture. Due to Bridge, Lucky, and her descendants spreading the better parts of woodcrafter culture amongst southern gravedigger-kind, over the centuries these issues were eliminated.
  • A Nazi by Any Other Name: The militaristic warmongers wish to genocide all other daydreamers due to considering them all inferior to themselves and turn their genocidal attention upon the gravediggers as well because their sapience serves as a threat to their beliefs.
  • Nearly Normal Animal: A variety of creatures are smart enough to develop culture in the Ultimocene, but none of them go on to invent agriculture or build cities. Sapience, the author says, is a spectrum:
    • The one bird that farms a species of snail for food, the farmerjay, does so instinctively, and is described as a clever animal with a strong ability to plan for the future, but not self-aware.
    • The porplets and seastrikers are at the very cusp of true sapience as opposed to just being very smart animals, being highly intelligent with rich inner lives. Eventually, the seastrikers make it, and after the daydreamer factions make peace with one another, the luddy, a descendant of the porplet, starts becoming even smarter as well and eventually becomes a sapient being, the greenskeeper.
    • The bluetailed chatteravens are near-sophonts partially descended from a sapient species who have a complex language and the ability to create tools, but apart from the truly sapient Brighteye are no more intelligent than a chimp.
  • Nested Mouths:
    • Some of the pseudornithopods evolve teeth on their tongues, which become a functional jaw to chew with teeth on their palate.
    • The softbilled birds have developed a muscular covering around their beaks, and the trunkos take it further as they have essentially developed a set of soft lips that conceal their beaks.
  • Nice Day, Deadly Night: The coastian thalassic gravediggers fear night because it's when the predatory savage gravediggers come out, who are smart enough to constantly probe their camp walls for weaknesses, alongside a whole host of other predators.
  • Nice Job Breaking It, Hero: The sea stewards managed to turn the oceans into a peaceful and bountiful paradise, but in doing so they made the entire marine ecosystem extremely fragile and utterly dependent on them. Once they disappear alongside the proliferation of greenhouse gases, the entire ocean biosphere collapses, leaving only a handful of surviving organisms.
  • No Mouth: The dayflight bird, which lives in its adult form for only one day, never even eating, much like a mayfly.
  • Non-Human Non-Binary: There are juvenile woodcrafters that choose not to fully mature in the absence of familiar males for aesthetic purposes, with some choosing to identify as female or nonbinary, with a similar phenomenon happening with the woodcrafter equivalent of transmen and transmasc humans taking on more masculine traits in the absence of cis male woodcrafters.
  • Normal Fish in a Tiny Pond:
    • The duckbilled sealumps are the smallest of the sealumps at only 500 pounds in weight, and aren't even that large for trunkos in general, but when they start colonizing the newly thawed Serinaustra whose only terrestrial fauna beforehand was the fox-sized snowscrounger and the slightly newer foxtrotter arrivals, they're the largest animal around and nothing there can threaten them initially until the snowscroungers start figuring out how to hunt them.
    • The aukvultures are the largest flying creatures in the early end Ultimocene with some reaching wingspans of 23 feet or more but this is still barely half the size of the large archangels of the early Ultimocene such as the stormsonors who had wingspans of up to 50 feet.
  • Not Allowed to Grow Up: The ornimorph birds go through a complex metamorphosis from aquatic fish-like larva to terrestrial reptile-like juvenile to feathered airborne adult. Some of the Ornimorphs, called squaves, became neotenic and reached maturity at the "reptile" stage. Still others, the efts, ceased to metamorphose at all and spend their entire adult life in an aquatic fish-like form.
  • Ocean Punk: The Ocean Age of the middle Ultimocene, informally marked by the death of the last woodcrafter, has most of Serina's surviving lifeforms turning more aquatic due to the glaciers rapidly decreasing the amount of habitable land left on the moon, with the social gravediggers taking to the sea and forming a fully marine society, though their terrestrial cousins, the southern gravediggers they branched off from and the tundra gravediggers of the far north, still hold on and evolve into new species, the icefisher and savage gravedigger respectively. In the ocean, the seastrikers have evolved into the sapient daydreamers who have numerous cultures.
  • Offing the Offspring:
    • Alpha female brushbounders are known to kill off the young of lower-ranking females to assert dominance and reduce competition for her own young. Though rare, the alpha is also known to eat her own cubs when food is scarce.
    • Female tiger varpikes are also prone to this, to such a degree that they have evolved to give birth off of tree branches so that the mothers never see and thus try to eat their offspring.
    • It's mentioned that mother gravediggers had a custom of killing all but the strongest of their offspring. However, Lucky didn't do this with her children thanks to her upbringing and they in turn cared for all their children, leading to the population of socialized gravediggers to grow more quickly.
    • In whaler daydreamer society, if a baby is born and there's no space in the pod for it, it will be killed within three days after birth. Warmongers also do it to weed out "undesirable" traits such as the yellow markings other daydreamers have, as was the case for a daughter of the warmonger matriarch who was killed by the matriarch's own mother.
  • Older Is Better:
    • Downplayed. Small perching birds similar to the original founding canaries remain present throughout Serina's history even as all these new exotic species rise and fall due to their highly unspecialized bodies and lifestyles, much like modern lizards and opossums being very similar to early reptiles and mammals respectively. Subverted eventually when the molodont tribbetheres evolve: being specialized for eating seeds, they quickly outcompete the perching birds, which decline sharply in the Ultimocene, although they still manage to hold out till near the end.
    • Zigzagged with the canitheres: primitive tribbetheres resembling larger versions of their earliest forms, they enjoy a fair amount of success early on during the Pangaeacene but are quickly outcompeted by carnivorous circuagodonts with higher intelligence and more specialized jaws, losing their apex predator status and being relegated to a few mesopredator niches akin to foxes and jackals. However, they end up having the last laugh over the circauagodogs when they go extinct due to competition with the sawjaw molodonts, but they survive into the Late Ultimocene.
    • The nimicorn is closer to the ancestral thorngrazer than the highly derived razorback, but its ability to run means that it's able to escape the fires that claim the lives of their fellow thorngrazer species during the Mid-Ultimocene mass extinction event.
  • One Bad Mother: Daydreamer society is matriarchal when it comes to leadership, and the expansionist and supremacist warmongers are no different, as their leader is a matriarch blinded in one eye.
  • Out with a Bang:
    • Male firetail changelings and sacrificial bumblets are semelparous, dying after a single intense mating season.
    • Brighteye kills Tyr-reet while the latter is victory mounting him.
  • Outside-Context Problem:
    • The warmongers trying to kill the gravediggers come across the issue that, while they're larger and better adapted to an aquatic environment, allowing them to easily dispatch the gravediggers upon capsizing their boats, the social gravediggers are not obligate aquatics, and can return to land and send warnings down the coast to other villages faster than a warmonger can swim. As a result, the warmongers soon find that there are no more gravediggers at sea for them to kill. They also weren't very aware of the gravedigger's ability to use tools, so when they give their daydreamer allies armor and weapons, the warmongers have no way of countering this and are soundly defeated. Said weapons are tipped with the poison of the fireslime lumpus, a toxic terrestrial species whose poison nothing in the sea has adapted to, so the warmongers die in droves.
    • Sea shoggoths aren't native to the open seas that warmongers hail from, so even if the blinded matriarch could've seen the sea shoggoth approaching her, she would not have known to flee before the ants could eat her alive.
    • During the Late Ocean Age, the encroachment of the glaciers creates a land bridge between the southernmost islands of Serinarcta and northern Serinaustra, allowing species from the former to move over to the latter, which gives the snowscrounger and glacier raven new terrestrial rivals. For instance, the glacial foxtrotter can easily hunt the young of clamcrackers, whose white coloration normally keeps the glacier ravens from picking them out from the air, by sniffing them out.
    • The sinking of the Meridian Islands brings rafts containing burrowing burdles and gupgops to the shores of Serinaustra, where the sea ravens, snowscroungers, and foxtrotters are naïve to them. Some of them try eating the latter, only to find them unpalatable due to their toxins.
    • The Visitor storyline has a probe from an alien planet 23.8 light years away arrive on Serina.
  • Painting the Medium: A timeless observer speaks directly to Ember, Brighteye, and Seeker in a floaty, cursive font.
  • Pair the Smart Ones: The daydreamers were born when two seers, one from a herding community and another from a nomadic hunting community, chose to mate despite both communities despising one another. Their loneliness borne from their higher intelligence makes them break the social taboos that had kept their communities separate for around 140,000 years. As a result, their children were mostly seers, and those who weren't often had children who were. After 200,000 years of the seers mostly breeding amongst one another, the seers fully diverged from the other seastrikers and became the daydreamers.
  • Panspermia: Of the "Alientelligent Design" form. The moon was seeded with select species by "mysterious creators", who then left them to evolve without intervention.
  • Partially Civilized Animal:
    • 240 million years post-establishment, a desert-dwelling corvid-like bird called the fork-tailed babbling jay develops sapience, a birdsong-based language, tool creation, art, and using fire to cook meat when they find it. Sadly, they only exist for about four millennia, never advancing past hunter-gatherers or learning to keep fire for themselves, until changing climates cause their habitat to fragment and shrink. They cannot adapt to wetter environments before diseases, rare in deserts, wipe them out.
    • The Middle Ultimocene also has the farmerjay, which has effectively domesticated a species of snail it eats by keeping them in larders of food, freeing itself from the need to forage, and lives in large cooperative "villages"... but is not truly sapient since their behaviors are mostly instinctual.
    • In the Late Ocean Age, the distant descendants of the babbling jays, the blue-tailed chatteravens, develop high intelligence, complex social behaviors and a rudimentary language, but never develop true sapience or personhood, save for Brighteye, an atavistic throwback to the sapient fork-tailed babbling jay in terms of intelligence.
    • The aukvultures of the Late Ocean Age, a descendant of the skydiver seraphs, are scavengers that have co-evolved alongside the sea stewards to the point that they're semi-domesticated, and have developed intelligence akin to the nonsapient sparrowgulls, living in tribes and teaching their children from a young age to be polite towards the sea stewards, as nicer scavengers get more scraps. It's clear that this behavior is learned instead of simply instinctual, because orphaned aukvultures not adopted by other aukvultures often grow up to be unusually rude and aggressive, and are treated as pariahs by other aukvultures due to their behavior reflecting badly on their whole species. 10,000 years post-coal seam fire, some of the aukvultures have become a sapient subspecies known as the reapers, diverging so recently that their ascension to sapience is still remembered in the form of dance.
  • People Farms: The near-sapient seastrikers develop the habit of harvesting the near-sapient ring-necked porplets by only eating the young ones so that the adults will breed and provide more food in the future. Their descendants, the pastoralist daydreamer cultures, continue to do this, although by their time a long process of artificial selection has turned the porplets into the passive, barely intelligent nops.
  • Pieces of God: The fisher daydreamers believe that the world was shaped by a single creator deity who then splintered itself into three essences — a flying creature, a terrestrial one and an aquatic one, each of which then split apart into myriad smaller copies of itself — to better experience all the realms of the world. They believe themselves to be the far-scattered fragments of the marine essence, and that one day they will find and reunite with the fragments of the other two and, having learned all that the world has to offer, reform into the creator. In comparison, the warmongers believe that only they descend from the pieces of a dead god and view themselves as above all other life, including other daydreamers.
  • Poisoned Weapons: In their second battle against the warmongers, the gravediggers give their daydreamer allies spears tipped with paralytic poison derived from the fireslime lumpus, a terrestrial tribbet, which means the sea-dwelling warmongers have no resistance to it. This also leads to a Cruel and Unusual Death for these warmongers, as their large size and ability to hold their breath for extended periods means that they sink to the bottom and slowly drown while remaining fully cognizant the entire time, something that traumatizes the daydreamers doing the stabbing.
  • Poisonous Person: The spitfire sniffler of the Ocean Age cactaiga is a trunko species that has developed an immunity to the poison of the fireslime lumpus, and spreads its deadly poison on its quills to defend itself from predators and deal with competitors, leaving it the sole snifffler species in the area.
  • Polyamory: Skystrike flocks as a rule don't pair bond like most other sparrowgulls, with the flock members all breeding amongst one another and raising all their chicks as their own.
  • Population Control: Due to lack of food, whalers strictly control their population by strongly encouraging homosexual relationships, having sex only for procreation, and culling their children out of necessity if one is born before an older member dies. This can have the downside of entire clans dying out because the adults all turned infertile before being able to have children.
  • Portmanteau: Some of the names, such as the gmu (gnu + emu), the burdle (bird + turtle), the dolfinch (dolphin + finch) and the squork (squid + stork). Naturally, they resemble their two namesake animals combined.
  • Precision F-Strike: As Brighteye lays dying from smoke inhalation and becomes aware of Serina's Mysterious Watcher, his last words in response to its apology for its manipulations is a pointed "Fuck you", for setting up the death of everything he ever loved.
  • Predators Are Mean:
    • Zigzagged with the sapient gravediggers. While they can be quite aggressive with each other when it's not breeding season, otherwise they lack malice and will even hang out with prey species when not hungry. It's noted that while they don't feel guilt while hunting, they have no malice towards their prey either, only seeing death as necessary for their own survival. This is played for a darker tone later when the gravediggers are noted to feel little in the way of guilt when reports come back about their warmonger enemies drowning slowly and fully aware as a result of the poison they supplied their daydreamer allies.
    • A version of this is a central part of the fisher daydreamers' belief system. In their view, hunting intelligent beings for food is morally unacceptable, and one should only subsist on simple-minded creatures such as fish. Consequently, they view the large-prey ecotype cultures, such as pastoralists and whalers who feed on other large marine birds, as being monsters and murderers.
  • Predator Turned Protector: The fisher daydreamers have long since stopped hunting other dolfinches and have come to believe that it is their moral duty to protect the smaller species that can't protect themselves, strongly paralleling the herbivorous woodcrafters. The luddy porplets have even learned to tell the difference between the fishers and the pastoral daydreamers and will stick by them for protection. Upon becoming the fully sapient greenskeeper, or grazer in the shared tongue of the multispecies civilization, they continue to view both the nova daydreamer (Known as "hunters") and thalassic gravedigger ("Walkers") as protectors of not only themselves but the whole ecosystem.
  • Pregnant Reptile: The vivas are a successful clade of birds that develop a form of vivipary from retaining their huge eggs until they're ready to hatch. True placental avians eventually evolve in the Pangaeacene. The predatory burdles evolve ovoviviparity after developing leathery eggs and retaining them internally until they hatch, which allows them to become fully aquatic.
  • Prehensile Tail: The clongers are a group of snake-like tribtiles that have lost their front legs and whose single rear foot has evolved into a functional hand. Most just use it for burrowing but some have found other uses for it: the sparrowsnatcher uses it to dangle from tree branches and catch birds out of the air, the diamond clonger clicks its claws together to warn predators of its venomous bite like a rattlesnake, and the cloa is a larger species that grabs the necks of its prey to either strangle it to death or puncture its jugular.
  • Profane Last Words: As Brighteye lays dying, his last words to the observer are "Fuck you." in response to its apology for using him as a pawn since it was responsible for both his death and the deaths of the wumpos.
  • Proportional Aging:
    • While it's not mentioned how long gravediggers live relative to humans or woodcrafters (although it's later noted that woodcrafters rarely live past fifty), they do grow more quickly than humans, with a four-month-old gravedigger being roughly equivalent to a human seven or eight year old, and become functionally adults at about twelve months, though they don't gain their adult plumage until later.
    • The last woodcrafter dies at around fifty-eight, when most of her kind doesn't make it to fifty, making her roughly equivalent to a human centenarian.
    • Daydreamers age more slowly than humans, reaching sexual maturity in their late 20s, entering menopause in their 70s, and live for around 130 to 140 years, making them the longest lived of Serina's sophonts.
    • In the Late Ocean Age, thalassic gravediggers and greenskeepers are said to live roughly half as long as the novan daydreamers. In a group of friends consisting of a greenskeeper, two thalassic gravedigger sisters, and a novan daydreamer, the latter takes so long to mature that she ends up serving as a babysitter for one of her gravedigger friend's grandchildren while still the equivalent of a human teenager. By comparison, gravediggers and greenskeepers age at roughly similar rates.
  • Pyrrhic Victory: Retally, a woolly wumpo widemind of the Tidelands Herd, managed to drive the thalassic gravediggers who hunted his kind away from the shoreline until the time of Blaze's great-great grandparents using the power of fire, but his lack of control over it led to the deaths of most of his herd. While Retally was among the survivors, he was so changed from the experience that he headed north and was never heard from again.
  • Raised by Wolves: Deconstructed by the carnivorous circuagodonts, who sometimes adopt and raise young of their herbivorous prey. As awesome as this may sound, it hardly ends well for the adopted youngster, as it identifies with the carnivorous species, loses its fear of them, and ends up getting eaten by other packs of carnivores unfamiliar with its scent.
  • Raptor Attack: The banshees are essentially re-evolved velociraptors, with sickle claws on their feet, long balancing tails, and wings modified into claws for grabbing prey. They resemble accurate dromaeosaurs save for having a serrated beak and barbed tongue instead of a toothed snout.
  • Reality Is Unrealistic:
    • The handfish tribbets modifying their individual fin spines into separate multiple spider-like legs seems completely absurd, but it's actually very similar to the real-life sea robin, a bottom-dwelling fish that "walks" around on the sea floor on three pairs of modified fin spines that act as six separate somewhat insect-like legs.
    • On a similar note, ray-finned fish developing tetrapod-like legs sounds seemingly implausible, but then there's the Frogfish, a group of ray-finned fish that walk across the seafloor using fins that greatly resemble stubby legs. One species in particular, the Sargassum Frogfish, even has prehensile fingers that let it climb through seaweed.
    • The tufted frogjar, a metamorph bird whose newt-like larva is bigger than the adult, sounds downright improbable... until you learn about the real-life paradoxical frog, which metamorphoses from a truly immense giant tadpole... to a tiny adult barely half its size.
  • The Remnant: The reapers are described as the last people of the Ocean Age, having descended from the aukvultures that co-evolved with the sea stewards.
  • Renegade Splinter Faction: The warmongers started out as a clan of the highly communistic pelagans who wanted to abandon this way of life in favor of a every family for itself system. They were exiled to the southern oceans after they started raiding other pelagan clans and became the large, brutish cannibals they are now.
  • Retcon: When first introduced, the seagoing gravediggers were referred to as the thalassic gravediggers, existed three million years after the extinction of the woodcrafters, and had diverged enough from their ancestors, such as by developing salt-filtering glands in their nostrils, to be defined as a distinct species. Sheather eventually changed this to their simply being a seaborne culture of social gravediggers, and to exist around five thousand years after the last woodcrafters but later gained enough adaptations to aquatic and social life to be considered a new species after three million years.
  • Ridiculously Cute Critter:
    • Most of the founding species of Serina are cute animals like canaries, guppies, and ladybugs.
    • Certain tribbets, particularly tribbetheres, being mammal analogues with many of the same features such as big eyes and expressive rounded ears. Dogbeast cubs are specifically noted to be as cute to human eyes as any Earth puppy but are not as playful due to lower intelligence.
    • Viva chicks are fuzzy and yellow with Black Bead Eyes like baby chickens, only with stumpy tails and disproportionately long legs. Even some adult vivas remain fairly cute in a deer-like way.
    • Hoppers, early tribbets that resemble a cross between a rodent and a frog.
    • The baby armox as well, despite its mighty hulking adult form.
    • The fluffy gigaduck chicks on their parent's back. Some of them are even sleeping.
    • Fork-tailed babbling jays, on the other hand, consider baby birds with feeding gapes resembling those of their own chicks to be cute. They'll even capture the chicks of other bird species to keep as pets for this reason.
  • Rodents of Unusual Size: The molodont tribbetheres evolve to be rodent-like, and one group, the circuagodonts, become the dominant herbivore group and become deer-sized herbivores resembling long-legged tripodal rabbits.
    • Omniphages are a group of molodonts that can weight up to 1,500 pounds, making them the largest land dwelling tribbetheres.
    • The rakewhales are marine molodonts around 30 feet long.
  • Running on All Fours: Certain bird species become quadrupedal, notably the deer-like serezelles and their descendants, the sauropod-like boomsingers, as well as the bumblets and their predatory descendants the bumblebadgers.
  • Sand Worm: The Serinian bullworm, a giant earthworm in the early Hypostecene that can reach lengths of over thirty feet.
  • Sapient Eat Sapient:
    • One bumblebadger species, the gravedigger, becomes highly intelligent and learns to construct elaborate traps to catch its prey, the herbivorous antlears. Pressured by the gravediggers' increasingly elaborate traps, one species of antlears becomes more and more intelligent as well in an arms race to avoid their clever predators, culminating in both gravediggers and antlears, now the woodcrafters becoming truly sapient, and waging war on each other. The conflict finally stops when the two species make peace as a result of two of the latter getting adopted by the former.
    • Downplayed with the porplets and seastrikers, which haven't achieved full sapience yet, but are intelligent enough to have complex thoughts and emotions, all while the latter regularly hunts the former. Eventually a fully sapient species called the daydreamers emerges from the seastrikers who still feed on the porplets, but some come to view eating such intelligent creatures as morally reprehensible and choose to eat fish instead.
    • Later on, the warmonger daydreamers, a subgroup of whalers, a cultural group adapted for hunting large prey, comes to be sufficiently physically and behaviorally distinct enough from the shallow-water daydreamer cultures that they no longer view them as fellow people — to them, they're just meat on the fin. When the warmonger leadership finds out about the gravediggers and their sapience being a threat to their beliefs, because it would prove the fisher and pastoralist creation tale correct, they decide to attempt genociding them too to prevent their soldiers from finding out and turning against them.
    • The woolly wumpos consider the thalassic gravediggers demons due to the latter hunting them for generations after making first contact, seemingly unaware of their sapience since outwardly they appeared no different from the nonsapient sealump trunkos, before a widemind named Retally managed to drive them off by using their own fire tactics against them, but at the cost of most of his herd when he couldn't control the flames.
  • Scavengers Are Scum:
    • Zigzagged. This is played somewhat straight by the sea ravens, a scavenging sea bird known for its belligerent temperament that will aggressively steal food from other animals, including the sea stewards, whose children they'll sometimes attack. However, this is completely averted with the aukvulture, these birds are very gentle as they have learned that the sea stewards will give them their leftovers if they are polite about it, especially since they keep the sea ravens away.
    • This is completely inverted with the reapers, a sapient population of aukvultures, who are just as much of scavengers but they have a very strong code of ethics that forbids killing outside of mercy and espouses empathy to other lifeforms. Their nature as scavengers also gives them a very spiritual outlook on life with concepts similar to an afterlife and souls but for all living things.
  • Scenery Gorn: The shores of Serinaustra 1,500 years after the great coal fire are described as being covered in piles of the rotting corpses of dead sea animals that are, in turn, coated by swarms of insects. However, to the scavenging snowscroungers, foxtrotters, and burrowing burdles, it's a veritable buffet.
  • Sea Monster: Swordwhale fish such as the gulpy and gigadon, birdwhales, bloons, king trawlers, predator burdles, and giant filter-feeding dolfinches like the banded maw, the last of which are said to be the largest birds Serina has ever seen. Special mention goes to the sea rex of the ocean age. They're huge 50ft apex predators with crushing jaws and armored skin that makes them virtually unbeatable as adults, even to the pelagic daydreamers who are large powerful predators in their own right. This forces them to target the beasts when they are young and small when dwindling food supplies causes the fully grown sea rexes to start hunting the pelagans instead.
  • Serial Escalation:
    • In the first few million years, the evolved canaries develop into forms similar to modern and prehistoric bird species like hawks, moas, and penguins. As time goes on, they derive even further; some species take on saurian, reptilian, and even mammalian characteristics. By the time of the Ultimocene, many species such as boras, lumberbeests, trunkos, and neotenic metamorphs have ceased to resemble birds at all.
    • The tribbets as well. Descending from the mudskipper-like Mudwickets, they came to first resemble a bizarre three-legged fusion of fish and frog. However, as they became more and more derived, they developed jointed forearms, flexible necks and erect limbs, and their descendants the tribbetheres came as far as to evolve fur, external ears and erect limbs, looking every bit like a three-legged mammal with only their extensible jaws betraying their true heritage as fish. Then things get even stranger when some evolve into flying bat-like forms and secondarily-aquatic whale-like forms...
  • Shout-Out:
    • A type of small, rabbit-like circuagodont often preyed upon by repandors is called a smeerp.
    • One million years post-establishment, the largest invertebrate on the moon is a giant earthworm known as the Serinan bullworm.
    • The antlear and gravedigger saga is an homage to doeprince's Golden Shrike, which is a story about deer and shrikes (gravediggers essentially behaving like giant, flightless shrikes). Dylan Bajda and "doeprince" follow each other and communicate.
    • Fellstar, an alien probe that visits Serina after the disappearance of the Sea Stewards, bears a striking resemblence to the probes in Alien Planet. It's brightly coloured, has large, childlike eyes and a simple artificial intelligence; likewise, it appears to have been made to study life on the moon.
  • Shown Their Work: Compared to the wild-type luddy, who look more or less the same as do most wild animals, the domesticated nops show clear signs of neoteny in the form of a very chick-like head and come in numerous colors.
  • Simple, yet Awesome: The surfscoter secondarily evolved to be semi-aquatic in order to avoid its aquatic predators, which is implied to be what allowed it to survive the Great Thaw that killed off the other dolfinches, as it was able to access food sources in places that the other species couldn't, such as Serinarcta's marches.
  • Single-Biome Planet: Serina is initially terraformed into one of these. The entire winding supercontinent of Cirrus is covered in tropical grassland engineered to support canaries. However, this is not sustainable without long-term artificial maintenance and the organisms evolve rapidly to balance the ecosystem, a process that takes millions of years of flux.
  • Skeletons in the Coat Closet: The gravediggers outfit the daydreamers with armor made from animal bones and shells in the second fight with the warmongers.
  • Slashed Throat: Sawjaws attack their thorngrazer prey by jumping on their backs and using their jaws to slice their unprotected necks.
  • Sliding Scale of Anthropomorphism:
    • In the Pangaeacene, there are the bludgebirds and the babbling jays. The bludgebirds are quite intelligent creatures and can use tools and weapons, but ultimately are no more advanced than an ape. Babbling-jays, on the other hand, have a true language, a sense of aesthetic art, cultural traditions, and even oral tradition. Tragically, both species become extinct at the end of the Thermocene due to changing climates before they could advance further.
    • Animal intellectual complexity peaks the Ultimocene, with the majority of land vertebrates having primate-level intelligence. However, it's stated that sapience is a spectrum: some animals, such as the snail-farming bird, have complex behaviors, but do them instinctively, while others are capable of higher learning capabilities but are not self-aware. A few animals are offhandedly mentioned to have developed self-awareness: however, it's stated that unless specific conditions are met, it's highly unlikely for them to build a civilization.
    • The mid-Ultimocene produces several near-sapients such as the childlike porplets, the spear-crafting bone-bower bird, and the skystrikes, which use a well-developed vocal language to coordinate their hunts.
    • Vibropteran tribbats are also noted for their intelligence, displaying problem-solving tactics as well as tool use. They were originally planned to produce a sapient species, but were ultimately left like this.
  • Sliding Scale of Idealism vs. Cynicism: Surprisingly, the Ultimocene saga leans heavily on the idealism side, despite many, many interactions that more easily could have gone down a more dreadful route, like the war between gravediggers and woodcrafters, the woodcrafters' genocidal crusade on innocent carnivores, the seastrikers domesticating their own relatives the porplets for food, or the coming of the cannibalistic, nigh-fascist warmongers. All of these incidents are resolved in an unexpectedly wholesome way, with the gravediggers and woodcrafters forging a genuine friendship, the daydreamers finding unity and even befriending the sapient descendant of their former prey, and even the warmongers have shown to be redeemable without the influence of the matriarch. Overall, despite the impending extinction of all life, the saga of the Ultimocene sophonts has the general feel of being worth it, in the sense that it was the journey, and not the destination, that truly mattered.
  • Small Role, Big Impact:
    • The water snuffle, a duck-sized platypus-like bird from the isolated Kyran Islands, is one of the few avians to survive the Thermocene-Pangaeacene mass extinction. As a result, its descendants the tentacle birds end up taking over many megafaunal land niches by the Ultimocene.
    • Strackbirds are given a few paragraphs of description as Cryocene songbirds that assist large predators by flushing out prey and then share their kills in return. Due to this lifestyle making it difficult to tie oneself down to a nest for a prolonged period of time, their chicks evolved to hatch at less developed yet more independent states so the parents could just drop meat into the nest and leave again, and then simply fill their nests with larders and abandon them. This formed the basis of the changelings' insect-like reproductive cycle, which granted the lineage incredible adaptability into a huge variety of niches in the coming Thermocene and Pangaeacene.
    • The mudwickets, small mudskipper-like descendants of guppies, arise twenty-five million years post-establishment, seemingly just as a random fluke of evolution. However, they later give rise to the froglike tribbets in the Thermocene and later the tribbetheres in the Pangaeacene and Ultimocene, becoming a dominant clade of life that eventually comes to rival the birds.
  • Soul Eating: In the religious beliefs of the woolly wumpos, those killed by predators have their souls completely devoured, barring them from their afterlife. As a result, it obligates them to kill their predators on sight so that as much of the family can survive death as possible.
  • Speaks Fluent Animal:
    • The fork-tailed babbling jays can speak the much simpler languages of the non-sapient birds they share the desert with.
    • Daydreamers can communicate with most of their non-sapient dolfinch cousins, who the small-prey ecotype perceives as akin to their own children in terms of intelligence.
  • Speculative Fiction LGBT: This comes up in descriptions of sapient species' cultures:
    • It's briefly mentioned that same-sex pair bonds are rare but not unheard of among fork-tailed babbling jays.
    • While the woodcrafter antlears do have gender roles, due to an evolutionary holdover regarding hormonal development and group dominance composition it's possible for their males to mature without developing full adult male traits and for their females to become masculinized and more attracted to females. The former are most often considered a third gender while the latter are considered and identify as male. Sexual preferences are highly variable among individual woodcrafters and they do not pair-bond, but male-male mating is more common than female-female.
    • Amongst the whaler daydreamers, obligate homosexuality is enforced in order to ensure population control. As a result homosexual pairings are about as common as heterosexual ones in their society. There is also a significant asexual population, who are referred to as clearwaters due to being considered undistracted by sexual matters, and often become sages and shamans sought out for their wisdom.
    • Of the four childhood friends who act as viewpoint characters for the Sea Steward civilization, the thalassic gravedigger Pebble and the greenskeeper Seeker never have offspring, the former because "she didn't really like males", the latter because "he didn't have much of an interest in settling with anybody".
    • When Blaze and her daughter are arguing over what to do with Brighteye and Whitecrown, the latter alludes to a same-gender partner who was killed by "biters".
  • Starfish Language:
    • The language of the fork-tailed babbling jays is highly complex birdsong spoken too quickly to be understood by the human ear. This is presumably also the case for their descendants the blue-tailed chatteravens, although theirs is considerably simpler.
    • It's mentioned that the woodcrafter language sounds similar to elk calls.
    • Gravedigger languages consist of gravelly, croaking, and hissing sounds that are very difficult for woodcrafters and later daydreamers to understand. In the case of the latter, it takes their equivalent of teenagers who still have the plasticity to learn in order to communicate with them.
    • The language of the whalers has diverged so much from other daydreamers that the fishers find it even less comprehendible than gravedigger speech due to it being deep and slow.
    • Sea shoggoths communicate through the rhythmic clicking of their mandibles.
    • Woolly wumpos communicate primarily through infrasound that most other species can't hear.
    • The reapers are only capable of making simple sounds like guttural honking so they mostly communicate using gestures and elaborate dances.
  • Starfish Robots: Fellstar, the alien probe Eve befriends, has a rather unusual appearance. It somewhat resembles some kind of animal but not any earthly one, having a pod-shaped body with six spindly legs, two cable-like tendrils for arms and a long neck with a large pair of camera eyes.
  • Stars Are Souls: In the religious beliefs of the woolly wumpos, their loved ones watch over them as stars.
  • Stone Wall: The lumphead grumpus, a very strange Thermocene fish, actually won its arms race of defense from gigadon attacks by specializing into this. It is large and very slow-swimming, but its long defensive spines ensure that few predators will take one on.
  • Sufficiently Advanced Alien: Word of God reveals that this is what the observer actually is, rather than a literal deity. It's a being with such advanced technology that it seems like a supernatural entity to the less technologically advanced sophonts.
  • Sugar Bowl:
    • Serina at establishment is as much this as a biosphere can be. It begins as a Single-Biome Planet of warm sunny grassland punctuated by blooming clovers and cheery sunflowers. There are no predators larger than an insectivorous canary, and even the fish and insects are cute as such creatures go. It doesn't last long, however.
    • The oceans become this during the Late Ocean Age, in contrast to the comparatively harsh and barren land. The plant life is abundant and supports a healthy and diverse ecosystem, the animals are all tame and even the most dangerous creatures are kept placid through regular feeding. However, the only reason it can even be this nice is because it was being artificially maintained by the sea stewards and the moment they disappear it immediately starts to breakdown.
  • Super Drowning Skills: Thorngrazers are noted to be very poor swimmers, preventing them from colonizing islands in the same way they have the Serinarctan mainland.
  • Swans A-Swimming: While not aquatic, the swan-like archangels certainly fit the trope, being peaceful elegant grazing giants with long graceful necks and snowy white plumage.
  • The Swarm: This happens twice in Serina's natural history. The first happens in the first few million years with the empire ants who live in enormous supercolonies. However, they are arguably a Deconstruction of this trope as they quickly consume all the creatures that can sustain them and eventually die out. The second time are the billon stingers, which are like army ants on steroids. They don't live in supercolonies, so their numbers are sustainable, but they can still skeletonize larger animals in minutes. By the mid-Ultimocene, the billion-stingers have given rise to the sea shoggoth, colonies of which function like individual animals, using linked groups of specialized ant castes to move the colony and catch prey.
  • Sympathetic P.O.V.:
    • We are first introduced to the gravediggers by hearing about how they hunted the sapient antlears before eventually being driven out, and there's even a picture of one standing over a trap with a dead, skewered antlear inside it which might cause our sympathies to lie with the antlears. Later on however, we get to learn more about how they operate and that they even have an artistic side that has allowed them to develop a kind of culture despite being solitary by nature, complete with a picture of a mother gravedigger showing her young chick how to draw. Later still we also see that the antlear's descendants, the woodcrafters have developed a bit of a cruel streak that they express by indiscriminately killing any predator that they can find, including the gravediggers that don't even hunt them anymore.
    • The warmongers are first introduced as fascist genociders, and from the view of the gravediggers and other daydreamers are perceived as Always Chaotic Evil, but are later shown to not be inherently evil, but are instead merely the product of their environment and shielded from most outside influences.
    • Even the warmonger matriarch is given this when she is blinded and exiled: despite the misery she caused, despite the deaths borne by her own doing, we get a brief look into her mind, and see all her regrets, all her past mistakes she cannot undo, and ultimately, how in the end, her goal was only to ensure that her people survive — despite her questionable means of doing so.
  • Tailfin Walking: A variant of this. The mudwickets use their tail and pectoral fins as three walking legs to move on land. Their descendants the tribbets turn the tail into a proper leg with the foot derived from the tailfin, and by the time of the tribbetheres their hind leg is virtually identical to a mammal's as an erect limb with knee and ankle joints.
  • Take That, Critics!: After many users complained about the header image of the site being redesigned, Bajda responded by replacing the second version with a more crude and cartoony drawing. He then replaced that version with an even lower-quality stick drawing after Reddit users noticed the joke.
  • Terrestrial Sea Life:
    • The tribbets are land-dwelling fish descended from the amphibious mudwickets, with many of the more primitive forms filling the niches of lizards and frogs, while the furry, warm-blooded tribbetheres become analogues of mammals.
    • There are also many species of terrestrial crabs, many of which fill the niches of spiders.
    • The colossal quadclaw is a giant terrestrial hermit crab that no longer needs to even go to water to breed like most terrestrial crabs do, instead hatching as juvenile crabs from eggs hidden under their mother's abdomen.
    • Inverted with sea bamboo and planktants, which are formally terrestrial lifeforms adapted to the sea.
  • Time Abyss:
    • Daydreamer civilization goes back more than three million years, with accurate historical accounts going back to more than 500,000 years ago. For comparison, Homo sapiens has only existed as a species for about 200,000-300,000 years. The Alliance of the daydreamers, thalassic gravediggers, and greenskeepers then exists for a further five million years, allowing them to radically alter the ocean ecosystem and the biology of the animals that live within it despite being stuck in Medieval Stasis.
    • Some hiddenwood clonal colonies are millions of years old.
  • Took a Level in Jerkass: The non-sapient aukvultures 10,000 years post-coal seam fire have fallen prey to their more aggressive instincts in the absence of the sea stewards, fighting amongst one another and even being willing to kill young aukvultures if they won't get out of their way, something the sapient reapers find horrifying due to how much they value the few children they're able to have.
  • Took a Level in Kindness:
    • Compared to their southern gravedigger ancestors, due to aggressive territoriality not being a useful survival trait in their arctic environment, while still relatively asocial icefishers prefer avoiding conflict rather than partaking in it. They also no longer regularly commit infanticide.
    • After the Great Thaw, the sea ravens become much less aggressive due to the more hospitable conditions and abundance of shore carrion for them to feed on.
    • 10,000 years after the coal seam fire, the nimicorns have started tolerating the presence of island wumpos as sentries, even protecting them and smaller trunkos like the snoots when under attack by allowing them inside their herd huddles with their young, and have a more symbiotic rather than destructive relationship with the environment. As Eve and Fellstar travel across Serinarcta, both observe nimicorns and island wumpos just placidly hanging around one another without the former trying to eat or otherwise attack the latter.
  • Toothy Bird:
    • Aardgeese and their descendants the vivas develop teeth on their tongue and upper jaw, allowing them to grind tougher plant material.
    • While they don't have teeth, the mittens might be considered a downplayed example. They can chew their food by grinding it in their beaks thanks to their tentacles granting them greater facial-muscle kinesis.
  • Translation Convention: As reapers lack a throat structure that would allow them to use a spoken language, limiting their vocal language to mostly horse honking sounds, it's safe to assume Eve's story is being interpreted from her dancing and other movements.
  • Translator Buddy: Since the gravediggers can't hear the low-frequency infrasound the woolly wumpos use to communicate, and only one third of the sea stewards are capable of writing, Brighteye serves as a translator due to his ability to copy the gravedigger tongue.
  • Trap Master: The gravediggers hunt by making various kinds of traps for their prey, and they are very good at it thanks to their tendency to closely observe the behavior of the creatures they hunt so they can learn to take advantage of it. It's also something that they are taught at a young age since Bridge already knew how to make snares and pit-traps for small animals at only four months of age, which is his species equivalent to a human eight-year-old.
  • Trauma Conga Line: At the end of his life, Brighteye loses his best friend Blaze from old age and only finds out after she's already been buried, meets Whitecrown again only to lose him when he and his flock are vaporized by the flames caused by the coal seam fire they started, loses his wumpo family when they're overtaken by the same flames setting most of Serinarcta ablaze, and in his very last moments learns that he's been a pawn of Serina's watcher the whole time.
  • T. Rexpy: On a number of occasions, some of the descendants of the canaries become adapted for life as large, flightless predators of megafauna. In the earlier periods of Serina's history, where the original avian form is still relatively unmodified, this results in forms reminiscent of the tyrannosaurs.
    • The tyrant serins are enormous flightless apex predators with powerful bone-crushing beaks, wings reduced to vestigial appendages, and tail-like extensions of their pygostyles to balance their immense heads. They are mostly adapted for preying on the similarly flightless, elephant-sized serestriders, which they kill with guillotine-like bites to the neck.
    • Coronas arise around forty million years later, and belong to a group that evolved a number of mammal-like traits such as fur-like feathers, liplike fleshy coverings over their beaks, and teeth. They're also huge, flightless bipeds — one ton in weight and ten feet tall — with tail-like hindquarters like the earlier tyrant serins. Unlike the serins, their arms are large and muscular, and end in a single strong, hooked claw each.
    • Sea rexes are an unusual case, as they're four-flippered, orca-like descendants of scaled seagoing birds adapted to prey on marine megafauna. The resulting creature resembles a heavily-built, shell-less sea turtle, with an avian head whose beak is filled with serrated keratinous teeth and built to crush the skulls and spines of other large marine animals. Sea rexes can grow to be sixty tons in weight and reach two centuries of life, and while their juveniles are vulnerable the adults are functionally impossible for other creatures to harm. Ultimately, however, they died out as a result of collapsing marine food chains killing off the large marine birds they eat, combined with a desperate effort by the sapient daydreamers to kill off their young in an effort to stave off their own extinction.
  • True-Breeding Hybrid:
    • The woolly wumpos of the Late Ocean Age arose through hybrid speciation of two closely related species that existed at the onset of the ice age, the desert wump and the mammoth trunko, as they were forced together by shrinking habitats. By joining in this manner, the two species' descendants ended up being better-suited for the new environment than either ancestor by itself, as they possessed both the wumps' physical adaptations for life in harsh, cold environments with scarce food and the trunkos' social habits and preference for living in multi-generational herds led by the most experienced members.
    • The island wumpos are cousins of the woolly wumpo that are also the result of hybridization between the desert wump and mammoth trunko, born when as few as 10 early wump/trunko hybrids swam the 25 mile distance to two small isolated islands off the coast of Serinarcta's western refugial peninsula in a desperate search for food during a cold spell, splitting with the woolly wumpos roughly 500,000 years prior. Unlike their cousins, they are only near-sophonts due to having higher wump than trunko admixture, are much smaller by being on average only man-sized, and exhibit island tameness due to not evolving alongside any predators. Due to their lack of cold adaptations, they prefer to stay near the coast.
  • True Companions: Packs of skystrikes are made up of unrelated individuals who come together as adolescents, rather than family members as in wolves or harems as in lions, described as "a group of compatible friends."
  • Turtle Power: The mucks are a family of ectothermic avians that resemble shell-less, bipedal turtles with a single large claw on their front limbs. Their evolutionary history is a little complex, however: they started out as slow-moving arboreal herbivores similar to tree sloths, but a group of them rafted to the Kyran islands and evolved into the Maritime Muck, which was more similar to the marine iguana. After the mass extinction at the end of the Thermocene they evolved into more distinctly turtle-like forms, including the sea-turtle-like burdles and giant-tortoise-like lumberbeests.
  • Uncanny Valley:
    • An In-Universe example with the sapient woodcrafter antlears. They greatly dislike their non-sapient bestial relatives due to their more animalistic appearance, the way some humans may find apes unnerving. They also find it unnerving that beings that look so much like them lack much in the way of rational thought.
    • The nop is described as fitting into the luddy's uncanny valley due to how different they are despite having a shared ancestor.
    • Woolly wumpos are implied to find carnackles and other obligate carnivore trunko species creepy just because they can can see the physical similarities despite their differences in diet.
    • The savage gravediggers or wildwalkers, the descendants of the tundra gravedigger, are considered unnerving by the thalassic gravediggers due to their physical similarity but inability to speak and lack of sapience.
  • Underground Monkey: The only real difference between the steppestalker and the shadowstalker it evolved from is that the former has lighter coloration.
  • Uneven Hybrid:
    • As the tundra gravediggers were forced south by the growing ice age, they entered the territory of the southern gravediggers and for the most part forcibly displaced them, driving them extinct except for a smaller group that retreated onto marine ice shelves. Before this happened, some tundra gravediggers forcefully mated with southern gravediggers, creating hybrids that afterwards bred back with both surviving populations. Eventually, the resulting descendant species were both primarily descended from one ancestor group, with a small contribution from the other — the savage gravediggers descend primarily from tundra gravediggers with a small southern contribution, while the icefishers descend chiefly from southern gravediggers and a few southern-tundra hybrids.
    • The woolly wumpos are descended from hybridization between the closely-related desert wump and mammoth trunko species, but as the trunkos were more common they also contributed more of their genome — about eighty percent of the final total. Further, natural selection favored the persistence of different traits from each parent species, so that the trunkos' genetic legacy mostly came in the form of their larger size, higher intelligence, and social behavior, while the wumps' mainly passed down physical traits for more efficient digestion and resource use, physical endurance, and a stronger sense of smell. Their closest cousins, the island wumpos, were also born from a mix between the wumps and trunkos, but the wumps contributed a higher amount of genes to their genome, and so between that and their island environment they're smaller and while intelligent are still near-sophonts at most.
  • Unfortunate Names: The neckbeard is a species of tentacle bird that broods its eggs in a fluffy throat pouch... named for stereotypical ungroomed nerds often associated with friendzones, whiteknighting, and incel culture.
  • Unseen Pen Pal: The gravediggers communicate with one another using images that they draw into the trees and rocks that border their territories. This allows them to form relationships with each other without ever physically meeting. In fact, doing so is necessary as they are naturally solitary despite their sapience and if they were to ever meet outside of mating season then their territorial instincts would kick in and they'd get into a violent fight.
  • Unwitting Pawn: It's revealed to Brighteye in his last moments that he has served as a pawn of the watcher to keep the experiment going longer than it otherwise would've. Brighteye is understandably angry about this revelation because while he may have helped save the world, his actions damned him, his family, and a large portion of Serinarcta's terrestrial life to a fiery end.
  • Unwitting Instigator of Doom: The gravediggers teach Brighteye how to make fire, he and the wumpos inadvertently teach the nonsapient but still intelligent Whitecrown how to make fire, and he ends up using it to become lord amongst the bluetails despite being an otherwise hated albino, but their indiscriminate burning heralds the end of the Late Ocean Age, and their entire world with it.
  • Vegetarian Carnivore:
    • Averted with Bridge. The woodcrafter who adopted him knew that he wouldn't be able to subsist off the same tree-based diet as himself. At first, he fed him with fish he caught from nearby rivers, but it didn't take Bridge long to start hunting the small molodonts and smeerps infesting the village of his own volition.
    • Played straight with the marine social gravediggers. When they started living on the ocean, they would sometimes eat small amounts of seaweed to supplement their diets. Their discovery of fire made it easier for them to digest when cooked, so they would start regularly consuming more and more until the seaweed made up around a quarter of their natural diet.
    • A variation occurs with some of the daydreamers. They are physically designed to feed on larger prey animals like porplets and other dolfinches, but after some of them come to believe that feeding on these intelligent, closely related animals is immoral, they stop eating them all together and start eating things like fish and other smaller sea creatures exclusively. Much like how some humans give up meat like beef and chicken but will still eat fish for protein.
  • Vertebrate with Extra Limbs:
    • Inverted with the amphibian-analogue tribbets and their descendants, the tribtiles and tribbetheres. All of them have two forelegs and one hind leg derived from their mudskipper-like ancestor's tail, with the foot derived from the tailfin.
    • Spiderfrogs are a true example, ironically descended from tribbets. Two fin-ray-derived digits on each hand have grown so large that they function as limbs and have their own digits, making these arboreal creatures hexapedal.
  • Voice Changeling: Bluetails can mimick the calls of other animals. Brighteye uses this to save Blaze from a dire bumblebear by imitating the cries of a distressed cub to draw it away. This also gives them the Required Secondary Powers that allow them to easily memorize and learn new languages when bluetails with different dialects form new clans. In the case of Brighteye, it allows him to learn some of the gravedigger language after spying on them for several months.
  • The Watcher: In the late Ultimocene, a timeless, unseen observer that seeded life on Serina has been increasingly making its presence known to various sophonts and gets concerned that the sea steward's discovery of fossil fuels will end up unravelling its natural experiment.
  • Wham Line:
    • An In-Universe example occurs for the thalassic gravediggers when the bluetail Brighteye reveals his sapience to them when he asks them how to make fire.
    • Part 1 of "The Visitor" ends with Eve revealing that Serina was visited by an alien being.
      Eve: ...when the visitor came down from the stars.
  • War Arc: The Daydreamer Saga tells the story of how the daydreamers came to be and their wars against one another, most prominently the war between the warmongers of the open sea and the fishers and pastoralists of the coastal areas assisted by the social gravediggers, which ends with the daydreamers and gravediggers all becoming one diverse but united civilization.
  • Weak, but Skilled:
    • Sparrowgulls as a group make up for their lack of size or exotic features with their high intelligence, allowing them to succeed in harsh environments with such skills as weapon-crafting and cooperative pack hunting.
    • The social gravediggers are small and poor swimmers compared to the warmongers, but their skill at making weapons and knowledge of poisons allows the fishers and pastoralists to turn the war completely against them.
  • Weak to Fire:
    • The sea shoggoths can be warded off by fire thanks to an ancestral fear of it due to evolving from terrestrial ancestors that had to evade brush fires.
    • The thorngrazers have a strong hatred of fire, and it's the only thing that keeps them from overrunning the gravedigger fortresses. It ends up meaning the end for the razorbacks in particular during the Mid-Ultimocene coal seam fire, as they're 1) too slow to outrun the flames and 2) have huddling down as their instinctual response to fear, allowing the fire to consume them.
  • We Hardly Knew Ye:
    • The merwals, aquatic canitheres resembling dolphins that descended from the seal-like mertribs, tragically are a short-lived clade, as they were less efficient at hunting fish than the porporants and turned to feeding on shellfish to avoid competition... but then came the aquatic molodonts, and unable to adapt to a different diet, the merwals quickly declined after just having recently evolved.
    • The reapers, sapient aukvultures, last only around 500 years before dying out due to inbreeding depression.
  • We Have Reserves: Porplets survive against predators by sacrificing other members of their group to them, in particular the seastrikers. Such is their self-preservation instinct that they only rarely defend other members of the group from predators, as having a certain percentage of the young, sick, and old die is considered safer than risking the whole group. They can afford this strategy because they're also capable of reproducing very quickly.
  • We Used to Be Friends: The giant mole crickets of the early Tempuscene start out as having a symbiotic relationship with the burrowing molebirds: the cricket digs the burrows and tolerates the birds moving in, as they serve as its alarm against predators. However, as both further specialize, the birds become more independent of the cricket and capable of digging on their own, while the cricket evolved to burrow even deeper and avoid predators entirely. Not needing each other's partnership anymore, the mole crickets soon evolve to be predatory and start hunting their former avian partners.
  • What Measure Is a Non-Human?:
    • Or rather, What Measure Is a Non-Woodcrafter? The woodcrafters, a species of sapient antlear, view other, non-sapient species of antlear with great disdain, finding it very uncomfortable to see creatures so alike to themselves yet devoid of rational thought. They also view their former predators, the gravediggers, with disdain and culled them from their forest refugia millennia ago, only to change their views once they find out their old enemy's sapience and gravediggers end up being raised amongst them, though some woodcrafters attempted to keep the gravedigger's sapience secret at first out of a fear of losing the glory gained from predator hunting.
    • The seagoing gravediggers would avert this. Due to the woodcrafters becoming almost godlike figures in their religions despite looking nothing like them, the avians developed a culture of valuing all life and not viewing themselves as inherently superior to the animals they live with.
    • When Blaze the woolly wumpo asks her daughter Thistle what the difference is between the bluetails hunting and them eating "mice"note  in order to survive when the latter objects to having Brighteye and Whitecrown around due to being "biters", the latter responds that they don't have souls like the wumpos do.
  • White and Red and Eerie All Over: Whitecrown causing devastation with fire is portrayed as white rimmed with a demonic red.
  • A Wolf in Sheep's Clothing:
    • The early carnivorous circuagodonts of the Pangaeacene would sometimes use their resemblance to their herbivorous cousins to their advantage by pretending to be herbivores themselves which would cause the plant-eaters to lower their guard and allow their clanmates to flank and ambush the herd and score multiple kills. However, this was only something that would work for a short time as after the first deception the herbivorous circuagodonts would become wise to this trick. There's also the fact that, as the carnivores become better adapted to a predatory lifestyle, their appearance will diverge further from the herbivores.
    • Early gravediggers often traveled alongside their intended prey for long periods of time, letting them become used to them; because they didn't act aggressively towards them, the animals they stalked simply never associated the slow, small, plodding creatures with danger and barely even acknowledged their presence. This allowed the gravediggers to memorize their habitual routes, and thus to dig their traps in locations where they knew they would pass over soon.
  • The Worm That Walks: Or rather, swims. The seas of the Ultimocene are home to the sea shoggoth, colonies of billion-stinger ants that live entirely independent from the land in floating nests made entirely out of their own bodies. Certain castes link themselves into paddles to propel and steer, masses of ants contracting like muscles. Food is caught via long, tentacle-like chains of ants extended from the main body, then cut up and distributed by another caste to individuals throughout. A colony acts much like an individual animal, even "mating" with other colonies by exchanging drones. By the time of the Late Ocean Age, they've entered an arrangement with the sea stewards in which they eat their refuse, such as the leftovers of bloat carcasses and the bodies of their dead, and in return the ants leave everyone else alone. However, it's noted that everyone involved is aware that this is a business arrangement, not friendship, and if their food payments aren't timely, everything else is back on the menu. Following the end of the sea steward civilization, the shoggoths start doing exactly that, hunting down the floating bloats.
  • Would Hurt a Child:
    • The seastrikers will deliberately kill the young of the porplet herds they attack so the adults will make more. It's even mentioned that they have a tendency to pass the calves around one another while they're still alive and writhing.
    • The warmonger daydreamers are introduced by one killing a baby fisher daydreamer, and both they and their pelagan cousins will cull their own children if born when there isn't any space for them.
    • The pelagans decide to protect themselves from extinction by killing off the young of the sea rex, their only rival in the open ocean, before they can grow big enough to threaten them. As a result, between the loss of their prey to the changing environment and their babies to the jaws of the daydreamers, they eventually go extinct.
  • Wouldn't Hurt a Child:
    • Babbling jays have a taboo against killing the chicks and fledglings of any altricial bird, intelligent or not. This however doesn't extend to the adult non-sapient birds they prey upon (somewhat like humans who recoil at the killing of veal calves but have no problem eating meat from adult cows).
    • The adult gravediggers become instinctively hostile towards any other adults of their species who trespass in their territories outside of breeding season, but they will tolerate the orange-coated adolescents who pass through as long as they don't stick around for too long.
    • The shallow-water daydreamers and the gravediggers have a naturally strong instinct to protect and nurture their offspring, as such, when warmonger children wander innocently into their territories to look for food, they do not harm them despite the initial animosity they had for their parents. The adult warmongers use this to their advantage by having their kids beg for food to feed their families.
  • Xenophobic Herbivore: The woodcrafters have a culture where casting off oppression is a large facet of their philosophy, including the oppression of their original place on the food chain, causing them to systemically kill or drive off their predators, first out of survival but later out of a sense of cruel arrogance. They also drive away any browsing herbivores that might damage the trees they rely on for food and shelter, with the main exception being the mammoth trunko, which they view with spiritual reverence. This ends up being deconstructed as their elimination of all predators, even those who didn't hunt woodcrafters, leads to a mass population boom for the pests of the woodcrafters' trees, and starvation for the woodcrafters as a result.
  • You Kill It, You Buy It: The daydreamers manage to eliminate their old foes, the predator burdles, but this means that they have to take over their role in balancing the ecosystem.
  • You No Take Candle: While Brighteye speaks in complex sentences, his nonsapient bluetail brethren speak in a far more simplistic way.
  • Zerg Rush:

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