As the colonists of Serina 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 in shape: 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.
- The pickbirds are close to oxpeckers and contrast the chimp aspects of their bluetail ancestors by being akin to bonobos in terms of being less violent and solving disputes through sex, while the Hothouse Age viridescent sawjaws they sometimes ally with now resemble dromaeosaurs whose formerly mostly useless third limbs have effectively become tails once again like their guppy ancestors.
- The monstrocorn, a nimicorn descendant, is akin to a rhino or ceratopsian.
- The crested kittyhawk's hunting technique of dancing around prey to tire it out before killing it brings to mind a stoat hunting rabbits, especially when it's the smallest species of kittyhawk.
- The platyporp acts like a platypus in terms of shape and feeding habits, being duck-billed bottom-feeders, but their tendency to build nests upon the water brings to mind grebes.
- Following the collapse of the previous oceanic ecosystem, the escardine snarks of the early Late Ultimocene take on the role and even shape of shoaling fish such as sardines and herring, a similar strategy to the fishlike sea slugs of the genus Phylliroe. (The main difference is their tail movement is vertical like a cetacean's rather than horizontal as in fish and ichthyosaurs) They themselves are hunted by the calacarna snarks that have taken on the role of sharks combined with squid that communicate through bioluminescence. Another group, the shimmershiners, have become akin to giant manta rays as massive filter feeders with five-meter long flipper wings.
- The hoglump is a sealump descendant that has taken on the role of a boar, having evolved hardened bony knobs on their facial flanges and a blunt keratinized claw on their trunk in order to better root around in the dirt for both tubers and worms.
- The murds are burdles that share a combined niche of monkey and seed-eating parrot, being arboreal frugivores.
- The royal villaingull takes the role of a frigatebird, mobbing tribbets and other smaller seabirds for their food.
- The battering helmethead, a thorngrazer species native to the uplands, takes the role of a mountain goat, being small herbivores who climb cliffs and headbutt one another in dominance clashes.
- The chatterchasers, cursorial descendants of the chatteravens native to the uplands, take the general shape and niche of a seriema.
- The slayer carnackle is fairly analogous to the Carnotaurus, being a cursorial bipedal predator with horns above its eyes, a blunt snout, and kills by using its head like an axe.
- The cookiecutter kittyhawk has elements of a leopard, being an ambush predator who stashes their kills in trees.
- The soggobbler is a dead-ringer for the Nigersaurus, being a 30 ft long sauropod-like animal with a duck bill that feeds on low-lying swamp plants,
- The springheel is a grassland hunter with tufted ears and catches birds by leaping into the air like a caracal.
- The sanguine squibis is a species of scrounger that is essentially the Serinan version of an ibis combined with a flamingo, being long-legged wading birds that eat via filter-feeding.
- The heffalump is similar to elephants in both social structure (except with the presence of males) and in physical appearance, with a grasping trunk, facial flanges that look like tusks and upper flanges that look like ears and also used as heat sinks.
- Skueasels are skuorcs filling the same niche as weasels, while lutrine skueasels are analogous to otters.
- The rivercarver is a murd that's become analogous to beavers, being a monogamous semi-aquatic ecosystem engineer that actively creates the waterways it thrives in, which has a dramatic impact on the surrounding environment.
- The tribbybara is a molodont that has convergently evolved the same niche and body plan as the capybara, being a semi-aquatic, mostly docile grazer.
- The bogbeast is a scrounger that is described as having converged upon the niche of a bear, being a large omnivore that eats plants but is more than willing to hunt for protein when necessary.
- The megamurds of the Thorn Atoll have converged upon the giant Galapagos tortoises living on the more arid islands, as the sole food for the turtle-like burdles is cactaiga.
- The sniper whelican is Serina's answer to the archerfish, being an aquatic species that shoots down prey from trees using jets of water.
- The snail-eating skewer is essentially Serina's answer to the snail kite, being a snail-eating specialist that hunts its prey with the help of its specially-evolved beak.
- The whiskerwhales are skuorcs that have convergently evolved to a dolphin's body plan like the dolfinches have.
- The black snipper is a whiskerwhale that evolved jaws similar to a cookie-cutter shark to take small, non-fatal bites out of prey.
- The arctic snagglejaw is essentially the Late Hothouse's answer to a mix of polar and grizzly bear, being an apex predator of the polar basin, but its relation to the latter becomes especially clear when you see the latter will partake in mass consumption of waterhorses in Serina's version of a salmon run.
- The corocotta is a unicorn that acts as Serina's answer to African wild dogs, being pack-based hunters with a complex whistle-based language.
- The mollyminnows domesticated by the farmackle are guppies that have converged upon the same niche as koi carp, being raised for both food and ornamental purposes.
- The scarreots are primarily herbivorous flickbills that have converged on the role of parrots like the murds.
- The grandiose kawku, the largest of the scarreots, partially resembles a macaw and is also a large seedeating bird.
- The molrus is a molodont that has converged on the role of a walrus, being a tusked aquatic animal that primarily feeds on shellfish.
- The lacer, a fully aquatic descendant of the cookiecutter kittyhawk, has converged upon the niche of a leopard seal, being an aggressive aquatic hunter.
