History UsefulNotes / PrehistoricLifeOtherExtinctCreatures

[[/folder]]

'''The First Flyers''

Insects. The most abundant, diversified, biomechanically efficient, and last but not least, by far the most studied animals by modern fauna zoologists. Sadly, in paleontology this is not the same. Their fossil record is ''extremely'' poor, for understandable reasons: their tiny bodies aren't precisely the best-suited to turn into stone, and their terrestrial habitat doesn't help either - most fossil animals discovered so far were aquatic, just because water helps a lot in the process of fossilization. However, for what we do know about the ancient relatives of modern insects, we have to thank pines, firs, spruces and larches. Remember ''Film/JurassicPark'', and those fossilized mosquitoes in amber from which dinosaurian DNA was extracted? The DNA extraction thing is obviously fictional, but the amber thing itself is TruthInTelevision. Insects preserved in amber are perhaps the most marvelous fossils a paleontologist could wish for. Not only are they perfectly preserved in every detail, included external anatomy and ''even color'' (an ''extreme'' rarity among fossils), they even have their original tissues preserved, single cells included. And they can provide extraordinary clues to understanding the entire ecosystem in which they lived in indirect ways. Unfortunately, most insects fossilized in amber come from the Cenozoic era (the Mammal Age), a period by which insects were already similar to their modern relatives. We know little about their Mesozoic ancestors, still less about the Paleozoic ones - except for those living in the Carboniferous (such as the aforementioned ''Meganeura'') because many of them did preserve well in coal. Anyway, we know some things with a good degree of certainty. The first insects appeared in the Devonian[[note]]Technically these were the first hexapods, since springtails are no longer considered proper insects by modern entomologists; however, we follow the traditional view because it's more convenient.[[/note]], later than scorpions and millipedes: they were still wingless, like modern [[http://en.wikipedia.org/wiki/Springtail springtails]] and [[http://en.wikipedia.org/wiki/Silverfish silverfish]], but then the Carboniferous saw their success: the ''very first'' flying animals appeared, among them the now-extinct Palaeodictiopterans with ''six'' wings. In this period they reached large sizes - the four-winged ''[[UsefulNotes/StockDinosaursNonDinosaurs Meganeura]]'' had a wingspan of more than two feet - and started their radiations, which continue even today: not only dragonflies, but also cockroaches, grasshoppers and beetles appeared first in the Carboniferous. Other groups began their history in the Triassic: moths, wasps, flies and true bugs appeared at that time or a bit later, as well as parasitic kinds like fleas and lice. [[http://en.wikipedia.org/wiki/Insect_evolution Insect evolution]] has always been intertwined with that of terrestrial plants. It's worth noting, however, that this relationship has always been ''far more strict'' than one may think: biologists talk about a veritable co-evolution between insects and seed-producing plants, especially the flowering ones (angiosperms). This partnership reached its climax in the Cretaceous, when flowering plants became the new dominant group, just because of the relationship with two new kinds of insects that had just appeared: pollinators and social insects. These categories aren't clades, but describe behavior and have some overlap - pollinators include butterflies, moths, bees, wasps, flies, mosquitoes, and even some beetles, while social insects include ants, bees, wasps, and termites. Both began to affect their ecosystems dramatically, indirectly conditioning the evolution of ''all'' the other terrestrial animals, dinosaurs included. Many paleontologists think that if modern birds and placental mammals are the most diversified land vertebrates today, they have to thank the insect-plant mutualism which has created suitable habitats for their (initial) small size and varied diets. Think about those birds and bats who feed only upon nectar, anteaters and pangolins which feed upon nothing but social insects, or the countless insectivorous/"angiospermivorous" modern animals. And think about all the plant-related products we humans utilize today. Keep this in mind, every time you crush a bug.

[[/folder]]

[[folder:Molluscs & Other Invertebrates]]

No other animal group has had a greater importance in paleontology than molluscs. Their fossils are extremely abundant, to the point that many rocky formations are composed mostly of fossilized mollusc shells. Among molluscs cephalopods deserve a mention apart, being much more "evolved" than the others. Together with arthropods, cephalopods are the extinct invertebrates you're most likely to see in media - at least, documentary media; you'll [[SmallTaxonomyPools rarely see]] a trilobite, ammonite, sea scorpion or nautiloid in Fictionland. If it happens, they'll be simple "ambient critters", and good luck if the animal [[NoNameGiven is mentioned]]. There isn't much to say about the portrayal of extinct non-arthropod/non-cephalopod invertebrates in media: they [[SeldomSeenSpecies rarely appear]] even in books and documentaries, much less in Fictionland, and when they do, they are almost [[NoNameGiven never named]] (except sometimes for the names of each group, but only in popular science works). As an example, the original Disney's ''WesternAnimation/{{Fantasia}}'' showed several ''modern'' critters to symbolize the early evolution of invertebrates, but [[SmallTaxonomyPools few or no]] ''truly'' prehistoric ones. The ''Walking With'' series did the same: only modern jellyfish, sponges and sea urchins appear, all live-action. Indeed, many modern invertebrate groups have populated our seas since the Cambrian Period, but many others are extinct today. Among modern land arthropods expect to see dragonflies, scorpions, centipedes, spiders, cockroaches, beetles, and sometimes crickets. They will be oversized: [[BigCreepyCrawlies roaches the size of a rat, scorpions as big as cats]], and so on. Finally, let's not forget a staple in every Paleozoic or Mesozoic sea: a jellyfish, used as the symbol of the most ancient forms of life.

'''Early Tentacles:''' Extinct Octopuses and Squid

* Extinct cephalopods have given fuel to many legends, even before paleontology itself was "invented" by [[http:/en.wikipedia.org/wiki/Georges_Cuvier Georges Cuvier]] at the end of the 18th century. Before that, those strange things today called fossils were believed to be Nature's jokes, the Earth's flowers, or other things (only Creator/LeonardoDaVinci correctly recognized their nature, but his discovery was long ignored). And then there are more specific legends about cephalopod fossils. [[UsefulNotes/StockDinosaursNonDinosaurs Ammonites]] were believed to be stony horns ("ammonite" comes from Amun, an Ancient Egyptian deity who was often portrayed with rams' horns), or petrified snakes.[[note]]Some had fun sculpting snake heads on the shells' extremities to make them look like snakes![[/note]] The lesser-known [[UsefulNotes/StockDinosaursNonDinosaurs belemnites]] (technically belemnoids), with their straight pointed shape, were believed to be stony arrows, or even the Devil's fingers! Belemnites were cephalopods living in the Mesozoic era together with ammonites, and probably gave rise to squid. Like ammonites, only their shells are usually preserved. This shell was ''inside'' the animal's body and invisible in life; belemnites would resemble simple squid or cuttlefish if alive today. Their lifestyle was more active than ammonites, and they were probably able to do the same things modern squid do (spraying ink, swimming using the lateral "fins", catching prey with their suckers, seeing images with their eyes). True modern squid became widespread in the Cretaceous, and the first octopuses (''[[http://en.wikipedia.org/wiki/Proteroctopus Proteroctopus]]'' for example) were already around in the Middle Jurassic; these molluscs (called "coleoids") usually have no shell inside, or at least only a remnant of shell (ex. the famous cuttle-bone). Some Cretaceous squid were as large as a modern giant or colossal squid.

'''Finding Nemo:''' ''[[http://en.wikipedia.org/wiki/Orthoceras Orthoceras]]'' & the other "Nautiloids"

* Some fossil animals' names recall literary characters, rather than mythical things: nautiloids (literally "similar to the Nautilus") are named for the modern ''[[http://en.wikipedia.org/wiki/Nautilus Nautilus]]'', whose name (meaning "sailor" in Greek) incidentally recalls [[Creator/JulesVerne Nemo's submarine]] (we're talking about the human captain, NOT the cartoon fish!). Actually, nautiloids are an artificial assemblage of all cephalopods which were neither ammonoids (ammonites) nor coleoids (octopodes, squids, belemnites etc.). They include both the modern nautilus and the most ancient cephalopods, widespread in the Paleozoic. Their traits were probably like those of the nautilus: their shell was divided in sections which could be filled alternately with water or with air like in a submarine. This allowed them to regulate their buoyancy (ammonites had a similar inner-shell anatomy and probably did the same). As the nautilus' eyes are simple chambers lacking any lens and incapable of forming images, this was probably true for other nautiloids as well. They likely had dozen of sucker-less tentacles, and were probably slow swimmers. However, many Paleozoic nautiloids had straight conical shells, not curly like the nautilus; ''Orthoceras'' ("straight horn") is the classic example. Its shell even shows traces of its original colors. ''Rhizoceras'' ("root horn") had a slightly curved but still conical shell. ''Rayonnoceras'' was more similar to ''Orthoceras'', but was longer than a human and lived in the Carboniferous. The ''Walking With'' series has popularized another straight-shelled nautiloid, the Ordovician ''[[UsefulNotes/StockDinosaursNonDinosaurs Cameroceras]]'' (named the "giant orthocone"), chosen as the prototypical Paleozoic cephalopod only because it [[BiggerIsBetter was 10m long]] and the biggest known nautiloid so far (and one of the largest Paleozoic animals in general).

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'''Clams and pseudo-Clams:''' [[http://en.wikipedia.org/wiki/Rudist Rudists]] & prehistoric ''[[http://en.wikipedia.org/wiki/Lingula Lingula]]''

* Gastropods, scaphopods, bivalves, brachiopods, chitons, monoplacophorans: [[RiddleMeThis who's the intruder?]] All these invertebrate groups were "shellfish", and all but one were molluscs: the exception is the brachiopods. They were only distant mollusc relatives, and more closely related to the coral-like bryozoans (see "sessile invertebrates" below). As a whole, molluscs and brachiopods are extremely abundant in fossil records of all ages, from the early Paleozoic up to the modern era. However, while molluscs are still a dominant group in modern seas, brachiopods are nearly extinct today, and thus cited as "living fossils". The most representative is probably ''Lingula'' ("small tongue"), a clam-like, filter-feeding animal that lives anchored to the sea floor with a fleshy protrusion (the "tongue"); prehistoric ''Lingula'' have been identical to modern ones since the Early Ordovician! Among extinct non-cephalopod molluscs worthy of note are the Rudists like ''Hippurites''. Exclusively Cretaceous, these clams are notable both for their often great size (some were as tall as a human), and for their unique shape. They can be described as giant cups with a lid: the lower valve (the one attached to the sea bed) was conical and much bigger than the flat upper valve. Like ''Lingula'', rudists were probably almost motionless creatures that filter-fed on tiny organisms.

'''Geometrical Guys:''' [[http://en.wikipedia.org/wiki/Cystoid Cystoids]], [[http://en.wikipedia.org/wiki/Blastoid blastoids]] & [[http://en.wikipedia.org/wiki/Crinoid prehistoric crinoids]]

* Crinoids, echinoids, asteroids[[note]]NOT [[AsteroidThicket those]] asteroids![[/note]], ophiuroids, holoturoids, blastoids, cystoids, carpoids: [[RiddleMeThis who's the intruder?]] To some extent the carpoids (see the following paragraph); all the others are confirmed to have been echinoderms. The asteroids ("star-like") are the starfish; ophiuroids are nicknamed "brittle stars" or "serpentine stars"; the echinoids ("husk-like") are the sea urchins and sand-dollars; while the holoturioids are the sea cucumbers or trepang. Thanks to their hard "skeleton", all these groups (except for the soft-bodied sea cucumbers) are common fossils, and have roamed the seas since the start of the Paleozoic. However, we're going to talk more about three other less-familiar groups of echinoderms: crinoids, blastoids and cystoids. Crinoids ("sea lilies") are the only ones still living, but are today a rarer sight than the four groups above; like brachiopods, they are considered "living fossils". They're not-very-movable filter feeders, and like all echinoderms, they more resemble plants than animals: symmetrically rayed and with several "arms" that make them look like ferns or flowers (hence "sea lily"). Adult echinoderms lack eyes, limbs and heads (but have a mouth nonetheless) and they usually lack distinct right and left sides to their bodies - however, their tiny planktic larvae ''do have'' bilateral symmetry. The astonishing thing is, echinoderms are among the closest relatives of vertebrates, being Deuterostomes like us and not Protostomes (like most invertebrates). Blastoids and cystoids are known exclusively from fossils, and were similar to crinoids but without the "arms"; their lifestyle was probably similar to the sea lilies'. Also worthy of mention are the (also extinct) [[http://en.wikipedia.org/wiki/Edrioasteroid edrioasteroids]], which were perhaps similar to sand dollars or sea urchins.

'''Our Relatives?:''' [[http://en.wikipedia.org/wiki/Graptolite Graptolites]] & [[http://en.wikipedia.org/wiki/Homalozoa Calcichordates]]

* In Prehistory, some odd-looking invertebrates were even closer relatives to us vertebrates than echinoderms were: graptolites and calcichordates (or homalozoans). Graptolites are among the most common fossils in the Paleozoic, and used as index fossils as an alternative to trilobites. They resembled floating aquatic plants, but the "plant" was ''not'' the whole organism. They were colonial animals like modern corals, and the individuals were actually ''inside'' the colony. Like brachiopods and crinoids, graptolites were passive filter feeders. Calcichordates (remember, they are the carpoids above) have been variably classified as primitive echinoderms, relatives of the graptolites, or even true chordates (that is, the group including sea-squirts and their relatives + lancelets + vertebrates). Calcichordates lived at the bottom of the sea, were movable animals (and bilaterally symmetrical unlike a typical echinoderm), with armor and a sort of "tail".[[note]]Note that only chordates have tails - tail-like structures in invertebrates are ''never'' real tails; even the scorpion's is just the extremity of its abdomen, with the anus near the sting![[/note]] However, one of the most depicted calcichordates, ''[[http://en.wikipedia.org/wiki/Cothurnocystis Cothurnocystis elizae]]'', lost its bilateral symmetry altogether for unknown reasons.

'''Survival of the Toughest:''' [[http://en.wikipedia.org/wiki/Sessile_animal Prehistoric sessile invertebrates]]

* This is a merciless law even in palaeontology. With rare exception, only hard parts of organisms' bodies fossilize: bones, shells, armor, jaws, teeth, and whatnot. Many surviving invertebrate groups which don't have such tough elements have left little if any fossil record. For examples, most "worms" (annelids aka segmented worms, nematodes aka round worms, platyhelmintes aka flatworms, nemertheans aka ribbonworms, the microscopic rotifers aka "wheel-animals", the equally tiny tardigrades aka "water-bears", and many others) are virtually unknown in paleontology, and their evolution can only be guessed at. This is also true for coelenterates - that is, the cnidarians (jellyfish, sea anemones, hydrae, siphonophores) and the ctenophores (comb jellies). At least, the totally soft ones; fortunately, corals (which are also cnidarians) build tough external skeletons that fossilize well, and their extinct relatives are well-known from the start of the Paleozoic. The same is true of the unfamiliar bryozoans (moss animals), very similar to corals, but more closely related to the brachiopods. Finally, the enigmatic sponges (which many zoologists scarcely consider real animals) are also common fossils. They too have had an inner "skeleton" made of limestone (and sometimes glass-like silicon or a horny material, but these usually don't fossilize); one extinct group of possible sponge relatives were the [[http://en.wikipedia.org/wiki/Archaeocyatha archaeocyathans]], which became the planet's first reef-building animals in the Early Cambrian.

'''A Treasure in the Rocks:''' [[http://en.wikipedia.org/wiki/Foraminifera Foraminifers]], including [[http://en.wikipedia.org/wiki/Nummulite nummulites]]

* Foraminifers ("forams" for friends) are ''really'' a treasure in the rock, in all senses. They have helped confirm the deep impact theory of dinosaur extinction, their shells have contributed to the formation of sedimentary rocks around the world, and they are cool in their own right, with their immense variety of shapes. The biggest forams, the nummulites, look often like literal coins emerging from the rocks (''nummulus'' means "little coin" in Latin); they are used as index fossils for the Cenozoic era, and also created the material for the [[BuildLikeAnEgyptian Egyptian pyramids]]! But wait: what are actually the foraminifers? Originally, scientists thought they were molluscs or mollusc-like critters; today we know they weren't even true animals. They were protozoans, aka single-celled organisms with animal-like traits. Most other one-celled "animals" have left very little if any fossil material; the ancestors of ''Amoeba'', ''Paramecium'', ''Noctiluca'', ''Euglena'', ''Vorticella'', and so on are a mystery. Even the radiolarians: their shells are siliceous, and silicon usually dissolves before fossilising. However, the [[http://en.wikipedia.org/wiki/Tintinnid Tintinnids]] (little-known ciliates today) have left noteworthy remains of their "shells" in the fossil record.

!!Once Upon a Time... The Cambrian Animals

'''An Unbelievable Luck'''

* The Cambrian. The first period of the Paleozoic era, in which the famous [[http://en.wikipedia.org/wiki/Cambrian_explosion Cambrian explosion]] of life happened. The less famous fact is that we're ''unbelievably lucky'' to know anything about this remote event. At that time, animals just were starting to achieve hard parts in their bodies, and we already know that, usually, soft-bodied organisms don't fossilize at all. By astounding luck, one of the greatest exceptions to this rule are some deposits from the Cambrian period: it almost seems the natural world [[BecauseDestinySaysSo did this deliberately for us]]. The most famous and historically relevant is the [[http://en.wikipedia.org/wiki/Burgess_Shale Burgess Shale]] in British Columbia (first found in 1909 by Charles Walcott), but others are known (for example that of Chengjiang, China). For obvious reasons, our first question is: which were the first animals (not counting protozoans) that thrived in our oceans? Well, the answer isn't simple, but we can divide them into two groupings. One is made of those clades either still alive today or that went extinct several ages after the Cambrian: among the former, most non-arthropod/non-cephalopod invertebrate groups already mentioned; among the latter, the trilobites. We'll talk here about the second grouping: many Cambrian invertebrates were indeed ''exclusively of the Cambrian'' and didn't survive long, not even reaching the following period, the Ordovician - in which the most famous Paleozoic critters, sea scorpions, nautiloids, ostracoderms, etc. appeared. Thus, many of them are classically viewed as RealLife examples of OurMonstersAreWeird by paleo-fanatics. We still know very very little about their lifestyles, but their appearance is extraordinarily well-known, because these Cambrian deposits ''have preserved soft bodies''; not only that, they have preserved them very well! It would take too long to mention [[http://en.wikipedia.org/wiki/Fossils_of_the_Burgess_Shale all the members]] of the Cambrian fauna: see [[http://www.trilobites.info/triloclass.htm the image here]] to get an idea. The large guy in the center is immediately recognizable, by far the biggest creature in this fauna: ''[[UsefulNotes/StockDinosaursNonDinosaurs Anomalocaris]]''. Of course it is the most portrayed Cambrian animal in documentaries and illustrations, often called "[[SeaMonster the first sea monster to appear on Earth]]". Actually, if alive today, the "terrible" anomalocaridid would look vaguely like a lobster, 3 ft long, shell-less and pincer-less... nothing dangerous for a tough-boned, tough-muscled, tough-skinned mammal such as a human.

'''An Ancient Sea Zoo'''

* Apart from ''Anomalocaris'', the three probably most-portrayed Cambrian animals were very different from each other: ''[[http://en.wikipedia.org/wiki/Hallucigenia Hallucigenia]]'', ''[[http://en.wikipedia.org/wiki/Opabinia Opabinia]]'', and ''[[http://en.wikipedia.org/wiki/Pikaia Pikaia]]''. The first has a name that means "hallucination generator"; it was a sort of "worm" with long paired spikes on its back, of uncertain purpose, and long soft paired legs. The reconstruction of ''Hallucigenia'' was an astounding ScienceMarchesOn tangle for many years: it was first reconstructed ''upside-down'', with the dorsal spikes believed to be legs, and the legs pointing upwards and thought to each end with a small mouth! Its taxonomy is uncertain, but it's tentatively classified as a lobopod, a distant relative of arthropods. ''Opabinia'' was related to ''Anomalocaris'', but even weirder-looking; perhaps no other fossil animal more resembles a fictional space alien. It had ''five eyes'' placed in circular fashion on its head, and a pincer at the end of a long, flexible proboscis, often mistaken for the mouth, which was actually located behind the proboscis. When it was first described, many paleontologists didn't believed its describer was serious and openly laughed at it! But the most important find is the third guy, ''Pikaia'': despite its rather insignificant slug-like appearance, it is the most well-known vertebrate ancestor, a sort of prehistoric relative of our [[http://en.wikipedia.org/wiki/Lancelet lancelet]] (the closest extant relative of vertebrates). This relevance has made ''Pikaia'' one of the unofficial symbols of evolution, just like the ur-amphibian ''Ichthyostega'', the ur-bird ''Archaeopteryx'' and the ur-horse ''Eohippus''.

'''Missed Opportunity'''

* But wait... have you sees these critters on TV at least once? Unlikely, even if you watched ''Series/WalkingWithMonsters''. In this RuleOfCool-filled show, the ''only real'' Cambrian invertebrate to appear is... Guess what? Well, the superpredator ''Anomalocaris'' of course! The other two invertebrates that show up are... a modern jellyfish and an [[AnachronismStew anachronistical phacopid trilobite]] - remember that phacopids first evolved in the Ordovician, while Cambrian trilobites looked very different from the classic image we have when thinking about these animals. The absence of such awesome animals like ''Opabinia'' and ''Hallucigenia'' - and still others, like the multi-tentacled ''[[http://en.wikipedia.org/wiki/Wiwaxia Wiwaxia]]'', the trilobite-like ''[[http://en.wikipedia.org/wiki/Marrella Marrella]]'', the caterpillar-like ''[[http://en.wikipedia.org/wiki/Aysheaia Aysheaia]]'', the slug-like ''[[http://en.wikipedia.org/wiki/Amiskwia Amiskwia]]'', the shrimp-like ''[[http://en.wikipedia.org/wiki/Waptia Waptia]]'', the lobster-like ''[[http://en.wikipedia.org/wiki/Sidneyia Sidneyia]]'', the jellyfish-like ''[[http://en.wikipedia.org/wiki/Eldonia Eldonia]]'', the "hairy worm" ''[[http://en.wikipedia.org/wiki/Canadia_(annelid) Canadia]]'', etc. - is another egregious example of a [[TheyWastedAPerfectlyGoodPlot missed opportunity]]. Speaking of ''Pikaia'', this time its absence is less of a problem: the aforementioned proto-vertebrate ''Haikouichthys'' filled its role. And another thing: if you read the list of creatures from the Burgess Shale, you'll note almost all animals (the main exception being ''Anomalocaris'') have uncommonly short scientific names, most of them ending in '''-a'''. Rather amusing to read, and - let's face it - a ''true'' oasis of happiness among so many other unutterable, absurdly-difficult names.

[[/folder]]

[[folder:Plants]]

When thinking about fossils, we tend to think of animals. But plants have also left many remains, some of them just as spectacular as the animal ones (think about the [[http://en.wikipedia.org/wiki/Petrified_wood petrified woods]], the most famous being that in Arizona), and others less striking but even more significant, such as prints of leaves (very common in some deposits) and even fossilized ''pollen'' which has allowed us to understand not only the composition of ancient flora, but also the climate they lived in. And, naturally, the aforementioned [[Film/JurassicPark amber]] which has often caught insects inside.

'''A Floral Aroma in the Cretaceous:''' Prehistoric [[http://en.wikipedia.org/wiki/Magnolia magnolias]], [[http://en.wikipedia.org/wiki/Nymphaeaceae water lilies]] & [[http://en.wikipedia.org/wiki/Arecaceae true palms]]

* The most familiar plants today are the angiosperms aka flowering plants, including most modern trees, bushes, and herbs, but also seemingly non-flowering plants such as grass, palms, bamboos, and even some "seaweed" (like ''[[http://en.wikipedia.org/wiki/Posidonia_oceanica Posidonia]]''). But as a group, they appeared only in the Cretaceous, or at least, became widespread only in that period. In modern taxonomy the angiosperms are called magnoliophytes (literally "magnolia plants"). Indeed, the magnolia was one of the earliest flowering plants to ever appear, in the Lower Cretaceous. This is the most commonly shown angiosperm in paleo works, which often portray herbivorous dinosaurs like ''[[UsefulNotes/StockDinosaursTrueDinosaurs Iguanodon]]''s and ''[[UsefulNotes/StockDinosaursTrueDinosaurs Triceratops]]''es eating magnolia leaves[[note]]It was hypothesized that dinosaurs actually helped flowering plants to became more widespread[[/note]]. Among the other earliest angiosperms are water lilies. The first palm trees also appeared in the Cretaceous (but note that most Cretaceous palm-like trees were ''not'' palms, see further). However, most modern flowering greens - roses, apples, figs, oaks, etc. - appeared (or became a main component of the vegetation) only AFTER the dinosaurs' extinction. The angiosperms' success is tied to their relationship with pollinating animals, especially insects (see in the Arthropod section above), but also to those mammals/birds which still aid them in dispersing their seeds by eating their fruits, or by other means. However, some flowering plants returned again to traditional strategies, using the wind to disperse their pollen like the more archaic pines/firs do. Among them, ironically, are the most highly evolved and successful ones: the Poaceae, aka the grasses. See below.

'''Grasslands at last!:''' Prehistoric [[http://en.wikipedia.org/wiki/Poaceae grasses]]

* Early in the Age of Mammals, landscapes were already similar to those surrounding us today... except for one thing: grasslands were still totally missing. Prairies and savannah appeared only 30-20 million years ago in the middle of the Cenozoic. Grasses were already living in the Cretaceous, but they still didn't form grasslands, they grew isolated within the undergrowth. Grasslands have had a crucial role in Earth's ecosystems: all modern herbivorous mammals living in the modern African savannah (just to take one example) were able to evolve ''only'' thanks to grass. They developed special teeth to cope with this especially tough food, and thanks to the scarcity of trees, they were able to become bigger and faster. We humans have to be grateful to the grasses, too. All cereals and most fodder belong to this family of plants, as well as bamboo and sugar cane, as well, naturally, as the common grass of lawns. However, their importance has been even greater than what you might think: if the grasses didn't evolve million years ago... you would not be here to read this. Simply put, without grasslands, the human race still would be small-brained, hairy, chimp-like apes. (see [[UsefulNotes/PrehistoricLIfeMammals in the Mammal section]]).

'''Dinosaur Trees:''' Prehistoric [[http://en.wikipedia.org/wiki/Ginkgophyta ginkgos]]

* For the majority of the Age of Reptiles, however, most land plants had no flowers. Non-flowering plants belonged to two main groupings: those reproducing with seeds, and those reproducing with spores. The former are traditionally called "gymnosperms" ("naked seeds", due to the fact that their seeds aren't enclosed in fruits like flowering plants' are), but are actually several groups of plants not particularly closely related to each other. The most familiar gymnosperms are, obviously, the conifers (see below). In paleo-books, however, you'll often see mention of ''[[http://en.wikipedia.org/wiki/Ginkgo_biloba Ginkgo biloba]]''. This is, indeed, the ''only'' surviving member of a whole group of seed plants (the Ginkgophyta) that were among the dominant greens in the Mesozoic. Its special status results in the ginkgo often being cited as a ''living fossil''. However, it doesn't look like a pine or a fir: with its wide leaves and soft, fruit-like seeds, it resembles a typical flowering plant that you just never catch flowering. Indeed, ginkgophytes are probably the closest relatives of angiosperms. Even though the modern ginkgo is grown around the world as an ornamental tree, its wild ancestor lives only in East Asia.

'''A Resiny Aroma in the Jurassic:''' Prehistoric [[http://en.wikipedia.org/wiki/Pinaceae pines and firs]], [[http://en.wikipedia.org/wiki/Sequoioideae redwoods]], [[http://en.wikipedia.org/wiki/Yew yews]], [[http://en.wikipedia.org/wiki/Podocarp podocarps]] & [[http://en.wikipedia.org/wiki/Araucaria monkey puzzles]]

* Fictional media would typically have us believe the trees from the Mesozoic were all palm-shaped. If non-palmlike trees appear, they usually have the shape of an angiosperm. Pines, firs, spruces, larches, cypresses and cedars are usually unseen in Fictionland... possibly because are usually associated with ''cold'' in the writers' minds (while OneMillionBC is ''always'' a very hot world filled with volcanoes). In RealLife things were very different. Conifers were among the dominant plant groups for the whole Mesozoic, and a common food source for camarasaurs, camptosaurs, centrosaurs, cetiosaurs, chasmosaurs, corythosaurs, and so on. However, there weren't just pines and firs [[note]]or rather, their ancestors were adapted to a warmer climate than the modern ones are[[/note]] at the time: more common were some kinds of conifers which are rare or extinct today. For example, the araucarians (monkey puzzles), the podocarps, the yews, and the most spectacular of all, the sequoia[[note]]One sequoia was nicknamed "Mammoth Tree" for its size, but a mammoth would be a midget next to its green namesake![[/note]]. If you think sauropods were the real titans of the Jurassic, think again: a ''[[UsefulNotes/StockDinosaursTrueDinosaurs Giraffatitan]]'' near a redwood would look like a house cat next to a full-grown man.

'''Palms, but Not:''' [[http://en.wikipedia.org/wiki/Seed_fern Seed ferns]], [[http://en.wikipedia.org/wiki/Bennettitales pseudo-cycads]] & prehistoric [[http://en.wikipedia.org/wiki/Cycad cycads]]

* These are the Mesozoic seed plants that most resemble those seen in fictional portrayals of the Dinosaur Age. They ''did'' look like palm trees, but were ''not'' related to them at all. Cycads are the only ones still living, often used to embellish our cities. Bennettitales or cycadeoids ("pseudo-cycads") went extinct at the end of the Mesozoic. These two groups were very abundant in dinosaur times, but were already present before the Triassic (as well as the little-known [[http://en.wikipedia.org/wiki/Cordaitales Cordaitales]], which may have been the ancestors of the conifers). Pteridosperms ("seed ferns") are so-called because of their external appearance, but were not true ferns, which reproduce with spores. Seed ferns were among the very first seed plants that ever appeared, in the Devonian, and survived until the Cretaceous. They actually predate the evolution of seed-bearing organs (cones and flowers), instead bearing seeds on their fronds, like true ferns do with spores. One of them, the Triassic ''[[http://en.wikipedia.org/wiki/Glossopteris Glossopteris]]'', was widespread in the southern portion of the Pangaea supercontinent. This pteridosperm has been used to demonstrate the Pangaea hypothesis itself: its fossils have been found in every modern southern continent, showing landmasses were still united at the beginning of the Dinosaur Age (see also ''[[UsefulNotes/StockDinosaursNonDinosaurs Lystrosaurus]]'' and ''[[UsefulNotes/StockDinosaursNonDinosaurs Mesosaurus]]'' on other pages).

'''The Mesozoic Undergrowth:''' Prehistoric [[http://en.wikipedia.org/wiki/Fern ferns]] & [[http://en.wikipedia.org/wiki/Equisetum horsetails]]

* One of the worst errors in popular media (sometimes even documentary media) is to portray ''grasslands'' [[MisplacedVegetation in the Mesozoic]]. Arguably, writers think grass is the simplest kind of plant ever... thus, the first ever to appear on Earth. As seen above, grass are actually some of the ''most derived'' plants and among the latest to become widespread on our planet. In the Dinosaur Age, the dominant small land plants were much, much more primitive: ferns, their close relatives, and horsetails. These are collectively called pteridophytes, and their modern descendants still make up a wide portion of the undergrowth in many forests. In the Mesozoic, ferns and horsetails already made up much forest undergrowth, but also formed true prairies where trees were absent. Only in the Age of Mammals were fern prairies definitively replaced by grasslands. But don't think ferns and horsetails were always small: in Prehistoria there were also giant horsetails and tree ferns, both deceptively similar to trees. In some places, they still live today: the 10m tall ''[[http://en.wikipedia.org/wiki/Equisetum_giganteum Equisetum giganteum]]'' is found in tropical landscapes. And tree ferns are still present in Australia and New Zealand - to the point that in the latter country they have become a national symbol, just like the kiwi bird. Indeed, the LandDownUnder and its neighbor archipelago are a real mine of "living fossils", not limited to the platypus, the echidna, the kiwi, or the tuatara.

'''The Paleozoic Overgrowth:''' ''[[http://en.wikipedia.org/wiki/Lepidodendron Lepidodendron]]'' & ''[[http://en.wikipedia.org/wiki/Sigillaria Sigillaria]]''

* In some ways, Mesozoic vegetation wasn't so different from ours. True, most land plants in dinosaur times were pine-like, palm-like or fern-like, and flowering plants were still a minority... but conifer forests are still widespread today in northern territories. But if our time machine could bring us to the Carboniferous (aka the Coal Age, 100 million years before the Triassic), landscapes would ''really'' look like a sort of Otherworld. At the time, all the plant groups mentioned above were either a small portion of Earth's vegetation, or hadn't yet appeared. The dominant plants were the so-called lycopods - named after ''[[http://en.wikipedia.org/wiki/Lycopodium Lycopodium]]'' (lit. "wolf foot"), a tiny plant which is one of the few examples still surviving. Many of them would resemble extraterrestrial trees if alive today: ''Lepidodendron'' (lit. "scaly tree") and ''Sigillaria'' are two often-cited examples. Their trunks were indeed scaly, they sometimes had only ''two'' branches, and some grew up to 30 meters tall! Despite their massive aspect, they were quite fragile giants: giant lycopods were easily felled by the frequent Carboniferous storms. This was less a liability for them as a species than it would be for modern trees, because even giant lycopods grew rapidly, with a life cycle of no more than 10 or 15 years. The rotting logs then carbonized, becoming the fossil coal we burn today (hence "Carboniferous", meaning "coal-bearing"). It's worth noting that lycopods, ferns and horsetails have always been strictly tied with water; their spores can develop in adult individuals only in humid habitats, and this explains why they were so common in the Carboniferous swamp world. Then, in the following Permian period, the Earth mostly dried out, and giant lycopods weren't able to survive the change. Seed plants have become the more successful plant group since then: seeds are a bit like the reptiles' and insects' shelled eggs, well-adapted to survive in arid environments.

'''Paleo-Christmas Trees:''' ''[[https://en.wikipedia.org/wiki/Calamites Calamites]]''

* These conifer-looking trees were a common sight in the Paleozoic era from the late Devonian period up to the early Permian period, with the Carboniferous period being the peak of their diversity. Despite their looks, however, ''Calamites'' were actually distant relatives of modern horsetails, and thus, like with other early plants like it, were strictly tied to swampy environments. Their trunks were usually hollow and resemble modern bamboo with vertical growth lines from the base to the canopy, and each segment contained rows of branches with 25 needle-shaped leaves each. They were known to reproduce by directly cloning themselves from underground root structures called rhizomes, the only plant of its age to even do so, which allowed them to remain anchored to loose wet ground and spread rapidly. Their resemblance to Christmas trees lead to many paleontologists joking about if a time traveler were to spend the Christmas holidays in the Carboniferous, ''Calamites'' are the way to go.

'''The "First Tree":''' ''[[http://en.wikipedia.org/wiki/Archaeopteris Archaeopteris]]''

* Sometimes it seems paleontologists have fun making cryptic jokes with scientific names. While the traditional "first bird" is called ''[[UsefulNotes/StockDinosaursTrueDinosaurs Archaeopteryx]]'', one of the first land plants to ever appear is the almost-homonymous ''Archaeopteris''. But wait, ''Archaeopteryx'' means "ancient wing", ''Archaeopteris'' means "ancient fern". This plant lived in the Devonian (before the Carboniferous), just when the proto-amphibian ''Ichthyostega'' made the first step on dry land; it was one of the first terrestrial plants to develop to the size of a tree. Since at the time land animals were very few and mostly carnivorous or detritivorous, ''Archaeopteris'' and its relatives were able to spread worldwide, but never far from water, just like amphibians. Their appearence was like that of a tree fern: indeed, the fern's shape is considered one of the most primitive body plans among terrestrial plants. However, plants went on land ''before'' the amphibians. In the Silurian period (before the Devonian) there were already some aquatic plants (ex. the Psilophytes) emerging out of water; ''[[http://en.wikipedia.org/wiki/Cooksonia Cooksonia]]'' is an often-cited example. These tiny plants still kept their roots underwater, but their "branches" grew above the water's surface, capturing extra light. Terrestrial plants are actually very evolved organisms and have worked hard to develop adaptations for surviving outside the liquid element - among them, a vascular system (that is, tiny vessels for the flow of fluids), waterproof "skin", and fibers to make their stalks more robust against gravity.

'''Fungus Humongous:''' ''[[https://en.wikipedia.org/wiki/Prototaxites Prototaxites]]''

* This species was first described in 1843, and for the longest time experts couldn't decide ''what'' it was. Many thought it was a conifer tree (its name means "First yew"), others thought it was a giant aquatic alga. It wasn't until 2007 that scientists confirmed it was a [[FungusHumongous giant terrestrial fungus]]! Since this thing grew up to 8 meters, it would've been the tallest organism of its time. Many are still confused as to how such an organism could grow like that without photosynthesis.

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'''Plants?:''' Prehistoric [[http://en.wikipedia.org/wiki/Moss Mosses]], [[http://en.wikipedia.org/wiki/Alga Algae]], [[http://en.wikipedia.org/wiki/Fungus Fungi]] & [[http://en.wikipedia.org/wiki/Lichen Lichens]]

* These beings, important in the modern world, are poorly known in paleontology. Their "bodies" fossilize very rarely, but they have been major components of both water and land ecosystems since the Paleozoic. On a side note, only bryophytes (mosses, hornworts and liverworts) can correctly be called "plants". Algae is an informal group of not very closely-related clades, some of which (cyanobacteria or blue-green algae) aren't even plants in modern systematics. Neither are fungi (mushrooms, toadstools, molds and yeasts), which can't even perform photosynthesis - they are actually more closely related to animals than to plants! And lichens are not even true organisms: they are the result of a symbiotic relationship between a fungus and an alga. Diatoms, single-celled algae, have a shell made of silicon (like the protozoan radiolarians) but silicon usually doesn't fossilize in rocks.

[[/folder]]

[[folder:The Origin of Life]]

The creatures here are from the Precambrian, and lived/originated ''before'' the other organisms listed in all the other "Prehistoric Life" pages. Describing them is a difficult matter even for the most skilled biologists. Our minds have trouble imagining how the first living beings even looked, let alone how they lived. However, not everything is unknown to us.

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'''The Greatest Paleontological Mystery:''' [[http://en.wikipedia.org/wiki/Ediacara_biota The Ediacara creatures]]

* Prior to 1956, the general consensus was that complex life didn't really start appearing until the Cambrian explosion, but a landmark discovery in England that year proved just how wrong that was when the 560-million-year-old organism ''[[https://en.wikipedia.org/wiki/Charnia Charnia]]'' was found. Since then, a myriad of different creatures have been discovered from the so-called Ediacaran period that existed between the [[https://en.wikipedia.org/wiki/Cryogenian Cryogenian Glaciation]] and the Cambrian explosion. Many experts think they were [[OurMonstersAreWeird neither plants nor animals]], but something else entirely. Notable groups include the uniquely tri-radial [[https://en.wikipedia.org/wiki/Trilobozoa Trilobozoa]], the ribbed oval "bags" knows as [[https://en.wikipedia.org/wiki/Proarticulata Proarticulata]], the fern- or sea pen-like [[https://en.wikipedia.org/wiki/Rangeomorph Rangeomorpha]] of which ''Charnia'' was a member, and the, um... [[BuffySpeak "fleshy spiral"]] ''[[https://en.wikipedia.org/wiki/Eoandromeda Eoandromeda]]''. But despite all these Ediacaran Biota (often improperly called "Ediacaran Fauna") being wildly different in appearance, they do have things in common that define life from this era: they almost universally exhibit [[https://en.wikipedia.org/wiki/Glide_reflection glide reflection]] in their body plan, they appear completely unrelated to modern animals/plants/fungi as mentioned above, they almost completely disappeared at the end of the Ediacaran period, and they were arguably completely sessile, probably either filtering nutrients out of the water or "growing" on top of microbial mats on which they fed on through "roots". This unique aspect has caused the group to sometimes be referred to as "the Garden of Ediacara". More of what we would call traditional animals also started to appear toward the end of the period, such as the slug-esque ''[[https://en.wikipedia.org/wiki/Kimberella Kimberella]]'' (which might also have been one of the first creatures capable of locomotion), the arthropod/trilobite like ''[[https://en.wikipedia.org/wiki/Spriggina Spriggina]]'' and the Cnidarian/jellyfish relative known as ''[[https://en.wikipedia.org/wiki/Haootia Haootia]]'', which was rather similar to the modern freshwater [[https://en.wikipedia.org/wiki/Hydra_viridis Green Hydra]].

'''The First Earthlings:''' [[http://en.wikipedia.org/wiki/Stromatolite Prehistoric Stromatolites]] and other bacteria

* One-celled organisms are usually not preserved in fossil records (the aforementioned foraminifers are a well-known exception). However, we're certain that the first Earthicans were bacteria[[note]]For [[GeniusBonus expert readers]]: we're talking about bacteria in the broader sense, including the Archaea[[/note]]. They are the simplest forms of life, even lacking the nucleus which is the hallmark of the Eukarya - that is, animals + plants + fungi + algae + protozoans + other lesser-known organisms, ''all'' with nucleate cells. Some bacteria, the photosynthetic cyanobacteria (improperly called "green-blue algae"), have built strange rocky structures called stromatolites (they produce them still today); the most ancient stromatolites are from 2,000 million years ago, ''three times'' older than the first multi-celled organisms. They are among the most ancient forms of life that have left some fossils. It's worth noting that parasitic bacteria (those that carry diseases) could only have appeared ''after'' multi-celled organisms: otherwise [[FridgeLogic what could have they infected?]] The same is true of the non-living viruses[[note]]They are basically simple aggregates of proteins, lipids, and a bit of DNA or RNA capable of self-replication: if we consider them "living", then we'd do the same with the chromosomes inside our cells, which are also aggregates of DNA and proteins able to replicate themselves[[/note]]: they could have appeared only ''after'' true living things for the same reasons (some viruses infect bacteria, mind you). How life as a whole originated is one of the most fascinating fields within human knowledge, but here we're outside paleontology and science in general. It mostly remains a matter of speculation and philosophy, even though molecular biologists are undertaking great efforts to find the answer.

'''The RNA World'''

* [[https://en.wikipedia.org/wiki/RNA_world The RNA world]] is about as far as we can look back. The RNA world is a well-founded hypothesis - it has enough evidence to be generally believed, but insufficient to be considered proven. In the modern world, DNA codes genes. Genes are copied to messenger RNA. Messenger RNA is read by ribosomes to create proteins. Almost all the functions of the cell are performed by proteins, including duplicating DNA and copying DNA to RNA, and most of the ribosome is protein. This works great, but how could it have started? DNA can't replicate without proteins, and proteins can't be made without the instructions in DNA. However, RNA can both store information ''and'' catalyze reactions. Although it would be grossly inefficient by modern standards, life based on RNA with no DNA and no proteins is quite plausible. The RNA world hypothesis is that such RNA life existed, and is ancestral to modern life. Evidence for this is functional RNA (RNA which does stuff directly, rather than simply being instructions to ribosomes), which performs just a few cellular functions, but very critical ones. Most central is that RNA forms the reactive core of the ribosomes.

* The Cambrian. The first period of the Paleozoic era, in which the famous [[http://en.wikipedia.org/wiki/Cambrian_explosion Cambrian explosion]] of life happened. The less famous fact is that we're ''unbelievably lucky'' to know anything about this remote event. At that time, animals just were starting to achieve hard parts in their bodies, and we already know that, usually, soft-bodied organisms don't fossilize at all. By astounding luck, one of the greatest exceptions to this rule are some deposits from the Cambrian period: it almost seems the natural world [[BecauseDestinySaysSo did this deliberately for us]]. The most famous and historically relevant is the [[http://en.wikipedia.org/wiki/Burgess_Shale Burgess Shale]] in British Columbia (first found in 1909 by Charles Walcott), but others are known (for example that of Chengjiang, China). For obvious reasons, our first question is: which were the first animals (not counting protozoans) that thrived in our oceans? Well, the answer isn't simple, but we can divide them into two groupings. One is made of those clades either still alive today or that went extinct several ages after the Cambrian: among the former, most non-arthropod/non-cephalopod invertebrate groups already mentioned; among the latter, the trilobites. We'll talk here about the second grouping: many Cambrian invertebrates were indeed ''exclusively of the Cambrian'' and didn't survive long, not even reaching the following period, the Ordovician - in which the most famous Paleozoic critters, sea scorpions, nautiloids, ostracoderms, etc. appeared. Thus, many of them are classically viewed as RealLife examples of OurMonstersAreWeird by paleo-fanatics. We still know very very little about their lifestyles, but their appearance is extraordinarily well-known, because these Cambrian deposits ''have preserved soft bodies''; not only that, they have preserved them very well! It would take too long to mention [[http://en.wikipedia.org/wiki/Fossils_of_the_Burgess_Shale all the members]] of the Cambrian fauna: see [[http://www.trilobites.info/triloclass.htm the image here]] to get an idea. The large guy in the center is immediately recognizable, by far the biggest creature in this fauna: ''[[UsefulNotes/StockDinosaursNonDinosaurs Anomalocaris]]''. Of course it is the most portrayed Cambrian animal in documentaries and illustrations, often called "[[SeaMonster the first sea monster to appear on Earth]]". Actually, if alive today, the "terrible" anomalocaridid would look vaguely like a lobster, 3 ft long, shell-less and pincer-less... nothing dangerous for a tough-boned, tough-muscled, tough-skinned mammal such as a human.

----

* Apart from ''Anomalocaris'', the three probably most-portrayed Cambrian animal were very different from each other: ''[[http://en.wikipedia.org/wiki/Hallucigenia Hallucigenia]]'', ''[[http://en.wikipedia.org/wiki/Opabinia Opabinia]]'', and ''[[http://en.wikipedia.org/wiki/Pikaia Pikaia]]''. The first has a name that means "hallucination generator"; it was a sort of "worm" with long paired spikes on its back, of uncertain purpose, and long soft paired legs. The reconstruction of ''Hallucigenia'' was an astounding ScienceMarchesOn tangle for many years: it was first reconstructed ''upside-down'', with the dorsal spikes believed to be legs, and the legs pointing upwards and thought to each end with a small mouth! Its taxonomy is uncertain, but it's tentatively classified as a lobopod, a distant relative of arthropods. ''Opabinia'' was related to ''Anomalocaris'', but even weirder-looking; perhaps no other fossil animal more resembles a fictional space alien. It had ''five eyes'' placed in circular fashion on its head, and a pincer at the end of a long, flexible proboscis, often mistaken for the mouth, which was actually located behind the proboscis. When it was first described, many paleontologists didn't believed its describer was serious and openly laughed at it! But the most important find is the third guy, ''Pikaia'': despite its rather insignificant slug-like appearance, it is the most well-known vertebrate ancestor, a sort of prehistoric relative of our [[http://en.wikipedia.org/wiki/Lancelet lancelet]] (the closest extant relative of vertebrates). This relevance has made ''Pikaia'' one of the unofficial symbols of evolution, just like the ur-amphibian ''Ichthyostega'', the ur-bird ''Archaeopteryx'' and the ur-horse ''Eohippus''.

The Cambrian. The first period of the Paleozoic era, in which the famous [[http://en.wikipedia.org/wiki/Cambrian_explosion Cambrian explosion]] of life happened. The less famous fact is that we're ''unbelievably lucky'' to know anything about this remote event. At that time, animals just were starting to achieve hard parts in their bodies, and we already know that, usually, soft-bodied organisms don't fossilize at all. By astounding luck, one of the greatest exceptions to this rule are some deposits from the Cambrian period: it almost seems Ol'Mother Nature [[BecauseDestinySaysSo did this deliberately for us]]. The most famous and historically relevant is the [[http://en.wikipedia.org/wiki/Burgess_Shale Burgess Shale]] in British Columbia (first found in 1909 by Charles Walcott), but others are known (for example that of Chengjiang, China). For obvious reasons, our first question is: which were the first animals (not counting protozoans) that thrived in our oceans? Well, the answer isn't simple, but we can divide them into two groupings. One is made of those clades either still alive today or that went extinct several ages after the Cambrian: among the former, most non-arthropod/non-cephalopod invertebrate groups already mentioned; among the latter, the trilobites. We'll talk here about the second grouping: many Cambrian invertebrates were indeed ''exclusively of the Cambrian'' and didn't survive long, not even reaching the following period, the Ordovician - in which the most famous Paleozoic critters, sea scorpions, nautiloids, ostracoderms, etc. appeared. Thus, many of them are classically viewed as RealLife examples of OurMonstersAreWeird by paleo-fanatics. We still know very very little about their lifestyles, but their appearance is extraordinarily well-known, because these Cambrian deposits ''have preserved soft bodies''; not only that, they have preserved them very well! It would take too long to mention [[http://en.wikipedia.org/wiki/Fossils_of_the_Burgess_Shale all the members]] of the Cambrian fauna: see [[http://www.trilobites.info/triloclass.htm the image here]] to get an idea. The large guy in the center is immediately recognizable, by far the biggest creature in this fauna: ''[[UsefulNotes/StockDinosaursNonDinosaurs Anomalocaris]]''. Of course it is the most portrayed Cambrian animal in documentaries and illustrations, often called "[[SeaMonster the first sea monster to appear on Earth]]". Actually, if alive today, the "terrible" anomalocaridid would look vaguely like a lobster, 3 ft long, shell-less and pincer-less... nothing dangerous for a tough-boned, tough-muscled, tough-skinned mammal such as a human. Apart from ''Anomalocaris'' we can mention other three invertebrates which are stock in drawings: ''[[http://en.wikipedia.org/wiki/Hallucigenia Hallucigenia]]'', ''[[http://en.wikipedia.org/wiki/Opabinia Opabinia]]'', and ''[[http://en.wikipedia.org/wiki/Pikaia Pikaia]]''. The first has a name that means "hallucination generator"; it was a sort of "worm" with long paired spikes on its back, of uncertain purpose, and long soft paired legs. The reconstruction of ''Hallucigenia'' was an astounding ScienceMarchesOn tangle for many years: it was first reconstructed ''upside-down'', with the dorsal spikes believed to be legs, and the legs pointing upwards and thought to each end with a small mouth! Its taxonomy is uncertain, but it's tentatively classified as a lobopod, a distant relative of arthropods. ''Opabinia'' was related to ''Anomalocaris'', but even weirder-looking; perhaps no other fossil animal more resembles a fictional space alien. It had ''five eyes'' placed in circular fashion on its head, and a pincer at the end of a long, flexible proboscis, often mistaken for the mouth, which was actually located behind the proboscis. When it was first described, many paleontologists didn't believed its describer was serious and openly laughed at it! But the most important find is the third guy, ''Pikaia'': despite its rather insignificant slug-like appearance, it is the most well-known vertebrate ancestor, a sort of prehistoric relative of our [[http://en.wikipedia.org/wiki/Lancelet lancelet]] (the closest extant relative of vertebrates). This relevance has made ''Pikaia'' one of the unofficial symbols of evolution, just like the ur-amphibian ''Ichthyostega'', the ur-bird ''Archaeopteryx'' and the ur-horse ''Eohippus''. But wait... have you sees these critters on TV at least once? Unlikely, even if you watched ''Series/WalkingWithMonsters''. In this RuleOfCool-filled show, the ''only real'' Cambrian invertebrate to appear is... Guess what? Well, the superpredator ''Anomalocaris'' of course! The other two invertebrates that show up are... a modern jellyfish and an [[AnachronismStew anachronistical phacopid trilobite]] - remember that phacopids first evolved in the Ordovician, while Cambrian trilobites looked very different from the classic image we have when thinking about these animals. The absence of such awesome animals like ''Opabinia'' and ''Hallucigenia'' - and still others, like the multi-tentacled ''[[http://en.wikipedia.org/wiki/Wiwaxia Wiwaxia]]'', the trilobite-like ''[[http://en.wikipedia.org/wiki/Marrella Marrella]]'', the caterpillar-like ''[[http://en.wikipedia.org/wiki/Aysheaia Aysheaia]]'', the slug-like ''[[http://en.wikipedia.org/wiki/Amiskwia Amiskwia]]'', the shrimp-like ''[[http://en.wikipedia.org/wiki/Waptia Waptia]]'', the lobster-like ''[[http://en.wikipedia.org/wiki/Sidneyia Sidneyia]]'', the "hairy worm" ''[[http://en.wikipedia.org/wiki/Canadia_(annelid) Canadia]]'', etc. - is another egregious example of a [[TheyWastedAPerfectlyGoodPlot missed opportunity]]. Speaking of ''Pikaia'', this time its absence is less of a problem: the aforementioned proto-vertebrate ''Haikouichthys'' filled its role. And another thing: if you read the list of creatures from the Burgess Shale, you'll note almost all animals (the main exception being ''Anomalocaris'') have uncommonly short scientific names, most of them ending in '''-a'''. Rather amusing to read, and - let's face it - a ''true'' oasis of happiness among so many other unutterable, absurdly-difficult names.

[[/folder]]

[[folder:Plants]]

When thinking about fossils, we tend to think of animals. But plants have also left many remains, some of them just as spectacular as the animal ones (think about the [[http://en.wikipedia.org/wiki/Petrified_wood petrified woods]], the most famous being that in Arizona), and others less striking but even more significant, such as prints of leaves (very common in some deposits) and even fossilized ''pollen'' which has allowed us to understand not only the composition of ancient flora, but also the climate they lived in. And, naturally, the aforementioned [[Film/JurassicPark amber]] which has often caught insects inside.

'''A Floral Aroma in the Cretaceous:''' Prehistoric [[http://en.wikipedia.org/wiki/Magnolia magnolias]], [[http://en.wikipedia.org/wiki/Nymphaeaceae water lilies]] & [[http://en.wikipedia.org/wiki/Arecaceae true palms]]

* The most familiar plants today are the angiosperms aka flowering plants, including most modern trees, bushes, and herbs, but also seemingly non-flowering plants such as grass, palms, bamboos, and even some "seaweed" (like ''[[http://en.wikipedia.org/wiki/Posidonia_oceanica Posidonia]]''). But as a group, they appeared only in the Cretaceous, or at least, became widespread only in that period. In modern taxonomy the angiosperms are called magnoliophytes (literally "magnolia plants"). Indeed, the magnolia was one of the earliest flowering plants to ever appear, in the Lower Cretaceous. This is the most commonly shown angiosperm in paleo works, which often portray herbivorous dinosaurs like ''[[UsefulNotes/StockDinosaursTrueDinosaurs Iguanodon]]''s and ''[[UsefulNotes/StockDinosaursTrueDinosaurs Triceratops]]''es eating magnolia leaves[[note]]It was hypothesized that dinosaurs actually helped flowering plants to became more widespread[[/note]]. Among the other earliest angiosperms are water lilies. The first palm trees also appeared in the Cretaceous (but note that most Cretaceous palm-like trees were ''not'' palms, see further). However, most modern flowering greens - roses, apples, figs, oaks, etc. - appeared (or became a main component of the vegetation) only AFTER the dinosaurs' extinction. The angiosperms' success is tied to their relationship with pollinating animals, especially insects (see in the Arthropod section above), but also to those mammals/birds which still aid them in dispersing their seeds by eating their fruits, or by other means. However, some flowering plants returned again to traditional strategies, using the wind to disperse their pollen like the more archaic pines/firs do. Among them, ironically, are the most highly evolved and successful ones: the Poaceae, aka the grasses. See below.

'''Grasslands at last!:''' Prehistoric [[http://en.wikipedia.org/wiki/Poaceae grasses]]

* Early in the Age of Mammals, landscapes were already similar to those surrounding us today... except for one thing: grasslands were still totally missing. Prairies and savannah appeared only 30-20 million years ago in the middle of the Cenozoic. Grasses were already living in the Cretaceous, but they still didn't form grasslands, they grew isolated within the undergrowth. Grasslands have had a crucial role in Earth's ecosystems: all modern herbivorous mammals living in the modern African savannah (just to take one example) were able to evolve ''only'' thanks to grass. They developed special teeth to cope with this especially tough food, and thanks to the scarcity of trees, they were able to become bigger and faster. We humans have to be grateful to the grasses, too. All cereals and most fodder belong to this family of plants, as well as bamboo and sugar cane, as well, naturally, as the common grass of lawns. However, their importance has been even greater than what you might think: if the grasses didn't evolve million years ago... you would not be here to read this. Simply put, without grasslands, the human race still would be small-brained, hairy, chimp-like apes. (see [[UsefulNotes/PrehistoricLIfeMammals in the Mammal section]]).

'''Dinosaur Trees:''' Prehistoric [[http://en.wikipedia.org/wiki/Ginkgophyta ginkgos]]

* For the majority of the Age of Reptiles, however, most land plants had no flowers. Non-flowering plants belonged to two main groupings: those reproducing with seeds, and those reproducing with spores. The former are traditionally called "gymnosperms" ("naked seeds", due to the fact that their seeds aren't enclosed in fruits like flowering plants' are), but are actually several groups of plants not particularly closely related to each other. The most familiar gymnosperms are, obviously, the conifers (see below). In paleo-books, however, you'll often see mention of ''[[http://en.wikipedia.org/wiki/Ginkgo_biloba Ginkgo biloba]]''. This is, indeed, the ''only'' surviving member of a whole group of seed plants (the Ginkgophyta) that were among the dominant greens in the Mesozoic. Its special status results in the ginkgo often being cited as a ''living fossil''. However, it doesn't look like a pine or a fir: with its wide leaves and soft, fruit-like seeds, it resembles a typical flowering plant that you just never catch flowering. Indeed, ginkgophytes are probably the closest relatives of angiosperms. Even though the modern ginkgo is grown around the world as an ornamental tree, its wild ancestor lives only in East Asia.

'''A Resiny Aroma in the Jurassic:''' Prehistoric [[http://en.wikipedia.org/wiki/Pinaceae pines and firs]], [[http://en.wikipedia.org/wiki/Sequoioideae redwoods]], [[http://en.wikipedia.org/wiki/Yew yews]], [[http://en.wikipedia.org/wiki/Podocarp podocarps]] & [[http://en.wikipedia.org/wiki/Araucaria monkey puzzles]]

* Fictional media would typically have us believe the trees from the Mesozoic were all palm-shaped. If non-palmlike trees appear, they usually have the shape of an angiosperm. Pines, firs, spruces, larches, cypresses and cedars are usually unseen in Fictionland... possibly because are usually associated with ''cold'' in the writers' minds (while OneMillionBC is ''always'' a very hot world filled with volcanoes). In RealLife things were very different. Conifers were among the dominant plant groups for the whole Mesozoic, and a common food source for camarasaurs, camptosaurs, centrosaurs, cetiosaurs, chasmosaurs, corythosaurs, and so on. However, there weren't just pines and firs [[note]]or rather, their ancestors were adapted to a warmer climate than the modern ones are[[/note]] at the time: more common were some kinds of conifers which are rare or extinct today. For example, the araucarians (monkey puzzles), the podocarps, the yews, and the most spectacular of all, the sequoia[[note]]One sequoia was nicknamed "Mammoth Tree" for its size, but a mammoth would be a midget next to its green namesake![[/note]]. If you think sauropods were the real titans of the Jurassic, think again: a ''[[UsefulNotes/StockDinosaursTrueDinosaurs Giraffatitan]]'' near a redwood would look like a house cat next to a full-grown man.

'''Palms, but Not:''' [[http://en.wikipedia.org/wiki/Seed_fern Seed ferns]], [[http://en.wikipedia.org/wiki/Bennettitales pseudo-cycads]] & prehistoric [[http://en.wikipedia.org/wiki/Cycad cycads]]

* These are the Mesozoic seed plants that most resemble those seen in fictional portrayals of the Dinosaur Age. They ''did'' look like palm trees, but were ''not'' related to them at all. Cycads are the only ones still living, often used to embellish our cities. Bennettitales or cycadeoids ("pseudo-cycads") went extinct at the end of the Mesozoic. These two groups were very abundant in dinosaur times, but were already present before the Triassic (as well as the little-known [[http://en.wikipedia.org/wiki/Cordaitales Cordaitales]], which may have been the ancestors of the conifers). Pteridosperms ("seed ferns") are so-called because of their external appearance, but were not true ferns, which reproduce with spores. Seed ferns were among the very first seed plants that ever appeared, in the Devonian, and survived until the Cretaceous. They actually predate the evolution of seed-bearing organs (cones and flowers), instead bearing seeds on their fronds, like true ferns do with spores. One of them, the Triassic ''[[http://en.wikipedia.org/wiki/Glossopteris Glossopteris]]'', was widespread in the southern portion of the Pangaea supercontinent. This pteridosperm has been used to demonstrate the Pangaea hypothesis itself: its fossils have been found in every modern southern continent, showing landmasses were still united at the beginning of the Dinosaur Age (see also ''[[UsefulNotes/StockDinosaursNonDinosaurs Lystrosaurus]]'' and ''[[UsefulNotes/StockDinosaursNonDinosaurs Mesosaurus]]'' on other pages).

'''The Mesozoic Undergrowth:''' Prehistoric [[http://en.wikipedia.org/wiki/Fern ferns]] & [[http://en.wikipedia.org/wiki/Equisetum horsetails]]

* One of the worst errors in popular media (sometimes even documentary media) is to portray ''grasslands'' [[MisplacedVegetation in the Mesozoic]]. Arguably, writers think grass is the simplest kind of plant ever... thus, the first ever to appear on Earth. As seen above, grass are actually some of the ''most derived'' plants and among the latest to become widespread on our planet. In the Dinosaur Age, the dominant small land plants were much, much more primitive: ferns, their close relatives, and horsetails. These are collectively called pteridophytes, and their modern descendants still make up a wide portion of the undergrowth in many forests. In the Mesozoic, ferns and horsetails already made up much forest undergrowth, but also formed true prairies where trees were absent. Only in the Age of Mammals were fern prairies definitively replaced by grasslands. But don't think ferns and horsetails were always small: in Prehistoria there were also giant horsetails and tree ferns, both deceptively similar to trees. In some places, they still live today: the 10m tall ''[[http://en.wikipedia.org/wiki/Equisetum_giganteum Equisetum giganteum]]'' is found in tropical landscapes. And tree ferns are still present in Australia and New Zealand - to the point that in the latter country they have become a national symbol, just like the kiwi bird. Indeed, the LandDownUnder and its neighbor archipelago are a real mine of "living fossils", not limited to the platypus, the echidna, the kiwi, or the tuatara.

'''The Paleozoic Overgrowth:''' ''[[http://en.wikipedia.org/wiki/Lepidodendron Lepidodendron]]'' & ''[[http://en.wikipedia.org/wiki/Sigillaria Sigillaria]]''

* In some ways, Mesozoic vegetation wasn't so different from ours. True, most land plants in dinosaur times were pine-like, palm-like or fern-like, and flowering plants were still a minority... but conifer forests are still widespread today in northern territories. But if our time machine could bring us to the Carboniferous (aka the Coal Age, 100 million years before the Triassic), landscapes would ''really'' look like a sort of Otherworld. At the time, all the plant groups mentioned above were either a small portion of Earth's vegetation, or hadn't yet appeared. The dominant plants were the so-called lycopods - named after ''[[http://en.wikipedia.org/wiki/Lycopodium Lycopodium]]'' (lit. "wolf foot"), a tiny plant which is one of the few examples still surviving. Many of them would resemble extraterrestrial trees if alive today: ''Lepidodendron'' (lit. "scaly tree") and ''Sigillaria'' are two often-cited examples. Their trunks were indeed scaly, they sometimes had only ''two'' branches, and some grew up to 30 meters tall! Despite their massive aspect, they were quite fragile giants: giant lycopods were easily felled by the frequent Carboniferous storms. This was less a liability for them as a species than it would be for modern trees, because even giant lycopods grew rapidly, with a life cycle of no more than 10 or 15 years. The rotting logs then carbonized, becoming the fossil coal we burn today (hence "Carboniferous", meaning "coal-bearing"). It's worth noting that lycopods, ferns and horsetails have always been strictly tied with water; their spores can develop in adult individuals only in humid habitats, and this explains why they were so common in the Carboniferous swamp world. Then, in the following Permian period, the Earth mostly dried out, and giant lycopods weren't able to survive the change. Seed plants have become the more successful plant group since then: seeds are a bit like the reptiles' and insects' shelled eggs, well-adapted to survive in arid environments.

'''Paleo-Christmas Trees:''' ''[[https://en.wikipedia.org/wiki/Calamites Calamites]]''

* These conifer-looking trees were a common sight in the Paleozoic era from the late Devonian period up to the early Permian period, with the Carboniferous period being the peak of their diversity. Despite their looks, however, ''Calamites'' were actually distant relatives of modern horsetails, and thus, like with other early plants like it, were strictly tied to swampy environments. Their trunks were usually hollow and resemble modern bamboo with vertical growth lines from the base to the canopy, and each segment contained rows of branches with 25 needle-shaped leaves each. They were known to reproduce by directly cloning themselves from underground root structures called rhizomes, the only plant of its age to even do so, which allowed them to remain anchored to loose wet ground and spread rapidly. Their resemblance to Christmas trees lead to many paleontologists joking about if a time traveler were to spend the Christmas holidays in the Carboniferous, ''Calamites'' are the way to go.

'''The "First Tree":''' ''[[http://en.wikipedia.org/wiki/Archaeopteris Archaeopteris]]''

* Sometimes it seems paleontologists have fun making cryptic jokes with scientific names. While the traditional "first bird" is called ''[[UsefulNotes/StockDinosaursTrueDinosaurs Archaeopteryx]]'', one of the first land plants to ever appear is the almost-homonymous ''Archaeopteris''. But wait, ''Archaeopteryx'' means "ancient wing", ''Archaeopteris'' means "ancient fern". This plant lived in the Devonian (before the Carboniferous), just when the proto-amphibian ''Ichthyostega'' made the first step on dry land; it was one of the first terrestrial plants to develop to the size of a tree. Since at the time land animals were very few and mostly carnivorous or detritivorous, ''Archaeopteris'' and its relatives were able to spread worldwide, but never far from water, just like amphibians. Their appearence was like that of a tree fern: indeed, the fern's shape is considered one of the most primitive body plans among terrestrial plants. However, plants went on land ''before'' the amphibians. In the Silurian period (before the Devonian) there were already some aquatic plants (ex. the Psilophytes) emerging out of water; ''[[http://en.wikipedia.org/wiki/Cooksonia Cooksonia]]'' is an often-cited example. These tiny plants still kept their roots underwater, but their "branches" grew above the water's surface, capturing extra light. Terrestrial plants are actually very evolved organisms and have worked hard to develop adaptations for surviving outside the liquid element - among them, a vascular system (that is, tiny vessels for the flow of fluids), waterproof "skin", and fibers to make their stalks more robust against gravity.

The Cambrian. The first period of the Paleozoic era, in which the famous [[http://en.wikipedia.org/wiki/Cambrian_explosion Cambrian explosion]] of life happened. The less famous fact is that we're ''unbelievably lucky'' to know anything about this remote event. At that time, animals just were starting to achieve hard parts in their bodies, and we already know that, usually, soft-bodied organisms don't fossilize at all. By astounding luck, one of the greatest exceptions to this rule are some deposits from the Cambrian period: it almost seems Ol'Mother Nature [[BecauseDestinySaysSo did this deliberately for us]]. The most famous and historically relevant is the [[http://en.wikipedia.org/wiki/Burgess_Shale Burgess Shale]] in British Columbia (first found in 1909 by Charles Walcott), but others are known (for example that of Chengjiang, China). For obvious reasons, our first question is: which were the first animals (not counting protozoans) that thrived in our oceans? Well, the answer isn't simple, but we can divide them into two groupings. One is made of those clades either still alive today or that went extinct several ages after the Cambrian: among the former, most non-arthropod/non-cephalopod invertebrate groups already mentioned; among the latter, the trilobites. We'll talk here about the second grouping: many Cambrian invertebrates were indeed ''exclusively of the Cambrian'' and didn't survive long, not even reaching the following period, the Ordovician - in which the most famous Paleozoic critters, sea scorpions, nautiloids, ostracoderms, etc. appeared. Thus, many of them are classically viewed as RealLife examples of OurMonstersAreWeird by paleo-fanatics. We still know very very little about their lifestyles, but their appearance is extraordinarily well-known, because these Cambrian deposits ''have preserved soft bodies''; not only that, they have preserved them very well! It would take too long to mention [[http://en.wikipedia.org/wiki/Fossils_of_the_Burgess_Shale all the members]] of the Cambrian fauna: see [[http://www.trilobites.info/triloclass.htm the image here]] to get an idea. The large guy in the center is immediately recognizable, by far the biggest creature in this fauna: ''[[UsefulNotes/StockDinosaursNonDinosaurs Anomalocaris]]''. Of course it is the most portrayed Cambrian animal in documentaries and illustrations, often called "[[SeaMonster the first sea monster to appear on Earth]]". Actually, if alive today, the "terrible" anomalocaridid would look vaguely like a lobster, 3 ft long, shell-less and pincer-less... nothing dangerous for a tough-boned, tough-muscled, tough-skinned mammal such as a human. Apart from ''Anomalocaris'' we can mention other three invertebrates which are stock in drawings: ''[[http://en.wikipedia.org/wiki/Hallucigenia Hallucigenia]]'', ''[[http://en.wikipedia.org/wiki/Opabinia Opabinia]]'', and ''[[http://en.wikipedia.org/wiki/Pikaia Pikaia]]''. The first has a name that means "hallucination generator"; it was a sort of "worm" with long paired spikes on its back, of uncertain purpose, and long soft paired legs. The reconstruction of ''Hallucigenia'' was an astounding ScienceMarchesOn tangle for many years: it was first reconstructed ''upside-down'', with the dorsal spikes believed to be legs, and the legs pointing upwards and thought to each end with a small mouth! Its taxonomy is uncertain, but it's tentatively classified as a lobopod, a distant relative of arthropods. ''Opabinia'' was related to ''Anomalocaris'', but even weirder-looking; perhaps no other fossil animal more resembles a fictional space alien. It had ''five eyes'' placed in circular fashion on its head, and a pincer at the end of a long, flexible proboscis, often mistaken for the mouth, which was actually located behind the proboscis. When it was first described, many paleontologists didn't believed its describer was serious and openly laughed at it! But the most important find is the third guy, ''Pikaia'': despite its rather insignificant slug-like appearance, it is the most well-known vertebrate ancestor, a sort of prehistoric relative of our [[http://en.wikipedia.org/wiki/Lancelet lancelet]] (the closest extant relative of vertebrates). This relevance has made ''Pikaia'' one of the unofficial symbols of evolution, just like the ur-amphibian ''Ichthyostega'', the ur-bird ''Archaeopteryx'' and the ur-horse ''Eohippus''. But wait... have you sees these critters on TV at least once? Unlikely, even if you watched ''Series/WalkingWithMonsters''. In this RuleOfCool-filled show, the ''only real'' Cambrian invertebrate to appear is... Guess what? Well, the superpredator ''Anomalocaris'' of course! The other two invertebrates that show up are... a modern jellyfish and an [[AnachronismStew anachronistical phacopid trilobite]] - remember that phacopids first evolved in the Ordovician, while Cambrian trilobites looked very different from the classic image we have when thinking about these animals. The absence of such awesome animals like ''Opabinia'' and ''Hallucigenia'' - and still others, like the multi-tentacled ''[[http://en.wikipedia.org/wiki/Wiwaxia Wiwaxia]]'', the trilobite-like ''[[http://en.wikipedia.org/wiki/Marrella Marrella]]'', the caterpillar-like ''[[http://en.wikipedia.org/wiki/Aysheaia Aysheaia]]'', the shrimp-like ''[[http://en.wikipedia.org/wiki/Waptia Waptia]]'', the lobster-like ''[[http://en.wikipedia.org/wiki/Sidneyia Sidneyia]]'', the "hairy worm" ''[[http://en.wikipedia.org/wiki/Canadia_(annelid) Canadia]]'', etc. - is another egregious example of a [[TheyWastedAPerfectlyGoodPlot missed opportunity]]. Speaking of ''Pikaia'', this time its absence is less of a problem: the aforementioned proto-vertebrate ''Haikouichthys'' filled its role. And another thing: if you read the list of creatures from the Burgess Shale, you'll note almost all animals (the main exception being ''Anomalocaris'') have uncommonly short scientific names, most of them ending in '''-a'''. Rather amusing to read, and - let's face it - a ''true'' oasis of happiness among so many other unutterable, absurdly-difficult names.

* These beings, important in the modern world, are poorly known in paleontology. Their "bodies" fossilize very rarely, but they have been major components of both water and land ecosystems since the Paleozoic. On a side note, only bryophytes (mosses, hornworts and liverworts) can correctly be called "plants". Algae is an informal group of not very closely-related clades, some of which (cyanobacteria or blue-green algae) aren't even plants in modern systematics. Neither are fungi (mushrooms, toadstools, molds and yeasts), which can't even perform photosynthesis - they are actually more closely related to animals than to plants! And lichens are not even true organisms: they are the result of a symbiotic relationship between a fungus and an alga.

'''A Floral Aroma in the Cretaceous:''' Prehistoric [[http://en.wikipedia.org/wiki/Magnolia magnolias]], [[http://en.wikipedia.org/wiki/Nymphaeacaea water lilies]] & [[http://en.wikipedia.org/wiki/Arecaceae true palms]]

* These are the Mesozoic seed plants that most resemble those seen in fictional portrayals of the Dinosaur Age. They ''did'' look like palm trees, but were ''not'' related to them at all. Cycads are the only ones still living, often used to embellish our cities. Bennettitales or cycadeoids ("pseudo-cycads") went extinct at the end of the Mesozoic. These two groups were very abundant in dinosaur times, but were already present before the Triassic (as well as the little-known Cordaitales, which may have been the ancestors of the conifers). Pteridosperms ("seed ferns") are so-called because of their external appearance, but were not true ferns, which reproduce with spores. Seed ferns were among the very first seed plants that ever appeared, in the Devonian, and survived until the Cretaceous. They actually predate the evolution of seed-bearing organs (cones and flowers), instead bearing seeds on their fronds, like true ferns do with spores. One of them, the Triassic ''[[http://en.wikipedia.org/wiki/Glossopteris Glossopteris]]'', was widespread in the southern portion of the Pangaea supercontinent. This pteridosperm has been used to demonstrate the Pangaea hypothesis itself: its fossils have been found in every modern southern continent, showing landmasses were still united at the beginning of the Dinosaur Age (see also ''[[UsefulNotes/StockDinosaursNonDinosaurs Lystrosaurus]]'' and ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Mesosaurus]]'' on other pages).

* One of the worst errors in popular media (sometimes even documentary media) is to portray ''grasslands'' [[MisplacedVegetation in the Mesozoic]]. Arguably, writers think grass is the simplest kind of plant ever... thus, the first ever to appear on Earth. As seen above, grass are actually some of the ''most derived'' plants and among the latest to become widespread on our planet. In the Dinosaur Age, the dominant small land plants were much, much more primitive: ferns, their close relatives, and horsetails. These are collectively called pteridophytes, and their modern descendants still make up a wide portion of the undergrowth in many forests. In the Mesozoic, ferns and horsetails already made up much forest undergrowth, but also formed true prairies where trees were absent. Only in the Age of Mammals were fern prairies definitively replaced by grasslands. But don't think ferns and horsetails were always small: in Prehistoria there were also giant horsetails and tree ferns, both deceptively similar to trees. In some places, they still live today: the 10m tall ''[[http://en.wikipedia.org/wiki/Equisetum_giganteum Equisetum giganteum]]'' is found in tropical landscapes. And tree ferns are still present in Australia and New Zealand - to the point that in the latter country they have become a national symbol, just like the kiwi bird. Indeed, the LandDownUnder and its neighbor archipelago are a real mine of "living fossils", not limited to the platypus, the kiwi, or the tuatara.

* In some ways, Mesozoic vegetation wasn't so different from ours. True, most land plants in dinosaur times were pine-like, palm-like or fern-like, and flowering plants were still a minority... but conifer forests are still widespread today in northern territories. But if our time machine could bring us to the Carboniferous (aka the Coal Age, 100 million years before the Triassic), landscapes would ''really'' look like a sort of Otherworld. At the time, all the plant groups mentioned above were either a small portion of Earth's vegetation, or hadn't yet appeared. The dominant plants were the so-called lycopods - named after ''[[http://en.wikipedia.org/wiki/Lycopodium Lycopodium]]'' (lit. "wolf foot"), a tiny plant which is one of the few examples still surviving. Many of them would resemble extraterrestrial trees if alive today: ''Lepidodendron'' (lit. "scaly tree") and ''Sigillaria'' are two often-cited examples. Their trunks were indeed scaly, they sometimes had only ''two'' branches, and some grew up to 30 meters tall! Despite their massive aspect, they were quite fragile giants: giant lycopods were easily felled by the frequent Carboniferous storms. This was less a liability for them as a species than it would be for modern trees, because even giant lycopods grew rapidly, with a life cycle of no more than 10 or 15 years. The rotting logs then carbonized, becoming the fossil coal we burn today (hence "Carboniferous", meaning "coal-bearing"). It's worth noting that lycopods, ferns and horsetails have always been strictly tied with water; their spores can develop in adult individuals only in humid habitats, and this explains why they were so common in the Carboniferous swamp world. Then, in the following Permian period, the Earth mostly dried out, and giant lycopods weren't able to survive the change. Seed plants have become the more successful plant group since then: seeds are a bit like the reptiles' and insects' shelled eggs, well-adapted to survivie in arid environments.

* Foraminifers ("forams" for friends) are ''really'' a treasure in the rock, in all senses. They have helped confirm the deep impact theory of dinosaur extinction, their shells have contributed to the formation of sedimentary rocks around the world, and they are cool in their own right, with their immense variety of shapes. The biggest forams, the nummulites, look often like literal coins emerging from the rocks (''nummulus'' means "little coin" in Latin); they are used as index fossils for the Cenozoic era, and also created the material for the [[BuildLikeAnEgyptian Egyptian pyramids]]! But wait: what are actually the foraminifers? Originally, scientists thought they were molluscs or mollusc-like critters; today we know they weren't even true animals. They were protozoans, aka single-celled organisms with animal-like traits. Most other one-celled "animals" have left very little if any fossil material; the ancestors of ''Amoeba'', ''Paramecium'', ''Euglena'', ''Vorticella'', and so on are a mystery. Even the radiolarians: their shells are siliceous, and silicon usually dissolves before fossilising. However, the [[http://en.wikipedia.org/wiki/Tintinnid Tintinnids]] (little-known ciliates today) have left noteworthy remains of their "shells" in the fossil record.

The Cambrian. The first period of the Paleozoic era, in which the famous [[http://en.wikipedia.org/wiki/Cambrian_explosion Cambrian explosion]] of life happened. The less famous fact is that we're ''unbelievably lucky'' to know anything about this remote event. At that time, animals just were starting to achieve hard parts in their bodies, and we already know that, usually, soft-bodied organisms don't fossilize at all. By astounding luck, one of the greatest exceptions to this rule are some deposits from the Cambrian period: it almost seems Ol'Mother Nature [[BecauseDestinySaysSo did this deliberately for us]]. The most famous and historically relevant is the [[http://en.wikipedia.org/wiki/Burgess_Shale Burgess Shale]] in British Columbia (first found in 1909 by Charles Walcott), but others are known (for example that of Chengjiang, China). For obvious reasons, our first question is: which were the first animals (not counting protozoans) that thrived in our oceans? Well, the answer isn't simple, but we can divide them into two groupings. One is made of those clades either still alive today or that went extinct several ages after the Cambrian: among the former, most non-arthropod/non-cephalopod invertebrate groups already mentioned; among the latter, the trilobites. We'll talk here about the second grouping: many Cambrian invertebrates were indeed ''exclusively of the Cambrian'' and didn't survive long, not even reaching the following period, the Ordovician - in which the most famous Paleozoic critters, sea scorpions, nautiloids, ostracoderms, etc. appeared. Thus, many of them are classically viewed as RealLife examples of OurMonstersAreWeird by paleo-fanatics. We still know very very little about their lifestyles, but their appearance is extraordinarily well-known, because these Cambrian deposits ''have preserved soft bodies''; not only that, they have preserved them very well! It would take too long to mention [[http://en.wikipedia.org/wiki/Fossils_of_the_Burgess_Shale all the members]] of the Cambrian fauna: see [[http://www.trilobites.info/triloclass.htm the image here]] to get an idea. The large guy in the center is immediately recognizable, by far the biggest creature in this fauna: ''[[UsefulNotes/StockDinosaursNonDinosaurs Anomalocaris]]''. Of course it is the most portrayed Cambrian animal in documentaries and illustrations, often called "[[SeaMonster the first sea monster to appear on Earth]]". Actually, if alive today, the "terrible" anomalocaridid would look vaguely like a lobster, 3 ft long, shell-less and pincer-less... nothing dangerous for a tough-boned, tough-muscled, tough-skinned mammal such as a human. Apart from ''Anomalocaris'' we can mention other three invertebrates which are stock in drawings: ''[[http://en.wikipedia.org/wiki/Hallucigenia Hallucigenia]]'', ''[[http://en.wikipedia.org/wiki/Opabinia Opabinia]]'', and ''[[http://en.wikipedia.org/wiki/Pikaia Pikaia]]''. The first has a name that means "hallucination generator"; it was a sort of "worm" with long paired spikes on its back, of uncertain purpose, and long soft paired legs. The reconstruction of ''Hallucigenia'' was an astounding ScienceMarchesOn tangle for many years: it was first reconstructed ''upside-down'', with the dorsal spikes believed to be legs, and the legs pointing upwards and thought to each end with a small mouth! Its taxonomy is uncertain, but it's tentatively classified as a lobopod, a distant relative of arthropods. ''Opabinia'' was related to ''Anomalocaris'', but even weirder-looking; perhaps no other fossil animal more resembles a fictional space alien. It had ''five eyes'' placed in circular fashion on its head, and a pincer at the end of a long, flexible proboscis, often mistaken for the mouth, which was actually located behind the proboscis. When it was first described, many paleontologists didn't believed its describer was serious and openly laughed at it! But the most important find is the third guy, ''Pikaia'': despite its rather insignificant slug-like appearance, it is the most well-known vertebrate ancestor, a sort of prehistoric relative of our [[http://en.wikipedia.org/wiki/Lancelet lancelet]] (the closest extant relative of vertebrates). This relevance has made ''Pikaia'' one of the unofficial symbols of evolution, just like the ur-amphibian ''Ichthyostega'', the ur-bird ''Archaeopteryx'' and the ur-horse ''Eohippus''. But wait... have you sees these critters on TV at least once? Unlikely, even if you watched ''Series/WalkingWithMonsters''. In this RuleOfCool-filled show, the ''only real'' Cambrian invertebrate to appear is... Guess what? Well, the superpredator ''Anomalocaris'' of course! The other two invertebrates that show up are... a modern jellyfish and an [[AnachronismStew anachronistical phacopid trilobite]] - remember that phacopids first evolved in the Ordovician, while Cambrian trilobites looked very different from the classic image we have when thinking about these animals. The absence of such awesome animals like ''Opabinia'' and ''Hallucigenia'' - and still others, like the multi-tentacled ''[[http://en.wikipedia.org/wiki/Wiwaxia Wiwaxia]]'', the trilobite-like ''[[http://en.wikipedia.org/wiki/Marrella Marrella]]'', the caterpillar-like ''[[http://en.wikipedia.org/wiki/Aysheaia Aysheaia]]'', the lobster-like ''[[http://en.wikipedia.org/wiki/Sidneyia Sidneyia]]'', the "hairy worm" ''[[http://en.wikipedia.org/wiki/Canadia_(annelid) Canadia]]'', etc. - is another egregious example of a [[TheyWastedAPerfectlyGoodPlot missed opportunity]]. Speaking of ''Pikaia'', this time its absence is less of a problem: the aforementioned proto-vertebrate ''Haikouichthys'' filled its role. And another thing: if you read the list of creatures from the Burgess Shale, you'll note almost all animals (the main exception being ''Anomalocaris'') have uncommonly short scientific names, most of them ending in '''-a'''. Rather amusing to read, and - let's face it - a ''true'' oasis of happiness among so many other unutterable, absurdly-difficult names.

The Cambrian. The first period of the Paleozoic era, in which the famous [[http://en.wikipedia.org/wiki/Cambrian_explosion Cambrian explosion]] of life happened. The less famous fact is that we're ''unbelievably lucky'' to know anything about this remote event. At that time, animals just were starting to achieve hard parts in their bodies, and we already know that, usually, soft-bodied organisms don't fossilize at all. By astounding luck, one of the greatest exceptions to this rule are some deposits from the Cambrian period: it almost seems Ol'Mother Nature [[BecauseDestinySaysSo did this deliberately for us]]. The most famous and historically relevant is the [[http://en.wikipedia.org/wiki/Burgess_Shale Burgess Shale]] in British Columbia (first found in 1909 by Charles Walcott), but others are known (for example that of Chengjiang, China). For obvious reasons, our first question is: which were the first animals (not counting protozoans) that thrived in our oceans? Well, the answer isn't simple, but we can divide them into two groupings. One is made of those clades either still alive today or that went extinct several ages after the Cambrian: among the former, most non-arthropod/non-cephalopod invertebrate groups already mentioned; among the latter, the trilobites. We'll talk here about the second grouping: many Cambrian invertebrates were indeed ''exclusively of the Cambrian'' and didn't survive long, not even reaching the following period, the Ordovician - in which the most famous Paleozoic critters, sea scorpions, nautiloids, ostracoderms, etc. appeared. Thus, many of them are classically viewed as RealLife examples of OurMonstersAreWeird by paleo-fanatics. We still know very very little about their lifestyles, but their appearance is extraordinarily well-known, because these Cambrian deposits ''have preserved soft bodies''; not only that, they have preserved them very well! It would take too long to mention [[http://en.wikipedia.org/wiki/Fossils_of_the_Burgess_Shale all the members]] of the Cambrian fauna: see [[http://www.trilobites.info/triloclass.htm the image here]] to get an idea. The large guy in the center is immediately recognizable, by far the biggest creature in this fauna: ''[[UsefulNotes/StockDinosaursNonDinosaurs Anomalocaris]]''. Of course it is the most portrayed Cambrian animal in documentaries and illustrations, often called "[[SeaMonster the first sea monster to appear on Earth]]". Actually, if alive today, the "terrible" anomalocaridid would look vaguely like a lobster, 3 ft long, shell-less and pincer-less... nothing dangerous for a tough-boned, tough-muscled, tough-skinned mammal such as a human. Apart from ''Anomalocaris'' we can mention other three invertebrates which are stock in drawings: ''[[http://en.wikipedia.org/wiki/Hallucigenia Hallucigenia]]'', ''[[http://en.wikipedia.org/wiki/Opabinia Opabinia]]'', and ''[[http://en.wikipedia.org/wiki/Pikaia Pikaia]]''. The first has a name that means "hallucination generator"; it was a sort of "worm" with long paired spikes on its back, of uncertain purpose, and long soft paired legs. The reconstruction of ''Hallucigenia'' was an astounding ScienceMarchesOn tangle for many years: it was first reconstructed ''upside-down'', with the dorsal spikes believed to be legs, and the legs pointing upwards and thought to each end with a small mouth! Its taxonomy is uncertain, but it's tentatively classified as a lobopod, a distant relative of arthropods. ''Opabinia'' was related to ''Anomalocaris'', but even weirder-looking; perhaps no other fossil animal more resembles a fictional space alien. It had ''five eyes'' placed in circular fashion on its head, and a pincer at the end of a long, flexible proboscis, often mistaken for the mouth, which was actually located behind the proboscis. When it was first described, many paleontologists didn't believed its describer was serious and openly laughed at it! But the most important find is the third guy, ''Pikaia'': despite its rather insignificant slug-like appearance, it is the most well-known vertebrate ancestor, a sort of prehistoric relative of our [[http://en.wikipedia.org/wiki/Lancelet lancelet]] (the closest extant relative of vertebrates). This relevance has made ''Pikaia'' one of the unofficial symbols of evolution, just like the ur-amphibian ''Ichthyostega'', the ur-bird ''Archaeopteryx'' and the ur-horse ''Eohippus''. But wait... have you sees these critters on TV at least once? Unlikely, even if you watched ''Series/WalkingWithMonsters''. In this RuleOfCool-filled show, the ''only real'' Cambrian invertebrate to appear is... Guess what? Well, the superpredator ''Anomalocaris'' of course! The other two invertebrates that show up are... a modern jellyfish and an [[AnachronismStew anachronistical phacopid trilobite]] - remember that phacopids first evolved in the Ordovician, while Cambrian trilobites looked very different from the classic image we have when thinking about these animals. The absence of such awesome animals like ''Opabinia'' and ''Hallucigenia'' - and still others, like the multi-tentacled ''[[http://en.wikipedia.org/wiki/Wiwaxia Wiwaxia]]'', the trilobite-like ''[[http://en.wikipedia.org/wiki/Marrella Marrella]]'', the caterpillar-like ''[[http://en.wikipedia.org/wiki/Aysheaia Aysheaia]]'', the lobster-like ''[[http://en.wikipedia.org/wiki/Sidneyia Sidneyia]]'', the "hairy worm" ''[[http://en.wikipedia.org/wiki/Canadia Canadia]]'', etc. - is another egregious example of a [[TheyWastedAPerfectlyGoodPlot missed opportunity]]. Speaking of ''Pikaia'', this time its absence is less of a problem: the aforementioned proto-vertebrate ''Haikouichthys'' filled its role. And another thing: if you read the list of creatures from the Burgess Shale, you'll note almost all animals (the main exception being ''Anomalocaris'') have uncommonly short scientific names, most of them ending in '''-a'''. Rather amusing to read, and - let's face it - a ''true'' oasis of happiness among so many other unutterable, absurdly-difficult names.

* Foraminifers ("forams" for friends) are ''really'' a treasure in the rock, in all senses. They have helped confirm the deep impact theory of dinosaur extinction, their shells have contributed to the formation of sedimentary rocks around the world, and they are cool in their own right, with their immense variety of shapes. The biggest forams, the nummulites, look often like literal coins emerging from the rocks (''nummulus'' means "little coin" in Latin); they are used as index fossils for the Cenozoic era, and also created the material for the [[BuildLikeAnEgyptian Egyptian pyramids]]! But wait: what are actually the foraminifers? Originally, scientists thought they were molluscs or mollusc-like critters; today we know they weren't even true animals. They were protozoans, aka single-celled organisms with animal-like traits. Most other one-celled "animals" have left very little if any fossil material; the ancestors of ''Amoeba'', ''Paramecium'', ''Euglena'', ''Vorticella'', and so on are a mystery. Even the radiolarians: their shells are siliceous, and silicon usually dissolves before fossilising. However, the Tintinnids (little-known ciliates today) have left noteworthy remains of their "shells" in the fossil record.

* This is a merciless law even in palaeontology. With rare exception, only hard parts of organisms' bodies fossilize: bones, shells, armor, jaws, teeth, and whatnot. Many surviving invertebrate groups which don't have such tough elements have left little if any fossil record. For examples, most "worms" (annelids aka segmented worms, nematodes aka round worms, platyhelmintes aka flatworms, nemertheans aka ribbonworms, the microscopic rotiferans, the tardigrades, and many others) are virtually unknown in paleontology, and their evolution can only be guessed at. This is also true for coelenterates - that is, the cnidarians (jellyfish, sea anemones, hydrae, siphonophores) and the ctenophores (comb jellies). At least, the totally soft ones; fortunately, corals (which are also cnidarians) build tough external skeletons that fossilize well, and their extinct relatives are well-known from the start of the Paleozoic. The same is true of the unfamiliar bryozoans (moss animals), very similar to corals, but more closely related to the brachiopods. Finally, the enigmatic sponges (which many zoologists scarcely consider real animals) are also common fossils. They too have had an inner "skeleton" made of limestone (and sometimes glass-like silicon or a horny material, but these usually don't fossilize); one extinct group of possible sponge relatives were the [[http://en.wikipedia.org/wiki/Archaeocyatha archaeocyathans]], which became the planet's first reef-building animals in the Early Cambrian.

* In Prehistory, some odd-looking invertebrates were even closer relatives to us vertebrates than echinoderms were: graptolites and calcichordates (or homalozoans). Graptolites are among the most common fossils in the Paleozoic, and used as index fossils as an alternative to trilobites. They resembled floating aquatic plants, but the "plant" was ''not'' the whole organism. They were colonial animals like modern corals, and the individuals were actually ''inside'' the colony. Like brachiopods and crinoids, graptolites were passive filter feeders. Calcichordates (remember, they are the carpoids above) have been variably classified as primitive echinoderms, relatives of the graptolite, or even true chordates (that is, the group including sea-squirts and their relatives + lancelets + vertebrates). Calcichordates lived at the bottom of the sea, were movable animals (and bilaterally symmetrical unlike a typical echinoderm), with armor and a sort of "tail".[[note]]Note that only chordates have tails - tail-like structures in invertebrates are ''never'' real tails; even the scorpion's is just the extremity of its abdomen, with the anus near the sting![[/note]] However, one of the most depicted calcichordates, ''[[http://en.wikipedia.org/wiki/Cothurnocystis Cothurnocystis elizae]]'', lost its bilateral symmetry altogether for unknown reasons.

* This is a merciless law even in palaeontology. With rare exception, only hard parts of organisms' bodies fossilize: bones, shells, armor, jaws, teeth, and whatnot. Many surviving invertebrate groups which don't have such tough elements have left little if any fossil record. For examples, most "worms" (annelids aka segmented worms, nematodes aka round worms, platyhelmintes aka flatworms, nemertheans aka ribbonworms, and many others) are virtually unknown in paleontology, and their evolution can only be guessed at. This is also true for coelenterates - that is, the cnidarians (jellyfish, sea anemones, hydrae, siphonophores) and the ctenophores (comb jellies). At least, the totally soft ones; fortunately, corals (which are also cnidarians) build tough external skeletons that fossilize well, and their extinct relatives are well-known from the start of the Paleozoic. The same is true of the unfamiliar bryozoans (moss animals), very similar to corals, but more closely related to the brachiopods. Finally, the enigmatic sponges (which many zoologists scarcely consider real animals) are also common fossils. They too have had an inner "skeleton" made of limestone (and sometimes glass-like silicon or a horny material, but these usually don't fossilize); one extinct group of possible sponge relatives were the [[http://en.wikipedia.org/wiki/Archaeocyatha archaeocyathans]], which became the planet's first reef-building animals in the Early Cambrian.

* One-celled organisms are usually not preserved in fossil records (the aforementioned foraminifers are a well-known exception). However, we're certain that the first Earthicans were bacteria[[note]]For [[GeniusBonus expert readers]]: we're talking about bacteria in the broader sense, including the Archaea.[[/note]]. They are the simplest forms of life, even lacking the nucleus which is the hallmark of the Eukarya - that is, animals + plants + fungi + algae + protozoans + other lesser-known organisms, ''all'' with nucleate cells. Some bacteria, the photosynthetic cyanobacteria (improperly called "green-blue algae"), have built strange rocky structures called stromatolites (they produce them still today); the most ancient stromatolites are from 2,000 million years ago, ''three times'' older than the first multi-celled organisms. They are among the most ancient forms of life that have left some fossils. It's worth noting that parasitic bacteria (those that carry diseases) could only have appeared ''after'' multi-celled organisms: otherwise [[FridgeLogic what could have they infected?]] The same is true of the non-living viruses[[note]]They are basically simple aggregates of proteins, lipids, and a bit of DNA or RNA capable of self-replication: if we consider them "living", then we'd do the same with the chromosomes inside our cells, which are also aggregates of DNA and proteins able to replicate themselves.[[/note]]: they could have appeared only ''after'' true living things for the same reasons (some viruses infect bacteria, mind you). How life as a whole originated is one of the most fascinating fields within human knowledge, but here we're outside paleontology and science in general. It mostly remains a matter of speculation and philosophy, even though molecular biologists are undertaking great efforts to find the answer.

* This guy deserves his own section. ''Beelzebufo'' was an enormous relative of modern horned frogs that lived in Madagascar during the Cretaceous period, alongside the herbivorous crocodile ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Simosuchus]]''. It could grow up to sixteen inches in length, and weigh over nine pounds, making it larger than any modern frog, including the already gigantic goliath frog of Africa. It's also known as the "devil frog" (which is what its scientific name means). Given the eating habits of its modern relatives (which will devour mice) this amphibian could have easily eaten baby dinosaurs. With that said, it still would have lived in fear of large carnivorous dinosaurs such as ''[[UsefulNotes/PrehistoricLifeLargeTheropods Majungasaurus]]'' that also lived in the area.

* The only true amphibians in modern taxonomy, lissamphibians (frogs + salamanders + caecilians) appeared in the Triassic together with the first dinosaurs, but their deepest origins and their relationship with extinct amphibian groups are still unclear. The first frogs (''Triadobatrachus'', meaning "Triassic frog", is the most cited example) were already like modern ones, only with shorter hind legs less adapted for hopping. Frogs are possibly the most derived amphibians ever, with their complex social behaviours and the ability to produce loud vocal sounds (this ability is atypical for non-mammal/non-archosaur vertebrates). On the other hand, extinct salamanders retained the primitive crawling shape of earlier amphibians. In the curious case of ''[[http://en.wikipedia.org/wiki/Andrias_scheuchzeri Andrias scheuchzeri]]'' (a close relative of the modern Japanese Giant Salamander), the remains were initially believed to be ''a human who during the Biblical Great Deluge!'' ("Andrias" simply means "man" in Greek.) The legless worm-like caecilians are as little-known in paleontology as they are in RealLife. Their fossils are extremely rare, but they are believed to have had small limbs at the start of their evolution (ex. ''Eocaecilia'', "dawn caecilian").

Insects. The most abundant, diversified, biomechanically efficient, and last but not least, by far the most studied animals by modern fauna zoologists. Sadly, in paleontology this is not the same. Their fossil record is ''extremely'' poor, for understandable reasons: their tiny bodies aren't precisely the best-suited to turn into stone, and their terrestrial habitat doesn't help either - most fossil animals discovered so far were aquatic, just because water helps a lot in the process of fossilization. However, for what we do know about the ancient relatives of modern insects, we have to thank pines, firs, spruces and larches. Remember ''Film/JurassicPark'', and those fossilized mosquitoes in amber from which dinosaurian DNA was extracted? The DNA extraction thing is obviously fictional, but the amber thing itself is TruthInTelevision. Insects preserved in amber are perhaps the most marvelous fossils a paleontologist could wish for. Not only are they perfectly preserved in every detail, included external anatomy and ''even color'' (an ''extreme'' rarity among fossils), they even have their original tissues preserved, single cells included. And they can provide extraordinary clues to understanding the entire ecosystem in which they lived in indirect ways. Unfortunately, most insects fossilized in amber come from the Cenozoic era (the Mammal Age), a period by which insects were already similar to their modern relatives. We know little about their Mesozoic ancestors, still less about the Paleozoic ones - except for those living in the Carboniferous (such as the aforementioned ''Meganeura'') because many of them did preserve well in coal. Anyway, we know some things with a good degree of certainty. The first insects appeared in the Devonian[[note]]Technically these were the first hexapods, since springtails are no longer considered proper insects by modern entomologists; however, we follow the traditional view because it's more convenient.[[/note]], later than scorpions and millipedes: they were still wingless, like modern [[http://en.wikipedia.org/wiki/Springtail springtails]] and [[http://en.wikipedia.org/wiki/Silverfish silverfish]], but then the Carboniferous saw their success: the ''very first'' flying animals appeared, among them the now-extinct Palaeodictiopterans with ''six'' wings. In this period they reached large sizes - the four-winged ''[[UsefulNotes/StockDinosaursNonDinosaurs Meganeura]]'' had a wingspan of more than two feet - and started their radiations, which continue even today: not only dragonflies, but also cockroaches, grasshoppers and beetles appeared first in the Carboniferous. Other groups began their history in the Triassic: moths, wasps, flies and true bugs appeared at that time or a bit later, as well as parasitic kinds like fleas and lice. [[http://en.wikipedia.org/wiki/Insect_evolution Insect evolution]] has always been intertwined with that of terrestrial plants. It's worth noting, however, that this relationship has always been ''far more strict'' than one may think: biologists talk about a veritable co-evolution between insects and seed-producing plants, especially the flowering ones (angiosperms). This partnership reached its climax in the Cretaceous, when flowering plants became the new dominant group, just because of the relationship with two new kinds of insects that had just appeared: pollinators and social insects. These categories aren't clades, but describe behavior and have some overlap - pollinators include butterflies, bees, wasps, flies and even some beetles, while social insects include ants, bees, wasps, and termites. Both began to affect their ecosystems dramatically, indirectly conditioning the evolution of ''all'' the other terrestrial animals, dinosaurs included. Many paleontologists think that if modern birds and placental mammals are the most diversified land vertebrates today, they have to thank the insect-plant mutualism which has created suitable habitats for their (initial) small size and varied diets. Think about those birds and bats who feed only upon nectar, anteaters and pangolins which feed upon nothing but social insects, or the countless insectivorous/"angiospermivorous" modern animals. And think about all the plant-related products we humans utilize today. Keep this in mind, every time you crush a bug.

* The Devonian is rightly called "the Fish Age". Almost every main fish group was present in Devonian waters: lobe-finned fish, ray-finned fish, cartilaginous fish, acanthodians, and several jawless fish (see further). But the perhaps most typical Devonian fish group was another one entirely: the Placoderms. Their name means "skin with plates", and they're nicknamed "armored fish"; their scales were notably thick and broad and covered their forebody like true armor. However, this armor was still flexible and didn't form a "shell", making these fish more agile than their armored predecessors, ostracoderms; unlike the latter, they were active predators. There were two main placoderm groups: antiarchs and arthrodires. The former had bizarre pectoral fins more similar to crustacean legs than the fins of other fish, and lived near the bottom of the seas: ''Bothriolepis'' and ''Pterichthyodes'' are the best-known examples. The latter had strange scissor-like teeth for cutting meat, and probably lived in more open waters. Ex. ''Coccosteus'' and ''[[UsefulNotes/StockDinosaursNonDinosaurs Dunkleosteus]]''. Another interesting placoderm is ''Lunaspis'', with its crescent-shaped body. There is a curious thing about the evolutionary origin of jaws and teeth: the former arose from the first pair of ''gills'' of the earliest jawless fish, while teeth had the same origin as ''scales''. After all, modern sharks still have enamel-covered scales on their body, the same shape as their teeth (only smaller). [[note]]Reptilian and bird scales have nothing to do with fish scales: the latter are pieces of bone covered or not with enamel; reptilian ones are simple horny protrusion of the skin, like our nails.[[/note]] In a sense, you could even say teeth are the ''only'' fish scales we human still preserve.

'''Finding Nemo:''' ''[[http://en.wikipedia.org/wiki/Orthoceras Orthoceras]]'' and the other "Nautiloids"

'''Clams and pseudo-Clams:''' [[http://en.wikipedia.org/wiki/Rudist Rudists]] and prehistoric ''[[http://en.wikipedia.org/wiki/Lingula Lingula]]''

'''Geometrical Guys:''' [[http://en.wikipedia.org/wiki/Cystoid Cystoids]], [[http://en.wikipedia.org/wiki/Blastoid blastoids]], and [[http://en.wikipedia.org/wiki/Crinoid prehistoric crinoids]]

'''Our Relatives?:''' [[http://en.wikipedia.org/wiki/Graptolite Graptolites]] and [[http://en.wikipedia.org/wiki/Homalozoa Calcichordates]]

'''A Floral Aroma in the Cretaceous:''' Prehistoric [[http://en.wikipedia.org/wiki/Magnolia magnolias]], [[http://en.wikipedia.org/wiki/Nymphaeacaea water lilies]], and [[http://en.wikipedia.org/wiki/Arecaceae true palms]]

'''A Resiny Aroma in the Jurassic:''' Prehistoric [[http://en.wikipedia.org/wiki/Pinaceae pines and firs]], [[http://en.wikipedia.org/wiki/Sequoioideae redwoods]], [[http://en.wikipedia.org/wiki/Yew yews]], [[http://en.wikipedia.org/wiki/Podocarp podocarps]], and [[http://en.wikipedia.org/wiki/Araucaria monkey puzzles]]

'''Palms, but Not:''' [[http://en.wikipedia.org/wiki/Seed_fern Seed ferns]], [[http://en.wikipedia.org/wiki/Bennettitales pseudo-cycads]] and prehistoric [[http://en.wikipedia.org/wiki/Cycad cycads]]

'''The Mesozoic Undergrowth:''' Prehistoric [[http://en.wikipedia.org/wiki/Fern ferns]] and [[http://en.wikipedia.org/wiki/Equisetum horsetails]]

'''The Paleozoic Overgrowth:''' ''[[http://en.wikipedia.org/wiki/Lepidodendron Lepidodendron]]'' and ''[[http://en.wikipedia.org/wiki/Sigillaria Sigillaria]]''

'''Plants?:''' Prehistoric [[http://en.wikipedia.org/wiki/Moss Mosses]], [[http://en.wikipedia.org/wiki/Alga Algae]], [[http://en.wikipedia.org/wiki/Fungus Fungi]], and [[http://en.wikipedia.org/wiki/Lichen Lichens]]

'''Hopping, crawling, and slithering:''' ''[[http://en.wikipedia.org/wiki/Triadobatrachus Triadobatrachus]]'', ''[[http://en.wikipedia.org/wiki/Karaurus Karaurus]]'', and ''[[http://en.wikipedia.org/wiki/Eocaecilia Eocaecilia]]''

'''Boomerang-heads, eel-bodies, and whip-tails:''' ''[[http://en.wikipedia.org/wiki/Urocordylus Urocordylus]]'', ''[[http://en.wikipedia.org/wiki/Phlegetontia Phlegetontia]]'' and the other [[http://en.wikipedia.org/wiki/Lepospondyli Lepospondyls]]

'''Amphibians of the Paleozoic:''' ''[[https://en.wikipedia.org/wiki/Prionosuchus Prionosuchus]]'', ''[[http://en.wikipedia.org/wiki/Cacops Cacops]]'', ''[[http://en.wikipedia.org/wiki/Platyhystrix Platyhystrix]]'', and ''[[http://en.wikipedia.org/wiki/Crassigyrinus Crassigyrinus]]''

'''Amphibians of the Mesozoic:''' ''[[http://en.wikipedia.org/wiki/Trematosaurus Trematosaurus]]'', ''[[http://en.wikipedia.org/wiki/Gerrothorax Gerrothorax]]'', ''[[http://en.wikipedia.org/wiki/Metoposaurus Metoposaurus]]'', and ''[[http://en.wikipedia.org/wiki/Koolasuchus Koolasuchus]]''

'''Close to becoming Reptiles:''' ''[[http://en.wikipedia.org/wiki/Proterogyrinus Proterogyrinus]]'', ''[[http://en.wikipedia.org/wiki/Westlothiana Westlothiana]]'', and ''[[http://en.wikipedia.org/wiki/Diadectes Diadectes]]''

'''Fish with limblike Fins:''' ''[[http://en.wikipedia.org/wiki/Coelacanthus Coelacanthus]]'', ''[[http://en.wikipedia.org/wiki/Macropoma Macropoma]]'', ''[[http://en.wikipedia.org/wiki/Mawsonia Mawsonia]]'', ''[[http://en.wikipedia.org/wiki/Dipterus Dipterus]]'', and ''[[http://en.wikipedia.org/wiki/Ceratodus Ceratodus]]''

'''Fish that crawled onto Land:''' ''[[http://en.wikipedia.org/wiki/Osteolepis Osteolepis]]'', ''[[http://en.wikipedia.org/wiki/Holoptychius Holoptychius]]'', ''[[http://en.wikipedia.org/wiki/Panderichthys Panderichthys]]'', ''[[http://en.wikipedia.org/wiki/Tiktaalik Tiktaalik]]'', and ''[[http://en.wikipedia.org/wiki/Acanthostega Acanthostega]]''

'''The most common Fish Group today:''' ''[[http://en.wikipedia.org/wiki/Leedsichthys Leedsichthys]]'', ''[[http://en.wikipedia.org/wiki/Lepidotes Lepidotes]]'', ''[[http://en.wikipedia.org/wiki/Leptolepis Leptolepis]]'', ''[[http://en.wikipedia.org/wiki/Enchodus Enchodus]]'', and ''[[http://en.wikipedia.org/wiki/Knightia Knightia]]''

'''The first Fish with Fishbones:''' ''[[http://en.wikipedia.org/wiki/Palaeoniscum Palaeoniscum]]'' and ''[[http://en.wikipedia.org/wiki/Cheirolepis Cheirolepis]]''

'''Spiny Sharks?:''' ''[[http://en.wikipedia.org/wiki/Acanthodes Acanthodes]]'' and ''[[http://en.wikipedia.org/wiki/Climatius Climatius]]''

'''The earliest "sharks":''' ''[[http://en.wikipedia.org/wiki/Cladoselache Cladoselache]]'', ''[[http://en.wikipedia.org/wiki/Stethacanthus Stethacanthus]]'', ''[[http://en.wikipedia.org/wiki/Xenacanthus Xenacanthus]]'', and ''[[http://en.wikipedia.org/wiki/Helicoprion Helicoprion]]''

'''Shark Tales:''' ''[[http://en.wikipedia.org/wiki/Hybodus Hybodus]]'', ''[[http://en.wikipedia.org/wiki/Edestus Edestus]]'', ''[[http://en.wikipedia.org/wiki/Ptychodus Ptychodus]]'', ''[[http://en.wikipedia.org/wiki/Cretoxyrhina Cretoxyrhina]]'', and prehistoric rays

'''Tough Guys:''' ''[[http://en.wikipedia.org/wiki/Bothriolepis Bothriolepis]]'', ''[[http://en.wikipedia.org/wiki/Pterichthyodes Pterichthyodes]]'', ''[[http://en.wikipedia.org/wiki/Coccosteus Coccosteus]]'', ''[[http://en.wikipedia.org/wiki/Lunaspis Lunaspis]]'', and the other Placoderms

'''The Aspis Family:''' ''[[http://en.wikipedia.org/wiki/Hemicyclaspis Hemicyclaspis]]'', ''[[http://en.wikipedia.org/wiki/Arandaspis Arandaspis]]'', ''[[http://en.wikipedia.org/wiki/Astraspis Astraspis]]'', ''[[http://en.wikipedia.org/wiki/Drepanaspis Drepanaspis]]'', and the other "Ostracoderms"

'''Our Earliest Origins:''' ''[[http://en.wikipedia.org/wiki/Haikouichthys Haikouichthys]]'', ''[[http://en.wikipedia.org/wiki/Yunnanozoon Yunnanozoon]]'' and ''[[http://en.wikipedia.org/wiki/Myllokunmingia Myllokunmingia]]''

'''Crabs and pseudo-Crabs:''' Prehistoric [[http://en.wikipedia.org/wiki/Crustacea crustaceans]] and [[http://en.wikipedia.org/wiki/Xiphosura xiphosurans]]

'''Scorpions of the Sea?:''' ''[[http://en.wikipedia.org/wiki/Eurypterus Eurypterus]]'', ''[[http://en.wikipedia.org/wiki/Megarachne Megarachne]]'', and the other eurypterids

'''Out of Water at last!''' ''[[http://en.wikipedia.org/wiki/Palaeophonus Palaeophonus]]'', ''[[http://en.wikipedia.org/wiki/Arthrolycosa Arthrolycosa]]'', ''[[http://en.wikipedia.org/wiki/Euphoberia Euphoberia]]'', ''[[http://en.wikipedia.org/wiki/Rhyniella Rhyniella]]'', and other non-insect land arthropods

* Together, ray-finned fish and lobe-finned fish make up the traditional Osteichthyes, aka bony fish. Indeed, a bony skeleton was their main invention - all earlier fish groups had cartilaginous skeletons, while their bones were only ''outside'' their body in the form of scales and teeth. Bony fish (both lobefins and rayfins) appeared in the Paleozoic era, 200 million years before the first dinosaur.[[note]]Once, ichthyologists called the most primitive rayfins "Chondrostei" (including the modern sturgeon and paddlefish), and those in the middle between them and the Teleostei were called "Holostei": the only surviving "holosteans" are the gars (aka the Lepisosteids) and the bowfin (''Amia calva'').[[/note]] Among the earliest ray-finned fish, ''Palaeoniscum'' (traditionally called "Palaeoniscus") and the Devonian ''Cheirolepis'' ("hand scale") resembled a cross between a shark and a modern bony fish: mouth placed downwards and asymmetrical caudal fin like a shark's; fins, opercula, and smooth scales like a bony fish's. Curiously some extant archaic rayfins like the sturgeon still preserve this [[MixAndMatchCritter mixed look]]. Others, like ''Polypterus'' (bichir) of freshwater Africa, deceptively resemble lungfish in shape & habits.

'''Cone Teeth:''' the [[http://en.wikipedia.org/wiki/Conodont conodonts]]

* Finally, we could not forget the enigmatic conodonts. These tiny fossils similar to toothed jaws (conodont means "cone tooth") have been a real headache for scientists (invertebrates? early vertebrates? worms?). Today we know they belonged to early jawless fishes that lived during the whole Paleozoic, but their lifestyle is still uncertain; they may have been the ancestors of the lampreys.

'''Our Earliest Origins:''' ''[[http://en.wikipedia.org/wiki/Haikouichthys Haikouichthys]]'', ''[[http://en.wikipedia.org/wiki/Yunnanozoon Yunnanozoon]]'', ''[[http://en.wikipedia.org/wiki/Myllokunmingia Myllokunmingia]]'', and the [[http://en.wikipedia.org/wiki/Conodont conodonts]]

* However, ostracoderms were ''not'' the most primitive fish; they were already highly evolved animals, with complex brains, fins, and keen senses (''Cephalaspis'' seemingly even shows electric sensors!). Their anatomy is unusually well-known because the inner portion of their head shows imprints of the brain, nerves, inner ear, and other soft tissues.[[note]] Ostracoderms and the other jawless fish shared a curious anatomical trait: one single nostril on their head (all jawed vertebrates share two paired nasal openings like us humans).[[/note]] Actually ostracoderms descended from unarmored fish, among them the very first fish that appeared. Sadly, as soft tissues don't usually fossilize, they are virtually unknown to science. Three exceptions are ''Haikouichthys'' ("Haikou's fish"), ''Yunnanozoon'' ("Yunnan's animal": Yunnan is one of the southernmost province of China), and ''Myllokunmingia'' (Kunming is the capital city of Yunnan); all from the Cambrian period and found in China, they were similar to the famous invertebrate lancelet, or to the larval stage of the modern lamprey (the so-called ammocoetes). ''Haikouichthys'' was a tiny animal the size of a human nail, and was probably a harmless filter feeder. Incredibly, ''Series/WalkingWithMonsters'' managed to transform even this inconspicuous critter in a "terror": here, a shoal of ''Haikouichthys'' is seen feeding on the flesh of a wounded ''Anomalocaris'' like modern lampreys and hagfish would do. Actually, lampreys and hagfish (aka the cyclostomates) are highly evolved parasitic animals capable of feeding on large prey despite their [[LampreyMouth lacking of jaws]]; their evolution is very poorly known. Finally, we could not forget the enigmatic conodonts. These tiny fossils similar to toothed jaws (conodont means "cone tooth") have been a real headache for scientists (invertebrates? early vertebrates? worms?). Today we know they belonged to early jawless fishes that lived during the whole Paleozoic, but their lifestyle is still uncertain; they may have been the ancestors of the lampreys.

* What ''was'' this thing? Found in 1966, and very common in the Carboniferous Mazon Creek Beds of Illinois, it looked like nothing paleontologists had ever seen before. It had a jaw like a crab claw, the body plan of a cuttlefish, and two weird stalked lumps on both sides of its body. The only thing anyone could classify this as was as an invertebrate, probably some kind of worm. [[ScienceMarchesOn Until 2016]]. A study by Yale University revealed the Tully Monster's true identity, and it was the last one anyone expected. They noticed the remains of a primitive notochord in the creature, meaning it was a vertebrate, and the weird lumps turned out to be ''eyestalks''. Using these, and other parts of the fossil, they came to the conclusion that it was a jawless "fish", closely related to the lamprey.

'''The first Fish with Fishbones:''' ''[[http://en.wikipedia.org/wiki/Palaeoniscum Palaeoniscum]]'', ''[[http://en.wikipedia.org/wiki/Cheirolepis Cheirolepis]]'', ''[[http://en.wikipedia.org/wiki/Acanthodes Acanthodes]]'', and ''[[http://en.wikipedia.org/wiki/Climatius Climatius]]''

* Together, ray-finned fish and lobe-finned fish make up the traditional Osteichthyes, aka bony fish. Indeed, a bony skeleton was their main invention - all earlier fish groups had cartilaginous skeletons, while their bones were only ''outside'' their body in the form of scales and teeth. Bony fish (both lobefins and rayfins) appeared in the Paleozoic era, 200 million years before the first dinosaur.[[note]]Once, ichthyologists called the most primitive rayfins "Chondrostei" (including the modern sturgeon and paddlefish), and those in the middle between them and the Teleostei were called "Holostei": the only surviving "holosteans" are the gars (aka the Lepisosteids) and the bowfin (''Amia calva'').[[/note]] Among the earliest ray-finned fish, ''Palaeoniscum'' (traditionally called "Palaeoniscus") and the Devonian ''Cheirolepis'' ("hand scale") resembled a cross between a shark and a modern bony fish: mouth placed downwards and asymmetrical caudal fin like a shark's; fins, opercula, and smooth scales like a bony fish's. Curiously some extant archaic rayfins like the sturgeon still preserve this [[MixAndMatchCritter mixed look]]. In the Paleozoic there was also a unique fish group that went totally extinct before the Mesozoic: the acanthodians (so-called from their namesake ''Acanthodes'', "the spiny one"). They were externally similar to the earliest ray-finned fishes above, but with a cartilaginous inner skeleton like a shark. Their name means "spiky" from their spiny fins, and have been nicknamed "spiny sharks", but they were actually closer to bony fish than to sharks. Among the other acanthodians we can mention ''Climatius''. Together, sharks, acanthodians, bony fish and placoderms (see below) have one thing in common: jaws. See also "Tough Guys" below.

* What ''was'' this thing? Found in 1966, and very common in the Carboniferous Mazon Creek Beds of Illinois, it looked like nothing paleontologists had ever seen before. It had a jaw like a crab claw, the body plan of a cuttlefish, and two weird stalked lumps on both sides of its body. The only thing anyone could classify this as was as an invertebrate, probably some kind of worm.\\
[[ScienceMarchesOn Until 2016]].\\
A study by Yale University revealed the Tully Monster's true identity, and it was the last one anyone expected. They noticed the remains of a primitive notochord in the creature, meaning it was a vertebrate, and the weird lumps turned out to be ''eyestalks''. Using these, and other parts of the fossil, they came to the conclusion that it was a jawless "fish", closely related to the lamprey.

* "Fish" is a catch-all word containing all non-tetrapod vertebrates; that is, all backboned animals which are ''not only'' fully-aquatic, but descend from fully-aquatic ancestors as well. Ichthyosaurs, plesiosaurs, mosasaurs and dolphins aren't fish, just because they ''did'' descend from land-living creatures (except they are... in the same way birds are dinosaurs, but in this case even humans are fish!). There are only two groups of fish which are still successful today: sharks and ray-finned fish. Not so in Prehistory, as you'll understand soon.