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== Amphibians ==
In paleontology, the word "Amphibian" has traditionally had a much broader meaning than that commonly attributed. Amphibians have been all [
Lissamphibians excluded, prehistoric amphibians are traditionally called "labyrinthodonts" or "stegocephalians", but these terms shouldn't be used today, just like "thecodonts" for basal Archosaurs or "pelycosaurs" for basal Synapsids. This because they don't indicate any natural grouping of animals, but are instead catch-all words with little scientific significance [[Science Marches On|in modern phylogenetic systematics]]. Labyrinthodonts means "labyrinth teeth", because many of these animals had convoluted, labyrinth-like internal patterns inside their teeth, but this doesn't interest us too much. Their importance was much, much greater than this and lies upon another aspect. They were, simply, the links between fish and truly terrestrial vertebrates, a keystone group for mankind's evolution. And yet, just like mammal-like "reptiles" and mesozoic mammals, they have not gained much attention in pop-culture (it seems ''only apes and monkeys'' [[Small Reference Pools|were our ancestors]] in pop-consciousness...). Their [[Did Not Do the Research|apparently]] monotonous, uninteresting appearence may have contributed to this, or rather... just [[What Measure Is a Non-Human?|our mammalian pride]] generates a sort of "denial" towards our deep origins? Anyway, basal tetrapods ''weren't'' boring, uninteresting things: anything but. They were ''very'' diversified in shape, size and ecology; as we’ll se soon.
Hopping, crawling, and digging: ''[
* Lissamphibians have a rather mysterious story. Again, like lizards, snakes, birds, rodents and bats, their skeleton is way too fragile to fossilize well, and the reconstruction of their story has many holes within it. Anyway, we're pretty sure that, [[Sarcasm Mode|surprisingly]], both frogs and salamanders originated in the Triassic period. Yes, they too did it. And they already resembled our modern froggies/salamanders (except some details). ''Triadobatrachus'' is often mentioned as "the first frog", lived in Triassic and was very frog-like except for having shorter hindlimbs, and it wasn't probably capable to leap yet. But Jurassic frogs were already virtually identical to ours. While salamanders haven't changed much from their apparition in the Triassic, with animals like ''Karaurus'' being already proper salamanders in every detail. Among prehistoric salamanders is also worth to be cited ''Andrias scheuchzeri'', a very close relative of modern Giant Japanese Salamander (the largest modern lissamphibian); it has been one of the very first fossil animals ever described, in year 1726, when paleontology ''still'' didn't even exist yet as scientific field; because of its size (and scientific ignorance of those years), its human-sized skeleton was interpreted as belonging to a human dead during the Biblical Deluge! (please note ''Andrias'' [[Exactly What It Says On the Tin|just means man]] in Greek). Caecilians have the scantier fossil record among all lissamphibians: we don't even know when they appeared. But we're pretty sure the earliest ones still had limbs, just like snakes' ancestors.
Boomerang-heads, eel-bodies, and whip-tails: ''[
* As a whole, non-lissamphibian amphibians first appeared in the [
When amphibians were like crocs 1: ''[
* Protoamphibians managed to flourish in the successive two periods as well, Permian and Triassic, conviving well with the rapidly-evolving reptiles and mammal-ancestors. However, In Early Permian Earth became more and more arid, with the disappearing of many ancient swamps. The water-loving lepospondylans underwent a serious chrisis, while other paleo-amphibian groups more adapted to a terrestrial lifestyle become widespread and diversfied. The most successful Permian / Triassic amphibians were the Temnospondyls. These are also the most commonly-portrayed paleo-amphibians in media, because they include some of [[Rule of Cool|the biggest and most spectacular kinds.]] The definitively most-depicted has always been ''Eryops''. 10 ft long, it was similar to a shortened, armor-less alligator, with plump body, splayed limbs, short tail unapt to swim, and a wide, flat head with eyes and nostrils on the top and a very gatorish snout. Compared with crocodilians, ''Eryops'' had more teeth, more pointed but also more fragile; it could have been an ambush-predator of fish or smaller amphibians catched in water. When on land, the eryops could have become prey of the super-predator of its time, the famous ''Dimetrodon''. The fact ''Eryops'' lived with the latter may explain its status as the archetypical "giant amphibian". Even though "Giant amphibian" is the term usually utilized in pop-media when referring to it or to other Temnospondyls, many members of the group were really giants: for example, ''Cacops'' was dog-sized. Also Early Permian, this one was much more terrestrial than ''Eryops'', with stronger limbs and lateral eyes. This, along with a small armor over its back, makes ''Cacops'' deceptively reptile-looking; actually, reptiles descended from another totally different group of “amphibians” (see later). A close relative of ''Cacops'' was even more reptilian-looking: ''Platyhystrix'' (again from Early Permian) had a dorsal flat crest covered in skin, extremely similar to the one seen in the contemporary mammal-ancestors ''Dimetrodon'' and ''Edaphosaurus''. A group of temnospondyls in the Late Permian were the Archegosaurs. Particulary similar to crocodiles and gharials with their long snout and dorsal armor, they were among the largest amphibians ever (the record-holder to date is ''Prionosuchus'', 30 ft of length!),
When amphibians were like crocs 2: ''[
* Temnospondylan amphibians managed to survive the huge mass extinction at the end of the Permian. In Early Triassic, they recovered fast and became very diversified again. Among them, the Trematosaurs were very similar to the earlier Archegosaurs, and also reached large size. However, the biggest and most famous Triassic amphibian is ''Mastodonsaurus'' (sometimes misspelled "Mastodontosaurus"), the first paleo-amphibian ever found, in the first half of the 1800s. The same bulk of a hippo, it had an even huger head, as long as a human, and with carnivorous teeth. One usually-ignored trait is a couple of lower teeth which were threaded through the perforated upper jaw when the mouth closed. With its bulky body and short tail, the mastodonsaur was probably slow-moving on land, and is usually thought a water-living ambush-predator like its predecessor ''Eryops''. However, such giants were exceptions at their time: most other relatives were not bigger than modern amphibians. The most interesting is ''[
Egg-shells, what an invention!: ''[
* Here we’re talking about Reptiliomorphs ("reptile-shaped"); that is, tetrapods much closer to ''reptiles'' than to frogs or ''Eryops''es. They had the same variety in shape and size as the other paleoamphibians, but were generally more land-living than the others, and progressively gained those traits which allow us humans to remain costantly out of water without dehydratating: waterproof skin, efficient lungs and kidneys for storing water, but above all, amniotic eggs; that is, those oval, shelled things we use to eat for dinner, and that come to our mind when hearing the word "egg". Before that, eggs were just those tiny, soft marbles modern frogs still produce today. Among quasi-reptiles, the most mentioned has long been the Early Permian ''Seymouria'', because [[Science Marches On|it was once considered the missing-link between amphibians and reptiles]]; now is believed only a distant relative of Amniotes. Less-close to reptiles were the the Embolomers or Anthracosaurs, which were the dominant "amphibian" group in the Carboniferous, often (but not always) huge-sized. Examples: ''Eogyrinus'', ''Proterogyrinus''. Among the closest-to-reptiles reptiliomorphs is worth of mention the iguana-like ''Diadectes''. From Early Permian, it was maybe one of the first herbivorous vertebrates ever appeared. In textbooks written in the 1990s is often heard the name ''Westlothiana'', because was once considered the “first reptile ever appeared” (lived in Early Carboniferous, even before thr classic record-holder ''Hylonomus'').
Limbs, what an invention!: ''[
* Along with ''Eryops'', ''Ichthyostega'' has been the most famous paleoamphibian, but this time is a bit more justified: it has long had an enormous importance in paleontology indeed. Discovered in Greenland (still not the [[Grim Up North]] place we know today) and living in the Devonian Period, ''Ichthyostega'' has been the first four-limbed vertebrate known to science for almost a century: one of the icons of evolution thus, just like ''Archaeopteryx'' and horses. Today, many other "missing links" between fish and tetrapods are known to science: the most astonishing is ''Tiktaalik'' which was really a middle-way between a fish and an early "amphibian". ''Ichthyostega'' has often been described as a "fish with limbs", and with reason: its was still more fish-like than amphibian-like. Its 4 ft long body was streamlined like a fish; its head was smooth and very fish-like; its tail still retained a ''fin'' (albeit reduced); and its skin was, arguably, still covered with bony scales, just like fishes. But it had ''limbs'' instead of paired fins; very odd limbs to modern standards, since they had ''seven digits'' (all the other following tetrapods had only no more than five toes, a trait then inherited by reptiles-birds-mammals-humans). Expect to see it still mentioned as "the first land-living vertebrate". This is justified in works created some years ago, ex. Walking With Monsters, <ref>though the chosen animal in that show was, surprisingly, the much more obscure relative ''Hynerpeton'', but that CGI animal was pratically an ''Ichthyostega'' in shape and size, so it doesn't matter.</ref> but not in the most recent ones. [[Science Marches On|We now think it was completely aquatic]] and its limbs developed to move upon the bottom of swamps, rivers and lakes, since they would be too weak to support its bulk on land. And is ''very'' unlikey that it could emit loud screams as shown in ''Monsters'', as well as laying frog-like eggs; [[All Animals Are Dogs|not all amphibians are frogs]], and ''Ichthyostega'' and its kin were far more fish-like than frog-like in [[Real Life]].
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"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. There are only two groups of fish which are still successful today: sharks and ray-finned fish. Not so in Prehistory, as you'll get soon.
Lungs, what an invention! [
* Sarcopterygians, aka “Lobe-finned fish”. Actually, considering these animals as ''fishes'' may appear rather arbitrary to some paleo-fans. Rather than creatures we'd normally call fish, they were a sorta middle-way between typical fish and amphibians, and many of them spent part of their life ''outside'' water, thus breaking the "fully-aquatic" criterium. They are traditionally divided in three groups: Actinists, Lungfish and Rhipidists <ref>The third term it actually in disuse: today the correct one is "basal stegocephalians & tetrapodomorphs". But if we use the latter, the pun with "actinists" [[Rule of Funny|wouldn't work anymore]]</ref>. Actinists, better-known as Coelacanths from the common name of their only <s>one</s> [[Science Marches On|two]] surviving species, are perhaps the most famous, and at the same time, the least amphibian-like: indeed, they ''were'' fully-aquatic, thus "true fish". They appeared in the Devonian Period, and were marine creatures that have remained virtually unmodified since 400 million years: but now they seriously risk to go extinct soon or later, [[Humans Are Bastards|only because]] [[What Measure Is a Non-Cute?|they are not so cute]] [[Finding Nemo|as clownfish are]]. Lungfish were a bit closer to us: they really have [[Exactly What It Says On the Tin|lungs]] for breathing air other than classic gills, appeared in the Devonian as well and specialized themselves to muddy, marshy environment with very oxygen-poor waters: that's why their lifesaving airsacs evolved. Today are the most successful missing-links between fish and land vertebrates (although less than ten species are still alive today), and yet they are less-often-mentioned than Coelacanths. Finally, "rhipidists" are an artificial assemblage of not-related lobe-finned fish. Among them were ''the ancestors of mankind'', as well as all land-living vertebrates ever existed, from [[Digimon|dinosaurs]] to [[Hamtaro (Anime)|hamsters]]. ''Eusthenopteron'' has always been the stock rhipidist, probably because of the look of its tail that recalls [[Prongs of Poseidon]]; recently, the basically identical but far bigger ''Hyneria'' has gained some notoriety thanks to [[Walking With Dinosaurs|Walking With Monsters]], portrayed as a ''[[Jaws (Film)|Jaws]]''-like [[Carnivore Confusion|villain]]. It's the ''only'' lobe-finned fish represented in that show, and [[Somewhere a Paleontologist Is Crying|with no mention at all about the role of lobe-finned fish as our-ancestors]].
Bones, what an invention!: ''[
* Actinopterygians, aka “Ray-finned fish”. Or, more laconically, ''fish''. They are by far the most diversified non-tetrapods today, compounding the 90% of our modern ichthyofauna, but only a small percentage of the pre-dinosaurian one. They appeared in the Devonian, but reached their immense today-success only at the Cretaceous, when they underwent an explosive evolution. From seahorses to puffers, from swordfish to ocean-sunfish, from piranhas to deep-sea anglers; almost all the most today-familiar fishie-kinds appeared only ''after'' the Cretaceous/Tertiary Rock-Falls-<s>Everyone</s>-Someone-Dies event. Among the few modern ray-finned fish which were already in life during the mosasaur/plesiosaur/ichthyosaur existence, there were herrings, sturgeons, gars and few, few others. There were also now-extinct guys as well in the Cretaceous: the most portrayed is the 15-20ft long, bulldog-faced ''Xiphactinus'', which competed successfully with its neighbouring mosasaurs in the "large predator" role. There was an even more awesome fish in the Jurassic sea: the ''whale-sized'', filter-feeding ''Leedsicthys''. Among other smaller (yet still intriguing) Mesozoic fish, we can mention: the "Saber toothed herring" ''Enchodus''; the gar-like ''Aspidorhynchus''; the stocky ''Dapedium''; the herring-like ''Leptolepis''; and, above all, the carp-like ''Lepidotes''. The latter was a very successful genus, with dozens of species described which lived through most of the Mesozoic Era: this was the meal the fishing-dinosaur ''[[Stock Dinosaurs|Baryonyx]]'' might have preferred for lunch, as shown by remains of ''Lepidotes'' within its ribcage.
Jaws, what an invention!: [
* On the other hand, very few ray-finned fishes are known before the Triassic. ''Palaeoniscus'' and ''Cheirolepis'' are the most cited: their look was a sort of middle between a regular fish and a shark, but we'll understand later why. Some modern ray-finned fish have maintained this mixed look today: sturgeons are the most typical example. Also with the same, regular-fish/shark mixed look of the early rayfins, Acanthodes were only related with the latter. "Acanthode" means "spiky", and they indeed had plus [[Exactly What It Says On the Tin|many fin-spikes]]. They hadn't a great success compared to other groups, and became extinct at the end of the Permian, another victim of the most devastating mass-extinction of all times, that wiped out 90% of all living things. Despite this, Acanthodian fish were possibly among the most important fishes at all times. This because they probably were the very first vertebrates with ''jaws''. This is not a trivial thing at all: thanks to this invention (made in the Silurian Period, just before the Devonian), fish as a whole started to be the most important large-sized animals in marine and inland waters, becoming active predators and outcompeting the so-called "Sea Scorpions" (see in the Invertebrates section) in this role. This role obligated fish to become more mobile and faster, thus giving them one day the capability to get out the water and to become human-ancestors (this thing is called "Pre-adaptation" in evolutionary terms).
Shark tales 1: ''[
* Not always [[Everything's Even Worse With Sharks]], really. For many animal-lovers, they are among the most fascinating living things. And so is among paleo-fans. Prehistoric sharks were as diversified as modern shark are today, or rather, even more. But stop now. Things aren't always so simple as they seem. "Shark" is an ambiguous word: usually refers to ''some'' of the modern cartilaginous fish, expecially the most streamlined ones such as the Great White, but not, to say, the flattened rays and skates. But in paleontology, it usually refers to ''all'' cartilaginous fish, or at least, those belonging to the {{[http|//en.wikipedia.org/wiki/Elasmobranchii Elasmobranchian}} subgroup. The other main subgroup, the [
Shark tales 2: ''[
* In the Devonian, Elasmobranchs were represented with generic forms such as ''Cladoselache'', already with the familiar exposed gills, but with a ''terminal mouth'', unlike most modern sharks. Actually all the fish-groups seen so far get their success for the first time in this period: Devonian is called with reason "the Fish Age" because it was the age in which fish were more diversified than every else. Many Paleozoic "sharks" are very cool-looking: let's give a look at the "Ironing Board" shark ''Stethacanthus'', the eel-like freshwater sharks of the ''Xenacanthid'' family, and the weirdest of them all, the totally bizarre-toothed ''Helicoprion''. In the Mesozoic, the dominant group was made of more modern-looking animals: among them, the "Switchblade Shark" ''Hybodus'' and the ray-like ''Ptychodus''. However, the first true sharks appeared only in the Cretaceous, along with the first modern-looking bony fish; among them were also the first true rays/skates. Some sharks from that period were similar to ''[[Jaws (Film)|Jaws]]''-things. The "Ginsu Shark" ''Cretoxyrhina'', for example, growed to the size of Spielberg's beast, and preyed upon [[Badass|marine reptiles]]. Despite this, the biggest and most famous prehistoric shark was still alive ''just 1.5 million years ago'', when hominids were already existing: ''Carcharocles'', better known as [[Megalodon]].
Shark tales 3: ''[
* There's already a [[Megalodon|trope]] intentionally dedicated to it, but we'll add some paleontological information here. The "megalodont" is the largest fish known to science which could hunt large prey, but possibly not the largest shark ever; perhaps our modern [
Tough guys 1: ''[
* “Placoderms” (“plated skin”) is the correct name for the “jawed armored fish”. They were the most numerous and diversified fish group living in the Fish-Golden-Age (the Devonian), but no one seems to have survived in the following period, Carboniferous. Placoderms' fossil abundance in devonian rocks might also be related to their main anatomical feature: a thick [[Exactly What It Says On the Tin|body armor]] made by large, articulated plates that covered the first half of their body. Placoderms and the so-called "Ostracoderms" (see further) are the only ancient armored fish known. But wait, we've said an inaccuracy. The classic fish scales we commonly know actually ''are'' a kind of body-armor, just as the plates of placoderms: only much lighter. They have the same basic bony structure, but are very diversified among fish groups. Scales of Teleosteans (aka the subgroup including almost all modern ray-finned fish) are thin laminae visible under their skin; those of sharks and some archaic rayfins (like the [
Tough guys 2: ''[
* ''Bothriolepis'', ''Coccosteus'' and most other placoderms were small predators of invertebrates or smaller fish... but not ''Dunkleosteus''. Its name means "Dunkle's bone", but in older sources it used to be called "Dinicththys" ("fearsome fish"). But today nobody uses this name anymore. Just like the "Brontosaurus -> Apatosaurus" and "Diatryma -> Gastornis" examples, this is a pity for many long-standing paleofans: a really cool name deleted by [[Science Marches On]] and replaced by a really unexpressive one... This Devonian arthrodire was similar to ''Coccosteus'', just overgrown: 30 ft long, the size of a killer-whale, it was the largest vertebrate known so far which lived before dinosaurs. Its size is even more astounding, if you think most other Devonian armoured fishes were salmon-sized. It is one of the most famous prehistoric "leviathans" along with Megalodon, ''Liopleurodon'', ''Mosasaurus'' and ''Basilosaurus'', and was the fiercest-looking among them, thanks to its armour, and also its strange-looking teeth, [[Madness Mantra|as we'll see later]]; no surprisingly, it is a staple in those not-so-common paleobooks which show also pre-dinosaurian fauna, always described as a [[Prehistoric Monster|"monstrous killing machine"]]. Surprisingly, despite all this, ''Dunkleosteus'' has had ''very'' few apparitions in TV to date, much less than, to say, the not-so-impressive ''Elasmosaurus'' (another egregious case of [[Everything's Better With Dinosaurs]]: OK, elasmo wasn't a dino, but lived in the same age...) Perhaps the only relevant example in recent media is [[Walking With Dinosaurs|Sea Monsters]], where ''Dunkleosteus'' was portrayed with [[Hellish Pupils|cat eyes to make it even scarier-looking]] (while most drawings show rounded, fish-like pupils), with a non-proved [[I Am a Humanitarian|cannibalistic attitude]], and, to put the cherry on the cake, its hide was ''[[Colour-Coded for Your Convenience|blood red]]''. If you have watched that show, you'll remember those strange, blade-like teeth which cut like scissors (at last, we're talking about them); these are instead [[Truth in Television]]. Only... they weren't ordinary teeth; they were ''bony plates'', the same kind of those which covered its forebody. And this is not an isolated case in the fish-world; remember we talked about sharks, and their enamel-covered, teeth-like scales? Finally we'll get it. At the start of fish evolution, scales and teeth ''were the same thing''. Then, body scales were lost by land vertebrates, never to return: the so-called reptilian "scales" are a totally different thing, just horny thickening of the skin (usually) without bony core, just like our fingernails. But ''mouth scales'' remained, and how: and they allow us to chew our meals today. Our incisors, canines, premolars and molars are, really, the only remaining fish-scales we still have. Keep this in mind, every time you go to the dentist.
Tough guys 3: ''[
* Ostracoderms (“armored skin”) is the traditional name for the “jaw-less armored fish”. Ostracoderms appeared about 480 million years ago, during the [
Our earliest origins 1: [
* If you get in your hands an old textbook, you'll probably read Ostracoderms were "the first fish ever", thus "the first vertebrates": actually it's untrue. Ostracoderms, indeed, were already ''very'' evolved animals. Practically, their only archaic feature was the jawless mouth that obligated them to eat only little items: all their other traits were as sophisticated as those of the other fishes. Particularly well-preserved fossil finds show us they had complex brains and very kin senses just like modern fish. An they ''had'' a whole-fishy shape, with all the classic fins (though less-developed than those of more recent fish-groups). And they ''weren't'' the ancestors of the other fish (and thus of amphibians, mammals, mankind etc.): rather, jawless armored fish went extinct at the end of the Devonian without leaving offspring. The "most primitive vertebrate" title belongs to even more primitive animals. Sadly, the common ancestors of all vertebrates are extremely poorly-known in paleontology: this because, being so ancient, they hadn't ''any'' sort of bony-covering, and thus they hardly fossilize; despite this, more-basal-than-ostracoderm vertebrates were possibly as abundant as the latter in Ordovician and Silurian seas, and maybe were successful even beyond the Devonian, perhaps until the Triassic. The amazing thing is, unlike armoured fish, some of the basal, unarmored vertebrate groups ''have'' survived until now. We’re talking about [
Our earliest origins 2: ''[
* However, their earliest ancestors were very different animals: they were ''really'' tiny creatures, even smaller than ostracoderms, and were almost surely filter-feeders just like the latter. The most known among these critters has been, until few years, the recently discovered ''Haikouichthys'' that lived in the [
Our earliest origins 3: [
* Still another group of pre-fishian vertebrates is known to science, perhaps even more enigmatic than ''Haikouichthys'': the Conodonts. We known thousands and thousands of microscopic fossil "jaws" discovered everywhere from the Cambrian to Triassic terrains, attributed to them, but since few years ago, nothing from the rest of their body. In the past, scientist didn't even know if conodont remains pertained to vertebrate ancestor at all; recently, thanks to new discoveries, it has been found they were probably elongated, lamprey/hagfish-shaped critters: perhaps the ancestors of the latter? Conodonts are a prime example of the many still unresolved, intriguing mysteries of Paleontology.
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When thinking about animal fossils, our mind usually goes on the pietrified bones of dinosaurs. But dinosaurs in paleontology are ''extremely rare finds'' compared to other vertebrate groups, such as sea-reptiles, Cenozoic mammals and fish. And yet, vertebrates as a whole are in turn only a ''very small'' part of the total. Indeed, more than 90 % animal fossils that Earth left to us are from Invertebrates. Some invertebrate groups like Ammonites and Trilobites are so common they're object of collection by many paleo-fans; while it's ''unlikely'' dinosaur bones will receive this trade—although some trade of dinosaur bones do exist as well, but it's highly debated if it's a right thing to do, since dino fossils are such a rarity.
The first eyes: [
* There are things which are more important than others. Trilobites are among them. Their [
Crabs and pseudo-crabs: [
* Since Trilobites and Sea Scorpions (see further) are now extinct, we have today only <s>two</s> three remaining groups of marine arthropods: Crustaceans, Xiphosurans, and [
Our distant enemies? ''[
* Eurypterids, also known as Gigantostracians, are probably among the prehistoric critters with the most striking-sounding nickname: "Sea Scorpions"... just weren't scorpions. Even though scientist think they might be the ancestors of the ''true'' scorpions, those with the stingy thing on the tip of their... what? Tail? <ref>No, no. The scorpion's "tail" is only the rear-end of its abdomen - nobody'll ever see an arthropod with tail, believe us. The tail is a typical vertebrate feature.</ref>. "Marine scorpions", lived through most Paleozoic from Ordovician until the Great Permian/Triassic Extinction, nearly as long as the Trilobites. They are often cited as "the largest arthropods of all times", but [[Your Mileage May Vary|this might depend to who you ask]]: modern [
Out of water, at last! ''[
* The very first animals which made their first steps onto dryland weren't vertebrates, but Arthropods. It's easy to understand why. At the Silurian, vertebrates still were all fish-like and their fins weren't articulated structures which could make a leverage to substain the body constrasting the force of gravity; while Arthropods have had articulated legs since the Cambrian, 100 million years before. Thus, they were in clear advantage. The very first land arthropods weren't insects though; the latter have been a more recent appearence within Evolution. The first colonizer were the "Myriapods" (millipedes, centipedes and their extinct kin) and the [
Everything's better with Euras: ''[
* Which animal do you prefer, the largest land arthropod ever known to science, or the largest flying insect ever known to science? It almost seems intentional they have similar-sounding names; actually ''Arthropleura'' means "articulated flanks", ''Meganeura'' "large wing-veins", thus being only an incidence. Both from the Carboniferous, they represent well the tendence towards gigantism among Arthropods in this age. They were not the only overgrown land invertebrates in their world (and many other arthropods at that time were normal-sized, let's not forget it). But both made surely the [[Up to Eleven]] example. And yet, in the following age, the Permian, land insects and millipedes returned as small as we were initially at their Silurian/Devonian origins, and remained such for all Mesozoic and Cenozoic, until today. Why just in the Carboniferous? The most credited theory trots out the almost-universally utilized fuel within the animal kingdom: Oxygen. Thanks to the extraordinary luxury of vegetation typical of that period, the vital gas increased its level more than every other time in Prehistory. And since size of land arthropods is severly limited by the oxygen abundance (because of their particular [
=== Thank you bug! PREHISTORIC INSECTS ===
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Remember [[Jurassic Park]], and those fossilized mosquitoes in amber from which dinosaurian DNA was extracted ? The DNA extraction thing was obviously fictional, but the amber thing itself is [[Truth in Television]]. Insects preserved in amber are perhaps the most marvelous fossil a palaeontologist could wish in its life. Not only they are perfectly preserved in every detail, included external anatomy and ''even color'' (an almost unique example among fossils); they have ''their original tissues preserved, single cells included''. And they can provide an extraordinary clue to understand 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 in which insect were already similar to their modern relatives. But we still know little about their Mesozoic ancestors, still less about the Paleozoic ones--except for those living in the "Coal age", the Carboniferous (such as the aforementioned ''Meganeura'') because many of them did preserve well in coal.
Anyway... we know some things with a good grade of certainty. The first insects appeared in the Devonian <ref>Technically these were the first Hexapods, since springtails are no longer considered proper insects by modern enthomologists: however, we follow the traditional view because it's more convenient.</ref>, later than scorpions and millipedes: they were still wingless as modern [
[
Many paleontologists think if neornithan birds and placental mammals are the most today-diversified land vertebrates, they have to thank the insect-plant mutualism which has created well-suited habitats for their (initial) small size and eating-versatility. Think about those birds and bats who feed only upon nectar, anteaters and pangolins which feed upon nothing but social insects, or the infinite 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.
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== Cephalopods ==
Ammon's horns: [
* Is there anybody who has never seen those pietrified spiraled shells at least once in its life? Ammonites are probably the most iconic fossil invertebrate remains at all, thanks to their elegant shape and their extreme abundance in Mesozoic deposits, to the point they're used as index-fossils to identify Dinosaur-age-related rocks, just like Trilobites for the pre-dinosaurian ones. But wait... ammonites are ''not'' exclusive to Mesozoic! They appeared in the middle Paleozoic, but that's right, achieved their highlights in Mesozoic with kinds which are exclusive of this era: so, it works just the same. Before the first paleontologists were born, ammonites were already well-known to people, who asked themselves what the heck they are: Mother Nature's jokes, Pietrified snakes, "Ammon’s horns" (the meaning of their our-day name), or what? The very first human which understood their real nature was [[Leonardo Da Vinci]] in XVI century, but wasn't believed: we had to expect the Founder-of-Paleontology, Cuvier, after see the true fossil's nature understood at the end of the XVIII. Sometimes is heard the modern-day [
Stony arrows: [
* Ammonites ''were not'' the only tentacled things in the Mesozoic: Belemnites were just as abundant. They have left many remains as the former, but these aren't so iconic as ammonites are. This is easy to understand: they haven't any elegant external shell, just a sort of smooth, sharp internal cuttlebone which made people think about the most awesome things, from pietrified arrows to [[Everyone Is Satan in Hell|devil's fingers]]. Despite this, we know a bit more about belemnites than to ammonites: they were close relatives to modern squid and cuttles, and they arguably ''had'' octopusquid eyes and certainly had ten tentacles - or, better, ten ''arms'': the fussy guys tell us that the correct term for tentacles is "arms" while "tentacle" should be used only for those two long, thin things with a club-like end which are exclusive to cuttles/squids but not belemnites. If ammons are a rarity in TV, what about belemns? It they appear at all, they'll be [[Small Taxonomy Pools|identified as squids]]. On the other hand. if dealing with true octopusquids (more aptly called "new coleoideans"), they have a ''very scarce fossil'' record; most of them haven't any internal cuttlebone, often their only bodypart that fossilized is the "beaked mouth". And we already know how hard a soft-bodied animal fossilized. Thus, scientists are happy when founding complete remains of them. However, they lived during the whole Mesozoic Era (despite octopussies and argonauts seem a more recent thing), and [[Giant Squid]] -like forms already existed in the Cretaceous.
Finding Nemo: ''[
* Despite their name, “Nautiloids” have nothing to do with [[Twenty Thousand Leagues Under the Sea|Nemo's Nautilus]], still less with [[Finding Nemo|this Nemo]]... "nautiloid" is a catch-all term including all the most archaic cephalopods, from which ammonites and belemnites and [[Hurricane of Puns|cuttlenites and squidenites and octop...]] ahem... derived in a direct or indirect way. Indeed, nautiloids were not exclusively Paleozoic things as it's easy to think: they too were thriving in the Mesozoic like their relatives. But don't expect to see any nautiloid in media outside pre-dinosaurian Age, nor expect to see them in the Devonian, Carboniferous or Permian periods; more commonly, they are shown in the Ordovician and Silurian seas, aka in the early Paleozoic. It's not necessary to be a genius to understand why: in these periods, Nautiloids were the top-predators of the seas (along with sea-scorpions), [[Rule of Cool|while since Devonian they were outcompeted by fish, followed by marine reptiles and cetaceans]]. Basal cephalopods began with long, straight shells but later these became more and more coiled, until their only still-living direct descendant, the aforementioned Nautilus (hence nautiloids, "pseudo-nautiluses"), a triumphant example of "living fossil" just as the iconic Coelacanth. Some of these shells are so well preserved that ''even their original colors'' are partially conserved (for example ''Orthoceras'', the kind traditionally most portrayed, which had zigzaging lines on its cone-shaped shell). Indeed, the so-called "orthocones", aka cone-shelled nautiloids, are by far the most portrayed because their strange look of [[Bizarre Foods|living tentacled-icecreams]]. The Walking With series has chosen the "giant orthocone" ''Cameroceras'' as the archetypical nautiloid, [[Rule of Cool|for obvious reasons]]. But most nautiloids weren't bigger than a common cuttlefish in [[Real Life]]. To compensate, the "giant orthocone" has been represented with its correct anatomy: simple darkroom-like eyes and more than ten sucker-less tentacles (oops... arms), instead of the octopusquid eyes and sucker-filled appendixes often-seen in paleo-art.
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There is not much to say about the portrayal of extinct non-arthropod / non-cephalopod invertebrates in media: they rarely appear even in books/documentaries, much less in Fictionland, and when they do, they are almost never named (except sometimes for the names of each group, but only in popular-science works). As an example, the original Disney's [[Fantasia]] showed several ''modern'' critters to symbolize the early evolution of invertebrates, but few or nothing among the ''really'' prehistoric ones. The [[Walking With]] series did the same: only modern medusae, sponges and sea-urchins appear, all live-acted. Indeed, many modern invertebrate groups have populated our seas since the Cambrian Period, but many others are extinct today.
Clams and Pseudo-clams: [
* Among non-cephalopod mollusks, [
We love geometry: [
* Echinoderms are extremely abundant in fossil record from Cambrian to Recent, because their hard internal "skeleton" fossilizes well (with one exception: [
Odd relatives: [
* Believe it or not, sea-urchins, sea-lilies and whatnot are among ''the closest relatives of vertebrates''. But there is one now-extinct group that is even more unbelievably closer to us: Graptolites, so common in certain Paleozoic periods that are used like the more famous Trilobites as Index-Fossils. Graptolites were colonial animals more similar to the extremely more archaic cnidarians (jellies, corals etc.) in look, and their shape was awesomely diversified among species. If alive today, they'll resemble floating corals or something similar. Another group that is hard to believe to be close kin to vertebrates are the [
Survival of the toughest: [
* There is a general rule in Paleontology that ''no one living thing'' can escape: if you have hard portions within our body (shells, bones, armors etc.), you'll leave the memory of your importance in History of Life; it you have not these, you are probably destined to be forgotten forever. Sad, but true. This explains why so many modern relevant invertebrate groups are almost unknown in paleontology: for example, non-colonial cnidarians (medusae, sea-anemones) and several "worms" (annelids, nematodes, flatworms and so on). Who knows ''how many'' ancient important animal groups have ''actually'' existed in the Paleozoic and further, that we even know the existence... The odds do enhance however, if you are a colonial organism; if so, you probably have an external "skeleton" made of some sort of hard material (calcium carbonate, silicium, or simply horny matter like that of our hair and nails). Fortunately, many colonial groups are well-known in paleontology, and have had an unimaginable relevance not only for the evolution of life, but even for having ''building many portions of our planet''. Their skeletons, fossilized and transformed in hard rock, have accumulated in million years and became our sedimentary rocks, from sandstone to mudstone. Naturally all creatures with something hard inside or outside have contributed to this (molluscs for example have had a great role as well). Among colonial organisms we've already seen the floating Graptolites; among those still-living, the most important have been three group of "sessile invertebrates" (those fixed to the bottom of seas and lakes): [
A treasure in the rocks: [
* It may seem strange to you, but ''even'' microrganisms have left fossils, and a plenty of it. Of course these fossils do not receive much attention in media, but are of extreme interest among paleontologists. Again, the only-the-tough-ones-preserve rule also counts for single-celled Protozoans: pratically the only group which has left significative fossil record is the Foraminifers ("forams" for their friends), only because they have a sort of minute "shell" which covers their softer innerparts. But they have been ''very'' important for scientists in several ways. First, foraminifers have largely contributed to form sedimentary rocks like corals and molluscs: despite their minute size, they were so in high-numbers in ancient seas that their impact has been notable. Then, they have aided scientists to conferm the [[Rock Falls Everyone Dies]] thesis about non-avian dinosaur extinction. In rocks made ''before'' the mass-extinction forams abound, in those originated ''just after'' the extinction, they are almost missing (except few which managed to survive): a proof that the K/T extinction wasn't a slow journey to death, but a rapid cataclysm (geologically rapid, don’t forget it: it could be last 100,000 years, which is ''nothing'' in geology!). Third, they are inherently cool: some of them were not even ''microrganisms'', would well visible to a naked eye, and reached even 6 cm of width: the latter are called Nummulites (from "nummus", "coin" in Latin). They were indeed small, round calcareous disks, and being exclusive to the Cenozoic, they are considered the best index-fossils for the Mammal-Age. Nummulites are expecially abundant in Egypt (still underwater at the time), to the point that... [[Pyramid Power|egyptian pyramids]] are made by the so-called "nummulite limestone", derived from fossilized nummulite shells melted together.
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=== Once upon a time... CAMBRIAN ANIMALS ===
Cambrian. The first Paleozoic Period, in which the famous [
For obvious reason, our curiosity now reaches the top: which were the first animals (not counting protozoans) that thrived in our oceans? Well, the answer is not simple: we can divide them in two ensembles. One is made from those groups either still alive today or extinct several ages after the Cambrian: among the former, most non-arthropod / non-cephalopod invertebrate groups already seen; among the latter, the Trilobites. We'll talk here about the second ensemble: many Cambrian invertebrates were indeed ''exclusive of the Cambrian'' and didn't survive long enough, not even to reach the following period, Ordovician--in which the most famous Paleozoic critters, sea-scorpions, nautiloids, armored fish etc. appeared. Thus, is easy to imagine many of them were ''really'' [[Our Monsters Are Weird|bizarre-looking]] to our limited point of view. We still know very very few things about their lifestyle, but their appearence is extraordinarily well-known, because these Cambrian deposits ''have preserved soft-bodies''; not only that, they have preserved them very well!
It would be too long to mention [
However, at the anomalocaris’ time, every other organism was ''very small'': The other creatures you see in the linked image are not longer than your hand, all possible prey for anomalocarids. <ref> Except those which were so small that a full grown ''Anomalocaris canadensis'' (the largest know species) whould have ignored them</ref>. Creatures like ''Hallucigenia'' and ''Pikaia'' were hunted by smaller predators, such as ''Opabinia'' and ''Anomalocaris saron''. The later was the species shown in ''[[Walking With Monsters]]'', though ridiculously oversized (6 ft.!?) and prone to attack it's own kind, despite the fact that neither its mouth nor grasps could injur an equally sized specimen in the way it was depicted, let alone possibly eating it.
Apart from Anomalocaris, we can mention at least other three invertebrates which are stock in drawings: ''[
''Opabinia'' was related with ''Anomalocaris'', but had an even weirder look: maybe no other fossil animal resembles a fiction-related extraterrestrial thing more than ''Opabinia''. It had ''five eyes'' put in circular fashion on its head, and a pincer-like grasp at the end of a long, flexible proboscis, often mistaken for the creatures mouth which was actually located behind the proboscis. But the most important find is the third guy, ''Pikaia'': despite its rather insignificant appearence, it is the most well-known among ''vertebrate ancestor'', a sort of prehistoric relative of our [
But wait....have you see these critters in TV at least once? A hard thing, even if you watched [[Walking With Dinosaurs|Walking With Monsters]]. In this [[Rule of Cool]]-filled show, the ''only real'' Cambrian invertebrate to appear is....Guess what? Well, the superpredator ''Anomalocaris'' of course! The other two invertebrate guys shown up are... [[They Just Didn't Care|a modern jellyfish]] and an [[Anachronism Stew|anachronistical phacopid trilobite]]--remember that phacopids first evolved in the Ordovician, while Cambrian trilobites were very different-looking to the classic image we have when thinking about these animals. The absence of such awesome animals like ''Opabinia'' and ''Hallucigenia'' makes another egregious example of a missed opportunity, like the missing of the giant bird ''Argentavis'' and the “giant marsupials”.
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== Plants ==
When thinking about fossils, we automatically think about ''animals''. But also plants have left many remains, some of them just as spectacular than the animal ones (think about the [
A flowery smell from Cretaceous: [
* Dinosaur-Age-related vegetation wasn't so different to ours as commonly believed. Right, non-flowering plants were dominant at the time, but still today there are ''great'' extensions of dryland dominated by conifers - the siberian Taiga, not the Amazon, is the largest forest in our days. But not only because of that. If we have the chance to really [[Walking With Dinosaurs]] in the Cretaceous, we'll encounter many familiar critters. Most main groups of Angiosperms aka Flowering plants had already evolved: it has recently found that ''even grass'' populated the landscapes in which Triceratopses used to roam - though this doesn't justify at all the still-not-present ''grasslands'' so-common in Mesozoic [[Prehistoria]]. Most Cretaceous flowering plants were still trees then; most herbs have evolved later, despite they seem simpler-built. Some of the Cretaceous flowering trees have virtually unchanged since; the [
Dinosaur-tree: [
* When hearing the [[Stock Phrase]] "Living Fossil", our mind goes automatically to moving guys: the Coelacanth, the Tuatara, the Horseshoe Crab... It's easy to forget that living fossils exist even in the a-bit-disregarded plant word. The ''[
A resiny smell from Jurassic: [
* Really? Did pines, firs and spruces live alongside Jurassic Brontosaurs and Camptosaurs? And were they ''even'' their ''main food''? About the latter we're not sure; but about the former, yes, they did. At least, pine and fir ancestors, still non-adapted to cold climates. [[Prehistoria]] is ''always'' a warm place to pass some vacation, and pine-looking trees seem a bit out-of-place there for us folks... but [[Real Life|Real Life Is Always Different]] [[Somewhere a Paleontologist Is Crying|When Talking About Paleontology]]. But wait, we've not finished. Since in common thought conifer = [
Palms, or not? [
* These are the plants we usually associate with the idea of Prehistory (along with true ferns and lycopods, see later). They were very palm-looking, and the still-living Cycads are often confused with the latter in [[Real Life]]: however, true palms started to appear only at the end of the Cretaceous, thus ''Diplodocus'' whip-tail would never become twisted on palm-branches. On the other hand, cycads were perhaps the most abundant seed-producing plant in the Mesozoic, along with their close (and often confused with them) relatives, the Cycadeoids or Bennettitals. However, an ever more ancient group of seed plants was still more archaic-looking. These are called Pteridosperms, aka "seed ferns": they resembled ferns in shape, only they [[Exactly What It Says On the Tin|produced seeds for spreading their kind]] unlike the latter. One seed fern, the Triassic ''[
The Mesozoic undergrowth: [
* Horsetails and True Ferns are the today-most common archaic-looking plants. Watch one of them and your mind could travel back in time down to the ''Edaphosaurus'' days and even further. You'll note at this point that most archaic plants are either fern-looking, or palm-looking. This is not mere case: this "bodyplan" is the most ancient among terrestrial plants, and ''all'' the others - from the pine-like to grass-like - are simple evolutions of the latter. These spore-reproducing critters were already thriving in the Carboniferus, the Golden Age of Plants, but they have never been dominant compared to other groups: they have, rather, played the undergrowth role, and still play this today: but today they suffer the concurrence of modern herb-shaped floweringplants. This doens't mean, however, that ferns and horsetails have always been ''small things'': take a look to the aptly named [
The Paleozoic overgrowth: [
* However, the most striking-looking among prehistoric plants are maybe those which dominated the Carboniferous world. 100 ft tall or more, these plants, if alive today, would resemble odd-looking trees, but were actually archaic spore-reproducing critters. But wait, they ''were not ferns'', nor were they even close fern relatives. They were even more primitive plants: the Giant Lycopods. Lycopods are still-living today, but now they are nothing but tiny herb-like greens; in the Coal-Age, though, lycopods thrived in the widespread swamps with several species very different-looking among each other. ''[
The first shoot: ''[
* Carboniferous forests were not the very first ones in Earth's history: some tree-like plants had already existed in the preceeding period, the Devonian, and most were already shaped like their descendants (lycopods, tree-ferns etc.), for example ''[
== The origin of Life ==
Animals, or plants?: [
* It is sometimes said that multicellular organisms appeared at the "Cambrian Explosion". Actually, multicellular ''animals'' appeared then, but this doesn't mean all Pre-Cambrian forms of life were one-celled like modern "protozoans" and bacterians. We have the improperly-called “Ediacaran fauna”, which lived just before the beginning of the Paleozoic Era. Several macroscopic organisms lived then, but they are so different than even those of the Cambrian that we don't know for sure if they are plants or animals: more probably, they were neither. The distinction bewteen animals and plants is so fixed in our common sense that it's difficult to imagine a world were eterotrophic and autotrophic beings were still not distinguished each other. The fate of the Ediacar critters at the end of the Archeozoic (aka Pre-Cambrian) Era is just as mysterious as that of many Cambrian creatures: they really disappeared, or were the common ancestor of all Paleozoic --> Mesozoic --> Cenozoic --> Neozoic forms of life, ''ourselves'' included? It'll remain for long one of the greatest mystery in Paleontology.
The first Earthlings: [
* However, many unicellular creatures have left their track in Archeozoic rocks: obviously they are micro-fossils, thus not visible to a naked eye, but they are of immense importance, because they are the most ancient forms of life known to science. The most relevant are the so-called [
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