Prehistoric Life

This page talks about prehistoric life by making several examples of extinct creatures, from plants to non-human hominids. Of course dinosaurs receive more details than the other groups, but it would be a really, really incomplete list without non-dinos.

Important: This page only talks about non-stock animals: that is, creatures that may appear in popular-science works but have never been portrayed in film/comics/novels, or at least have been portrayed only occasionally. The vast majority of dinosaurs are in this category; and yet, they are as cool as their famous relatives. If you want to see thing about the most popular dinos and non-dinos, there is already some information here.

Time Scale
The geologic and biologic history of the Earth is divided into four eons: Hadean, Archean, Proterozoic, and Phanerozoic. Each eon is divided into eras, which are themselves subdivided into periods, which are in turn sub-sub-divided into epochs. Since we know a heck of a lot more about the recent past than we do about the very very ancient past, the first three eons are sometimes grouped together into a single "supereon" known simply as the Pre-Cambrian.

PRE-CAMBRIAN: Earth before 542 million years ago.
 * 1) Hadean eon: Starting from the formation of the Earth 4.6 billion years ago, and lasting until the Earth cooled, solidified, and generally calmed down enough that fossilized bacteria could form.
 * 2) Archean eon (formerly Archaeozoic): Starting 3.8 billion years ago, and lasting until oxygen started to build up in the Earth's atmosphere 2.5 billion years ago. This atmospheric oxygen was created by cyanobacteria, and spelled instant death for any life that couldn't evolve aerotolerance. It was the worst case of air pollution in the Earth's history.
 * 3) Proterozoic eon: Starting 2.5 billion years ago, and ending a scant 542 million years ago with the Cambrian Explosion. This eon saw the emergence of the first eukaryotic life forms (cells with a nucleus) 1.6-2.1 billion years ago, the first sexually-reproducing organisms 1-1.2 billion years ago, and the first multicellular organisms. The final final era of this eon was:
 * 4) Neoproterozoic era: Starting 1 billion years ago. At the onset of this era, a supercontinent named Rodinia straddled the Earth's equator. Ice ages came and went which were so severe that the ice sheets reached all the way to the equator, resulting in a Snowball Earth. Rodinia eventually broke up, only to re-form as another supercontinent named Pannotia. The final period of this era was:
 * 5) Ediacaran period (formerly Vendian): Starting 635 million years ago, which marked the "Dawn of Animal Life." Or so we think. In any case, multicellular life that probably (but not certainly) belongs to the kingdom Animalia first appears around 580 million years ago; possible fossils are found even earlier, near the beginning of the period, but nothing conclusive. Many possible ancestors of known invertebrate groups show up in the record, including comb-jellies, sponges, corals, anemones, and molluscs, and one fossil might even be a chordate (vertebrate ancestor). Fungi also emerge during this period.

PALEOZOIC ERA
 * 1) Cambrian period: The "Explosion of Life". Most of the main invertebrate groups appeared then, as well as the first vertebrate ancestors. Life was still water-exclusive. Probably. Graptolites, cephalopods, and chitons emerge during this period.
 * 2) Ordovician period: First true fish appeared. Arthropods venture onto land. Ended with a mass extinction.
 * 3) Silurian period: First jawed fish and later ray-finned fish appeared. Plants and scorpions started to colonize dryland.
 * 4) Devonian period: The Fish Golden Age. The first four-limbed vertebrates appeared. Insects, crabs, ferns, and sharks evolve. Ended with a mass extinction.
 * 5) Carboniferous period: Forests spread around the world. The Golden Age of Insects and Amphibians. Sharks reach large sizes, and ratfish, amniotes, synapsids, diapsids, and hagfish evolve.
 * 6) Permian period: The supercontinent of Pangea comes to light, and Earth becomes more arid. The Golden Age of the Mammal-Ancestors. Beetles and therapsids evolve. Temnospondyls and pelycosaurs diversify. Ended with the worst mass extinction ever.

MESOZOIC ERA
 * 1) Triassic period: Seed plants diversified. True reptiles replaced mammal-ancestors. Most of the main groups of land-vertebrates still alive today appeared, dinosaurs and mammals are among them. Many groups that did not leave modern descendants, such as pterosaurs and many marine reptile groups, evolved as well. Ended with a mass extinction.
 * 2) Jurassic period: Dinosaurs became the largest and most diversified land-animals, and some became fliers (including possible protobirds). New types of pterosaurs and marine reptiles evolved. The three still-living mammalian groups appeared.
 * 3) Cretaceous period: Dinosaurs further diversified, and the first dinosaurs universally recognized as birds appeared. Flowering plants and several groups of insects co-evolved, creating the most common land-ecosystem still present today. Modern groups of fish evolved. Despite the movie's name, most of the dinosaurs shown in Jurassic Park flourished in the Cretaceous period, not the Jurassic period. Ended with the last mass extinction since today, known as the K-T Boundary Event.

CENOZOIC ERA
 * 1) Paleogene period: Mammals underwent an explosive evolution, and most still-living lineages appeared, primates included. Birds, crocodilians, turtles, squamates and lissamphibians were among the other land-vertebrates which survived the mass-extinction. At the end, the Earth started to become colder, and polar ices started to form.
 * 2) Neogene period: Continents acquired their modern placement, and new mountain ranges appeared. Grasslands became a widespread environment, partially replacing forests. New mammalian kinds appeared, among them the first hominids.
 * 3) Quaternary period: Started 2.59 million years ago. Several Ice Ages alternated with Interglacials. All modern kinds of plants and animals were already present, but also many now-extinct species. True humans evolved and started to develop our modern traits. The age in which we are living today (specifically the Holocene Epoch) is included in this time period. The only survived human species, Homo sapiens sapiens, has become a prime environmental factor worldwide.

The first written records started to appear some 5000 years ago. That moment marked the beginning of recorded history. Anything more recent than that ain't prehistoric.

Translation Guide
When reading the examples of creatures we made, you'll note that many prehistoric critters can confidentially be put in their group simply observing their hallmark-suffix. Let's list the most common cases. But also note not all members of each group have their designated suffix; nor these suffixes are necessarily exclusive of these groups (think about the whale Basilosaurus).


 * 1) -saurus: Greek for "lizard": in paleontology identifies reptiles in general, not only dinos. Ex: Scutosaurus. Often identifies amphibians as well: ex. Mastodonsaurus.
 * 2) -ceratops: Greek for "horned face": identifies horned dinosaurs. Ex. Pentaceratops.
 * 3) -mimus: Greek for "mimic": mostly identifies small bird-like theropods, expecially ornithomimids (usually preceed by a bird-related prefix). Ex. Garudimimus. Also applies to some larger dinosaurs. Ex. Suchomimus.
 * 4) -raptor: Greek for "thief", "robber": since the Jurassic Park success identifies mainly dromaeosaurids, but many other theropod dinosaurs have this as well. Ex. Megaraptor.
 * 5) -dactylus: Greek for "digit": typically identifies pterosaurs, from the namesake [Ptero-]Dactylus ("winged digit"). Ex: Cearadactylus.
 * 6) -suchus: Greek for "croc": in paleontology identifies crocodilians, croc-looking reptiles or croc-looking amphibians. Ex: Rhamphosuchus, Koolasuchus.
 * 7) -therium: Greek for "beast", "wild animal"; identifies mammals - hence the name Walking With Beasts! Ex. Sivatherium.
 * 8) -pithecus: Greek for "monkey": the hallmark of most prehistoric primates, human ancestors included. Ex. Ardipithecus.
 * 9) -ornis: Greek for "bird": identifies... guess. Ex: Osteodontornis.
 * 10) -ichthys: Greek for "fish": indicates many fish aka non-tetrapod vertebrates. Ex. Leedsichthys.
 * 11) -aspis: Greek for "shield": almost all names of Ostracoderms and of some Placoderms (both armored fish) have this suffix. Ex. Pteraspis.
 * 12) -ceras: Greek for "horn": most Ammonites and Nautiloids (cephalopod molluscs) have this, due to their horn-shaped shells. Ex. Orthoceras.
 * 13) -pteris: Greek for "fern": many extinct fern-looking plants end with this. Ex. Archaeopteris.