This page is the index by geological period for Prehistoric Life, a series introducing extinct organisms one at a time. It follows the history of Earth from oldest to youngest, so you can see at a glance what was living in each period. New entries are added here as each article is published.
The divisions and dates follow the International Chronostratigraphic Chart of the International Commission on Stratigraphy (ICS). The periods themselves are covered in detail in the Earth Timeline series.
Precambrian (about 4.6 billion to 539 million years ago)
Just over four billion years, from the birth of Earth to the eve of the explosive increase in animals — close to 90 percent of Earth’s history. The leading players are microbes invisible to the eye, and only toward the end do organisms of visible size such as Dickinsonia appear. The cyanobacteria that filled the planet with oxygen are residents of this time as well.
| Charnia | A frond anchored to the seafloor about 560 million years ago. The first fossil formally accepted as Precambrian |
| Charniodiscus | A frond-like organism standing on a lightless seafloor, anchored by a disc. Not a plant |
| Cloudina | A small animal living inside a calcium carbonate tube about 550 million years ago. Among the oldest shells built by animals, and some carry holes drilled by predators |
| Cyanobacteria | The bacteria that filled Earth’s atmosphere with oxygen. Alive from about two billion years ago to the present |
| Dickinsonia | A flat oval organism lying on the Ediacaran seafloor. Identified as an animal from fat molecules preserved in the fossils |
| The Francevillian biota | Disc-shaped structures with radial folds from about 2.1 billion years ago. A candidate for the oldest multicellular life — if it is life at all, which is undecided |
| Grypania | A coiled ribbon from about 1.87 billion years ago. Among the oldest fossils visible to the naked eye, though whether it is an alga or a bacterium is undecided |
| Kimberella | A slug-like crawling animal from about 555 million years ago. The fan-shaped grazing marks it left on the seafloor were decisive in making it a candidate mollusk ancestor |
| Spriggina | A segmented animal a few centimeters long from about 550 million years ago. It looks bilaterally symmetrical, but the segments are offset by half a step, and its affinity is undecided |
| Tribrachidium | A hemispherical organism from about 550 million years ago with three arms curling into a spiral. Its triradial symmetry matches no animal alive today |
Cambrian (about 539 to 485 million years ago)
The Cambrian explosion, when the basic body plans of animals appeared all at once. Trilobites with hard shells and compound eyes crawled the seafloor while the predator Anomalocaris swam above them. This is also the period of the strange cast — Hallucigenia, Opabinia — that kept researchers arguing over how to reconstruct them.
| Anomalocaris | One of the largest predators in the sea about 508 million years ago. Its appendages were described as a shrimp, its mouth as a jellyfish and its body as a sea cucumber; assembling them into one animal took 90 years |
| Aysheaia | A soft animal with ten pairs of legs, thought to have gripped sponges about 508 million years ago. The orientation of its reconstruction has not changed since 1911, yet its affinity is still undecided |
| Haikouichthys | A jawless fish about 2.5 cm long from about 518 million years ago. Regarded as among the oldest vertebrates, and reported in 2026 to have had four eyes |
| Halkieria | A slug-shaped animal in an armor of scales from about 518 million years ago, with a shell-like plate at the front and rear of the body. Only the scales were known for a long time; the whole animal came to light in 1989 |
| Hallucigenia | A small lobopodian from about 508 million years ago, with seven pairs of spines on its back and ten pairs of legs gripping sponges. The 1977 reconstruction was upside down and back to front, and took nearly 40 years to correct |
| Hurdia | A relative of Anomalocaris from Middle Cambrian seas. It carried a hollow projection of three shield plates on the front of its head; its shield and other parts were described as separate animals until it was reconstructed as one in 2009 |
| Leanchoilia | An arthropod from about 505 million years ago with six long whips extending from the arms in front of its head. Taken for an eyeless mud-eater until re-examination showed a predator with eyes |
| Marrella | One of the first fossils found in the Burgess Shale, about 508 million years old. There are over 25,000 specimens, yet which arthropod lineage it belongs to is still undecided |
| Myllokunmingia | A jawless fish about 3 cm long from about 518 million years ago. It appears in textbooks as among the oldest vertebrates, yet only one reliable fossil exists |
| Nectocaris | A flattened predator with stalked eyes and a pair of tentacles, swimming the Burgess Shale sea about 508 million years ago. Read as a shrimp, a fish and a squid in turn, and in 2025 proposed as close to the ancestry of arrow worms |
| Opabinia | A small swimmer with five eyes from about 508 million years ago, grasping prey with a long claw-tipped proboscis. When the reconstruction was shown at a conference, the room laughed |
| Ottoia | A priapulid worm buried in the seafloor mud about 508 million years ago. Shells of what it ate remain in its gut, showing its diet directly |
| Pikaia | A small chordate about 4 cm long from the Burgess Shale, about 508 million years ago. Long called the oldest human ancestor, it gave up the title when older fish were found |
| Saccorhytus | A sack-like animal 1 mm long from about 535 million years ago. Announced as the oldest human ancestor, it was reclassified among the ecdysozoans five years later |
| Titanokorys | A relative of Anomalocaris, estimated at about 50 cm, from the Middle Cambrian seas of Canada. A huge flat head shield covered most of its body, and it sifted seafloor mud with rake-like front limbs |
| Trilobites | Arthropods that appeared about 521 million years ago and flourished in the sea for nearly 270 million years. Their eyes were built of calcite crystal |
| Wiwaxia | A slug-shaped animal covered in scales and spines about 508 million years ago. Its mouth resembles a mollusk’s and its scales an annelid’s, and which group it belongs to is undecided |
| Yunnanozoon | A fish-shaped animal a few centimeters long from about 518 million years ago. Its classification has swung between chordate and vertebrate stem lineage for over thirty years and is still unsettled |
Ordovician (about 485 to 444 million years ago)
A period in which marine life diversified further. Giant orthocone nautiloids with straight conical shells stood at the top, while jawless fish swam near the seafloor. Sacabambaspis, which became an internet favorite in recent years, is a fish of this period.
| Arandaspis | A jawless fish from about 465 million years ago. Its head was enclosed in bony shields, but no bone remains in the fossils — only molds pressed into sandstone |
| Cameroceras | A straight-shelled Ordovician cephalopod, famous as the “largest cephalopod ever” with a 9-metre shell. Confirmed shells reach only about 2 metres; the 9-metre figure rests on a report with no photograph or specimen |
| Crinoids | Relatives of sea urchins and starfish that stand on the seabed like flowers. They appeared about 480 million years ago and still live in the deep sea |
| Graptolites | Colonial animals preserved as thin pencil-like lines on black mudstone. The drifting species are a mainstay for dating Paleozoic strata, and the encrusting type still lives on today’s seafloor |
| Horseshoe Crab | A chelicerate lineage running from about 480 million years ago to today. Fossils 445 million years old already look almost the same as the four living species, one of which is found in Japan |
| Isotelus | A large trilobite from the seas of Ordovician North America. The largest species reached about 72 cm, the largest trilobite ever found complete |
| Lingula | A brachiopod that looks like a clam but is not one. Called a “living fossil” for its 500-million-year-old shell shape, though the genus itself can only be traced back to the end of the Cretaceous |
| Nautilus | A cephalopod that controls its buoyancy with a chambered shell. Its relatives with the same shell design ruled the Ordovician seas, but the modern genus is a relatively young lineage that appeared in the Cretaceous |
| Orthoceras | A cephalopod with a straight conical shell. Famous by name from the black souvenir fossil plates, but the true genus is confined to the Middle Ordovician of the Baltic |
| Sacabambaspis | A jawless fish from about 460 million years ago. A museum model in Helsinki went viral in Japan in 2023, but its shape matched the fossils |
| Starfish | Appeared about 480 million years ago and still crawl the seafloor almost unchanged. The larva is bilateral, and gene mapping shows the adult star-shaped body is almost entirely “head” |
Silurian (about 444 to 419 million years ago)
The period when life began moving onto land in earnest. Sea scorpions flourished in the water, while on land the earliest plants, a few centimeters tall, stood up as Cooksonia. This is also when Prototaxites, the enigmatic column eight meters high, towered over the landscape.
| Baragwanathia | A club moss from Australia about 425 million years ago, with stems densely covered in long narrow leaves. Its body was so much more complex than other plants of its time that the age of its fossils was doubted for decades |
| Birkenia | A jawless fish under 10 centimeters long from Scotland about 430 million years ago, with hooked spines along its back and a tail whose lower lobe was the longer one. For 25 years after it was named, it was drawn upside down |
| Cooksonia | A plant a few centimeters tall that grew on Silurian land, with no leaves or roots, just forking stems tipped with spore capsules. Known as the first land plant, but the fossils collected under this name turned out to be several different lineages |
| Entelognathus | An armored fish of about 20 cm from some 420 million years ago. A placoderm whose jaw bones match those of bony fishes, revealing where the bones of our face came from |
| Eurypterus | A sea scorpion that lived in shallow lagoons about 420 million years ago. It accounts for more than 90 percent of all known sea scorpion fossils, but most of them are molted shells rather than dead animals |
| Favosites | A tabulate coral whose broken surface looks like a honeycomb. One of the main reef builders of the Silurian and Devonian, and the growth lines in its skeleton showed that a year back then had about 400 days |
| Guiyu | A fish about 30 cm long from 425 million years ago, the oldest bony fish known from a body preserved head to trunk. It carried fin spines and a pelvic girdle of dermal bone like a placoderm’s |
| Halysites | A tabulate coral from reefs about 430 million years ago. Its thin tubes joined in single rows to form a chain-like pattern. Among the first Silurian fossils found in Japan |
| Pneumodesmus | A small millipede from the Scottish coast known from a single fossil about 1 centimeter long. Spiracles on its sides show it breathed air, making it a candidate for the oldest known land animal, but whether its rock is Silurian or Devonian is still debated |
Devonian (about 419 to 359 million years ago)
The Age of Fishes. Dunkleosteus, its head sheathed in bony armor, ruled the sea, and Tiktaalik, with arm bones inside its fins, took a step toward land. Earth’s first forests also date from the Devonian.
| Brontoscorpio | The largest scorpion known, estimated at about 1 m long, from the rivers of Early Devonian Britain. In 2026 it was found to be the same animal as Praearcturus, named in the 1870s as a giant woodlouse |
| Coelacanth | A lobe-finned fish that appeared in the Devonian. Its fossil record ends in the Late Cretaceous and it was thought extinct, until a living fish was caught off South Africa in 1938. Two species live today, in the deep waters of the Comoros and Indonesia |
| Dunkleosteus | A placoderm fish of the Late Devonian seas with bony plates over its head and front body and jaw bones honed into blades instead of teeth. Long said to be 6 to 10 meters long, it shrank to 3 to 4 meters when the size estimate was redone in 2023 |
| Jaekelopterus | A giant sea scorpion from the brackish waters of Early Devonian Germany. A fossil claw 46 cm long gave an estimated length of about 2.5 m, making it the “largest arthropod ever,” though no complete body has been found |
| Lungfish | Lobe-finned fishes with lungs as well as gills that gulp air at the surface. They appeared in the Devonian, and six species survive in Australia, South America and Africa; the African species sleep through the dry season in a cocoon in the mud |
| Materpiscis | A placoderm fish about 25 cm long from a Late Devonian reef in Western Australia. An embryo linked by an umbilical cord was preserved inside it, the oldest evidence of live birth in vertebrates |
| Prototaxites | A columnar organism up to 8 meters tall that stood on land before forests existed. Read as a conifer, a seaweed and a giant fungus in turn, and in 2026 judged not to be a fungus either, so its identity is still open |
| Pterygotus | A sea scorpion about 1.6 m long, mostly Devonian, that hunted with heavy claws and sharp compound eyes. Its name, “the winged one”, dates from when its discoverer took it for a fish |
| Tiktaalik | A large flat-headed lobe-finned fish from rivers about 375 million years ago, with a neck and arm and wrist bones inside its front fins. Its discoverers worked out from the age of the rocks where it had to be and dug it up in the Canadian Arctic |
Carboniferous (about 359 to 299 million years ago)
The age of giant forests and giant insects. Meganeura, a dragonfly the size of a crow, flew overhead, and the millipede Arthropleura, over two meters long, crawled the ground. The forests of this period became the coal of later ages.
| Arthropleura | A giant myriapod of the Carboniferous and early Permian that reached about 2.6 m long. The largest land invertebrate known, and an early member of the millipede lineage |
| Cockroaches | Flat, cockroach-like insects that swarmed the swamp forests of the Carboniferous. Females had a long egg-laying tube at the tip of the abdomen, and they belonged to a different lineage from modern cockroaches |
| Lepidodendron | A “scale tree” over 30 m tall, a giant relative of clubmosses that formed Carboniferous swamp forests. Its trunk was covered in scale-like leaf scars, and it helped form coal |
| Meganeura | A giant dragonfly-like insect from Late Carboniferous France with a wingspan of about 70 cm. A predator of other insects in the skies of its time |
| Megarachne | A sea scorpion from the lakes and wetlands of Argentina near the end of the Carboniferous, about 300 million years ago. Described in 1980 as the largest spider ever, it was shown to be a sea scorpion in 2005 |
| Tully Monster | A soft-bodied animal from Late Carboniferous Illinois, with a long toothed tube and eyes on the ends of a sideways bar. Its place among animals is still unresolved |
Permian (about 299 to 252 million years ago)
The close of the Paleozoic. Lineages leading to mammals were the leading players on land, including the sail-backed Dimetrodon. At the end came the largest mass extinction in history, replacing the cast of living things root and branch.
| Dimetrodon | A meat-eating land animal of the Early Permian with a large sail on its back. Not a dinosaur, but a synapsid on the lineage that leads to mammals. Species ranged from about 1.7 to 4.6 m long |
| Diplocaulus | An amphibian about 1 m long that lived in the rivers and swamps of early Permian North America, with a flat, boomerang-shaped head whose back corners flared out to the sides |
| Fusulinids | Single-celled foraminifera with rice-grain-sized spindle-shaped shells that lived in shallow seas from the Carboniferous to the Permian. Used to date rock layers, they built the limestones of Akiyoshidai and Kinshozan in Japan |
| Glossopteris | A tree that formed Permian forests across the Southern Hemisphere, known for tongue-shaped fossil leaves from every southern continent, including the Antarctic specimens Scott’s party carried to the end in 1912 |
| Helicoprion | A large cartilaginous fish of the Permian seas with a spiral “tooth whorl” of saw-like teeth inside its lower jaw. Related to modern ratfish rather than sharks |
| Mesosaurus | A slender reptile about a meter long from an Early Permian inland sea. The first amniote known to have returned to the water, with fossils found in both South America and Africa |
Triassic (about 252 to 201 million years ago)
A fresh start after the great extinction. The earliest dinosaurs such as Eoraptor, about a meter long, appeared, while ichthyosaurs 17 meters long were already swimming in the sea. The first pterosaurs and the ancestors of mammals also arrived in this period.
| Chirotherium | Fossil footprints shaped like a human hand, found in Triassic rocks. They are thought to have been made by reptiles several meters long on the line leading to crocodiles |
| Plateosaurus | A long-necked plant-eating dinosaur of Late Triassic Europe, 4.8 to 10 m long as an adult, and an early member of the lineage that led to the giant sauropods |
| Tanystropheus | A Middle Triassic shoreline reptile with a stiff neck about three times as long as its trunk. Two species, one large and one small, hunted fish and small shelled animals in the water |
Jurassic (about 201 to 145 million years ago)
The period when dinosaurs grew large. Long-necked, long-tailed sauropods walked the land at over 20 meters, and Archaeopteryx, with feathered wings, appeared in the sky. The sea belonged to ichthyosaurs and plesiosaurs.
| Allosaurus | The most commonly found large meat-eating dinosaur of Late Jurassic North America, 8–10 m long. Its famous injury-scarred specimen “Big Al” was assigned to the new species Allosaurus jimmadseni in 2020 |
| Archaeopteryx | A raven-sized feathered, winged animal from Late Jurassic Germany. A theropod near the root of the bird lineage that still had teeth, finger claws and a long bony tail |
| Belemnites | Squid-like cephalopods of the Jurassic and Cretaceous seas. Their hard, bullet-shaped guards are found as fossils around the world |
| Brachiosaurus | A giant long-armed sauropod from Late Jurassic North America, 18 to 22 m long. Once pictured living in lakes with only its head above water, it is now thought to have fed on tall trees on dry land |
| Brontosaurus | A long-necked, long-tailed plant-eating sauropod from the Late Jurassic of North America, about 20–22 m long. Once treated as the same animal as Apatosaurus, it was recognized again as a separate genus in 2015 |
| Dilophosaurus | A 6–7 m meat-eating dinosaur from Early Jurassic North America, with two thin, plate-like crests on top of its head |
| Ichthyosaurus | An ichthyosaur about 2 m long from the Early Jurassic seas around Britain. It had a dolphin-like body and gave birth to live young at sea |
| Liopleurodon | A short-necked, big-headed plesiosaur from the seas of the latest Middle Jurassic. It reached up to about 8 m and was the top predator in the seas around what is now Britain |
| Megalosaurus | A meat-eating dinosaur about 6 m long from Middle Jurassic England. In 1824 it became the first dinosaur to receive a scientific name |
| Stegosaurus | A four-legged plant-eater from about 150 million years ago with a row of bony plates along its back. It was said to have a “second brain” in its hips, but that cavity held no brain at all |
Cretaceous (about 145 to 66 million years ago)
The climax of the age of dinosaurs. Tyrannosaurus and Triceratops on land, mosasaurs and ammonites in the sea, and the giraffe-sized pterosaur Quetzalcoatlus in the air. It all ended with an asteroid impact.
| Ammonites | Coiled-shell cephalopods that flourished from the Early Devonian to the end of the Cretaceous. Their fossils are abundant worldwide, but the body inside the shell remains poorly known |
| Ankylosaurus | A fully armored plant-eater from the end-Cretaceous of North America. Its tail club was long seen as a weapon against predators, but research suggests it was used mainly in fights between members of its own species |
| Elasmosaurus | A plesiosaur about 10 m long from the Late Cretaceous inland sea of North America. Its neck had 72 vertebrae and was about 7 m long |
| Futabasaurus | A long-necked elasmosaurid plesiosaur of the Late Cretaceous, found in 1968 by a high school student in Iwaki, Fukushima, Japan. It was named as the new genus and species Futabasaurus suzukii in 2006 |
| Giganotosaurus | A large meat-eating dinosaur about 12 to 13 m long from Cretaceous South America. Found in Argentina, it ranks with Tyrannosaurus among the largest known theropods |
| Iguanodon | A plant-eating dinosaur, 9 to 11 m long, from Early Cretaceous Europe. The second dinosaur ever named, with a large spike on each thumb |
| Kamuysaurus | A hadrosaurid dinosaur about 8 m long from Late Cretaceous Hokkaido. Known as the Mukawa dinosaur, it is the largest complete dinosaur skeleton found in Japan, and it came from marine rocks |
| Maiasaura | A duck-billed dinosaur of Late Cretaceous North America, up to about 9 m long, whose nests full of young suggest that parents cared for their hatchlings |
| Nipponites | A heteromorph ammonite of Late Cretaceous seas around Hokkaido, whose shell bends in U-shapes into a knot-like tangle; the symbol of the Palaeontological Society of Japan |
| Parasaurolophus | A duck-billed dinosaur of Late Cretaceous North America, 7.5–9.5 m long, with a tubular crest sweeping more than a metre back from its head. The airway loops inside the crest, which is thought to have worked as a resonator for its calls |
| Protoceratops | A horned dinosaur about 2 m long from Late Cretaceous Mongolia, with a parrot-like beak and a frill. Hundreds of fossils are known, from hatchlings to adults |
| Psittacosaurus | A dog-sized early ceratopsian from Early Cretaceous Asia with a parrot-like beak. Known from a huge number of specimens, including one that preserves the light and dark shading of its skin |
| Quetzalcoatlus | A pterosaur from the very end of the Cretaceous in Texas, with a wingspan of about 10 to 11 m. One of the largest flying animals known |
| Spinosaurus | A large fish-eating dinosaur with a sail on its back that lived in North Africa about 95 million years ago. It is still reconstructed both as a swimmer and as a wader |
| Tambatitanis | A sauropod about 15 m long that lived in Japan in the Early Cretaceous, nicknamed the Tamba dragon. Its fossil was found on a riverbed in Tamba City, Hyogo |
| Triceratops | A large horned dinosaur of 68–66 million years ago, with three horns and a bony frill. Whether its close relative Torosaurus, with holes in its frill, was simply an aged Triceratops is still undecided |
| Tyrannosaurus | A 12–13 m carnivorous dinosaur of North America, about 68–66 million years ago. It had one of the most powerful bites of any land animal and vanished in the end-Cretaceous mass extinction |
| Velociraptor | A turkey-sized feathered predator from Mongolia, about 75 million years ago. The movie raptor was modeled on a different genus, Deinonychus |
Paleogene (about 66 to 23 million years ago)
Mammals filling the seats left empty in a world without dinosaurs. The ancestors of whales returned from land to the sea as four-legged walkers and grew into Basilosaurus, 15 meters long. Paraceratherium, the largest land mammal in history, and Titanoboa, a 13-meter snake, also date from this period.
| Basilosaurus | An archaic whale of the late Eocene seas, 15 to 20 m long, with a slender body and tiny hind legs, first taken for a marine reptile and named “king lizard” |
| Darwinius | A small, long-tailed primate from Messel, Germany, about 47 million years ago. Unveiled in 2009 as a “missing link” toward humans, it is now widely seen as closer to the lemur side of the primates |
| Pakicetus | A wolf-sized early whale that lived in Pakistan about 50 million years ago. It walked on four legs and lived in shallow streams |
| Titanoboa | A giant relative of boas that lived in South American rainforests during the Paleocene, about 13 m long and over a tonne in weight. The largest snake known |
Neogene (about 23 to 2.58 million years ago)
The period in which today’s cast of living things came together. In the sea, Megalodon, among the largest sharks ever. On land, grasslands spread and horses ran across them, and in Africa the story of human ancestry began to move.
| Desmostylus | A four-legged mammal nearly 3 m long from Miocene North Pacific coasts, with molars like bundled pillars. Complete skeletons are known from Japan and Sakhalin |
| Livyatan | A giant relative of the sperm whale, about 13 to 17 m long, from the Miocene seas off Peru. Both its upper and lower jaws held teeth more than 36 cm long |
| Megalodon | A giant shark of the Miocene and Early Pliocene seas, known mostly from its teeth. Most estimates put it at 15 to 20 m long, though one study suggests more than 24 m |
Quaternary (about 2.58 million years ago to the present)
Our own period, cycling between glacials and interglacials. Woolly mammoths and Smilodon walked the ice-age landscape, and Homo sapiens spread across the world. This is also the period when other humans lived alongside us — Neanderthals and Denisovans.
| Dire Wolf | A wolf-sized carnivore of the dog family from Pleistocene North and South America. It looked like a wolf but belonged to a separate lineage that split off about 5.7 million years ago |
| Elephant Bird | A giant flightless bird from Madagascar, 2–3 m tall and weighing several hundred kilograms, that survived until about 1,000 years ago. Its closest relative is the kiwi of New Zealand |
| Frilled Shark | A deep-sea shark up to about 2 m long, found in places such as Suruga Bay in Japan. It has six pairs of frilled gills and is called a “living fossil” |
| Ginkgo | A tree with fan-shaped leaves and the only surviving species of Ginkgoales, a group that once spread worldwide. A “living fossil” and a seed plant whose sperm swim |
| Metasequoia | A deciduous conifer of the cypress family that formed forests across the Northern Hemisphere from the Cretaceous and grew in Japan until the Early Pleistocene. It was named from fossils in 1941, and living trees were later found in a mountain village in China |
| Naumann’s elephant | An elephant that lived across the Japanese archipelago during the Pleistocene. Males stood about 2.5 m at the shoulder. It is the most commonly found fossil elephant in Japan and survived until about 35,000 years ago |
| Smilodon | A large saber-toothed cat of Pleistocene North and South America, popularly called the saber-toothed tiger, though it belonged to a separate lineage from tigers |
| Steller’s Sea Cow | A giant relative of the dugong, 7 to 10 m long, from the cold North Pacific. Recorded alive in 1741, it was hunted to extinction around 1768 |
| Tuatara | A reptile about 50 cm long found only in New Zealand. Not a lizard, it is the only surviving species of Rhynchocephalia, a group that flourished in the Triassic |
| Woolly Mammoth | A long-haired elephant of the Ice Age northern grasslands, about 3 m tall at the shoulder in males, that outlived its mainland relatives on Arctic islands until about 4,000 years ago |
Sources
The divisions and dates follow the International Chronostratigraphic Chart of the International Commission on Stratigraphy (ICS).
・International Chronostratigraphic Chart (ICS): https://stratigraphy.org/chart
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