Mammals & synapsids

01Cenozoic

They lived not on endless ice, but in a wind-shaped grassland ecosystem.

02Cenozoic

Its enormous canines were only part of the weapon; the real power lay in exceptionally strong forelimbs.

18Paleozoic

This sail-backed predator was closer to mammals than to dinosaurs.

19Paleozoic

A beaked, tusked survivor became extraordinarily common after Earth’s greatest mass extinction.

20Cenozoic

Standing on its hind legs, this elephant-sized sloth could reach high branches with huge claws.

21Cenozoic

A domed shell of fused armor protected this car-sized relative of armadillos.

22Cenozoic

The largest deer antlers known were seasonal structures for display and competition.

23Cenozoic

A heavy-jawed canid hunted the large herbivores of Ice Age America.

24Recently extinct

Australia’s striped marsupial predator survived longest in Tasmania.

27Recently extinct

This enormous, slow sirenian grazed kelp in cold shallow water.

38Paleozoic

Long saber canines armed one of the largest predators of the latest Permian.

63Cenozoic

The largest known land mammal was a hornless rhinoceros relative built to browse high foliage.

64Cenozoic

Knob-like skull horns and long canines crowned this rhinoceros-sized herbivore.

65Cenozoic

This long-bodied early whale still carried tiny external hind limbs.

66Cenozoic

Huge teeth in both jaws armed a macropredatory sperm whale.

67Cenozoic

Ever-growing saber canines evolved independently in this marsupial relative.

68Cenozoic

This long-necked hoofed mammal belonged to a uniquely South American lineage.

69Cenozoic

A heavy-bodied native ungulate grazed and browsed beside Ice Age giants.

70Cenozoic

This enormous grazing rhinoceros probably supported a large horn on its forehead.

71Cenozoic

A thick coat and flattened horn equipped this rhinoceros for cold, dry mammoth steppe.

72Recently extinct

This plains zebra had bold stripes in front fading into a plain brown rear body.

73Recently extinct

The powerful wild ancestor of domestic cattle once ranged across three continents.

74Recently extinct

The only seal endemic to the Caribbean rested and bred on warm sandy shores.

75Recently extinct

This unusually tame island canid was the Falklands’ only native land mammal.

79Recently extinct

The bucardo was the first extinct animal briefly brought back as a clone—and the first to go extinct twice.

84Paleozoic

A thick skull roof capped this heavy plant-eating mammal relative.

92Cenozoic

Long clawed forelimbs made this horse relative walk on its knuckles.

93Cenozoic

A huge deep-skulled omnivore belonged to the entelodonts, not to true pigs.

94Cenozoic

A spiked tail club completed the armor of this giant glyptodont.

96Cenozoic

A broad face, forward-looking eyes and single-toed feet distinguished this giant kangaroo.

97Cenozoic

This black-bear-sized beaver had ridged teeth and depended on extensive wetlands.

100Recently extinct

This large coastal sea lion bred on rocky islands across the Sea of Japan.

105Paleozoic

Crossbars projected from the spines of its tall sail above a broad plant-processing body.

111Cenozoic

Nearly everything known directly comes from one enormous skull, leaving the body unusually uncertain.

112Cenozoic

It resembled a rhinoceros but belonged to the extinct brontotheres and carried paired nasal horns.

113Cenozoic

A massive body, broad feet and four ossicones made this giraffid resemble both deer and cattle.

114Cenozoic

Short blade-like canines, long forelimbs and a sloping back suited pursuit of large prey.

115Cenozoic

Ice Age art usually shows this immense cat without the heavy mane of many modern male lions.

116Cenozoic

Without large predators, this heavy island rabbit evolved small ears and lost efficient hopping.

120Recently extinct

This palm-sized insect bat fell from island-wide abundance to a final acoustic signal in 2009.

138Paleozoic

Paired bony bosses formed a rough crown on the skull of this large, probably plant-eating therapsid.

140Cenozoic

Two enormous hollow nasal horns and a smaller rear pair belonged to an embrithopod, not a rhinoceros.

169Paleozoic

A tiny head joined a barrel-shaped giant body whose broad ribs enclosed a vast plant-fermenting digestive system.

176Cenozoic

Strong limbs could still bear weight, yet long feet paddled through water and the ear region was adapting to underwater sound.

177Cenozoic

Bundles of enamel-wrapped tooth columns and broad limbs helped it crop aquatic plants in tidal flats and shallow water.

178Cenozoic

Rear-shifted nostrils and four tusks document a distinctive skull; a short trunk is a soft-tissue reconstruction inferred from the bones.

179Cenozoic

This rhinoceros-sized marsupial clipped plants with two forward incisors and moved between seasonal water sources.

218Paleozoic

A beak, short tusks and powerful forelimbs made this one of the most common burrowing herbivores of the Late Permian.

219Paleozoic

Long upper canines and a wide gape made it an early experiment in saber-toothed predation.

241Cenozoic

Tapir-sized and short-faced, it lived before proboscideans acquired the elephant's long trunk and giant body.

242Cenozoic

A widened jaw and flattened lower tusks formed a shovel-like cutting edge for tough vegetation.

243Cenozoic

Only the lower jaw carried tusks, curving downward beneath a body taller than most modern elephants.

244Cenozoic

Two upper and two lower tusks gave its elongated head a four-tusked profile absent from living elephants.

245Cenozoic

A long skull held powerful jaw muscles, while slicing molars evolved independently from carnivoran carnassials.

246Cenozoic

A bear-heavy torso combined with a dog-like long skull and tail, inspiring the name bear-dog.

247Cenozoic

A skull nearly half a meter long and robust shearing teeth placed it among the largest terrestrial mammalian carnivores.

248Cenozoic

Dense bones helped it submerge and long claws anchored it on the bottom—an extraordinary marine experiment among ground sloths.

249Cenozoic

It may have approached a tonne, with giant incisors capable of generating exceptional bite forces.

261Paleozoic

Its long skull and deep tail suggest a waterside animal that was still a capable walker.

262Paleozoic

Low vertebral ridges accompanied a deep skull and strongly differentiated teeth.

263Paleozoic

A light build, long limbs and small skull bosses combine primitive and therapsid features.

264Paleozoic

A huge skull combined thickened impact surfaces with long canines in a formidable predator.

265Paleozoic

A domed, massively thick skull crowned the barrel body of this giant herbivore.

266Mesozoic

A whiskered snout, differentiated teeth and burrowing life approach the mammalian body plan.

267Mesozoic

A dog-like snout, slicing cheek teeth and upright hind limbs made it a major cynodont predator.

291Cenozoic

Long hind legs and a balancing tail powered a distinctive hopping gait through the forest floor.

293Cenozoic

Hoof-like toes and a large predatory skull belonged to a carnivorous mammal with no modern equivalent.

294Cenozoic

Its body still walked on land, while a distinctive ear region identified it as an early whale.

295Cenozoic

A streamlined whale body still carried tiny external hind limbs with no walking function.

296Cenozoic

A broad hollow nasal ram rose from the skull of this immense brontothere.

297Cenozoic

A forked Y-shaped nasal horn joined two brow horns in the most elaborate protoceratid display.

298Cenozoic

Short legs and a barrel body gave this grazing rhinoceros a hippo-like outline.

299Cenozoic

Thick hide reinforced by tiny bony nodules protected this large ground sloth.

300Cenozoic

Huge curved claws belonged to a forest browser whose name is tied to Thomas Jefferson.

341Cenozoic

Deep jaws and slicing teeth suggest an ancient kangaroo relative that ate meat.

342Cenozoic

A bear-like carnivore used powerful jaws to pry and crush shellfish.

343Cenozoic

Long limbs converged on cheetah proportions, but its closest ties were to cougars.

344Cenozoic

Grasping feet and flexible shoulders reveal a large climbing marsupial.

345Recently extinct

Island scarcity shrank a giant-elephant lineage to about one meter at the shoulder.

346Recently extinct

It was hunted out for fur before scientists could describe a living animal.

347Recently extinct

Its blue cast likely came from gray hair over dark skin rather than bright fur.

348Recently extinct

Broad multi-tined antlers formed a crown above floodplain grasslands.

465Cenozoic

A bear-sized Caribbean ground sloth survived near the period of human arrival.

466Cenozoic

A mobile snout, huge claws and strange forelimbs belonged to a marsupial unlike any tapir.

467Cenozoic

A cow-sized wombat relative carried a broad snout and heavy limbs.

468Cenozoic

Three pairs of skull bosses and long canines crowned a rhino-sized herbivore.

469Cenozoic

A short face, tusk-like canines and grinding cheeks marked a herd-forming artiodactyl relative.

470Cenozoic

Massive jaws and rounded carnassials crushed bone, though it was not a modern hyena.

471Cenozoic

Huge cutting teeth came from a hyaenodont predator heavier than a modern lion.

472Cenozoic

A flexible proboscidean crossed many habitats and ate mixed vegetation.

498Cenozoic

This fox-sized perissodactyl was a palaeothere relative, not a direct horse ancestor.

499Cenozoic

Short legs, a broad body and high-set eyes adapted a hornless rhinoceros relative to semiaquatic life.

500Cenozoic

Palmate branching antlers made this East Asian giant deer especially conspicuous.

545Cenozoic

Five-toed feet and generalized teeth record an early radiation of hoofed-mammal relatives.

546Cenozoic

A short trunk and upper and lower tusks mark an early stage of proboscidean evolution.

547Cenozoic

A bear-sized heavy body and five-toed feet belonged to a pantodont herbivore.

548Cenozoic

A hornless, long-limbed rhinoceros was built for travel across open woodland.

549Cenozoic

A small hornless body combined traits near the early split of rhinos and tapirs.

550Cenozoic

A barrel body, short legs and large canines marked one of the first widespread large mammals.

568Cenozoic

A short face, low-crowned teeth and three-toed feet belonged to a European herbivore near horse relatives.

569Cenozoic

A horse-like head and enormous curved claws belonged to a herbivorous perissodactyl walking on its knuckles.

570Cenozoic

Only tapir-sized and hornless, it already possessed the short face and teeth of early brontotheres.