Prehistoric mammals are groups of mammals that lived before humans developed writing. 164 million years ago, in the Jurassic period, Castorocauda lutrasimilis, a mammal-like (mammaliaform) animal weighing about 500 grams (1.1 lb), had a full mammalian pelt, with guard hairs and under fur, webbed feet, and scales on the tail like a modern beaver, as well as teeth specialized for catching fish.

Later, about 130 million years ago in the Cretaceous, there existed larger mammals, including Repenomamus giganticus and Repenomamus robustus. Fossils up to one meter (3¼ ft) long have been found, with dinosaur remains in their stomach contents.

The lineages of many varieties continued through the Tertiary period where some reached very large sizes. Most of the very large mammals became extinct in the last ice age, but have smaller descendants.

List of prehistoric mammals

Prehistoric mammals include:

• Amebelodon
• American Cheetah
• American Camel
• American Zebra
• Anancus
• Ancient Bison
• Ancient Narwhal
• Andrewsarchus
• Archaeobelodon
• Arsinoitherium
• Atzlan Rabbit
• Barytherium
• Basilosaurus
• Bone-crushing Dog
• Brontotherium
• Castorocauda lutrasimilis
• Cave Bear
• Cave Lion
• Chalicothere
• Chalicotherium
• Deinotherium
• Diminutive Pronghorn
• Diprotodons
• Dire Wolf
• Doedicurus
• Dorudon
• Dwarf Killer Whale
• Dwarf Polar Bear
• Elasmotherium
• Embolotherium
• Entelodont
• Eobasileus
• European Jaguar
• European Hippopotamus
• Four-Tusked Elephant
• Giant Orangutan
• Giant Koala
• Giant Meerkat
• Giant Long-horned Buffalo
• Giant Lynx
• Giant Vampire Bat
• Giant Beaver
• Giant Killer Whale
• Giraffe Camel
• Glyptodon
• Gomphotherium
• Hypselephas
• Hyracotherium
• Indricotherium/Baluchitherium/Paraceratherium
• Irish Elk
• Kennalestes
• Knife-flippered Killer Whale
• Japanese Dwarf Elephant
• Harrison's Whale
• Horned Narhwal
• Hyaenodon
• Humpback Narhwal
• Japanese Cougar
• Juxia
• Macrauchenia
• Mammoths

• Columbian Mammoth
• Woolly Mammoth
• Pygmy Mammoth
• Imperial Mammoth
• Tundra Mammoth
• Wrangel Island Mammoth

Malagasy River Dolphin

Marsupial Lion

Mastodons

• American Mastodon
• Palaeomastodon
• Sinomastodon

Megaloceros

Megatherium

Meninatherium

Menodus

Metamynodon

Moeritherium

North American Camel

North American Lion

North American Llama

Paratetralophodon

Phiomia

Platybelodon

Primelephas

Propalaeotherium

Purgatorius

Pygmy Polar Bear

Pygmy Giant Panda

Powerful Killer Whale

Repenomamus giganticus and r.robustus

Rhynchotherium

Rinston's Bottlenose Dolphin

Saber-toothed cats

• Smilodon

Samotherium

Sivatherium

Shark-toothed Dolphin

Short-faced Skunk

Shuler's Pronghorn

Stegodon

Stubby-Tusked Narwhal

Sensitive Ibex

Swan-necked Seal

Synthetoceras

Teleoceras

Tetrabelodon

Tetralophodon

Toxodon

Trilophodon

Uintatherium

Walrus Whale

Wilmington's Ground Sloth

Wanda's Fox

Woolly Rhinoceros

See also

• Synapsid
• Therapsid
• Cynodont
• Mammaliaformes
• List of extinct mammals