Note: Unless otherwise referenced in the text, generic synonymies are standardized based on the data contained in http://fossilworks.org/
Abderites: Small, rodent-like, frugivorous marsupial
Acaremys: Small, ground-dwelling, herbivorous rodent related to guinea pigs
Acdestis: Small, rodent-like, omnivorous marsupial
Aceratherium: Seven- to eight-foot-long, herbivorous, browsing rhinoceros, weighing about one ton
Achaenodon: Six-foot-long, herbivorous, pig-like entelodont or terror pig, weighing about 500 pounds
Acipenser: Carnivorous sturgeon
Aciprion: Ominovorous lizard related to other iguanas
Acrocyon: Swift, wolf-like, carnivorous marsupial
Adelphomys: Small, ground-dwelling, herbivorous rodent related to guinea pigs
Adinotherium: Five-foot-long, quadrupedal, herbivorous, hippo-like, notoungulate mammal, weighing about 250 pounds
Adjidaumo: Small, ground-dwelling, herbivorous relative of pocket gophers and kangaroo rats
Aelurodon: Large, hyaena-like, bone-crushing dog
Aepycamelus: Ten-foot-tall, ten-foot-long, browsing camel, weighing about a ton
Aetobatis: Marine, eagle ray
Agriochoerus: Clawed, even-toed, herbivorous ungulate
“Alethesaurus”: Extinct lizard now called Chamops
Aleurocyon: Weasel- or badger-like, carnivorous predator related to weasels and otters
Albanerpeton: Salamander-like amphibian
Allacodon: Small, herbivorous, multituberculate mammal
Allognathosuchus: Extinct, five-foot-long, carnivorous alligator
“Allops”: Large, herbivorous, odd-toed ungulate now called Megacerops
Allosaurus: Large, bipedal, carnivorous saurischian dinosaur about 25–30 feet long and weighing around 2.5 tons
Alphadon: Quick, ground-dwelling, omnivorous marsupial mammal
Alphalagus: Herbivorous rabbit
Amia: Piscivorous bowfin fish
Amphicaeonpus: Browsing rhinoceros
Amynodon: Large, semi-aquatic, hippo-like, browsing, odd-toed ungulate related to rhinoceroses
Analcimorphus: Herbivorous ground sloth
Ancodon: Large, hippo-like, herbivorous, browsing, amphibious, even-toed, ungulate mammal
Ankylodon: Ground-dwelling, insectivorous elephant shrew
Apatosaurus: Long-necked, long-tailed, herbivorous sauropod dinosaur about 70 feet long and weighing 25 tons; now once again called Brontosaurus by some
Aphelops: Moderate-sized, herbivorous, odd-toed rhino, weighing up to three tons
Aramus: Ground-dwelling, two-foot-tall, carnivorous bird or limpkin
Archaeotherium: Large, pig-like, omnivorous, even-toed, hoofed “terror pig,” three feet tall, six feet long, weighing over 500 pounds
Ardynomys: Ground-dwelling, herbivorous rodent
Aspidertes: Aquatic, carnivorous, soft-shell turtle
Asterostemma: Armored, tank-like, omnivorous mammal called a glyptodont related to armadillos
Astrapothericulus: Hefty, herbivorous ungulate mammal
Astrapotherium: Eight-foot-long, hefty, herbivorous ungulate mammal, weighing around a ton
Astrodon: Long-necked, four-footed, herbivorous, sauropod dinosaur, around 30 feet tall and 50-60 feet long
Aublysodon: Large, carnivorous, bipedal dinosaur, closely related to other tyrannosaurs including Tyrannosaurus
“Aulocetus”: Carnivorous, suspension-feeding, baleen whale now called Cetotheriopsis
Axestemys: Aquatic, carnivorous or piscivorous, softshell turtle
Baena: Aquatic, carnivorous turtle
Barbourofelis: Lion- to lepoard-sized, saber-toothed, carnivorous predator only distantly related to true cats
Barosaurus: Extremely long-necked, 85-foot-long, herbivorous sauropod dinosaur, weighing about 20 tons
Basilemys: Enormous terrestrial turtle
Bathygenys: Small, even-toed, hoofed, herbivorous, pig-like oreodont, weighing about 15 pounds
Batodon: Small, insectivorous, placental mammal
Belonostomus: Carnivorous, ray-finned fish
Blastomeryx: Herbivorous, even-toed, hoofed, 2.5-foot-long musk deer with enlarged canines, weighing about 35 pounds
Borhyaena: Four- to five-foot-long, swift, wolf-like, carnivorous marsupial, weighing around 50 pounds
Bothriodon: Pig-sized, even-toed, hoofed, hippo-like ungulate
Brachychampsa: Nine-foot-long, amphibious, carnivorous crocodile
Brachyrhyncocyon: Relatively small, ground-dwelling, carnivorous “bear dog” or amphicyonid
“Brontops”: Small elephant-sized, rhino-like, horned, odd-toed, hoofed, browsing mammal, 8 feet tall at shoulder, 15 feet long, weighing about 3 tons and now called Megacerops
“Brontotherium”: Small elephant-sized, rhino-like, horned, odd-toed, hoofed, browsing mammal, 8 feet tall at shoulder, 15 feet long, weighing about 3 tons and now called Megacerops
Bufo: Large, stocky, carnivorous toad
“Caenopus”: Cow- or tapir-sized herbivorous rhino around 8 feet long, weighing about 800 pounds and now called Subhyracodon
Calamagras: Carnivorous snake related to modern boas
Calyptocephalella: Amphibious, helmeted water toad
Camarasaurus: Stocky, herbivorous sauropod dinosaur about 50 feet long and weighing around 20 tons
“Camelomeryx”: Deer-like, browsing even-toed ungulate now called Leptoredon
Campestrallomys: Burrowing, herbivorous mountain beaver
Camptomus: Small, multituberculate mammal
Captorhinus: Two- to three-foot-long, lizard-like, carnivorous reptile
Carcharhinus: Requiem shark
Carcharodon: White shark, close relative of modern great white shark, sometimes now called Carcharocles
Caudiverbera: Stout, amphibious frog
Centetodon: Small, shrew-like mammal
Ceratodus: Lungfish
Ceratops: Herbivorous, horned dinosaur
Ceratosaurus: Large, bipedal, carnivorous saurischian dinosaur, about 17 feet long and weighing one to 1.5 tons
Chamops: Polyglyphanodontian lizard
Champosaurus: Five- to 10-foot-long, aquatic, carnivorous reptile resembling a crocodile, although not closely related
Chrysemys: Aquatic, omnivorous painted turtle
Cimolestes: Quick, ground-dwelling, insectivorous placental mammal
Cimolomys: Small, herbivorous, multituberculate mammal
Cimolodon: Small, herbivorous, multituberculate mammal
Cimolomys: Small, herbivorous, multituberculate mammal
Cimolopteryx: Carnivorous shore bird
Cladosictis: Swift, somewhat hyaena-like, carnivorous marsupial
Clidastes: Seven- to 20-foot- long, marine monitor lizard called a mosasaur that probably ate fish and squid
Cochlops: Tank-like, armored, omnivorous glyptodont related to armadillos
Coelurus: Eight-foot-long, carnivorous, bipedal, theropod dinosaur, weighing about 40 pounds
Colodon: Ground-dwelling, odd-toed, browsing tapir
Colpodontosaurus: Extinct lizard
Coniophis: Small, burrowing, carnivorous snake
Contogenys: Extinct lizard
Coriops: Bone fish
Corythosaurus: Thirty-foot-long, crested, herbivorous, duckbill dinosaur, weighing about three tons
“Creosaurus”: Large, bipedal, carnivorous dinosaur now called Allosaurus
Crocodylus: Crocodile
Cuttysarkus: Amphibious salamander now called Prodesmodon by some paleontologists
Cylindrodon: Ground-dwelling, herbivorous rodent
Cyclopedius: A 4-foot-long, sheep-like, ground-dwelling, herbivorous oreodont
Cynodesmus: Coyote-sized, omnivorous true dog
Cynodictis: Small, martin-like, carnivorous “bear dog” or amphicyonid, about three feet long
Daemonelix: Large, corkscrew-shaped, fossilized burrow up to 6–8 feet long made by Palaeocastor
Daphoenus: Coyote-sized, carnivorous bear dog, distantly related to modern dogs
Deinodon: Large, carnivorous, bipedeal dinosaur closely related to Tyrannosaurus
Deinosuchus: Enormous alligator up to 35 to 40 feet long and weighing as much as 8 to 9 tons
Delotrochanter: Ground-dwelling, carnivorous “bear dog”
Desmatolagus: Ground-dwelling, grazing or browsing rabbit
Diadectes: Eight-foot-long, stocky, herbivorous, terrestrial, four-footed animal
Diadiaphorus: Swift, four-foot-long, somewhat horse-like, herbivorous, proterotheriid placental, mammal, weighing around 150 pounds
Diceratherium: Ground-dwelling, browsing rhinoceros, weighing about one ton
Didelphodon: Opossum-like and sized marsupial mammal
“Didelphops”: Small, marsupial mammal now called Didelphodon
Dimetrodon: Ten-foot-long, fin-backed, carnivorous early relative of mammals
Dinictis: Leopard-sized, cat-like, saber-toothed carnivore only distantly related to true cats
Dinohyus: Enormous, omnivorous, pig-like, “terror pig” with skull as long as 3 feet and standing almost 6 feet tall at the shoulder
Diplacodon: Large, browsing, odd-toed ungulate called a brontothere
Diplocaulus: Three-foot-long, boomerang-headed, primarily aquatic, carnivorous amphibian
Diploclonus: Large, quadrupedal, herbivorous, odd-toed ungulate called a brontothere
Diplodocus: Long-necked, long-tailed, small skulled, herbivorous sauropod dinosaur up to more than 80 feet long and weighing about 15 tons
“Dipriodon”: Small, multituberculate mammal now called Meniscoessus
Domnina: Small insectivorous shrew
Dryolestes: Small, insectivorous mammal
Dryptosaurus: Carnivorous, 25-foot-long, bipedal dinosaur, closely related to Tyrannosaurus and weighing about 3000 pounds
Echmatemys: Aquatic, herbivorous turtle
“Ectoconodon”: Opossum-like, marsupial mammal now called Didelphodon
Edaphosaurus: Ten-foot-long, fin-backed, herbivorous early relative of mammals
Edmontonia: Twenty-foot-long, herbivorous, tank-like, armored, nodosaurid dinosaur, related to ankylosaurs
Edmontosaurus: Bipedal, herbivorous, duckbill dinosaur up to 40 feet long, weighing 10 tons
“Elosaurus”: Enormous, long-necked, herbivorous sauropod dinosaur, now called Apatosaurus or Brontosaurus
Elotherium: Large, omnivorous, pig-like entelodont or “terror pig,” also called Ammodon
Entelodon: Large, 4.5-foot-tall, pig-like ungulate or entelodont, informally called a “terror pig”
Eocardia: Small, ground-dwelling, herbivorous rodent related to guinea pigs
Eomoropus: Large, browsing, odd-toed ungulate called a chalicothere
“Epigaulus”: Horned, ground-dwelling, gopher-like rodent, now called Ceratogaulus
Epihippus: Two-foot-tall, browsing horse
Epoicotherium: Insectivorous relative of the pangolins or “scaly anteathers”
Eporeodon: Moderate-sized, even-toed, herbivorous, ruminating oreodont, weighing around 250 pounds
Equus: Modern genus of horse
Eryops: Eight-foot-long, semi-aquatic, carnivorous amphibian
Essonodon: Arboreal, herbivorous, multituberculate mammal
“Euangelistes”: Ground-dwelling, omnivorous or frugivorous placental mammal now called Gypsonictops
Eucholoeops: Omnivorous ground sloth
Eucinepeltus: Armored, tank-like, omnivorous mammal called a glyptodont related to armadillos
Euhapsis: Amphibious, browsing beaver
Eumys: Six-inch long, herbivorous, mouse-like, ground-dwelling rodent
Eusmilus: Eight-foot-long, cat-like, saber-toothed carnivore only distantly related to true cats
Exostinus: Carnivorous anguimorph lizard
Galeocerdo: Tiger shark
Gavia: Ground-dwelling, carnivorous loon
Geochelone: Large, ground-dwelling, herbivorous tortoise
Glasbius: Small, herbivorous or frugivorous marsupial mammal
Glyptodon: Five-foot high, 11-foot-long, tank-like, omnivorous, armored mammal related to armadillos, weighing around two tons
Glyptops: Extinct, side-necked or cryptodire turtle
Glyptosaurus: Ground-dwelling, insectivorous or carnivorous, anguid lizard
Gomphotherium: Ten-foot-tall, four- to five-ton relative of elephants
Goniopholis: Six- to 12-foot-long, semi-aquatic, carnivorous, crocodile-like reptile
Gopherus: Burrowing, herbivorous tortoise
Gregorymys: Browsing pocket gopher
“Griphippus”: Small, herbivorous, three-toed, grazing horse now called Pseudhipparion
Gypsonictops: Ground-dwelling, omnivorous or frugivorous placental mammal
Habrosaurus: Five-foot-long, carnivorous salamander
Hadrosaurus: Large, herbivorous, duckbill dinosaur
“Hadroleptauchenia”: Herbivorous oreodont now called Leptauchenia
“Halodon”: Small multituberculate mammal now called Meniscoessus
Hapalops: Three-foot-long, primarily herbivorous ground sloth with some arboreal ability
Haplocanthosaurus: Large, long-necked, herbivorous sauropod dinosaur with spines on back, about 50 to 60 feet long and weighing around 13 tons
“Harpagosaurus”: Carnivorous lizard now called Exostinus
Hatcheritherium: Small, omnivorous, marsupial mammal
Hayoceros: Browsing, antelope-like pronghorn
Hegetotherium: Herbivorous notoungulate mammal
Heliscomys: Ground-dwelling, herbivorous rodent related to pocket gophers
Helodermoides: Carnivorous and insectivorous anguid lizard
Hemiauchenia: Six-foot-tall, seven-foot-long, herbivorous, llama-like camel, weighing about 600 pounds
Hemipristis: Ground shark
Hendryomeryx: Ground-dwelling, fruit-eating, even-toed, hoofed ruminant
Heptacodon: Large, hippo-like, browsing ungulate called an anthracothere
Hesperocyon: Primitive, 3-foot-long, slender, fox-like dog, weighing around five pounds
Hesperomys: Ground-dwelling, herbivorous mouse
Hipparion: Six-foot-long, six-foot tall, herbivorous horse weighing about 1000 pounds
Homalodotherium: Six-foot-long, herbivorous notoungulate mammal, weighing around 650 pounds
Homogalax: Browsing, tapir-like, odd-toed ungulate
Hoplophoneus: Leopard-sized, cat-like, saber-toothed carnivore only distantly related to true cats
Hyaenodon: Relatively large, massive skulled, small-brained, hyaena-like mammal, among the largest carnivores of it time
“Hyopotamus”: Browsing, hippo-like anthracothere now called Bothriodon
Hyopsodus: Swift, omnivorous, ungulate mammal called a condylarth
Hypertragulus: Small, even-toed, deer-like ruminant, weighing about 15 pounds and related to chevrotains
Hypisodus: Small deer-like, even-toed, hoofed ungulate related to chevrotains
Hyracodon: Swift, 5-foot-long, slender-legged rhino, probably forest and open grassland browser
Ictops: Ground-dwelling, insectivorous or carnivorous mammal related to Leptictis
Iguanavus: Lizard
Interatherium: Two-foot-long, quadrupedal, herbivorous notoungulate mammal
Ischyrocyon: Carnivorous “bear dog” or amphicyonid, weighing about 350 pounds
Ischyromys: Early, 2-foot-long, squirrel-like, arboreal rodent
“Ischyrotomus”: Ground-dwelling, herbivorous rodent now called Pseudotomus
Isectolophus: Browsing, tapir-like, odd-toed ungulate
Isurus: Mako shark
“Kindleia”: Carnivorous or piscivorous bowfin fish now called Cyclurus
Labidosaurus: Three-foot-long, heavily built, lizard-like, insectivorous reptile
“Lanceosaurus”: Extinct lizard now called Chamops
Leidyosuchus: Large, carnivorous crocodile
Leptictis: Primitive, 2- to 3-foot long, weasel-like mammal, possibly insectivorous
Leptauchenia: Ground-dwelling, even-toed, hoofed, herbivorous oreodont, weighing about 80 pounds
Lepisosteus: Large, carnivorous gar
Leptoceratops: Primitive, herbivorous, seven-foot-long member of horned dinosaurs weighing about 150–400 pounds
Leptochamops: One-foot-long, insectivorous lizard
Leptochoerus: Chevrotain-like, rabbit-sized, swift, hoofed ungulate, browsing herbivore
Leptomeryx: Three-foot-long deer-like, even-toed, hoofed, herbivorous ruminant
Leptoreodon: Browsing, deer-like, even-toed ungulate
Leptotomus: Ground-dwelling, herbivorous rodent
Leptotragulus: Browsing, deer-like, even-toed ungulate
Licaphrium: Swift, somewhat horse-like, herbivorous, proterotheriid, placental mammal
Limenetes: A 4-foot-long, sheep-like, ground-dwelling, herbivorous oreodont
Lisserpeton: Extinct salamander
Litakis: Polyglyphanodontian lizard
Lysorophus: Salamander-like, aquatic amphibian with reduced limbs
Mammut: Large, elephant-like mastodon
Mammuthus: Huge, elephant-like mammoth
“Mastodon”: Large, elephant-like mastodon, now called Mammut
Megacerops: Small elephant-sized, brontothere; rhino-like, horned, odd-toed, hoofed, browsing mammal, 8 feet tall at shoulder, 15 feet long, weighing about 3 tons
Megalagus: Large, ground-dwelling, herbivorous rabbit
Megalonychotherium: Large, herbivorous ground sloth
Megatylopus: Browsing, 14-foot-tall camel, weighing about two tons
Melvia: Carnivorous bowfin fish
Meniscoessus: Small, herbivorous, multituberculate mammal
Meniscognathus: Extinct lizard
Menoceras: Small, browsing, rhino about 5 feet long
“Menodus”: Large, herbivorous, rhino-like, odd-toed ungulate now called Megacerops
Merychippus: Three-toed, hoofed, grazing, 3-foot-high horse, with different species weighing up to 200 pounds
Merychyus: Pig- or sheep-like, even-toed, hoofed herbivorous ruminant, weighing about 200 pounds
Merycochoerus: Enormous, pig-like, even-toed, hoofed ruminating oreodont, weighing up to 900 pounds
“Merycodesmus”: Browsing, deer-like, even-toed ungulate now called Leptoreodon
Merycodus: Ground-dwelling, herbivorous, browsing and grazing, antelope-like ruminant
Merycoides: Moderate-sized, even-toed, herbivorous, ruminating oreodont, weighing around 150–250 pounds
Merycoidodon: Pig-like, even-toed, hoofed, herbivorous ruminating oreodont, four- to five-foot-long and weighing 200–300 pounds
Mesatirhinus: Large, herbivorous, odd-toed ungulate called a brontothere
Mesocyon: Small, carnivorous dog, weighing between 8 and 15 pounds
Mesodma: Small, herbivorous, multituberculate mammal
Mesohippus: Two-foot-tall, four-toed, browsing horse that stood and ran primarily on its middle toe
Mesonyx: Four-foot-long, carnivorous, wolf-like mammal called a condylarth
Mesoreodon: Large, pig-like, even-toed, hoofed, herbivorous grazing ruminating oreodont, weighing up to 500 pounds
Metamynodon: Large, amphibious, browsing, rhino-like, odd-toed ungulate
Metarhinus: Large, browsing, odd-toed ungulate called a brontothere
Metopotoxus: Armored, tank-like, omnivorous mammal called a glyptodont related to armadillos
Miacis: Weasel-like and sized, carnivorous, placental mammal
Microbiotherium: Small, opossum-like, insectivorous marsupial
Micropternodus: Shrew-like, insectivorous placental mammal
Microtus: Ground-dwelling, herbivorous vole
Miohippus: Four-foot-long, three-toed, browsing horse, weighing about 60 pounds
Moropus: Large, odd-toed, clawed, herbivorous chalicothere, weighing up to 650 pounds
Mosasaurus: Up to 55-foot-long marine monitor lizard called a mosasaur that fed on fish, turtles, ammonites smaller mosasaurs, birds, pterosaurs, and plesiosaurs
Mylagaulus: Beaver-like, herbivorous rodent
Myledaphus: Carnivorous mackerel shark
Mylodon: Ten-foot long, herbivorous ground sloth, weighing around one ton
Mytonomys: Ground-dwelling, herbivorous rodent
Nanomyops: Small, herbivorous, multituberculate mammal
Necrolestes: Six-inch-long, somewhat shrew-like, insectivorous, non-therian mammal
Nematherium: Large, herbivorous ground sloth
Neohipparion: Four-foot tall, three-toed, grazing horse, weighing about 300 pounds
Neoreomys: Small, ground-dwelling, herbivorous rodent related to guinea pigs
Nesodon: Nine-foot-long, herbivorous, quadrupedal, hippo-like, notoungulate mammal, weighing about 1200 pounds
Nimravides: Swift, carnivorous, five- to six-foot long, tiger-like cat, weighing about 225 pounds
Nothocyon: Meat-eating and omnivorous, true carnivore most closely related to bears
Notorhynchus: Sevengill shark
“Nyssodon”: Small, carnivorous or insectivorous, opossum-like, placental mammal now called Cimolestes
Odaxosaurus: Anguid lizard
Odontaspis: Carnivorous, sand tiger shark
Oligospermophilus: Small, fruit or seed-eating squirrel
Opisthodactylus: Large, ground-dwelling, herbivorous bird called a rhea
Opisthotriton: Extinct salamander
Opthalmosaurus: Twenty-foot long, carnivorous, dolphin-like marine reptile called an ichthyosaur
“Oracodon”: Small, herbivorous, multituberculate mammal now called Meniscoessus
“Oreodon”: Herbivorous, sheep-like oreodont now called Merycoidodon
Oreonetes: Small, browsing, even-toed, hoofed, pig-like ruminant called an oreodont
Ornithomimus: Twelve- to fifteen-foot-long long, bipedal, toothless saurischian dinosaur weighing about 350 pounds
Orthacanthus: Ten-foot-long, carnivorous, fresh-water shark
Ourayia: Arboreal, insectivorous primate
Oxydactylus: Herbivorous, long-legged camel, weighing between 250 and 300 pounds
Pachycephalosaurus: Fifteen-foot-long, bony helmeted, herbivorous dinosaur, weighing about 1000 pounds
Pachyrukhos: One-foot-long, rabbit-like, herbivorous, notoungulate mammal
Palaearctomys: Seed- or fruit-eating squirrel
Palaeocastor: Two-foot long, burrowing beaver responsible for Daemonelix burrows
“Palaeoelaphe”: Carnivorous, rat snake now called Elaphe
Palaeolagus: Early, ten-inch long, ground-dwelling, herbivorous rabbit
Palaeosaniwa: Carnivorous monitor lizard
Palaeoscincus: Large, herbivorous, tank-like, armored, nodosaurid dinosaur related to ankylosaurs
Palaeospheniscus: Ground-dwelling, carnivorous penguin
Palaeospiza: Small, omnivorous mousebird
Palaeosyops: Large, browsing, odd-toed ungulate called a brontothere
Palaeothentes: Small, rodent-like, omnivorous marsupial
Panoplosaurus: Six-foot-high, 15- to 25-foot-long, tank-like, herbivorous, armored, nodosaurid dinosaur
Paraderma: Extinct, carnivorous monitor lizard
Paradjidaumo: A small, ground-dwelling, herbivorous relative of pocket gophers and kangaroo rats
Parahippus: Three-toed, three-foot-tall, grazing horse
Paralbula: Carnivorous ray-finned fish
Paramys: Ground-dwelling, herbivorous rodent
Parasaniwa: Carnivorous relative of monitor lizards
Parictis: Small, primitive bear
Paronychodon: Small, bird-like, carnivorous dinosaur closely related to Troodon
Pediomys: Ground-dwelling, insectivorous marsupial mammal
Peltosaurus: Lizard, possibly insectivorous, related to modern anguids such as glass lizards
Pelecyodon: Large, omnivorous ground sloth
Pelecyornis: Swift, ground-dwelling, carnivorous “terror bird” now called Psilopterus by some paleontologists
Peltephilus: Ground-dwelling, omnivorous armadillo
Peradectes: Opossum-like marsupial
Peratherium: Opossum-like marsupial
Perchoerus: Herbivorous or omnivorous peccary
Perimys: Ground-dwelling, herbivorous rodent
Phenacocoelus: Pig- or sheep-like, even toed, hoofed, herbivorous ruminating oreodont, weighing about 160 pounds
Phororhacos : Swift, eight-foot-tall, ground-dwelling, carnivorous “terror bird,” weighing almost 300 pounds (also sometimes spelled Phorusrhacos)
Piceoerpeton: Extinct aquatic salamander
Planops: Large, omnivorous ground sloth
Platacodon: Omnivorous bowfin fish
Platycarpus: Fourteen-foot-long, marine monitor lizard called a mosasaur that probably ate fish and squid
Plesiarctomys: Ground-dwelling, herbivorous rodent
Pliohippus: Six-foot-tall, eight-foot-long, grazing horse, weighing about 1,000 pounds
Pliolagostomus: Ground-dwelling, herbivorous rodent
Poebrotherium: Primitive, 3-foot-tall, 3-foot-long, slender, long-legged camel, possibly a mixed browser and grazer
Prepotherium: Large, herbivorous ground sloth
Priconodon: Large, tank-like, four-footed, herbivorous, armored, nodosaurid dinosaur, distantly related to ankylosaurs
“Prionosaurus”: Carnivorous lizard now called Exostinus
Priscodelphinus: Carnivorous, toothed whale
“Proamphicyon”: Coyote-sized, carnivorous “bear dog,” distantly related to modern dogs now called Daphoenus
Probaena: Herbivorous tortoise
Procamelus: Llama-like, 4-foot-tall, even-toed, hoofed, browsing camel, weighing about 120 pounds
Procaimanoidea: Extinct, carnivorous alligator
“Prodaphaenus”: Arboreal, carnivorous member of Carnivora now called Miacis
Prodesmodon: Amphibious salamander
Proeutatus: Ground-dwelling, insectivorous armadillo
Proictinia: Carnivorous hawk
“Proinia”: Carnivorous, dolphin-like, toothed whale now called Prosqualodon
Promeycochoerus: Three-foot long, hippo-like, even-toed, hoofed oreodont, probably amphibious
Propalaeohoplophorus: Relatively small, heavily armored, tank-like, omnivorous, glyptodont mammal related to armadillos
Prosciurus: Burrowing, herbivorous mountain beaver
Prosqualodon: Carnivorous, dolphin-like, toothed whale
Prosthennops: Omnivorous peccary
Protemnocyon: Ground-dwelling, carnivorous or omnivorous dog
Proterotherium: Swift, somewhat horse-like, herbivorous, proterotheriid, placental mammal
Prothylacynus: Swift, wolf-like, carnivorous marsupial
Protitanotherium: Large, browsing, odd-toed ungulate called a brontothere
Protoceras: Three-foot-long, browsing, deer-like, even-toed ungulate with horn-like ossicones on skull, weighing from 120 to 200 pounds
Protohippus: Three-toed, grazing horse
Protolambda: Small, omnivorous, marsupial mammal
Protomeryx: Ground-dwelling, browsing camel
Protoptychus: Ground-dwelling, herbivorous rodent
Protoreodon: Clawed, even-toed, herbivorous ungulate called an oreodont
Protamandua: Ground-dwelling, insectivorous anteater
Protylopus: Two and a half-foot-long, browsing, camel-like, even-toed ungulate, weighing about 55 pounds
Protypotherium: One-foot-long, quadrupedal, rodent-like, herbivorous notoungulate mammal
Prozaedius: Ground-dwelling, insectivorous armadillo
Pseudocylindrodon: Ground-dwelling, herbivorous rodent
Pseudhipparion: Large, grazing horse
Pseudotomus: Ground-dwelling, herbivorous rodent
Psilopterus: Swift, two and a half-foot-tall, ground-dwelling, carnivorous “terror bird,” weighing around 10 to 15 pounds
Pteranodon: Large, crested, fish-eating, flying reptile with webbed wings up to 20 feet across
Reithroparamys: Ground-dwelling, herbivorous rodent
Rhineura: Legless, amphisbaenian or worm lizard
Rhinoptera: Cownose ray
Rutiodon: Ten- to 25-foot-long, crocodile-like, carnivorous reptile called a phytosaur
Saniwa: Five- to six-foot-long, carnivorous relative of monitor lizards
Saurornithoides: Seven-foot-long, bird-like, bipedal, carnivorous dinosaur closely related to Troodon
“Serridentinus”: Mastodon-like proboscidean now called Gomphotherium
Scapherpeton: Extinct salamander
Scaptohyus: Pig-like, omnivorous entelodont, informally called a “terror pig”
Schismotherium: Large, omnivorous ground sloth
Schistomys: Small, ground-dwelling, herbivorous rodent related to guinea pigs
Sciamys: Small, ground-dwelling, herbivorous rodent related to guinea pigs
“Scottimus”: Six-inch long, herbivorous, mouse-like, ground-dwelling rodent now called Eumys
“Selenacodon”: Small, multituberculate mammal now called Meniscoessus
“Serridentinus”: Large, herbivorous, browsing, elephant-like gomphothere now called Gomphotherium
Sespia: Small, even-toed, hoofed, herbivorous, pig-like ruminant called an oreodont, weighing about 10 pounds
Simidectes: Swift, carnivorous mammal called a mesonychian
Sipalocyon: Swift, somewhat hyaena-like, carnivorous marsupial
Spaniomys: Small, ground-dwelling, herbivorous rodent related to guinea pigs
“Stagodon”: Opossum-like, marsupial mammal now called Didelphodon
Stegosaurus: Plated, spiked, herbivorous armored dinosaur 15 feet long and weighing 2.5 tons
Stegotherium: Ground-dwelling, insectivorous armadillo
Steiromys: Small, ground-dwelling, herbivorous rodent related to guinea pigs
Stenotephanos: Hippo-like, herbivorous notoungulate mammal
Stenomylus: Two-foot tall, gazelle-like, even-toed, herbivorous camel
Stenotatus: Ground-dwelling, insectivorous armadillo
Stichomys: Small, herbivorous, ground-dwelling rodent related to guinea pigs
Stygimoloch: Large, bone-helmeted, bipedal, herbivorous dinosaur, sometimes now called Pachycephalosaurus
Stylemys: Ground-dwelling tortoise
Stilotherium: Small, shrew-like, insectivorous marsupial
Subhyracodon: Eight-foot-long, browsing rhinoceros, weighing about 800 pounds
Sunkahetanka: Relatively small, bone-crushing dog, weighing around 30 pounds
Syllaemus: Mullet fish
Symborodon: Large, herbivorous, browsing brontothere
Synechodus: Aquatic, carnivorous shark
Tanymykter: Ground-dwelling, browsing camel, weighing about 300 pounds
“Tayra”: Swift, weasel-like carnivore, now called Eira
Telacodon: Small, insectivorous, placental mammal
Teleoceras: Large, short-legged, odd-toed, hoofed, hippo-like rhino, weighing up to 1.8 tons
Telmatherium: Large, browsing, odd-toed ungulate called a brontothere
Temnocyon: Small, carnivorous “bear dog” weighing about 50 pounds
Terrapene: Omnnivorous box-turtle
Testudo: Tortoise
Theosodon: Six-foot-long, llama-like, herbivorous, macrauchenid mammal, weighing about 350 pounds
Thescelosaurus: Bipedal, herbivorous ornithischian dinosaur, 10 to 15 feet long, weighing around 500–600 pounds
Thescelus: Baenid turtle
Thinohyus: Ground-dwelling, omnivorous peccary
Thoatherium: Swift, two-foot-long, somewhat horse-like, herbivorous, proterotheriid placental mammal
Ticholeptus: Pig-like, even-toed, hoofed ruminant, weighing up to 300 pounds
“Titanops”: Large, herbivorous, browsing brontothere now usually called Megacerops
“Titanotherium”: Large brontothere now called Megacerops
Trachodon: Large, herbivorous, duckbill dinosaur
Torosaurus: Twenty-five to thirty-foot-long, three-horned, herbivorous dinosaur, weighing around six tons
Triceratops: Quadrupedal, three-horned, herbivorous ornithischian dinosaur, up to 30 feet long and weighing 6 to 13 tons
Trigonias: Seven-foot-long, hornless rhino, weighing about 800 pounds
Trimerorhachis: Three-foot-long, primarily aquatic, carnivorous amphibian
Trionyx: Carnivorous, soft-shelled turtle
Triplopus: Gracile, long-limbed, browsing rhinoceros
“Tripriodon”: Small, herbivorous, multituberculate mammal now called Meniscoessus
Troodon: Seven-foot-long, swift, agile, bird-like, carnivorous dinosaur, fairly closely related to Velociraptor
Tylosaurus: Forty- to 45-foot-long, marine monitor lizard called a mosasaur that probably ate fish, sharks, marine birds and other mosasaurs
Tyrannosaurus: Bipedal, carnivorous, saurischian dinosaur up to 40 feet long and weighing 15 tons
Uintatherium: Thirteen-foot-long, five- to six-foot-tall, herbivorous, knobby-skulled mammal called a uintathere, weighing around two tons
Vulpes: Carnivorous to omnivorous fox
Xiphactinus: Enormous, predatory, bony fish up to 20 feet long that resembled a tarpon, but was not closely related to it
Ysengrinia: Ground-dwelling, carnivorous bear-dog, weighing about 160 pounds
Yumaceras: Horned, antilope-like, browsing ruminant