The Paleontology of North America

Mammals from North America

> Placentals | Marsupials | Monotremes | Other Mammals

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Leptauchenia nitia
Leptauchenia nitia
© 1998 Dr. Richard Paselk, Humboldt State University Natural History Museum

Eucrotaphus trigonocephalus
Eucrotaphus trigonocephalus
© 1996 public domain

Diceratherium annectens
Diceratherium annectens
© 1996 public domain

What are Mammals? Mammals are amniotes like their relatives and reptiles. They all share certain features in the skull, jaws, and teeth. All mammals are warm-blooded, have hair, and produce milk through mammary glands, which is how they got their name. Humans are mammals, as are many of the animals that share our lives as pets or farm animals. Many of the earliest mammals were tiny and are represented in the fossil record only by teeth, the most durable parts of the mammalian skeleton. The first mammals appear in the Late Triassic.

First known fossil occurrence: Triassic.

Last known fossil occurrence: Quaternary. This group has living relatives.

Fossils through time:
Choose a time period to see what life was like:

Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Precambrian