The Paleontology of North America

Extinct Marine Reptiles from North America

See More Images

Shonisaurus popularis
Shonisaurus popularis
© 2004 Maximo Salas

Plotosaurus bennisoni
Plotosaurus bennisoni
© 2004 UCMP

Shastasaurus pacificus
Shastasaurus pacificus
© 2004 UCMP

What are Extinct Marine Reptiles? Many reptiles returned to the water at different times in the Late Paleozoic and Mesozoic, and they developed different features for this mode of life. Although their skeletons were modified to different degrees, many had paddle-like limbs, elongated necks and tails, and reduced or absent shoulder and hip bones. Of the numerous extinct marine reptiles, some of the more familiar include: ichthyosaurs, named for their resemblance to large fish; mosasaurs, relatives of snakes and lizards; and plesiosaurs, with their long limbs and necks and small heads. The first members of this group appear in the Triassic, and the last members went extinct in the Cretaceous.

First known fossil occurrence: Triassic.

Last known fossil occurrence: Cretaceous.

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