Keichousaurus (Greek for "Kweichow lizard"); pronounced KAY-choo-SORE-us
Lakes and rivers of Asia
Triassic (245-210 million years ago)
Size and Weight:
About 6 to 12 inches long and 1 pound
Small size; long neck and tail; five-toed feet
The most prominent example of the obscure reptile order known as pachypleurosauria, Keichousaurus is among the oldest of all marine reptiles, and may (or may not) have been ancestral to the huge plesiosaurs and pliosaurs of the Jurassic and Cretaceous periods. Paleontologists believe Keichousaurus spent most of its time in the water, but may have been able to crawl occasionally onto land with its strong front legs. Because it was so small (only about a foot long), Keichousaurus has fossilized unusually well--it's not uncommon to find complete, articulated skeletons of this reptile embedded in rock, which are prized (and expensive) collector's items.