The Elements of Evolution (21-14-4) Nothosaurs


Nothosaurs were another early aquatic reptile (245–200 MYA). They were slender, long necked piscivores with sharp, interlocking teeth. Nothosaur bodies were somewhat like crocodiles: streamlined for aquatic predation, including webbed feet. Their lifestyle was like that of modern seals, in being largely aquatic, while coming ashore from time to time. Various nothosaur species ranged in size from several centimeters to 4 meters.

Nothosaurs propelled themselves over the seafloor by rowing their forelimbs in unison. Paddle feet scooped the soft mud, disturbing fish and shrimp there, which a nothosaur snapped up with its needle-sharp teeth.

Nothosaur limbs suggest that they could move on land, albeit with the sprawling gait of seals, which may have later adopted the nothosaur lifestyle: fishing at sea and relaxing on land.

Nothosaurs were supplanted by pleiosaurs. Both were sauropterygians: aquatic reptiles that evolved from terrestrial tetrapods soon after the end-Permian extinction. While nothosaurs and plesiosaurs are closely related, that nothosaurs begat plesiosaurs is uncertain.