The Nothosaurs

Nothosaurs seem adapted for a life like that of modern seals: catching food in water but coming ashore on rocks and beaches to sleep, mate, and hang out. Nothosaurs averaged around ten feet in length, and they had long bodies with long tails and long necks capped with elongated, flattened heads that were small in relation to their bodies. Paddle-like webbed feet helped them propel through the water, and they had tapered jaws filled with sharp, outward-pointing teeth that indicate a diet of fish and squid. 

an artist's rendition of Nothosaurus

Nothosaurus was the heavyweight of its namesake clade, the Nothosaurs; most species reached up to thirteen feet long, but some reached up to sixteen to twenty-three feet in length. Nothosaurus had long, webbed toes and may have even sported a fin on its tail – the webbed feet, slender body, and long tail (with or without a fin) helped steer it gracefully through the water. Nothosaur trackways found in China in 2014 have been interpreted as paddle impressions left as the animals dug into soft Triassic seabed with rowing motion of paddles, churning up hidden creatures doomed for the nothosaur’s stomach.

Nothosaurs consist of two suborders: Pachypleurosauria (small, primitive nothosaurs) and Nothosauria (which includes Nothosauridae and Simosauridae). Though the nothosaurs were adapted to a semi-aquatic lifestyle, their forebears the pachypleurosaurs don’t seem to share this trait; though in outward appearance they looked dead-on like nothosaurs, they were, in the first instance, much smaller (ranging from as little as seven inches to three feet in length), and, in the second instance, their pitiful limb girdles would’ve made moving around on land quite the exhausting experience. The semi-aquatic lifestyle seems to have evolved with the rise of the nothosaurs in the mid-Triassic. Though it’s generally accepted that nothosaurs proper evolved from the pachypleurosaurs, this isn’t wholly certain; some cladistics put these two groups as sister clades (making them more like ‘cousins’ than ‘mother-daughter’). Nothosaurs differed from their sister-clade Simosauridae in that Simosaurus had a different dental get-up: whereas Nothosaurs had sharp teeth geared towards eating fish and squid, Simosaurus had blunt teeth adapted for eating hard-shelled organisms like ammonites and clams. Most paleontologists believe that an off-branch of the nothosaurs evolved into the wholly marine plesiosaurs, which replaced them at the end of the Triassic Period; other scientists speculate that another branch of the Nothosaurs evolved into the pliosaurs of the Jurassic and Cretaceous periods. 

a pod of Nothosaurs on the prowl (or at play?)