Nothosaurs were long-necked, long-tailed, fish-eating sauropterygian reptiles ranging from a few inches to 20 feet (6 m) long - they were not dinosaurs. Nothosaurs lived during the Triassic period. They may have evolved into the plesiosaurs. These reptiles had a long, thin head with many sharp teeth; the front teeth were longer than the back teeth. The nostrils were on the top end of the snout. They breathed air but spent most of the time in the water. 