Barnum Brown
Below the surface, the sea was populated primarily by invertebrates such as ammonites and squid. Vertebrate life, apart from basal fish, included sea turtles, such as "Toxochelys", the plesiosaur "Styxosaurus", and the flightless diving bird "Parahesperornis". Mosasaurs were the most common marine reptiles, with genera including "Clidastes" and "Tylosaurus". At least some of these marine reptiles are known to have fed on "Pteranodon". Barnum Brown, in 1904, reported plesiosaur stomach contents containing "pterodactyl" bones, most likely from "Pteranodon".