The Sundance Sea was rich in many types of animals. The oyster "Gryphaea" was very common, and shark teeth have been found. Fish, belemnites and to an extent ammonites swarmed in shoals. Crinoids and bivalvia dotted the seafloor. "Ophthalmosaurus", a large ichthyosaur, swam in the seas using its large, long jaws to catch belemnite 'squid'. "Pantosaurus", a plesiosaur the size of a seal, went after the easier-to-catch fish. The largest marine reptile in the Sundance Sea was "Megalneusaurus", a large pliosaur similar to "Liopleurodon". Its fossils have been found in Alaska and Wyoming, which were both covered by the Sundance Sea when it was alive.