The streamlined shape of ichthyosaurs is not a mistake of their evolution. Secondarily aquatic reptiles, meaning their ancestors were land dwelling reptiles, these masters of the ocean began to populate the marine environment heavily during the earlier Triassic. During the early Jurassic Stenopterygius began to swim about the oceans as an identifiable differentiated genus. Specimens of the animal, as we have noted, are plentiful and its populations of species (four:S. quadriscissus Quenstedt, 1856 (type species) S. triscissus Quenstedt, 1856; S. uniter von Huene, 1931; S. aaleniensis Maxwell et al., 2012) were commanding the oceans they lived in as they ranged up to 13 feet (4 meteres) in length and swam much like a dolphin, probably out maneuvering and chasing down prey. Assuming intelligence and any group behavior, the dolphin-like Stenopterygius may have even had the ability to coordinate with others to hunt larger prey items or groups of prey. The main weapon it would have used in either instance, aside from its speed, would have been the small conical teeth lining its jaws that were suited to grasping fish on the fly.