Hyperphalangy was present among extinct ichthyosaurs, plesiosaurs, and mosasaurs. Genetics likely controlled sex in ichthyosaurs, mosasaurs and plesiosaurs. In the oceans, plesiosaurs, ichthyosaurs and ammonites were abundant. In the oceans, plesiosaurs, ichthyosaurs and ammonites dominated the seas. Their prey may have included fish, sharks, ichthyosaurs, dinosaurs and other plesiosaurs. If authentic, the embryos of plesiosaurs would have been very small like those of ichthyosaurs. New aquatic reptiles, such as ichthyosaurs and nothosaurs, proliferated in the seas. Less commonly, they fed on fish and other vertebrates, including smaller ichthyosaurs. The most commonly preserved gut contents in ichthyosaurs are the remains of cephalopods. Hupehsuchia is an order of diapsid reptiles closely related to ichthyosaurs. Pearce concluded from the fossil that ichthyosaurs had to have been viviparous. All ichthyosaurs belonged to the thunnosaurian clade Ophthalmosauria. "Temnodontosaurus" is one of the most basal post-Triassic ichthyosaurs. The presence of dorsal fins in ichthyosaurs has been controversial. With ichthyosaurs in the narrow sense, their snouts became very pointy.