Temnodontosaurus

Temnodontosaurus (meaning "cutting-tooth lizard") is an extinct genus of large ichthyosaurs that lived during the Lower Jurassic in what is now Europe and possibly Chile. The first known fossil is a specimen consisting of a complete skull and partial skeleton discovered on a cliff by Joseph and Mary Anning around the early 1810s in Dorset, England. The anatomy of this specimen was subsequently analyzed in a series of articles written by Sir Everard Home between 1814 and 1819, making it the very first ichthyosaur to have been scientifically described. In 1822, the specimen was assigned to the genus Ichthyosaurus by William Conybeare, and more precisely to the species I. platyodon. Noting the large dental differences with other species of Ichthyosaurus, Richard Lydekker suggested in 1889 moving this species into a separate genus, which he named Temnodontosaurus. While many species have been assigned to the genus, only five are currently recognized as valid, the others being considered as synonymous, doubtful or possibly belonging to other taxa.

Generally estimated at long, Temnodontosaurus is one of the largest known ichthyosaurs, although not as imposing as some Triassic forms. Specimens assigned to the genus may nevertheless have reached larger measurements. As an ichthyosaur, Temnodontosaurus had flippers for limbs and a fin on the tail. Boasting eye sockets measuring more than wide, Temnodontosaurus quite possibly had the largest eyes known in the entire animal kingdom, rivaling in size those of the colossal squid. The snout appears to be longer than the mandible, being equipped with several sharp teeth (hence its name). On the basis of numerous very complete skeletons, it is estimated that the animal had at least more than 40 presacral vertebrae. Temnodontosaurus is a basal representative of the parvipelvian subgroup of ichthyosaurs, in addition to being its largest representative. A monotypic family, Temnodontosauridae, was even established in 1974 to include the genus. Various phylogenetic analyses as well as diagnostic problems concerning the genus make it, for the moment, a polyphyletic taxon (unnatural grouping), and therefore in need of revision.