Kronosaurus

Kronosaurus ( ) is an extinct genus of large short-necked pliosaur that lived during the Aptian to Albian stages of the Early Cretaceous in what is now Australia. The first known specimen was received in 1899 and consists of a partially preserved mandibular symphysis, which was first thought to come from an ichthyosaur according to Charles De Vis. However, it was in 1924 that Albert Heber Longman formally described this specimen as the holotype of an imposing pliosaurid, to which he gave the scientific name K. queenslandicus, which is still the only recognized species nowadays. The genus name, meaning "lizard of Kronos", refers to its large size and possible ferocity reminiscent of the Titan of the Greek mythology, while the species name alludes to Queensland, the Australian state of its discovery. In the early 1930s, the Harvard Museum of Comparative Zoology sent an organized expedition to Australia that recovered two specimens historically attributed to the taxon, including a well known skeleton that is now massively restored in plaster. Several attributed fossils were subsequently discovered, including two large, more or less partial skeletons. As the holotype specimen does not present diagnostics to concretely distinguish Kronosaurus from other pliosaurids, these same two skeletons are proposed as potential neotypes for future redescriptions. Two additional species were proposed, but these are now seen as unlikely or belonging to another genus.

Kronosaurus is one of the largest known pliosaurs identified to date. Initial estimates set its maximum size at around long based on the Harvard skeleton. However, this skeleton had been reconstructed with an exaggerated number of vertebrae, so estimates published from the early 2000s reduce the size of the animal from to more than long. Like all plesiosaurs, Kronosaurus has four paddle-like limbs, a short tail and, like most pliosaurids, a long head and a short neck. The largest identified skulls of Kronosaurus dwarf those of the largest known theropod dinosaurs in size. The front of the skull is elongated into a rostrum (snout). The mandibular symphysis, where the front ends of each side of the mandible (lower jaw) fuse, is elongated in Kronosaurus, and contains up to six pairs of teeth. The large cone-shaped teeth of Kronosaurus would have been used for a diet consisting of large prey. The front teeth are larger than the back teeth. The limbs of Kronosaurus were modified into flippers, with the back pair larger than the front. The flippers would have given a wingspan of more than for the largest representatives.