title: The first freshwater mosasauroid (Upper Cretaceous, Hungary) and a new clade of basal mosasauroids.
abstract: Mosasauroids are conventionally conceived of as gigantic, obligatorily aquatic marine lizards (1000s of specimens from marine deposited rocks) with a cosmopolitan distribution in the Late Cretaceous (90-65 million years ago [mya]) oceans and seas of the world. Here we report on the fossilized remains of numerous individuals (small juveniles to large adults) of a new taxon, Pannoniasaurus inexpectatus gen. et sp. nov. from the Csehbánya Formation, Hungary (Santonian, Upper Cretaceous, 85.3-83.5 mya) that represent the first known mosasauroid that lived in freshwater environments. Previous to this find, only one specimen of a marine mosasauroid, cf. Plioplatecarpus sp., is known from non-marine rocks in Western Canada. Pannoniasaurus inexpectatus gen. et sp. nov. uniquely possesses a plesiomorphic pelvic anatomy, a non-mosasauroid but pontosaur-like tail osteology, possibly limbs like a terrestrial lizard, and a flattened, crocodile-like skull. Cladistic analysis reconstructs P. inexpectatus in a new clade of mosasauroids: (Pannoniasaurus (Tethysaurus (Yaguarasaurus, Russellosaurus))). P. inexpectatus is part of a mixed terrestrial and freshwater faunal assemblage that includes fishes, amphibians turtles, terrestrial lizards, crocodiles, pterosaurs, dinosaurs and birds.
authors.affiliation: Department of Paleontology and Geology, Hungarian Natural History Museum, Budapest, Hungary. iharkutia@yahoo.com
authors.forename: László
authors.initials: L
authors.lastname: Makádi
authors.forename: Michael W
authors.initials: MW
authors.lastname: Caldwell
authors.forename: Attila
authors.initials: A
authors.lastname: Ősi
mesh_terms: D000818:Animals; D004463:Ecology; D005580:Fossils; D005618:Fresh Water; D006814:Hungary; D008116:Lizards / Q000033:anatomy & histology / Q000145:classification*; D059166:Osteology; D010802:Phylogeny