Redescription and phylogenetic relationships ofMeridiosaurus vallisparadisi, a pholidosaurid from the Late Jurassic of Uruguay

Abstract

Meridiosaurus vallisparadisi Mones, 1980, a freshwater pholidosaurid from the Late Jurassic of Uruguay, is redescribed herein. It can be diagnosed by the possession of the following combination of features: (1) lateral constriction of the rostrum at premaxilla–maxilla contact, strong lateral expansion of the premaxilla with the fifth tooth placed in the widest portion; (2) sinusoidal premaxilla–maxilla suture in palatal view, posteromedially directed on its lateral half, and anteromedially directed along its medial region; (3) evaginated maxillary alveolar edges forming a discrete collar at each alveolus, lateroventrally oriented; (4) greater number of maxillary teeth (at least 27) with respect to Elosuchus (less than 20 maxillary teeth); (5) nasals do not meet premaxilla dorsally; (6) strong sinusoidal lateral contour of snout in dorsal view, with respect to the similar condition of Elosuchus, forming two waves (‘festooned’); and (7) third, fourth, and fifth alveoli are equally enlarged. A phylogenetic analysis was performed, including six pholidosaurids: Elosuchus, Meridiosaurus, Oceanosuchus, Pholidosaurus, Sarcosuchus, and Terminonaris. The analysis confirmed the monophyly of Pholidosauridae, and a new definition is proposed: a stem-based group name including Pholidosaurus schaumburgensis Meyer, 1841 and all taxa closer to it than to Dyrosaurus phosphaticus (Thomas, 1893) or Pelagosaurus typus Bronn, 1841. Pholidosauridae originated in Europe during the Middle Jurassic, dispersed to Africa, and North and South America, in several dispersal events, and completely disappeared in the Late Cretaceous. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272.