Redescription and phylogenetic relationships of Meridiosaurus vallisparadisi, a pholidosaurid from the Late Jurassic of Uruguay DANIEL FORTIER 1,2 *, DANIEL PEREA 3 and CESAR SCHULTZ 1 1 Departamento de Paleontologia e Estratigrafia, IG, UFRGS, Avenue Bento Gonçalves, 9500, Cx. P. 15001, Porto Alegre, RS, Brazil 2 Department of Geoscience, University of Iowa, 121 Trowbridge Hall, Iowa City, IA 52242, USA 3 Departamento de Evolución de Cuencas, Facultad de Ciencias, Iguá 4225, 11400 Montevideo, Uruguay Received 12 April 2010; accepted for publication 28 October 2010 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. doi: 10.1111/j.1096-3642.2011.00722.x ADDITIONAL KEYWORDS: aquatic crocodylomorph – mesoeucrocodylia – neosuchia – pholidosauridae – Tacuarembó. INTRODUCTION Pholidosauridae is a group of fossil longirostrine cro- codylomophs adapted to aquatic environments, reported from the Middle Jurassic (Owen, 1884; Mook, 1942) to Late Cretaceous (Mook, 1934; Wu, Russell & Cumbaa, 2001; Hua et al., 2007). Remains of Pholidosauridae occur in marine, estuarine, and fluviolacustrine sediments of North America (Shimada & Parris, 2007), South America (Buffetaut & Taquet, 1977), Africa (Sereno et al., 2001), and Europe (Salisbury, 2002). Despite some well-known species, like Terminonaris and Sarcosuchus, some pholidosaurids are still rather poorly known, like Pholidosaurus and Anglosuchus. There are three main Mesozoic longirostrine cro- codylomorph groups: Thalattosuchia, Dyrosauridae, *Corresponding author. E-mail: daniel.fortier@ufrgs.br Zoological Journal of the Linnean Society, 2011, 163, S257–S272. With 5 figures © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272 S257