The cranial anatomy of the sauropod Turiasaurus riodevensis and implications for its phylogenetic relationships

Abstract

The skull of Turiasaurus is known from a nearly complete posterior section (e.g. braincase, skull roof, quadrates and left mandible) and fragments of the snout (e.g. portions of premaxilla, maxilla, nasal and lacrimal). Skull material of the holotypic individual was discovered in close association. Comparisons with other sauropods suggest that the Turiasaurus skull most closely resembled those of Jobaria, Camarasaurus and Mamenchisaurus youngi, possessing large spatulate teeth, enlarged and partially retracted external nares, and a broadly rounded muzzle. The list of autapomorphies for Turiasaurus is augmented by the new cranial data, including features such as: (1) a shelf-like projection of bone from the medial surface of the distal end of the maxillary ascending process; and (2) a rounded boss-like area on the lateral surface of the jugal. There are also unusual character states, such as the excavation of the posterior surfaces of the basal tubera (present in Turiasaurus and Losillasaurus) that probably have a wider phylogenetic significance. Phylogenetic analyses, using two different datasets, support the view that Turiasaurus, Losillasaurus and Galveosaurus form a monophyletic Turiasauria clade that lies just outside of Neosauropoda. The addition of the new cranial data slightly strengthens the support for this topology, but the relationships of other taxa (such as Jobaria) become less stable. The Turiasauria might represent a distinct group of non-neosauropods with a wide geographic distribution across Europe and Africa during the Late Jurassic.

Keywords:

• cladistic analysis
• Late Jurassic
• phylogeny
• Riodeva
• Sauropoda
• skull

Acknowledgements

The first author gratefully acknowledges the support given by Gobierno de Aragón (Departamentos de Educación, Presidencia, Industria, Economía, Ciencia), FOCONTUR (Grupo de Investigación Consolidado E-62 and beca Ref.FMI030/09 Departamento de Ciencia, Tecnología y Universidad del Gobierno de Aragón) Ministerio de Educación, Gobierno de España (projects: CGL2006-13903; CGL2009-07792), Departamento de Educación, Cultura y Deporte del Gobierno de Aragón (Exp. 252/2002, 142/2003, 142/02/2003, 197/2005, 241/2006, 317/2006, 201 and 202/2007, 079/2009 and 101/2009), and Diputación Provincial de Teruel y Ayuntamiento de Riodeva. Special thanks to co-directors of Riodeva research projects Luis Alcalá and Alberto Cobos and also the team Ainara Aberasturi, Daniel Ayala, Eduardo Espílez, Nacho Fierro, Francisco Gascó, Ana González, Luis Luque and Luis Mampel at the Fundación Conjunto Paleontológico de Teruel-Dinópolis and Escuela Taller de Restauración Paleontológica II del Gobierno de Aragón for their assistance with fieldwork and laboratory work, and for useful discussion. Additional support was provided by University College London. We are very grateful to Sandra Chapman for her help with accessing the sauropod teeth in the collections of the Natural History Museum (London), to Daniela Schwarz-Wings for her assistance in the Humboldt Museum fur Naturkunde (Berlin), and Margarita Belinchón (Museo Ciencias Naturales de Valencia) for access to Losillasaurus. The second author wishes to thank the Palaeontological Association and the Abbey International Collaboration Grant Scheme for funding travel to the Fundación Conjunto Paleontológico de Teruel-Dinópolis, in order to study the Turiasaurus cranial material. Samantha Upchurch provided assistance with data collection. Finally, Paul M. Barrett and Jeffrey A. Wilson provided helpful reviews of an earlier draft of this paper.