New information on the anatomy and systematic position of Dinheirosaurus lourinhanensis (Sauropoda: Diplodocoidea) from the Late Jurassic of Portugal, with a review of European diplodocoids

Abstract

Although diplodocoid sauropods from Africa and the Americas are well known, their European record remains largely neglected. Here we redescribe Dinheirosaurus lourinhanensis from the Late Jurassic of Portugal. The holotype comprises two posterior cervical vertebrae, the dorsal series and a caudal centrum. Redescription demonstrates its validity on the basis of three autapomorphies: (1) posteriorly restricted ventral keel on posterior cervical vertebrae; (2) three small subcircular fossae posterior to the lateral coel on posterior cervical neural spines; (3) accessory lamina linking the hyposphene with base of the posterior centrodiapophyseal lamina in middle-posterior dorsal vertebrae. Phylogenetic analysis places Dinheirosaurus as the sister taxon to Supersaurus, and this clade forms the sister taxon to other diplodocines. However, this position should be treated with caution as Dinheirosaurus displays several plesiomorphic features absent in other diplodocids (including unbifurcated presacral neural spines, and dorsolaterally projecting diapophyses on dorsal vertebrae) and only four additional steps are required to place Dinheirosaurus outside of Flagellicaudata. We identify Amazonsaurus as the basal-most rebbachisaurid and recover Zapalasaurus outside of the South American Limaysaurinae, suggesting the biogeographic history of rebbachisaurids is more complex than previously proposed. Review of the European diplodocoid record reveals evidence for the earliest known diplodocid, as well as additional diplodocid remains from the Late Jurassic of Spain. A Portuguese specimen, previously referred to Dinheirosaurus, displays strong similarities to Apatosaurus from the contemporaneous Morrison Formation of North America, indicating the presence of a second Late Jurassic Portuguese diplodocid taxon. Along with Dinheirosaurus, these Portuguese remains provide further evidence for a Late Jurassic palaeobiogeographic connection between Europe and North America. No dicraeosaurids are currently known from Europe, but rebbachisaurids are present in the Early Cretaceous, with weak evidence for the earliest known representative from the Late Jurassic of Spain; however, more complete material is required to recognize early members of this clade.

Keywords:

• Dinosauria
• Diplodocidae
• Lourinhã
• Mesozoic
• Morrison Formation
• Rebbachisauridae

Acknowledgements

We wish to express our gratitude to all those who allowed us to study sauropod material in their care, in particular Paul M. Barrett, Brent Breithaupt, Jorge O. Calvo, Alberto C. Garrido, Alejandro Haluza, Scott A. Hartman, Amy C. Henrici, Stephen Hutt, Alejandro G. Kramarz, David M. Lovelace, Rafael Royo-Torres, Paul C. Sereno, Sean Smith and Fidel Torcida. Reviews by Oliver W. M. Rauhut and Matthew J. Wedel greatly improved an earlier version of this manuscript. PDM was supported by a University College London NERC studentship (NER/S/A/2006/14347) and would like to thank a Jurassic Foundation grant that enabled travel to South America to study sauropod specimens. PU received funding from The Palaeontological Association and the Abbey International Collaboration scheme, enabling study of sauropod specimens in Portugal and Spain. RNB is supported by NERC studentship NE/F012764/1. We are also grateful to John A. Whitlock for providing us with his diplodocoid phylogeny prior to publication.