Second specimen of the Late Cretaceous Australian sauropod dinosaur Diamantinasaurus matildaeprovides new anatomical information on the skull and neck of early titanosaurs

• Published in: Zoological Journal of the Linnean Society
• Main Authors: Poropat, Stephen F, Kundrát, Martin, Mannion, Philip D, Upchurch, Paul, Tischler, Travis R, Elliott, David A
• Other Authors: Australian Research Council, Swedish Research Council, Slovak Research and Development Agency, Royal Society University Research, Leverhulme Trust Research, European Regional Development Fund
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2021
• Subjects: Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.1093/zoolinnean/zlaa173; https://academic.oup.com/zoolinnean/article-pdf/192/2/610/49574256/zlaa173.pdf

Abstract The titanosaurian sauropod dinosaur Diamantinasaurus matildae is represented by two individuals from the Cenomanian–lower Turonian ‘upper’ Winton Formation of central Queensland, north-eastern Australia. The type specimen has been described in detail, whereas the referred specimen, which includes several elements not present in the type series (partial skull, atlas, axis and postaxial cervical vertebrae), has only been described briefly. Herein, we provide a comprehensive description of this referred specimen, including a thorough assessment of the external and internal anatomy of the braincase, and identify several new autapomorphies of D. matildae. Via an expanded data matrix consisting of 125 taxa scored for 552 characters, we recover a close, well-supported relationship between Diamantinasaurus and its contemporary, Savannasaurus elliottorum. Unlike previous iterations of this data matrix, under a parsimony framework we consistently recover Diamantinasaurus and Savannasaurus as early-diverging members of Titanosauria using both equal weighting and extended implied weighting, with the overall topology largely consistent between analyses. We erect a new clade, named Diamantinasauria herein, that also includes the contemporaneous Sarmientosaurus musacchioi from southern Argentina, which shares several cranial features with the referred Diamantinasaurus specimen. Thus, Diamantinasauria is represented in the mid-Cretaceous of both South America and Australia, supporting the hypothesis that some titanosaurians, in addition to megaraptoran theropods and possibly some ornithopods, were able to disperse between these two continents via Antarctica. Conversely, there is no evidence for rebbachisaurids in Australia, which might indicate that they were unable to expand into high latitudes before their extinction in the Cenomanian–Turonian. Likewise, there is no evidence for titanosaurs with procoelous caudal vertebrae in the mid-Cretaceous Australian record, despite scarce but compelling evidence for their ...