Reappraisal of Austrosaurus mckillopi Longman, 1933 from the Allaru Mudstone of Queensland, Australia’s first named Cretaceous sauropod dinosaur

Abstract

Poropat, S.F., Nair, J.P., Syme, C.E., Mannion, P.D., Upchurch, P., Hocknull, S.A., Cook, A.G., Tischler, T.R. & Holland, T. XX.XXXX. 2017. Reappraisal of Austrosaurus mckillopi Longman, 1933 from the Allaru Mudstone of Queensland, Australia’s first named Cretaceous sauropod dinosaur. Alcheringa 41, 543–580. ISSN 0311-5518

Austrosaurus mckillopi was the first Cretaceous sauropod reported from Australia, and the first Cretaceous dinosaur reported from Queensland (northeast Australia). This sauropod taxon was established on the basis of several fragmentary presacral vertebrae (QM F2316) derived from the uppermost Lower Cretaceous (upper Albian) Allaru Mudstone, at a locality situated 77 km west-northwest of Richmond, Queensland. Prior to its rediscovery in 2014, the type site was considered lost after failed attempts to relocate it in the 1970s. Excavations at the site in 2014 and 2015 led to the recovery of several partial dorsal ribs and fragments of presacral vertebrae, all of which clearly pertained to a single sauropod dinosaur. The discovery of new material of the type individual of Austrosaurus mckillopi, in tandem with a reassessment of the material collected in the 1930s, has facilitated the rearticulation of the specimen. The resultant vertebral series comprises six presacral vertebrae—the posteriormost cervical and five anteriormost dorsals—in association with five left dorsal ribs and one right one. The fragmentary nature of the type specimen has historically hindered assessments of the phylogenetic affinities of Austrosaurus, as has the fact that these evaluations were often based on a subset of the type material. The reappraisal of the type series of Austrosaurus presented herein, on the basis of both external morphology and internal morphology visualized through CT data, validates it as a diagnostic titanosauriform taxon, tentatively placed in Somphospondyli, and characterized by the possession of an accessory lateral pneumatic foramen on dorsal vertebra I (a feature that appears to be autapomorphic) and by the presence of a robust ventral mid-line ridge on the centra of dorsal vertebrae I and II. The interpretation of the anteriormost preserved vertebra in Austrosaurus as a posterior cervical has also prompted the re-evaluation of an isolated, partial, posterior cervical vertebra (QM F6142, the ‘Hughenden sauropod’) from the upper Albian Toolebuc Formation (which underlies the Allaru Mudstone). Although this vertebra preserves an apparent unique character of its own (a spinopostzygapophyseal lamina fossa), it is not able to be referred unequivocally to Austrosaurus and is retained as Titanosauriformes indet. Austrosaurus mckillopi is one of the oldest known sauropods from the Australian Cretaceous based on skeletal remains and potentially provides phylogenetic and/or palaeobiogeographic context for later taxa such as Wintonotitan wattsi, Diamantinasaurus matildae and Savannasaurus elliottorum.

Stephen F. Poropat* [[email protected]; [email protected]] Department of Chemistry and Biotechnology, Swinburne University of Technology, John St, Hawthorn, Victoria 3122, Australia; Jay P. Nair [[email protected]; [email protected]] School of Biological Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia; Caitlin E. Syme [[email protected]] School of Biological Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia; Philip D. Mannion [[email protected]] Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK; Paul Upchurch [[email protected]] Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK; Scott A. Hocknull [[email protected]] Geosciences, Queensland Museum, 122 Gerler Rd, Hendra, Queensland 4011, Australia; Alex G. Cook [[email protected]] School of Earth Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia; Travis R. Tischler [[email protected]] Australian Age of Dinosaurs Museum of Natural History, Lot 1 Dinosaur Drive, PO Box 408, Winton, Queensland 4735, Australia; Timothy Holland [[email protected]] Kronosaurus Korner, 91 Goldring St, Richmond, Queensland 4822, Australia. *Also affiliated with: Australian Age of Dinosaurs Museum of Natural History, Lot 1 Dinosaur Drive, PO Box 408, Winton, Queensland 4735, Australia.

Key words:

• Austrosaurus
• Dinosauria
• Sauropoda
• Titanosauriformes
• Australia
• Cretaceous
• Gondwana

Acknowledgements

The authors would like to thank: Eric & Lynne Slacksmith (Clutha Station) for allowing us access to the site; John Wharton (Richmond Shire Council) for relocating the site; Gary and Barb Flewelling, George Sinapius (AAOD), Kathrine Thompson (AAOD), Dennis Clancy, Alan & Lyn Scrymgeour, Mal & Jane Garden, John & Carry Jenkins, and Annie Just for their assistance in excavating Austrosaurus; Jose Carlos Mendezona, Tyrell Watson, and Dennis Friend (all Richmond Shire Council) for operating the earth-moving equipment; Richmond Shire Council for loaning the earth-moving equipment; H. B. Wade’s sons Peter and Richard Wade, and Dr M. J. McKillop’s daughters Elizabeth Cleary and Kathryn Evans for provision of images and information; David & Judy Elliott (AAOD) for provision of information, contacts and support; Tony Thulborn and Ralph Molnar for personal communications related to their expeditions to the Austrosaurus site; Felicity Tomlinson and Tanya Mellar (both AAOD) for providing transport to and from Richmond for SFP; Kristen Spring and Andrew Rozefelds (Queensland Museum) and Patrick Smith (Kronosaurus Korner) for access to specimens in their care; Trish Sloan (AAOD) for providing the photographs of the Diamantinasaurus ribs; Nicole Newman, Queensland X-Ray, Greenslopes Private Hospital, Rochelle Lawrence and Kristen Spring (both QM) for CT scanning the Austrosaurus mckillopi type series; and Phil Bell and Ignacio Cerda for their reviews of the manuscript. PU’s visit to Australia to examine sauropod specimens was supported by Leverhulme Trust Research Grant RPG-129.