Reappraisal ofAustrosaurus mckillopiLongman, 1933 from the Allaru Mudstone of Queensland, Australia’s first named Cretaceous sauropod dinosaur

Abstract

Austrosaurus mckillopi Longman, 1933 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 belonging toof the type individual of Austrosaurus mckillopi, in tandem with a reassessment of the type seriesmaterial 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 visualised through CT data, validates it as a diagnostic titanosauriform taxon (, tentatively placed in Somphospondyli),, and characterised by the possession of an accessory lateral pneumatic foramen on dorsal vertebra I (a feature which appears to be autapomorphic) and by the presence of a robust ventral midline 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”) derived 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

Taxonomic affinities of the putative titanosaurs from the Late Jurassic Tendaguru Formation of Tanzania: phylogenetic and biogeographic implications for eusauropod dinosaur evolution

“…Recently described remains (including Triunfosaurus leonardii) from the Rio Piranhas Formation (Hauterivian-Barremian) of northeastern Brazil have been assigned to Titanosauria (Ghilardi et al, 2016;Carvalho et al, 2017), although Poropat et al (2017) argued that these could not be confidently referred beyond Somphospondyli. The discovery of Padillasaurus in the late Barremian Paja Formation of Colombia (Carballido et al, 2015) confirms the presence of Somphospondyli in the pre-Aptian of South America .…”

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Diversity and palaeoecology of Australia's southern-most sauropods, Griman Creek Formation (Cenomanian), New South Wales, Australia

“…2016; Poropat et al . 2017). The osteological record of sauropods is supplemented by abundant and diverse sauropod tracks from the Valanginian–Barremian Broome Sandstone in Western Australia, which attest to the diversity and once‐wider distribution of sauropods in the northern half of the country (Salisbury et al .…”

New information on the Cretaceous sauropod dinosaurs of Zhejiang Province, China: impact on Laurasian titanosauriform phylogeny and biogeography

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