Diamantinasaurus

Abstract: Wintonotitan wattsi, a Cretaceous titanosauri-form sauropod from central Queensland, Australia, is re-described following a full revision of its osteology. The holotype specimen, a partial postcranial skeleton derived from the lower Upper Cretaceous Winton Formation, comprises axial and appendicular elements. Wintonotitan has been commonly resolved as a non-titanosaurian somphospondylan titanosauriform since its description, in contrast to its more derived contemporary Diamantinasaurus matildae. We provide a detailed redescription, taking this opportunity to correct four misinterpretations made in the original description of Wintonotitan that impact on our understanding of this taxon: the right ulna was originally described as the left and vice versa; the left metacarpus was incorrectly described as being from the right side; metacarpal IV was described as metacarpal V and vice versa; and the ilium was incorrectly oriented. The reassessment of the metacarpus is particularly important, since it shows that a proximal fossa is present on metacarpals I, II and III, which might have been occupied by either the strongly convex distal end of the radius or a (possibly unossified) carpal element. We provide a review of titanosauriform metacarpal morphology to support our reassessments. Our revision of the osteology of Wintonotitan results in the identification of several previously unrecognized autapomorphies, augmenting and revising its original diagnosis. We provide additional support for the previous referral of four caudal vertebrae from south-east of Winton, Queensland, to W. wattsi. Furthermore, we demonstrate that a tentative report of titanosaur osteoderms from the Winton Formation was based on misidentification of dorsal vertebral neural spines pertaining to the holotype of W. wattsi. Consequently, titanosaur osteoderms are currently unknown from Australia. Following our revision and reinterpretation of a number of elements, we re-examine the phylogenetic placement of Wintonotitan, supporting its position as a non-titanosaurian somphospondylan titanosauriform, with no close relationship with the contemporaneous lithostrotian titanosaur Diamantinasaurus.

Abstract: The Upper Cretaceous 'upper' Winton Formation of Queensland, Australia is world famous for hosting Dinosaur Stampede National Monument at Lark Quarry Conservation Park, a somewhat controversial tracksite that preserves thousands of tridactyl dinosaur tracks attributed to ornithopods and theropods. Herein, we describe the Snake Creek Tracksite, a new vertebrate ichnoassemblage from the 'upper' Winton Formation, originally situated on Karoola Station but now relocated to the Australian Age of Dinosaurs Museum of Natural History. This site preserves the first sauropod tracks reported from eastern Australia, a small number of theropod and ornithopod tracks, the first fossilised crocodyliform and ?turtle tracks reported from Australia, and possible lungfish and actinopterygian feeding traces. The sauropod trackways are wide-gauge, with manus tracks bearing an ungual impression on digit I, and anteriorly tapered pes tracks with straight or concave forward posterior margins. These tracks support the hypothesis that at least one sauropod taxon from the 'upper' Winton Formation retained a pollex claw (previously hypothesised for Diamantinasaurus matildae based on body fossils). Many of the crocodyliform trackways indicate underwater walking. The Snake Creek Tracksite reconciles the sauropod-, crocodyliform-, turtle-, and lungfish-dominated body fossil record of the 'upper' Winton Formation with its heretofore ornithopod- and theropod-dominated ichnofossil record.

Abstract: A new giant sauropod, Australotitan cooperensis gen. et sp. nov., represents the first record of dinosaurs from the southern-central Winton Formation of the Eromanga Basin, Australia. We estimate the type locality to be 270-300 m from the base of the Winton Formation and compare this to the semi-contemporaneous sauropod taxa, Diamantinasaurus matildae Hocknull et al., 2009, Wintonotitan wattsi Hocknull et al., 2009 and Savannasaurus elliottorum Poropat et al., 2016. The new titanosaurian is the largest dinosaur from Australia as represented by osteological remains and based on limb-size comparisons it reached a size similar to that of the giant titanosaurians from South America. Using 3-D surface scan models we compare features of the appendicular skeleton that differentiate Australotitan cooperensis gen. et sp. nov. as a new taxon. A key limitation to the study of sauropods is the inability to easily and directly compare specimens. Therefore, 3-D cybertypes have become a more standard way to undertake direct comparative assessments. Uncoloured, low resolution, and uncharacterized 3-D surface models can lead to misinterpretations, in particular identification of pre-, syn- and post-depositional distortion. We propose a method for identifying, documenting and illustrating these distortions directly onto the 3-D geometric surface of the models using a colour reference scheme. This new method is repeatable for researchers when observing and documenting specimens including taphonomic alterations and geometric differences. A detailed comparative and preliminary computational phylogenetic assessment supports a shared ancestry for all four Winton Formation taxa, albeit with limited statistical support. Palaeobiogeographical interpretations from these resultant phylogenetic hypotheses remain equivocal due to contrary Asian and South American relationships with the Australian taxa. Temporal and palaeoenvironmental differences between the northern and southern-central sauropod locations are considered to explain the taxonomic and morphological diversity of sauropods from the Winton Formation. Interpretations for this diversity are explored, including an eco-morphocline and/or chronocline across newly developed terrestrial environments as the basin fills.