New theropod remains and implications for megaraptorid diversity in the Winton Formation (lower Upper Cretaceous), Queensland, Australia

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Classifying isolated vertebrate bones to a high level of taxonomic precision can be difficult. Many of Australia’s Cretaceous terrestrial vertebrate fossil-bearing deposits, for example, produce large numbers of isolated bones and very few associated or articulated skeletons. Identifying these often fragmentary remains beyond high-level taxonomic ranks, such as Ornithopoda or Theropoda, is difficult and those classified to lower taxonomic levels are often debated. The ever-increasing accessibility to 3D-based comparative techniques has allowed palaeontologists to undertake a variety of shape analyses, such as geometric morphometrics, that although powerful and often ideal, require the recognition of diagnostic landmarks and the generation of sufficiently large data sets to detect clusters and accurately describe major components of morphological variation. As a result, such approaches are often outside the scope of basic palaeontological research that aims to simply identify fragmentary specimens. Herein we present a workflow in which pairwise comparisons between fragmentary fossils and better known exemplars are digitally achieved through three-dimensional mapping of their surface profiles and the iterative closest point (ICP) algorithm. To showcase this methodology, we compared a fragmentary theropod ungual (NMV P186153) from Victoria, Australia, identified as a neovenatorid, with the manual unguals of the megaraptoran Australovenator wintonensis (AODF604). We discovered that NMV P186153 was a near identical match to AODF604 manual ungual II-3, differing only in size, which, given their 10–15Ma age difference, suggests stasis in megaraptoran ungual morphology throughout this interval. Although useful, our approach is not free of subjectivity; care must be taken to eliminate the effects of broken and incomplete surfaces and identify the human errors incurred during scaling, such as through replication. Nevertheless, this approach will help to evaluate and identify fragmentary remains, adding a quantitative perspective to an otherwise qualitative endeavour.

Section: Discussionmentioning

confidence: 99%

Section: Methods and Workflowsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A three-dimensional approach to visualize pairwise morphological variation and its application to fragmentary palaeontological specimens

White

Campione

2021

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“…The only theropods heretofore reported from the Winton Formation are megaraptorids, notably Australovenator wintonensis (Hocknull et al, 2009;White et al, 2012;White et al, 2013;White et al, 2015a;White et al, 2015b;White et al, 2016;White et al, 2020). The type specimen of Australovenator preserves elements pertaining to both pedes, such that a composite pes can be assembled from left and right elements (Hocknull et al, 2009;Poropat et al, 2019b: Table S2; White et al, 2013;White et al, 2016).…”

Section: Description Of Track Morphotypesmentioning

confidence: 99%

A diverse Late Cretaceous vertebrate tracksite from the Winton Formation of Queensland, Australia

Poropat

White

Ziegler

et al. 2021

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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.

“… Note: Superscript numbers refer to citations: 1 ( Cook, 2005 ), 2 ( Hocknull, 1997 ), 3 ( Hocknull, 2000 ), 4 Hocknull personal observation (2002, 2009, 2019), 5 ( Ludbrook, 1985 ), 6 ( Fletcher & Salisbury, 2014 ), 7 ( Jell, 2004 ), 8 ( Elliott & Cook, 2004 ), 9 ( Salisbury, 2003 ), 10 ( Kemp, 1991 ), 11 ( Kemp, 1997 ), 12 ( Berrell et al, 2014 ), 13 ( Faggotter, Salisbury & Yabumoto, 2007 ), 14 ( Mond, 1974 ), 15 ( Salisbury, 2005 ), 16 ( Scanlon & Hocknull, 2008 ), 17 ( Salisbury et al, 2006 ), 18 ( Pentland et al, 2019 ), 19 ( Hocknull et al, 2009 ), 20 ( Poropat et al, 2016 ), 21 ( Hocknull et al, 2019 ), 22 ( Poropat et al, 2019 ), 23 ( Elliott, 2004 ), 24 ( White et al, 2020 ), 25 ( Thulborn & Wade, 1984 ), 26 ( Hocknull & Cook, 2008 ), 27 ( Salisbury et al, 2019 ), 28 ( Leahey & Salisbury, 2013 ), 29 ( Musser et al, 2009 ). …”

Section: Introductionmentioning

confidence: 99%

A new giant sauropod,Australotitan cooperensisgen. et sp. nov., from the mid-Cretaceous of Australia

Hocknull

Wilkinson

Lawrence

et al. 2021

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.