Browsing by Author "Bicknell, RDC"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    An earliest Triassic age for Tasmaniolimulus and comments on synchrotron tomography of Gondwanan horseshoe crabs
    (PeerJ, 2022-04-22) Bicknell, RDC; Smith, PM; Brougham, T; Bevitt, JJ
    Constraining the timing of morphological innovations within xiphosurid evolution is central for understanding when and how such a long-lived group exploited vacant ecological niches over the majority of the Phanerozoic. To expand the knowledge on the evolution of select xiphosurid forms, we reconsider the four Australian taxa:Austrolimulus fletcheri, Dubbolimulus peetae, Tasmaniolimulus patersoni, andVictalimulus mcqueeni. In revisiting these taxa, we determine that, contrary to previous suggestion,T. patersoniarose after the Permian and the origin of over-developed genal spine structures within Austrolimulidae is exclusive to the Triassic. To increase the availability of morphological data pertaining to these unique forms, we also examined the holotypes of the four xiphosurids using synchrotron radiation X-ray tomography (SRXT). Such non-destructive,in situimaging of palaeontological specimens can aid in the identification of novel morphological data by obviating the need for potentially extensive preparation of fossils from the surrounding rock matrix. This is particularly important for rare and/or delicate holotypes. Here, SRXT was used to emphasizeA. fletcheriandT. patersonicardiac lobe morphologies and illustrate aspects of theV. mcqueenithoracetronic doublure, appendage impressions, and moveable spine notches. Unfortunately, the strongly compactedD. peetaeprecluded the identification of any internal structures, but appendage impressions were observed. The application of computational fluid dynamics to high-resolution 3D reconstructions are proposed to understand the hydrodynamic properties of divergent genal spine morphologies of austrolimulid xiphosurids. 10.7717/peerj.13326 © 2022 Bicknell et al. Distributed under Creative Commons CC-BY 4.0
  • Thumbnail Image
    Item
    New ankylosaurian cranial remains from the lower cretaceous (upper albian) toolebuc formation of Queensland, Australia
    (Frontiers, 2022-03-28) Frauenfelder, TG; Bell, PR; Brougham, T; Bevitt, JJ; Bicknell, RDC; Kear, BP; Wroe, S; Campione, NE
    Australian dinosaur research has undergone a renaissance in the last 10 years, with growing knowledge of mid-Cretaceous assemblages revealing an endemic high-paleolatitude Gondwanan fauna. One of its most conspicuous members is ankylosaurs, which are rare but nonetheless occur in most Australian dinosaur-bearing formations spanning the uppermost Barremian to lower Cenomanian. Here we describe a partial ankylosaur skull from the marine Toolebuc Formation exposed near Boulia in western Queensland, Australia. This skull represents the oldest ankylosaurian material from Queensland, predating the holotype of Kunbarrasaurus ieversi, which was found in the overlying Allaru Mudstone. The ankylosaur skull is encased in a limestone concretion with the maxillary tooth rows preserved only as impressions. Synchrotron radiation X-ray tomography was used to non-destructively image and reconstruct the specimen in 3D and facilitate virtual preparation of the separate cranial bones. The reconstruction of the skull revealed the vomer, palatines, sections of the ectopterygoids and maxillae, and multiple teeth. The palate has posteriorly positioned choanae that differs from the more anterior placement seen in most other ankylosaurians, but which is shared with K. ieversi, Akainacephalus johnsoni, Cedarpelta bilbeyhallorum, Gobisaurus domoculus, and Panoplosaurus mirus. Phylogenetic analyses place the new cranial material within the recently named basal ankylosaurian clade Parankylosauria together with K. ieversi. This result, together with the anatomical similarities to the holotype of K. ieversi, permits its referral to cf. Kunbarrasaurus sp. This specimen elucidates the palatal anatomy of Australian ankylosaurs and highlights one of the most ubiquitous components of Australian mid-Cretaceous dinosaur faunas. © 2022 Frauenfelder, Bell, Brougham, Bevitt, Bicknell, Kear, Wroe and Campione. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).