Cranial osteology of the ankylosaurian dinosaur formerly known as Minmi sp. (Ornithischia: Thyreophora) from the Lower Cretaceous Allaru Mudstone of Richmond, Queensland, Australia

PeerJ. 2015 Dec 8:3:e1475. doi: 10.7717/peerj.1475. eCollection 2015.


Minmi is the only known genus of ankylosaurian dinosaur from Australia. Seven specimens are known, all from the Lower Cretaceous of Queensland. Only two of these have been described in any detail: the holotype specimen Minmi paravertebra from the Bungil Formation near Roma, and a near complete skeleton from the Allaru Mudstone on Marathon Station near Richmond, preliminarily referred to a possible new species of Minmi. The Marathon specimen represents one of the world's most complete ankylosaurian skeletons and the best-preserved dinosaurian fossil from eastern Gondwana. Moreover, among ankylosaurians, its skull is one of only a few in which the majority of sutures have not been obliterated by dermal ossifications or surface remodelling. Recent preparation of the Marathon specimen has revealed new details of the palate and narial regions, permitting a comprehensive description and thus providing new insights cranial osteology of a basal ankylosaurian. The skull has also undergone computed tomography, digital segmentation and 3D computer visualisation enabling the reconstruction of its nasal cavity and endocranium. The airways of the Marathon specimen are more complicated than non-ankylosaurian dinosaurs but less so than derived ankylosaurians. The cranial (brain) endocast is superficially similar to those of other ankylosaurians but is strongly divergent in many important respects. The inner ear is extremely large and unlike that of any dinosaur yet known. Based on a high number of diagnostic differences between the skull of the Marathon specimen and other ankylosaurians, we consider it prudent to assign this specimen to a new genus and species of ankylosaurian. Kunbarrasaurus ieversi gen. et sp. nov. represents the second genus of ankylosaurian from Australia and is characterised by an unusual melange of both primitive and derived characters, shedding new light on the evolution of the ankylosaurian skull.

Keywords: Ankylosauria; Braincase; Computed tomography; Dinosauria; Eurypoda; Gondwana; Nasal cavity; Thyreophora.

Grants and funding

This work was funded by a University of Queensland Research Scholarship and the Graduate School Research Travel Grant to LGL as well as the Australian Research Council (LP0347332 and LP0776851), in association with Land Rover Australia, Winton Shire Council, Isisford Shire Council (now part of Longreach Regional Council), the Queensland Museum and the Carnegie Museum of Natural History to SWS. LMW received funding support from the Ohio University Heritage College of Osteopathic Medicine and the National Science Foundation (IBN-0343744, IOB-0517257, IOS-1050154). The Ohio Supercomputing Center provided additional support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.