[Paleontology • 2015]
Kunbarrasaurus ieversi • Cranial Osteology of the Ankylosaurian Dinosaur formerly known as ''Minmi'' sp. (Ornithischia: Thyreophora) from the Lower Cretaceous Allaru Mudstone of Richmond, Queensland, Australia
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| Kunbarrasaurus ieversi
Leahey, Molnar, Carpenter, Witmer & Salisbury, 2015
illustration: AustralianGeographic.com.au | PeerJ.com/articles/1475/
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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: Dinosauria, Thyreophora, Eurypoda, Ankylosauria, Gondwana, Computed tomography, Nasal cavity, Braincase
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| The holotype skeleton of Kunbarrasaurus ieversi (QM F18101), Australia’s most complete dinosaur fossil, and one of the world’s most complete ankylosaurians.
image: Anthony O’Toole and Lucy Leahey
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SYSTEMATIC PALEONTOLOGY
Dinosauria Owen, 1842
Ornithischia Seeley, 1888
Thyreophora Nopcsa, 1915
Eurypoda Sereno, 1986
Ankylosauria Osborn, 1923
Kunbarrasaurus ieversi gen. et sp. nov.
(formerly Minmi sp. Molnar, 1996a)
Etymology. The generic name combines Kunbarra [kunbara], the Mayi (Wunumara) word for ‘shield’, and souros (σ αυρoς), the Greek word for ‘lizard’, and is a reference to the animal’s heavily ossified skin. The species name honours Mr Ian Ievers, discoverer of the holotype. The name therefore means ‘Ievers’ shield-lizard’.
Holotype. QM F18101, a near-complete ankylosaurian dinosaur
specimen that includes most of the skull and mandible, along with an
articulated postcranium.
CONCLUSIONS
The assignment of a new genus and species name Kunbarrasaurus ieversi to
QM F18101 (formerly known as Minmi sp.) is based on a significant
number of features that distinguish it from other ankylosaurians. Many
of the cranial sutures of K. ieversi have not fused, nor
are they obscured by dermal ossifications. The closure of the antorbital
and supratemporal fenestrae of K. ieversi is most likely due to the
expansion of cranial bones, and not the result of overgrowth of dermal
ossifications. The ornamentation of the skull of K. ieversi is the
result of both epidermal ossification (osteoderms) and periosteal
osteogenesis. Some aspects of the nasal cavity remain obscure, but there
is enough evidence to suggest that K. ieversi had a more complicated airway than in non-ankylosaurian outgroups. It is presently unclear whether K. ieversi
had a convoluted, looping nasal passage to the extent seen in more
advanced ankylosaurians. Some aspects of the braincase are potentially
unique among known species, such as the unusual inner ear, which is not
only extremely large but also has a divergent morphology due to lack of
ossification medially and ventrally.
Lucy G. Leahey, Ralph E. Molnar, Kenneth Carpenter, Lawrence M. Witmer
and Steven W. Salisbury. 2015. Cranial Osteology of the Ankylosaurian
Dinosaur formerly known as ''Minmi'' sp. (Ornithischia: Thyreophora) from the Lower Cretaceous Allaru Mudstone of Richmond, Queensland, Australia. PeerJ. 3; e1475. doi: 10.7717/peerj.1475
Kunbarrasaurus is Australia’s new armoured dinosaur - Australian Geographic http://www.australiangeographic.com.au/blogs/austropalaeo/2015/12/kunbarrasaurus-is-australia%E2%80%99s-new-armoured-dinosaur via @john_pickrell @AusGeo
Australia's new armoured dinosaur revealed http://phy.so/368778074 via @physorg_com
