The dentary of Australovenator wintonensis (Theropoda, Megaraptoridae); implications for megaraptorid dentition.

Matt A White,Alex G Cook,David A Elliott,Phil R Bell,Stephen F Poropat

doi:10.7717/peerj.1512

Matt A White, Alex G Cook + Show 3 more

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https://doi.org/10.7717/peerj.1512

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Abstract

Megaraptorid theropods were an enigmatic group of medium-sized predatory dinosaurs, infamous for the hypertrophied claw on the first manual digit. Megaraptorid dentition is largely restricted to isolated teeth found in association with skeletal parts; however, the in situ maxillary dentition of Megaraptor was recently described. A newly discovered right dentary pertaining to the Australovenator holotype preserves in situ dentition, permitting unambiguous characterisation of the dentary tooth morphology. The new jaw is virtually complete, with an overall elongate, shallow profile, and fifteen visible in situ teeth at varying stages of eruption. In situ teeth confirm Australovenator exhibited modest pseudoheterodonty, recurved lateral teeth with a serrate distal carina and reduced mesial carina, similar to other megaraptorids. Australovenator also combines of figure-of-eight basal cross-section with a lanceolate shape due to the presence of labial and lingual depressions and the lingual twist of the distal carina. Computed tomography and three-dimensional imagery provided superior characterisation of the dentary morphology and enabled an accurate reconstruction to a pre-fossilised state. The newly established dental morphology also afforded re-evaluation of isolated theropod teeth discovered at the Australovenator holotype locality and from several additional Winton Formation localities. The isolated Winton teeth are qualitatively and quantitatively similar to the in situ dentary teeth of Australovenator, but are also morphometrically similar to Abelisauridae, Allosauridae, Coelophysoidea, Megalosauridae and basal Tyrannosauroidea. Qualitative characters, however, clearly distinguish the teeth of Australovenator and the isolated Winton teeth from all other theropods. Evidence from teeth suggests megaraptorids were the dominant predators in the Winton Formation, which contrasts with other penecontemporaneous Gondwanan ecosystems.

Highlights

Australovenator wintonensis Hocknull et al, 2009 holds the distinction as Australia’s most complete theropod dinosaur comprising of mostly forearm (White et al, 2012) and hind limb elements (White et al, 2013a) (Fig. 1)
In the analysis of all 21 theropod tooth morphotypes, the first two axes constitute over 90% of the variation in the sample: Axis 1 is size dependent, and is dominated roughly by CBW, CBL, Table 3 Results from PCA of unmodified dataset of all teeth showing relative importance of first four principle components and relative loadings for each principle component
Morphometric analyses of all theropod teeth known from the Winton Formation found that, in general, isolated crowns could not be distinguished from the in situ dentary teeth of Australovenator corroborating the qualitative evidence that they are assignable to Australovenator wintonensis

Summary

Introduction

Australovenator wintonensis Hocknull et al, 2009 holds the distinction as Australia’s most complete theropod dinosaur comprising of mostly forearm (White et al, 2012) and hind limb elements (White et al, 2013a) (Fig. 1). The majority of these specimens were discovered and described following the holotype description as preparation of concretions from the holotype locality is ongoing. The right dentary is better preserved than the left and provides new information on megaraptorid lower jaw morphology, which is otherwise poorly known across Megaraptoridae (Novas, Ezcurra & Lecuona, 2008; Porfiri et al, 2014). Eotyrannus lengi Hutt et al, 2001 from Europe hints at a putatively wider but equivocal occurrence for Megaraptoridae

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