Complex neuroanatomy in the rostrum of the Isle of Wight theropod Neovenator salerii

Chris Tijani Barker,Orestis L Katsamenis,Gareth Dyke,Darren Naish,Elis Newham

doi:10.1038/s41598-017-03671-3

Abstract

The discovery of large, complex, internal canals within the rostra of fossil reptiles has been linked with an enhanced tactile function utilised in an aquatic context, so far in pliosaurids, the Cretaceous theropod Spinosaurus, and the related spinosaurid Baryonyx. Here, we report the presence of a complex network of large, laterally situated, anastomosing channels, discovered via micro-focus computed tomography (μCT), in the premaxilla and maxilla of Neovenator, a mid-sized allosauroid theropod from the Early Cretaceous of the UK. We identify these channels as neurovascular canals, that include parts of the trigeminal nerve; many branches of this complex terminate on the external surfaces of the premaxilla and maxilla where they are associated with foramina. Neovenator is universally regarded as a ‘typical’ terrestrial, predatory theropod, and there are no indications that it was aquatic, amphibious, or unusual with respect to the ecology or behaviour predicted for allosauroids. Accordingly, we propose that enlarged neurovascular facial canals shouldn’t be used to exclusively support a model of aquatic foraging in theropods and argue instead that an enhanced degree of facial sensitivity may have been linked with any number of alternative behavioural adaptations, among them defleshing behaviour, nest selection/maintenance or social interaction.

Highlights

Neovenator salerii is an allosauroid theropod from the Wessex Formation of the Isle of Wight, UK (Barremian, Early Cretaceous)[1, 2], known from a partial skeleton (Museum of Isle of Wight Geology (MIWG) 6348) that comprises extensive cranial, axial, and appendicular material preserved in excellent three-dimensional condition
We were intrigued by enlarged foramina present on both the lateral surface of the premaxilla, occasionally set within shallow grooves[2], and on the anterior ramus of the maxilla and hypothesised that they might be indicative of a rostral neuroanatomy similar to that reported in spinosaurids[10], and more recently, tyrannosaurids[11]
The presence of foramina on the lateral surfaces of the premaxilla and maxilla are typical, widespread amniote features[13] and only rarely are they given more than fleeting mention in descriptions and analyses

Summary

Introduction

Neovenator salerii is an allosauroid theropod from the Wessex Formation of the Isle of Wight, UK (Barremian, Early Cretaceous)[1, 2], known from a partial skeleton (Museum of Isle of Wight Geology (MIWG) 6348) that comprises extensive cranial, axial, and appendicular material preserved in excellent three-dimensional condition. The exceptional volume of these neuroanatomical structures has been linked to an aquatic tactile ability, consistent with narial position, jaw and tooth shape, limb proportions, and reduced medullary cavities in the long bones which have been regarded as indicative of an amphibious or aquatic mode-of-life[10]. These rostral structures of Spinosaurus were regarded as analogous to the dermal pressure receptors (DPR)[10] present in crocodylians. We revisit the cranial morphology of the Isle of Wight theropod Neovenator using microfocus μCT to investigate the distribution of its rostral foramina and any internal preservation. We use these data to inform inferences about the palaeobiology and behaviour of Neovenator and other large tetanuran theropods, whilst standardising our results to facilitate further analysis of theropod/dinosaurian cephalic vasculature

Methods

Results

Conclusion