A method for deducing neck mobility in plesiosaurs, using the exceptionally preserved Nichollssaura borealis.

Ramon S Nagesan,Jason S Anderson,Donald M Henderson

doi:10.1098/rsos.172307

Ramon S Nagesan, Jason S Anderson + Show 1 more

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https://doi.org/10.1098/rsos.172307

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Abstract

The elongate-necked aquatic plesiosaurs existed for 135 Myr during the Mesozoic. The function of this elongate neck is a point of debate. Using computed tomography and three-dimensional (3D) modelling, the range of motion (ROM) of the plesiosaur Nichollssaura borealis neck was assessed. To quantify the ROM, the intervertebral mobility was measured along the cervical vertebral column. This was done by manipulating the 3D models in the lateral and dorsoventral directions during two trials. The first assessed the mean intervertebral ROM between pairs of cervical vertebrae along the entire column, and the second assessed ROM with reduced intervertebral spaces. The results suggest that there may be preference for lateral neck movements in N. borealis, which could correspond to an ecological function related to prey capture. This study demonstrates that 3D modelling is an effective tool for assessing function morphology for structures where no good modern analogue exists.

Highlights

Plesiosauria is a clade of extinct, globally distributed marine reptiles that persisted for 135 Myr from the Triassic to the end Cretaceous [1,2,3,4]
In the minimum intervertebral space mobility (MISM) trial, we reduced the intervertebral space before conducting the range of motion (ROM) manipulations in Autodesk Maya
As mentioned in the description of N. borealis, several of the cervical vertebrae were damaged during excavation [23], which resulted in missing ROM measurements

Summary

Introduction

Plesiosauria is a clade of extinct, globally distributed marine reptiles that persisted for 135 Myr from the Triassic to the end Cretaceous [1,2,3,4]. Plesiosauria is rooted within the sauropterygian clade of reptiles, and may be a sister group to the lepidosaurs; 2018 The Authors. Sauroptergyian taxonomic relationships to other groups remain unclear [1]. 2 four paddle-like appendages and streamlined bodies exemplify the plesiosaur bauplan, which was adapted for a completely aquatic lifestyle [1,5,6]. There are three groups of uncertain relationship within Plesiosauria: the Plesiosauroidea, Pliosauridae and Rhomaleosauridae [4,7,8]. This study focuses on a leptocleidid plesiosaur, Nichollssaura borealis

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