Morphology of the jaw-closing musculature in the common wombat (Vombatus ursinus) using digital dissection and magnetic resonance imaging.

Alana C Sharp,Peter W Trusler,Kornelius Kupczik

doi:10.1371/journal.pone.0117730

Abstract

Wombats are unique among marsupials in having one pair of upper incisors, and hypsodont molars for processing tough, abrasive vegetation. Of the three extant species, the most abundant, the common wombat (Vombatus ursinus), has had the least attention in terms of masticatory muscle morphology, and has never been thoroughly described. Using MRI and digital dissection to compliment traditional gross dissections, the major jaw adductor muscles, the masseter, temporalis and pterygoids, were described. The masseter and medial pterygoid muscles are greatly enlarged compared to other marsupials. This, in combination with the distinctive form and function of the dentition, most likely facilitates processing a tough, abrasive diet. The broad, flat skull and large masticatory muscles are well suited to generate a very high bite force. MRI scans allow more detail of the muscle morphology to be observed and the technique of digital dissections greatly enhances the knowledge obtained from gross dissections.

Highlights

Many morphological characteristics reflect the grazing nature of wombats
The total weights for each muscle group, for each Vombatus ursinus specimen dissected, are compared to the data for Lasiorhinus latifrons provided by Crompton et al [4] (Table 1)
The soft tissue anatomy of the Vombatidae has been based on Lasiorhinus latifrons

Summary

Introduction

Many morphological characteristics reflect the grazing nature of wombats. Like other members of the order Diprotodontia, wombats have only two lower incisors, but they are unique among marsupials in having only one pair of upper incisors. The lower jaw moves sideways and upwards so that the blades of the molars meet to cut the grass stems [1,2]. They have a bilateral chewing function where only the muscles on the working side activate during the power stroke [3,4]. This is an efficient way of processing the course, abrasive grasses that are the wombat’s dominant food [1]

Methods

Results

Discussion

Conclusion