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

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.

Sexual dimorphism of craniomandibular size in the Korean water deer, Hydropotes inermis argyropus

Sexual dimorphism in the craniomandibular traits in the Korean water deer Hydropotes inermis argyropus was examined for the first time. Multivariate analyses using only cranial traits showed a clear separation between sexes. However, the separation was not obvious in the discriminant analysis using only mandibular traits. The most clearly dimorphic trait was in the incisive bone breadth, which was about 12% larger in males. The incisive bone width reflects the characteristically large canines in male. In contrast to this, most of the cranial measurements, except for the incisive breadth, were larger in female, indicating a larger overall skull size. Given that males are generally larger than females, this sexually dimorphic pattern is unique among mammals. We propose that factors, for example, a unique parental care, have influenced the larger skull size in the females of this species.