CYSTOPHORINAE, Gray, 1866

Koretsky, I. A., Rahmat, S. J. & Peters, N., 2014, Remarks On Correlations And Implications Of The Mandibular Structure And Diet In Some Seals (Mammalia, Phocidae), Vestnik Zoologii 48 (3), pp. 255-268 : 264

Subfamily CYSTOPHORINAE

Both species of the Subfamily Cystophorinae have very weak teeth, which could be the reason that representatives of this subfamily possess a superior-positioned mandibular ramus, very much elevated above the tooth-row. The bigger condyloid angle demonstrates the ability of these seals to eat large sized prey. Furthermore, the very well-developed masticatory muscles,such as the masseter and temporalis, could be the result of compensation for weak teeth. Thus, the powerful actions of the muscles of mastication would allow for a stronger bite and more forceful tearing of large prey. On the other hand, weakened teeth could be a direct result of the strong mastication muscles, with increased muscular force influencing the unnecessary need of strong teeth due to their ability to swallow prey whole. Future morphological studies would benefit greatly by examining the causal relationship between weak teeth and strong mastication muscles to determine exactly which structures dominate and which are the result of compensation. In addition, the condyloid angle and its measurements suggest a degree of sexual dimorphism among Cystophorinae , but few or no significant differences between the sexes of representatives in the other subfamilies. Mirounga is the only genus of Phocinae where sexual dimorphism is clearly displayed, mainly in size, color and cranial and postcranial skeletal elements. Therefore, sexual dimorphism in mandibular anatomy likely corresponds to cranial dimorphism.