Species-Specific Morphology of Masticatory Jaw Movements

Abstract

Ethology defines action patterns as relatively invariant, species-specific movement patterns. Action patterns are said to have species-specific form features, much like anatomical morphology contains species-specific form features. However, morphology exists in space, whereas movements take form in time. Thus, movements and morphology cannot be quantified in the same way. Standard methods of quantifying the spatial and temporal dimensions of animal movements are not amenable to statistical, cross-species comparative studies. This paper describes a method of quantifying masticatory jaw movements so that rigorous cross-species comparisons can be made. Results show that jaw movements contain species-specific features, many of which are not visually detectable. The results suggest that it is possible to interpret the action pattern definition literally in that masticatory jaw movements have a quantifiable form, which contains species-specific features. Furthermore, the results show that jaw movement forms appear to reflect an animal's phylogenetic history as well as its current feeding niche. Future investigations should be able to elucidate how phylogeny and dietary selection pressures interact to produce specific features of dentoskeletal morphology and masticatory movement form.