Masticatory morphological diversity and chewing modes in Southamerican caviomorph rodents (Octodontidae

OLIVARES, AI, VEZI, DH; VASSALLO, AI

JOURNAL OF ZOOLOGY (1987)

Cambridge University Press

Lugar: Londres; Año: 2004 vol. 263 p. 267 - 277

0952-8369

Abstract.- Relationship between masticatory morphology and chewing modes in all living genera of Octodontidae was analysed. Chewing directions and the patterns of molar occlusion were assessed. Factor and regression analyses of skull and jaw characters, and attributes of the adductor musculature, especially the line of action of masseters and pterygoids, were performed in order to check their relations with the chewing modes. Two basic chewing strategies are present in octodontids: oblique unilateral (associated with anterolingual jaw displacement, and alternate occlusion of left and right molar series), and propalinal bilateral (associated with mostly posteroanterior jaw displacement, and simultaneous occlusion). The skull and jaw characters examined resulted only partly related to these chewing strategies. The temporal pattern of muscle contraction provides a possible explanation for such a functional versatility. Propalinal grinding in octodontids could be achieved through simultaneous muscle contraction, with limited reliance concerning the line of action of the involved muscles. It would explain a similar propalinal masticatory mode in morphologically disparate genera. In accordance with phylogenetic information, oblique unilateral chewing is primitive in octodontids, and derived propalinal mode would have been developed independently at least twice in the evolution of the family.