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Enamel microstructure in Exaeretodon, a Late Triassic South American traversodontid (Therapsida: Cynodontia)

2007; Volume: 10; Issue: 2 Linguagem: Inglês

10.4072/rbp.2007.2.01

2236-1715

Fernando Abdala,

Ichthyology and Marine Biology

Exaeretodon is a well-known traversodontid cynodont mostly confined to the Upper Triassic of Argentina and Brazil.In this paper, the enamel structures of the upper postcanines of Exaeretodon frenguellii from the Ischigualasto Formation, northwestern Argentina, and of E. riograndensis from the Santa Maria Formation, southern Brazil, are examined using scanning electron microscopy.In E. frenguellii, the prismless enamel layer is usually thicker than 100 µm and comprised of parallel, short, discontinuous columns perpendicular to the outer enamel surface.Exaeretodon riograndensis also presents a prismless enamel layer thicker than 100 µm, made up of vaguely defined columns, with abundant and well-defined incremental lines.Dentine was also examined in different areas exposed to, and hidden from occlusion in E. frenguellii.In sagittal section, abundant dorsoventrally-oriented tubules are clearly observed in the dentine not exposed to occlusion, whereas they seem to be less abundant and certainly less evident in dentine exposed to occlusion.This difference might simply represent a change in the orientation of the tubules.