Postcanine microstructure in Cricodon metabolus, a Middle Triassic gomphodont cynodont from southeastern Africa.

HENDRICKX, C.; ABDALA, F.; CHOINIERE, J.N.

Salt Lake City

Conferencia; 76th Annual Meeting of the Society of Vertebrate Paleontology; 2016

Society of Vertebrate Paleontology

Cricodon metabolus is a trirachodontid cynodont from the Anisian (Middle Triassic) of eastern and southern Africa whose dentition includes labiolingually expanded (gomphodont) postcanines but also a sectorial tooth in the last postcanine locus. The crown microstructure of isolated sectorial and gomphodont postcanines belonging to the holotype specimen of this taxon was examined for the first time using scanning electron microscopy. The enamel of both teeth is prismless and composed of discontinuous columnar divergent units, confirming the consistent presence of synapsid columnar enamel in cynognathians. Abundant odontoblast tubules and numerous irregularly spaced incremental lines are also visible in the enamel and dentine layers in each tooth. This study reveals that the enamel thickness varies along the tooth row in Cricodon as the enamel layer of the gomphodont postcanines is 7.5 times thicker than that of the sectorialcrown. This difference likely reflects occlusal stresses and fewer replacements in gomphodont postcanines relative to sectorial teeth. Approximately one hundredinterdental growth lines of von Ebner are present in the dentine layer, indicating that the odontoblast deposition of the dentine occurred for four months before the animal?s death.