New information on the skull of the Early Triassic parareptile Sauropareion anoplus, with a discussion of tooth attachment and replacement in procolophonids

ABSTRACT

A partial reptile skull collected from the Lower Triassic (Induan) Barendskraal locality of South Africa is referable to the procolophonid parareptile Sauropareion anoplus. The specimen comprises the left side of the skull roof, palate, and mandible, and preserves areas not preserved or accessible in the skulls of previously published specimens, including fragmentary remains of the premaxilla, the anterior end of the maxilla, and the anterior end and lingual aspect of the mandible. The maxilla exhibits a maxillary depression that is similar in both shape and relative size to that seen in Procolophon trigoniceps, an anterolateral maxillary foramen that is indistinguishable from those seen in other procolophonoids, and 11 conical teeth. The suborbital foramen is formed ventrally by the palatine and the ectopterygoid. The dentary and the coronoid are fused together indistinguishably in lateral aspect. The marginal teeth appear to be anchored to the jaws by bone of attachment. The dentary teeth are exposed in lingual aspect and appear to be ankylosed to the summit of the bone, suggesting acrodont tooth implantation. Tooth replacement is seen in these teeth, where the lingual surface of a single tooth crown base in the middle of the dentary series is excavated for the apex of a replacement tooth crown, but the excavation does not extend ventrally onto the lingual surface of the bone. Considering that no extant reptiles with acrodont tooth implantation exhibit tooth replacement or bone of attachment, we tentatively regard protothecodonty to be present in S. anoplus.

ACKNOWLEDGMENTS

We thank Richard and Jenni Rogers (Hathersage, Middelburg District, Eastern Cape Province) for permission to prospect on Barendskraal, Jennifer Cooper (formerly Cape Breton University) for the photographs and specimen illustrations that appear in Figures 1 and 2, Diane Scott for the photograph that appears in Figure 3, Jennifer Botha-Brink for the loan of NMQR 3544, Bruce Rubidge for the loans of BP/1/4299 and BP/1/5779, Linda Tsuji and Laura Säilä for reviewing the manuscript, and editor Randall Irmis for his comments. BP/1/5779 was collected in the course of field work that was funded by National Geographic Society grant number 6269-00 (to R. Damiani). This project was funded by a Cape Breton University Research Policy grant (to S.P.M.), a Discovery Grant (no. 288126-07) from the Natural Sciences and Engineering Research Council (NSERC) of Canada (to S.P.M.), and a New Opportunities Fund award from the Canadian Foundation for Innovation (to S.P.M.).

Handling editor: Randall Irmis.