Morphology and intraspecific variation in the skull and mandible of the slider turtle Trachemys dorbigni (Testudines, Emydidae)

Abstract

Testudines generally presents a considerable wealth of osteological elements of the skull that makes crucial the detailed knowledge of these bone structures, mainly in solving problems of classification and determination of species. Emydidae is an important group of chelonians, but the cranial anatomy knowledge is limited, mainly of the species of the genus Trachemys. The aim of the present study is to describe the osteology (in particular, the intraspecific variations) of the skull and mandible of T. dorbigni. 82 specimens of T. dorbigni from the Herpetological Collection of the Laboratory of Vertebrate Zoology/Institute of Biology/Universidade Federal de Pelotas were used in this study. The results indicated a set of characteristics not previously described for the specie’s skull, as well as several characteristics intraspecifically variable. Intraspecific variation was found in the pattern of jugal, frontal, prefrontal, vomer, quadratojugal and exoccipital bones, further the cases of absence and diversification in the position of the foramina praepalatinum and foramen nervi hypoglossi, and an observation of foramens that were not described in literature. Therefore, it is possible to state that there is considerable intraspecific variation in the Trachemys dorbigni’s skull, although it maintains general characteristics similar to other Emydidae’s species.