Morphological study of the plastron of the African sideneck turtle (Pelusios castaneus)

Abstract

The morphological analysis of the plastron of the African sideneck turtle (Pelusios castaneus) was carried out using fifty adult turtles comprising twenty female and thirty male turtles picked up at different times from various river banks in Ibadan, Nigeria. The aim of the study was to provide baseline information that could be useful in the comparative osteology of sea and freshwater turtles as well as in the identification of the shell of the turtle in paleontological and archaeological investigations. Shells of the animals were prepared through hot water maceration while the scutes and bony elements of the shells were investigated using standard reptilian nomenclature and techniques.The plastron of the turtle has the following scutes anteroposteriorly: intergular, gular, humeral, pectoral, abdominal, femoral and anal. With the exception of the gular, all other scutes of the plastron are paired, one on each side of the medial sulcus of the plastron. The plastral formula of the turtle can be summarized as abd > fem > hum >< intergul > ana >< pec > gul; representing the abdominal, femoral, humeral, intergular, anal, pectoral and gular scutes, respectively. A structural depression was observed at the posterior portions of the xiphiplastron inall female turtleswhile a consistent concavity was found only on the dorsal surface of the femoral scute in male turtles. These are good landmarks of the plastron that could assist in sexual differentiation in the P. castaneus. This study therefore provides information useful in the comparative anatomy of the shells of sea and freshwater turtles as well as in species identification of turtle shells in paleontological and archaeological investigations.

Keywords: Plastron, morphology, scutes, bone, turtle