Geometric morphometric analysis of cranial variation in the Egernia depressa (Reptilia: Squamata: Scincidae) species complex

WA Museum Records and Supplements | Updated 7 years ago

ABSTRACT – Few studies have attempted to simultaneously examine geographic, ontogenetic and sexual variation of lizard crania. This study does so with a focus on the Egernia depressa species complex (Pygmy Spiny-tailed Skinks), which occur throughout much of arid Western Australia and inhabits fallen trees in the southern part of its range and rock crevices in disjunct boulder outcrops in the northern part of its range in the Pilbara. Geometric (i.e. landmark-based) morphometrics were used to examine variation in cranial shape in E. depressa, E. cygnitos and E. epsisolus. Cranial differences were evident among the different species; however, the differences depended on which aspect of the cranium was being analysed. A comparison also was made between E. depressa which inhabits tree hollows v. E. cygnitos and E. epsisolus which use rock crevices. The lateral aspect of the cranium of the rock-inhabiting species differs from the log-inhabiting species in having dorsal-ventral compression of the postorbital region. Egernia cygnitos which lives western portion of the Pilbara differs from other species in having a wider cranium with a correspondingly broader palatal region. Sexual dimorphism was not evident, but ontogenetic changes in cranial form were present.