Rigorous approaches to species delimitation have significant implications for African crocodilian systematics and conservation

Accurate species delimitation is a central assumption of biology that, in groups such as the Crocodylia, is often hindered by highly conserved morphology and frequent introgression. In Africa, crocodilian systematics has been hampered by complex regional biogeography and confounded taxonomic history. We used rigorous molecular and morphological species delimitation methods to test the hypothesis that the slender-snouted croco- dile (Mecistops cataphractus) is composed of multiple species corresponding to the Congolian and Guinean biogeographic zones. Speciation probability was assessed by using 11 mitochondrial and nuclear genes, and cranial mor- phology for over 100 specimens, representing the full geographical extent of the species distribution. Molecular Bayesian and phylogenetic species deli- mitation showed unanimous support for two Mecistops species isolated to the Upper Guinean and Congo (including Lower Guinean) biomes that were supported by 13 cranial characters capable of unam...