The slender-snouted crocodile ("M. cataphractus") was thought to be distributed across west Africa and into central Africa but the central African species has been separated as the Central African slender-snouted crocodile ("M. leptorhynchus") based on studies in 2014 and 2018 that indicated that both were distinct species. The name "cataphractus" is retained for the West African species as that species was described first based on specimens from western Africa. The two species diverged about 6.5–7.5 mya, living in different river drainage zones that were geographically separated from each other by the Cameroon Line.