Slender-snouted crocodiles were long treated as a single species, Mecistops cataphractus, distributed from West Africa across the Congo basin. Genetic and morphological work through the 2010s showed two deeply divergent lineages separated by the Cameroon Volcanic Line, and in 2018 the western form was retained as M. cataphractus while the Central African population was described as M. leptorhynchus.
The consequence for conservation was immediate. The combined species had looked moderately widespread. The western lineage alone occupies a fragmented remnant of the Upper Guinean forest zone, and surveys have found it absent from many rivers where it was formerly recorded. It is now assessed as Critically Endangered, with the wild population thought to number in the hundreds.
The long snout indicates a diet dominated by fish, taken with fast sideways sweeps of the head. Population figures remain approximate: the species is shy, nocturnal and hard to survey, and no comprehensive range-wide census exists.