A study on Lake Turkana in Kenya (informally this population would be placed in "C. n. pauciscutatus") has shown that the local crocodiles appear to have more osteoderms in their ventral surface than other known populations, thus are of lesser value in leather trading, accounting for an exceptionally large (possibly overpopulated) local population there in the late 20th century. The segregation of the West African crocodile ("C. suchus") from the Nile crocodile has been supported by morphological characteristics, studies of genetic materials and habitat preferences. The separation of the two is not recognized by the IUCN as their last evaluations of the group was in 2008 and 2009, years before the primary publications supporting the distinction of the West African crocodiles. DNA from West African crocodiles has indicated that, unlike the Nile crocodile, it is most closely related to East Asian species, such as the Philippine crocodile ("Crocodylus mindorensis"), than other extant crocodilians. At one time, the fossil species "Rimasuchus lloydi" was thought to be the ancestor of the Nile crocodile, but more recent research has indicated that "Rimasuchus", despite its very large size (about 20–30% bigger than a Nile crocodile with a skull length estimated up to ), is more closely related to the dwarf crocodile ("Osteolaemus tetraspis") among living species.