EATON, M.J. (2010)

Dwarf Crocodile - Osteolaemus tetraspis.

In: Crocodiles.Status Survey and Conservation Action Plan: 127-132.
Third Edition, ed. by S.C. Manolis and C. Stevenson. Crocodile Specialist Group: Darwin.

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The African dwarf crocodile historically ranged throughout the lowland regions of West and western Central Africa, from Senegal and The Gambia in the west to the eastern border of the Congo Basin in the Democratic Republic of Congo and Uganda. Northern Nigeria and Cabinda Province (Angola) are considered to be the northern and southern extents of the genus, respectively. The Central and West African dwarf crocodile (O. tetraspis) is now distinguished from Osborn’s dwarf crocodile (O. osborni), and new research suggests that populations further west are signifi cantly differentiated from lineages in Central Africa and the Congo Basin and warrant a unique species designation (Osteolaemus cf. tetraspis) (Eaton et al. 2009).

The taxonomy of the African dwarf crocodile has been under debate for almost 80 years. Osteolaemus tetraspis was first described in 1860 from Gabon. A second morphological form, discovered in the upper Congo River Basin, was described as a new genus (Osteoblepharon osborni, Schmidt 1919). This new genus was subsequently considered to be unwarranted, resulting first in osborni being relegated as species of Osteolaemus and then to a subspecies, Osteolaemus tetraspis osborni (Wermuth 1953). Some authorities have even suggested that sub-species status may not be merited. A recent morphological study, however, has confirmed fixed differences between tetraspis and osborni, suggesting that each should be resurrected as a distinct taxon. Additionally, a recent molecular  phylogenetic analysis of samples collected from the Republic of Congo, Gabon, Ivory Coast and Ghana supports the evolutionary distinctiveness of dwarf crocodiles in the Congo Basin (osborni) from those further west. This same investigation also revealed that the nominal form of O. tetraspis from Gabon’s Ogooué Basin is genetically distinct from dwarf crocodiles in West Africa, suggesting that at least one new morphologically cryptic species exists in the latter region.

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