Nilopegamys plumbeus Osgood 1928

Nilopegamys plumbeus Osgood 1928, Field Mus . Nat. Hist., Zool. Ser., 12: 185.

Type Locality: NW Ethiopia, Gojjam, Little Abbai, a small stream that is a tributary of the Blue Nile (11E7'20"N, 37E12'40"W); see Kerbis Peterhans and Patterson (1995) for additional information.

Vernacular Names: Ethiopian Amphibious Rat.

Distribution: Recorded only from the type locality.

Conservation: IUCN – Critically Endangered.

Discussion: Represented only by the type specimen, which is morphologically similar to Colomys . Kerbis Peterhans and Patterson (1995) enumerated the traits they considered to distinguish the two genera and noted that N. plumbeus has the largest cranial capacity and foramen magnum area of any African muroid sampled, close only to Colomys, Malacomys, and Deomys . Amphibious rodents exhibit large brains relative to body size with an enlarged medulla oblongata, which is correlated with an expansive foramen magnum (Voss, 1988). Kerbis Peterhans and Patterson (1995) contended that N. plumbeus has more morphological adaptations reflecting an amphibious life style than any other African muroid, including C. goslingi . That plumbeus represents a monophyletic group separate from the species of Colomys, however, is not universally accepted and the significance of the traits enumerated by Kerbis Pererhans and Patterson (1995) distinguishing Nilopegamys and Colomys is being tested by Hutterer and his colleagues within the context of a systematic revision of Colomys (R. Hutterer, in litt., 1999).