Africa has a rich mammalian fossil record, but early Cenozoic mammals are only known from northern Africa (Lavocat 1953; Pickford 1986; Rasmussen et al. 1992). Discovery of Paleocene-Eocene mammals from other parts of the continent offers the potential to broaden understanding of the origin and diversification of many modern mammalian groups (Krause and Maas 1990; Bowen et al. 2002), the origin and maintenance of endemicity in African faunas (Gheerbrant 1990; Holroyd and Maas 1994), and the biogeographic and phylogenetic implications of Afrotheria (Liu and Miyamoto 1999; Springer et al. 1999; Murphy et al. 2001). Here we report the oldest Cenozoic mammal discovered in sub-Saharan Africa. The specimen was found in crater lake sediments at Mahenge (Harrison et al. 2001) in north-central Tanzania and represents a partial skeleton of an echolocating bat. It has extremely large cochleae, indicating that it was capable of specialized high-duty-cycle constant-frequency (CF) echolocation like that seen in extant rhinolophid bats (Fenton et al. 1995).

Eocene microbats are known from North America, Europe, Australia, Africa, Asia, and possibly Antarctica (Schlosser 1910; Jepsen 1966; Russell and Gingerich 1981; Habersetzer and Storch 1987; Sigé 1985, 1991; Hand et al. 1994; Woodburne and Case 1996; Simmons and Geisler 1998). Four taxa, Icaronycteris (Early-Middle Eocene, North America), Archaeonycteris, Palaeochiropteryx, and Hassianycteris (Middle Eocene, Europe) are represented by virtually complete skeletons. All other Eocene bats are known only from fragmentary dental, cranial, and postcranial remains.

Four Eocene microbats have been described from Africa, Provampyrus (?=Vampyrus), Philisis and Dizzya (vespertilionids), and an indeterminate rhinolophoid (Schlosser 1910; Sigé 1985, 1991). Honrovits (North America) and Ageina (Europe) may represent a vespertilionoid and nataloid, respectively (Beard et al. 1992; Simmons and Geisler 1998). Australonycteris (Hand et al. 1994) (Australia) may share affinities with vespertilionids or molossids whereas Eppsinycteris (Hooker 1996) (Europe) may be an emballonurid. If the higher level relationships of these Eocene taxa are correct, then several modern superfamilies of bats existed by the late early Eocene.

Eocene microbats are more primitive than extant forms in some morphological features but possess fully developed wings and specializations of the shoulder, axial skeleton, and hind limbs indicating that all were capable of maneuverable, powered flight (Jepsen 1966; Habersetzer and Storch 1987; Simmons and Geisler 1998). All of these taxa possess relatively enlarged cochleae and other specialized features of the auditory region indicating that a complex mechanism for echolocation was present in bats by the early Eocene (Novacek 1987; Habersetzer and Storch 1992; Simmons and Geisler 1998).