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Tanzanycteris
Last update:  31-12-69

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The specimen reported here was found at the Mahenge locality, Singida Region, north-central Tanzania, and represents the oldest placental mammal ever found south of the equator on the African continent (Figure 1). The Mahenge fossiliferous deposits (Figure 2, Figure 3) are composed of alternating mudstones and variably silicified shales (Harrison et al. 2001) and represent crater lake sediments deposited in the top of a kimberlite pipe.  A diversity of plants and lower vertebrates is preserved at Mahenge (Herendeen and Jacobs 2000; Harrison et al. 2001). The fish assemblage from Mahenge suggests an early middle Eocene (Lutetian) age (Murray 2000). A Pb-U date of 45.83 Ma (+/- 0.17) was recently obtained from a zircon crystal at the base of the Mahenge sequence (Harrison et al. 2001). Based on studies of crater lakes in Europe and Africa, it is likely that sediments began to accumulate rather quickly in the Mahenge pipe after initial formation of the crater (Lorenz 1973; Smith 1986; Rayner 1987; Giresse et al. 1991; Cornen et al. 1992). Given sedimentation rates and compaction factors documented in modern maars, it can be argued that the crater at Mahenge would have been filled by sediments in 0.2-1.0 million years (Harrison et al. 2001).  Conservatively, this would place an upper age limit of approximately 45 Ma for the Mahenge sequence.

The bat consists of the anterior half of a skeleton (Figure 4) including skull, lower jaws, vertebral column, both shoulder girdles, and portions of both humeri and the left radius. The wrists, wing elements, most of the pelves, and the hind limbs are missing. Despite repeated attempts, we were unable to locate any teeth.  It may be that the expected (high) X-ray absorption of teeth is reduced in this specimen by demineralization in such a way that density differences between teeth and the surrounding matrix are minimal. The lack of any available tooth morphology limits our comparisons with other Eocene taxa to those that preserve comparable anatomical parts.

Higher level taxonomy follows Simmons (1998) and Simmons and Geisler 1998;. However, Springer et al. (2001) and Teeling et al. (2002) have recently presented molecular evidence supporting microchiropteran paraphyly. If this interpretation is true, then Tanzanycteris may be included in the suborder Yinpterochiroptera (Springer et al. 2001).


 
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