Mops cf. M. thersites, 1842

Gunnell, Gregg F., Butler, Percy M., Greenwood, Marjorie & Simmons, Nancy B., 2015, Bats (Chiroptera) from Olduvai Gorge, Early Pleistocene, Bed I (Tanzania), American Museum Novitates 2015 (3846), pp. 1-35 : 22-23

Mops cf. M. thersites

Figures 12 , 13

Molossidae indet. (in part), Butler, 1978: 66; Gunnell, 2010: 587.

REFERRED SPECIMENS: NMT.014/Bat, right distal humerus, FLK N1, layer 3, no. 4; NMT.028/Bat, right distal humerus, FLK NNI, layer 2; NMT.029/Bat, left complete humerus, FLK NNI, layer 2; NMT.033/Bat, left distal humerus, FLK NI, layer 3, Tr. III (see table 1 for measurements).

DESCRIPTION AND DISCUSSION: The Olduvai specimens referred above are very similar in size and morphology to the humeri of extant Mops thersites , which is today known from western and central equatorial Africa south and east to Mozambique and Zanzibar ( Simmons, 2005). The proximal end of NMT.029/Bat (fig. 12E) is similar in shape and proportions to all extant molossids except that head on the Olduvai specimen is relatively larger, especially proximodistally. The head is ovate with the long axis oriented slightly proximomedially to distolaterally. The proximal margin of the head is situated well below the proximal extent of the trochiter, but is even with the proximal extent of lesser tubercle. The deltopectoral crest is high anteriorly and relatively long. It is a very sharply defined crest with a well-developed overhanging lip developed medially, a crest that curves laterally toward the trochiter at its proximal end and forms the anterior border of a deep intertubercular fossa.

The distal end of the humerus is preserved in four specimens of Mops cf. M. thersites (figs. 12, 13). The capitulum is narrow, angled, and not offset from shaft. The lateral capitular tail is slightly less broad than the trochlear surface, and is separated from capitulum by a moderate groove. The trochlear groove is weak, the trochlear surface is relatively broad, and the trochlear lip is not sharply defined. The medial epicondylar process in NMT.029/Bat extends a short distance past the trochlear ridge and only slightly less far distally than is seen in Mops thersites . The groove on lateral surface of epicondyle is either absent or only weakly developed.

In general, molossids are rare in the African fossil record. There is an early Miocene Tadarida recorded from Kenya ( Arroyo-Cabrales et al., 2002) and a late Pleistocene or Holocene record of Mormopterus ( Sabatier and Legendre, 1985) from Madagascar and nothing else outside of the occurrences from Olduvai.

Figures

FIGURE 12. Left complete humerus of Mops cf. M. thersites (NMT.033/Bat). A, photograph and drawing in posteromedial view; B, drawing in medial view; C, drawing in lateral view; D, photograph and drawing in anterior view; E, close-up photograph of proximal end in posteromedial view; F, close-up photograph of distal end in anterior view.

FIGURE 13. Right distal humerus of Mops thersites (NHMUK 53.114.119) compared with Mops cf. M. thersites (NMT.014/Bat) in A, anterior, B, posterior, C, medial, and D, lateral views.