(Temminck, 1840)
Horsfield's bat
External characters (Table 71)
This is a medium-small species of Myotis with an average forearm length of 38.5 mm (36.5-41.5 mm) for specimens from peninsular India. The ears are naked, dark and with rounded tips (Fig. 142). The anterior border of each ear is evenly convex; the posterior border is concave above and convex below with a well defined notch in its midpart. The tragus is short, less than half the height of the pinna and relatively broad (Fig. 129). The feet are enlarged and exceed half the length of the tibiae (Fig. 143). The pelage is dark brown almost black on the dorsal surface (Mho2). On the ventral surface, it is deep brown with greyish tints near the base of the tail (Mho3). The interfemoral and wing membranes are deep chocolate brown. They are essentially naked, except for some light hairs on the interfemoral membrane adjacent to the body. The wings are attached to the outer metatarsal of each foot; in M. hasseltii they are attached to the ankle or tibia. The baculum is small, saddle-shaped and with a rounded tip (Fig. 131).
Cranial characters
The skull (Fig. 145) has an average condylo-canine length of 13.9 mm (13.4-14.3 mm) for specimens from peninsular India. The braincase is less inflated anteriorly than that of M. hasseltii and the gradient of the dorsal profile is shallower. The rostrum is robust with a shallow depression in its midline. The sagittal and lambdoid crests are present but not well developed. The braincase is rounded posteriorly with the slightly convex supraoccipital just forming the most posterior part of the skull. The zygomata are well developed and outwardly flared. The palate is concave. The coronoid process of each half mandible is distinctly more robust than that of M. longipes .
Dentition
- Upper toothrow length (C-M3) averages 5.7 mm (5.5-5.9 mm) for specimens from peninsular India. The teeth are robust in comparison to M. daubentonii . The upper canine is nearly twice the height of the third upper premolar (PM4). The first (PM2) and second (PM3) premolars are small (Fig. 146), but considerably less reduced than those of M. longipes (Fig. 139). PM3 is about half or more the crown area PM2, it lies within the toothrow or is sometimes displaced internally.
- Unlike M. daubentonii , the lower canine exceeds the third lower premolar (pm4) in height and crown area. The second lower premolar (pm3) is two-thirds the crown area of the first (pm2), it is sometimes crowded between pm2 and third premolar (pm4). The upper and lower molars are unremarkable.
Variation
Specimens from peninsular India are provisionally referred to M. h. peshwa on account of their slightly larger size and browner pelage. The taxon M. h. dryas is endemic to the Andaman Islands and averages smaller with a forearm length of 34.8-37.1 mm and a condylo-canine length of 13.3 mm (Hill, 1976b).