(Tomes, 1857)
Lesser Mouse-eared bat
External characters (Table 61)
This is a relatively large species of Myotis (Mbl1) with an average forearm length of 56.7 mm (55.5-58.3 mm). The ears are tall, ranging from 19-26 mm in extralimital material from Iran; the tips are bluntly rounded. The anterior border of each pinna is evenly convex, with a sharply projecting lobe at the base. There is a very faint median notch on the posterior border. The antitragus is small and low. The tragus is tall and narrow, about half the height of the pinna. It is widest just above the base and has a straight anterior margin which narrows to the tip, the posterior margin is gently convex in its middle part and sharply emarginated just above the projecting basal lobule. The muzzle is simple with crescentic nostrils that open laterally and a wide shallow internarial groove. The upper and lower lips, glandular swellings of the muzzle and the periorbital regions are only lightly haired; in contrast, the forehead and upper parts of the muzzle, almost to the rhinarium, are thickly haired. The pelage is woolly in texture (Mbl4). The hairs on the back are 7-8 mm long; they are distinctly shorter on the belly. The dorsal surface is buffy brown with dark grey hair roots. The ventral surface is paler but also has dark roots. The feet are not greatly enlarged; they slightly exceed half the length of the tibiae. The wings are rather broad in relation to their length; each wing is attached to the base of the phalanx of the outer metatarsal of its respective foot. The interfemoral and wing membranes are uniformly pale brown and hairless throughout, above and below. The tail is long and entirely enclosed within the interfemoral membrane except for its extreme tip.
Cranial characters
The skull (Mbl2) is relatively large, with an average condylo-canine length of 18.5 mm (18.1-18.9 mm). The braincase is not distinctly elevated above the rostrum and the dorsal profile slopes gradually upwards from nasals to the lambda (Mbl3). The rostrum is relatively short and broad and there are distinct supraorbital ridges. The zygomata are widely flared and greatly exceed the braincase in breadth. The postorbital region is not greatly restricted in width. The lambdoid crests are weak and merge with the sagittal crest at the lambda, this forms a small elevated triangular area with a flat surface. The supraoccipital is nearly vertical above the foramen magnum, so that the lambda just forms the most posterior part of the skull. The palate is concave and relatively broad; the anterior emargination is wide and extends back to a level equal to the posterior borders of the upper canines. The postdental extension of the palate is long; almost equal to the length of the mesopterygoid space. The hamular processes are blunt and inwardly sloping. The tympanic bullae are small relative to the size of the skull. Each half mandible is long and slender, with its posterior part high, so that the angular process is on a level with the alveolar line. The coronoid process is tall and bluntly triangular with its anterior border almost vertical; the angular process is rather small and narrow and is little deflected outwards and just projects behind the condyle.
Dentition:
- Upper toothrow length (C-M3) averages 8.4 mm (8.2-8.5 mm). The upper incisors are tall and slender with the second (I3) subequal in height to the first (I2). The upper canine is weak relative to the size of skull; its cingulum is without cusps. The second premolar (PM3) is variably displaced inwards from the toothrow, its crown area is about half that of first (PM2). Both teeth are small and closely crowded between the canine and the powerful third premolar (PM4) which attains about three-quarters the height of the canine. M2 is broader than M1 and with a greater crown area; the metacones predominate in both teeth and the hypocones are absent; the mesostyles are particularly well developed. M3 is greatly reduced; it is comprised of a parastyle, mesostyle and three commissures.
- The first lower incisor (i1) has three cusps; the second (i2) is also essentially tricuspidate but has an additional accessory cusp situated postero-medially; the third (i3) has four cusps and is almost square. The lower canine is low and broad with the cingulum well developed but without cusps. The small second premolar (pm3) is situated in the toothrow and is half the crown area of the first (pm2). The third premolar (pm4) is large; it is two-thirds the height and three-quarters the crown area of the canine. m2 slightly exceeds m1 in size. The talonid of m3 is reduced; it is about half the crown area of the trigonid.
Variation
Specimens from the Indian Subcontinent are referred to the nominate subspecies M. b. blythii (Strelkov, 1972).