(E. Geoffroy, 1810)
Egyptian Fruit bat
External characters (Table 1)
This is a robust fruit bat (BW2) with an average forearm length of 88.2 mm (83-90 mm). The muzzle is relatively heavy and deep with the nostrils directed slightly outwards and separated from each other by a deep groove. The eyes are large. The ears are simple in form, each with a weakly developed antitragal lobe. The hind feet are powerful. The thumb (first digit: comprised of metacarpal, phalanx and claw) of each wing is long, measuring in excess of 30 mm. The second digit bears a small terminal claw, with its tip protruding from the edge of the wing. The pelage is soft, fine and silky. It is grey-brown on the dorsal aspect (RL16), generally paler than that of R. leschenaulti . The glandular throat hairs of adult males have a yellow tinge and are elongated (RL17). The belly is a lighter grey than the back, with the hairs extending on to the narrow interfemoral membrane on either side of the tail, partially concealing it. The calcars are short and feebly developed. The wing membranes are attached to the base of the dorsum of the first toes. The baculum (Fig. 1) is flattened; it is expanded distally and proximally with a bilobate base and a slightly trifid distal extremity.
Cranial characters
The skull (BW1) averages larger than that of R. leschenaulti with a condylo-basal length of 38.8 mm (36.9-40.4 mm). The rostrum is more elongated than that of Cynopterus ; it is heavier and less tapered anteriorly than that of R. leschenaulti . The zygomatic arches are more abruptly flared anteriorly than those of R. leschenaulti and appear more angular in outline. The postorbital processes are powerful and the interorbital region between them is essentially smooth. The interorbital and postorbital constrictions are subequal. The ovoid braincase appears narrow on account of the broad rostrum. The temporal ridges fuse together to form a low sagittal crest behind the highest point of the braincase. The lambdoid crests are distinct in adult skulls, with the nearly vertical supraoccipital projecting behind them to form the most posterior part of the skull. The basicranial axis is moderately deflected downwards, so that the alveolar line when projected backwards passes through the middle of the exoccipital condyle. The dorsal profile rises gently in an almost straight line from the tip of the nasals to the postorbital constriction, the braincase then curving backwards and downwards to the lambda with a strong and even convexity. The palate is almost flat anteriorly and concave behind, its maximum width is opposite m2; the postdental palate is narrowed behind. The mesopterygoid space is U-shaped, with a median ridge extending back from the nasal septum. The lateral plate of each infraorbital foramen lies above the middle of m1. The tympanic bullae are without a bony auditory meatus. In each half mandible, there is a distinct indentation anterior to the angular process; it is more prominent than that of R. leschenaulti . The recurved coronoid process is taller and more narrowly rounded above.
Dentition
- The cheekteeth are robust with an average upper toothrow length (C-M2) of 16.0 mm (14.9-16.6 mm). The upper incisors (I2 and I3) are small and conical, with a distinct gap between the two pairs. The upper canine is robust, with a weak posterior basal cingulum. The first upper premolar (PM2) is greatly reduced, about equal in size with the first upper incisor; the second premolar (PM3) is caniniform, attaining three-quarters of the height of the canine; the third premolar (PM4) is molariform, essentially similar to M1; it has a median groove and cuspidate external and internal crests; the antero-external cusp is strongest, connected to the weak internal crest by a transverse ridge dividing the median groove in front of its mid-point. M2 is rather reduced, the crown narrowed posteriorly, but retaining distinct indications of the median groove and antero-external cusp.
- The lower incisors (i1 and i2) are subequal, bifid when unworn and almost in contact with each other and the canine. The lower canine is weak, scarcely exceeding the second lower premolar (pm3) in height. The first premolar (pm2) is reduced, about three times the size of a lower incisor. The crowns of m1 and m2 are lower than the third lower premolar (pm4); m1 is longer, with the median groove deeper and the outer ridge elevated into one weak cusp; m3 is reduced, its crown forming a hollowed oval cup.
Variation
Specimens from the Indian subcontinent are referred to R. a. arabicus . This taxon is distinguished from R. a aegyptiacus by its smaller skull, shorter and more slender muzzle, narrower ear tips, shorter wings, tibiae and feet (Andersen, 1912). Males exceed females in size.