Glischropus meghalayanus Saikia & Ruedi & Csorba 2022, n. sp.
Creators: name: Saikia, Uttam
name: Ruedi, Manuel
name: Csorba, Gabor
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Chiroptera
Vespertilionidae
Glischropus
Glischropus meghalayanus

description: Glischropus meghalayanus n. sp.
(Figs. 1–6; Table 1)
Holotype. V /M/ERS/682, adult male, in alcohol, skull and baculum extracted. Collected by Uttam Saikia, 1 st July 2020.
Type locality. Forest at Lailad, adjacent to Nongkhyllem Wildlife Sanctuary, in Ri-Bhoi district of Meghalaya, India (25°56’13” N, 91°46’24” E, 210 m a.s.l.)
External measurements of the holotype (in mm). HB= 40.0, TL= 41.0, E= 9.5, Tr= 4.2, FA= 32.5, 3 MT = 32.9, 4 MT = 31.4, 5 MT = 31.4, TB= 15.4, HF= 7.3, body mass= 4 g.
Paratype. V /M/ERS/683, adult male, in alcohol, skull (slightly damaged) and baculum (slightly damaged) extracted. The paratype was collected by Uttam Saikia from the same locality as the holotype on the 1 st July, 2020.
External measurements of the paratype (in mm). HB= 38.0, TL= 39.0, E= 9.9, Tr= 4.3, FA= 33.7, 3 MT = 33.6, 4 MT = 32.9, 5 MT = 32.6, TB= 15.1, HF= 7.1, body mass= 4 g.
Etymology. The specific epithet meghalayanus is derived from the Meghalaya state in north-eastern India from where it was discovered and also in honour of the 50 th anniversary of statehood in 2022. The proposed English name is Meghalaya thick-thumbed bat.
Diagnosis. A medium sized Glischropus with a forearm length of 32.5 mm and 33.7 mm, (Table 1). Dorsal fur dark brown with well demarcated beige coloured ventral fur. The skull has an elevated frontal region, globose braincase; the second incisor reaches at least two third the height of first; the baculum shaft is narrow, elongated, and strongly curved when viewed laterally.
Description. Forearm length of the holotype and the paratype is 32.5 mm and 33.7 mm, respectively, which are almost equal to the length of the third metacarpals. The head-body and tail lengths are subequal. The dorsal fur is dark brown while the ventral fur is beige; there is a clear demarcation between the two. Individual dorsal hairs are unicoloured throughout whereas the ventral hairs are dark at the base and lighter at the tips. The overall appearance, including the head shape, ear and tragus, is strikingly similar to that of smaller pipistrelles. However, unlike in Pipistrellus, oval-shaped thumb pads (ca. 2.7 mm long) and fleshy callosities at the base of the toes are present (Fig. 1). Thumb pads and foot soles were pinkish in live individuals but quickly turned white after preservation in alcohol. They are not as well developed as in other bamboo specialized species like Eudiscopus. The muzzle and chin are pinkish, ears dark brown. The wing membrane is dark brown and attaches to the base of the toes. The tail membrane is slightly lighter in colour and the calcar extends almost half the length of the free edge of tail membrane; calcar lobe is elongated. The terminal caudal vertebra protrudes out of the tail membrane. The penis is dorso-ventrally flattened, pendulous, 5.5 mm in length; the proximal half is mostly naked, whereas the distal half is strongly hirsute with whitish hairs (Fig. 1). The baculum is 2.38–2.46 mm long with paired basal lobes; the shaft is narrow and terminates in a deeply bifurcated tip. In lateral view, the baculum has a double curved silhouette.
The cranium has an elevated frontal region and a roundish braincase. The narial emargination is V-shaped, sagittal crest is absent and lamboid crest is poorly developed. The zygomatic arches are thin and straight. The first (I 2) and the second incisor (I 3) have similar crown area; I 3 lies almost fully laterally to I 2. The first incisor is only weakly bifid; the second incisor reaches about two third the height of the first incisor. The first upper premolar has a basal area equal to the first incisor; it is intruded from the toothrow and is largely obscured in lateral view (Fig. 2). The lower molars are nyctalodont. Dental formula is 2123/3123= 34.
Comparison with similar species. As attempts to obtain sequence data from the alcohol-preserved tissues of G. meghalayanus n. sp. were unsuccessful, our comparisons are necessarily restricted to morphological features.
A dental formula with 34 teeth, the labially directed concavity of the second upper incisor, and thickened pads at the base of thumbs are characteristics of the genus Glischropus. G. meghalayanus n. sp. can be distinguished from all its congeners by a suite of external, cranial, and dental characters. In contrast to all the species under this genus, the dark brown dorsal fur of the new species is demarcated from the beige ventral fur. The skull profile with a distinctly elevated frontal region and globose braincase is very similar to G. aquilus and G. bucephalus (Fig. 3). The new species, however, can be distinguished from both these two species by the following characters: a wider post-dental palatal width (PDW) of 2.9-2.98 mm (against 2.32 in G. aquilus and 2.19-2.40 mm in G. bucephalus), the first upper incisor is unicuspid (vs clearly bicuspid), and the second upper incisor reaches about two thirds the height of the first incisor (vs less than half its height in G. aquilus and G. bucephalus; Fig. 4). G. meghalayanus n. sp. can be further told apart cranially from the morphologically most closely resembling G. bucephalus by the more elongated rostral part and clearly less abruptly elevated frontal region. G. meghalayanus n. sp. can also be cranially differentiated from G. aquilus by the posteriorly narrowing V-shaped narial emargination (vs broad U-shaped in G. aquilus). The skull profile of another congener, G. tylopus, is distinctly flatter without any elevated frontal region and the second upper incisor lies postero-laterally to the first (in G. meghalayanus n. sp., they lie at the same level in a straight line; Fig 5). The baculum of G. meghalayanus n. sp. has a distinct double curved lateral profile, and the length of the bone is 2.38–2.46 mm (it is 1.21 mm in G. tylopus and 2.03–2.32 mm in G. bucephalus) (Fig. 6, Table 1).
Distribution. All Glischropus species known so far are reportedly distributed in the Southeast Asian region, from Myanmar and east to the Maluku archipelago. The present discovery of G. meghalayanus n. sp. constitutes the first record of this genus from India and South Asia, and therefore represents a significant (ca. 1000 km) westward range extension for the genus from the westernmost reported locality i.e. Kayah (Karenni) state in eastern Myanmar (Blanford 1888 -91: 602) (Fig. 7). G. meghalayanus n. sp. is currently known only from the type locality, i.e. forests at Lailad, in Ri-Bhoi district of Meghalaya, India.
Wing morphology. Based on mean wing measurements of the two adult male specimens caught in Meghalaya, we calculated a moderate aspect ratio (6.61) and low wing loading (4.83), coupled with relatively high tip-shape index (1.68). These wing characteristics suggest low flight speed and high manoeuvrability (Norberg and Rayner 1987) and imply that this species can be classified as an ‘edge-space aerial forager’ (Denzinger and Schnitzler 2013). This is akin to Tylonycteris and Eudiscopus bats which are adapted to a fair degree of clutter like bamboo forests (Saikia et al. 2021). Echolocation calls could also help infer the foraging ecology of these bats, but unfortunately, no recording could be obtained prior or after capture.
Ecological notes. The two specimens of G. meghalayanus n. sp. were caught in a mist-net set at one of the entrances of a tunnel-like, closed canopy forest with predominant bamboo growths of Dendrocalamus and Bambusa spp. (Fig. 8). The general forest habitats found in the area belong to the Tropical semi-evergreen type (Champion and Seth 1968). Bats were caught on the inner side of the net facing the tunnel indicating that they were emerging from inside the forest patch. The area was predominantly occupied by bamboo forest and the modifications like fleshy callosities in the thumbs and soles of the bats also indicate a roosting preference inside bamboo internodes. This was exactly the same spot where two specimens of another bamboo specialist, Eudiscopus denticulus, were caught in the same night (Saikia et al. 2021). It may also be noted that another bamboo dwelling bat Tylonycteris sp. was also caught by the senior author in a nearby area during the summer of 2016, indicating extremely high diversity of bamboo-dwelling bats in the area. The present collection locality lies just outside the boundary of Nongkhyllem Wildlife Sanctuary which encompasses similar habitats. These bats are therefore highly likely to be occurring in the Sanctuary area as well, which enjoys some degrees of protection. However, dense forests such as those existing around the type locality of G. meghalayanus n. sp. are under increasing pressure due to high demands for firewood and timber for construction. Further surveys of bats in such high-diversity region are therefore urgently needed to identify areas that are in immediate needs for conservation actions.
description: Published as part of Saikia, Uttam, Ruedi, Manuel & Csorba, Gabor, 2022, Out of Southeast Asia: A new species of thick-thumbed bat (Chiroptera: Vespertilionidae: Glischropus) from Meghalaya, north-eastern India, pp. 355-364 in Zootaxa 5154 (3) on pages 357-362, DOI: 10.11646/zootaxa.5154.3.8, http://zenodo.org/record/6644828