Glischropus bucephalus, Csorba, 2011

Csorba, Gábor, 2011, A new species of Glischropus from the Indochinese Subregion (Mammalia: Chiroptera: Vespertilionidae), Zootaxa 2925 (1), pp. 41-48 : 42-47

Glischropus bucephalus n. sp.

Figs. 1–4 , Table 1.

Type material. Holotype: HNHM 2006.34 .49. (field number CSOCA 113), adult male, in alcohol, skull extracted. Collected by G. Csorba, G. Ronkay and L. Duval on 29 January, 2006.

Type locality. Seima Biodiversity Conservation Area , Mondolkiri Province, Cambodia, 12°15'44N 107°03'49E, 360 m a.s.l.

Paratypes. BM(NH) 2006.545 (# SBCA 14), adult female, in alcohol, skull extracted; CBC 01202 (# SBCA 5) , adult male, skin and skull, skinned body in alcohol registered as HNHM 2005.82.5; HNHM 2006.34 .37. (# CSOCA 101), adult female, dry skin, skinned body in alcohol, skull extracted; HNHM 2006.34 .45. (# CSOCA 109), adult male, in alcohol, skull extracted; HNHM 2006.34 .46. (# CSOCA 110), adult male, in alcohol, skull extracted; HNHM 2006.34 . 48. (# CSOCA 112), adult female, in alcohol; HZM 1.39552 (# SBCA 13), adult male, in alcohol, skull extracted. All paratypes were collected on the same locality as the holotype specimen by J. Walston and B. Hayes on December 2003 and April 2005 and by G. Csorba , L. Duval and G. Ronkay on January, 2006 .

Referred material. THAILAND: PSUZC-MM 2005.206 adult male, in alcohol, skull extracted, Chantaburi Province . VIETNAM: HNHM 23061 adult male, in alcohol, skull extracted, Pu Huong NR., Nghe An Province ; HNHM 22859 adult female, in alcohol, skull extracted, Cat Tien NP., Dong Nai Province ; IEBR PL 47 adult male, in alcohol, skull extracted, Vinh Cuu NR., Dong Nai Province ; IEBR CT 25 subadult male and IEBR CT 26 subadult female, both in alcohol, skulls extracted, Cat Tien NP., Dong Nai Province .

Etymology. The specific epithet (meaning “ox-headed” in English) refers to the massive and elevated frontal region of the new species relative to its congeners. The proposed English name is ’Indochinese Thick-thumbed Bat’.

Description. Forearm length above 32 mm ( Table 1); ears moderate in size, rounded and dark colored; tragus relatively narrow, broadly rounded and angled slightly forward, typically Pipistrellus -like ( Fig. 1 ). The fur is rather long and dark brown without banding above and ventrally, individual hairs are dark brown basally, with the upper third a lighter, yellowish brown. The plagiopatagium is attached to the base of the toe and the calcar has a welldeveloped lobe supported by a central cartilage. The thumb has a large pinkish pad, which is oval in outline and ca. 3 mm in length. The sole of the foot is thickened and unpigmented.

The skull has an elevated frontal region and a relatively globose braincase ( Fig. 2 ). The narial emargination is narrow, the sagittal crest weak but present and the lambdoid crests are moderately developed. The zygoma is delicate without any dorsal projection or thickening. The basioccipital pits are ill-defined. The tips of the four upper incisors are situated in an almost straight line and the cavity of the second upper incisor (I 3) is turned outwards ( Fig. 3 ). The first incisor (I 2) is clearly bifid and I 3 reaches half the height of I 2. The main cusp of I 3 is much longer than the faint secondary cusplet of the same tooth and its tip is directed downwards ( Fig. 4 ). The first upper premolar is basally as large as I 2 and is fully intruded from the toothrow and almost completely obscured in the lateral view; its cusp reaches far beyond the cingulum of the posterior premolar. The upper and lower molars show no specific modifications and the lower molars are nyctalodont.

Comparisons. G. tylopus is significantly (p<0.001) smaller than G. bucephalus n. sp. in all measured characters ( Table 1) with no overlap in forearm length, upper molar width and rostral width. In addition, the skull of G. tylopus is flatter, with an almost straight rostral profile, no sagittal crest ( Fig. 2 ) and a wider narial emargination. Dentally, the second upper incisor (I 3) of G. tylopus is also much shorter than the secondary cusp of I 2 and the main cusp of I 3 barely exceeds the additional cusplet of the same tooth, with its tip directed slightly forwards ( Fig. 4 ).

The original description of G. batjanus by Matschie (1901: 277) was based on one juvenile and four adult (three females and one male) individuals. Although the specimens were not seen the forearm measurements (27.5– 29.0 mm) of the adult specimens and the upper toothrow length (4.2 mm) of the type specimen provided by Matschie fall into the size range of G. tylopus and consequently distinguish batjanus from G. bucephalus n. sp.

G. javanus , of which only the holotype specimen is available, is also significantly smaller than G. bucephalus n. sp. (p<0.001) with the exception of the interorbital width. Skull shape, sagittal crest development and upper incisor proportions in javanus are essentially the same as those of G. tylopus , and G. bucephalus n. sp. can therefore be separated from javanus on the same grounds.

Habitat. Roosts of Glischropus species within stalks of dead bamboo were reported for G. javanus by Chasen (1939) from Java and for G. tylopus by Kofron (1994) from Brunei. The type locality of G. bucephalus, Seima Biodiversity Conservation Area, comprises 3,034 km 2 of grasslands, secondary deciduous dipterocarp forest and some evergreen hill forest ( SCW 2006), and includes large stands of giant bamboo. Another bamboo specialist, Tylonycteris pachypus , also occurs in significant numbers at the site (Csorba, unpublished data). In Thailand, a male individual of Glischropus was caught at the edge of lowland wet evergreen forest, 100 m a.s.l (Bumrungsri, pers. comm.).

Distribution. This is the first published record of Glischropus from Cambodia. In Myanmar, Bates et al. (2005) cited a single record from Blanford (1888 –91) who mentioned G. tylopus from the Karen Hills. No further data was given in these papers.

In Thailand, Lekagul & McNeely (1977) referred to G. tylopus as “...found throughout the country whenever there are forests. It is rare.” but provided skull photographs of a specimen from Borneo (stored in the American Museum of Natural History Museum, New York) which clearly shows the cranial features of G. tylopus sensu stricto. However, Yenbutra & Felten (1986), in listing bat specimens in the Thai national reference collection (TISTR) in Bangkok and the Senckenberg Museum in Frankfurt, mentioned only a single locality for G. tylopus in the country: Bang Lan Dan in Yala Province, peninsular Thailand. As two other Thai specimens collected south of the Isthmus of Kra (studied in the collections of PSU and HNHM) represent G. tylopus , while one individual caught in Chantaburi Province north of this zoogeographic border proved to be G. bucephalus n. sp., the specimen mentioned by Yenbutra and Felten (1986) likely also represents G. tylopus sensu stricto.

In Lao P.D.R., Guillen et al (1997) and Francis et al. (1999) mentioned the occurrence of Glischropus from two areas (Phou Khao Khoay NBCA and Theun-Hinboun) without further details. However, forearm length measurements in 8 specimens from Laos —ranging from 32.7 to 34.6 mm — suggest these individuals represent G. bucephalus n. sp. (Francis, pers. comm.).

Judging from a skull drawing and forearm measurements of five individuals (32.8–35.7 mm) attributed to G. tylopus by Borissenko and Kruskop (2003: pp. 174, 184), G. bucephalus n. sp. also occurs in the Cat Loc area of Lam Dong Province, Vietnam. This is the only published record of the genus from the country to date ( Dang Ngoc Can et al. 2008).

The DNA-barcoded PSU specimen of G. tylopus from peninsular Thailand differed by an average of c. 11% from the three Glischropus specimens published in Francis et al. (2010) (Francis, pers. comm.). The latter (assigned in the above paper as G. tylopus ) originated from Vietnam and Laos and most likely represent the new species. These genetic data strongly support the view that G. bucephalus n. sp. is widely distributed in the Indochinese Subregion north of the Isthmus of Kra while specimens from peninsular Thailand represent G. tylopus .

Remarks. According to Menu (1987), G. javanus is somewhat intermediate in form between Glischropus and Pipistrellus having a less developed thumb pad and the second upper incisor rotated outwards to a lesser degree compared with G. tylopus . Examination of the holotype for G. javanus indicates, however, that this taxon clearly possesses the characters that define Glischropus and differentiate it from true Pipistrellus . G. javanus is larger externally than G. tylopus , though with the exception of the interorbital width, all of its craniodental measurements are within the range of the latter species. The skulls of G. tylopus and G. javanus type specimens show slight differences in profile ( Fig. 2 ); however, their range of variability falls within the individual variation observed in tylopus specimens. Accordingly, in spite of the views of Corbet and Hill (1992) and Koopman (1994), the two taxa cannot be distinguished on the basis of braincase inflation.

Unfortunately, other specimens recorded as G. javanus in the literature and museum collections proved on further investigation to represent other taxa. The RMNH 32617 specimen (skull in bad condition and determined by K.F. Koopman as G. javanus ) from Tjidjoedjoeng, Buitenzorg (= Mt. Pangrango, Bogor), Java is a Hypsugo presumably belonging to the “ imbricatus -subgroup”. Although no further data were provided by the authors, this specimen may represent the second (and therefore erroneous) record for G. javanus from Mt. Pangrango in Hutson et al. (2008). Further specimens identified as G. javanus from Krakatau, Indonesia and housed in the collection of MZB (16920, 16922) proved to be Pipistrellus .

Although some specimens of Glischropus from continental Southeast Asia mentioned in the literature were not available for study, the material investigated indicates a clear geographic division between G. tylopus and G. bucephalus n. sp., with the former occurring south of the Isthmus of Kra and the latter northwards of this region. Woodruff and Turner (2009) found no evidence for a narrow mammalian faunal transition near the Isthmus of Kra (contrary to the case in birds), but also acknowledged limitations in their data due to possible misidentifications of museum material, and further anticipated that systematic revisions, discovery of cryptic species and changes in species designations could challenge their findings in some instances. The discovery of a new species of thickthumbed bat in the Indochinese subregion and the likely restricted occurrence of its congeners to the Sundaic subregion may represent such a case.

Figures

FIGURE 1. Portrait of a living specimen of Glischropus bucephalus n. sp. (paratype, HNHM 2006.34.37., from Cambodia).

FIGURE 2. Lateral view of skulls of (A) Glischropus bucephalus n. sp. (holotype, HNHM 2006.34.49., from Cambodia) (B) G. tylopus (holotype, BM(NH) 70.2.10.2, from Borneo) (C) G.javanus (holotype, RMNH 15323, from Java). Scale = 5 mm.

FIGURE 3. Holotype of Glischropus bucephalus n. sp. (HNHM 2006.34.49.); (A) lateral view of left mandible (B) occlusal view of left upper and (C) right lower toothrows. Scale = 5 mm.

FIGURE 4. Frontal view of left upper incisors of (A) Glischropus bucephalus n. sp. (holotype, HNHM 2006.34.49., from Cambodia) (B) G. tylopus (BM(NH) 10.4.5.68, from Borneo). Scale = 1 mm.