Murina chayuensis Luo & Zhou sp. nov.

Figs 3, 4, Suppl. material 1: table S 1

Materials.

Holotype. • XZ 2023107 (36.51 mm FA and 16.83 mm GTL; Figs 3, 4) was collected by Pengfei Luo and Jiang Zhou on 17 August 2023, in Chayu County, Linzhi City, Xizang, China (28°29'51.12"N, 97°0'53.87"E, 1511 m a. s. l; Fig. 1). Paratypes. • Four specimens (XZ 2023085, XZ 2023086, XZ 2023088, and XZ 2023100) were collected by Pengfei Luo and Jiang Zhou from the same locality as the holotype (28°29'51.12"N, 97°0'53.87"E, 1511 m a. s. l; 28°29'1.47"N, 97°1'23.07"E, 1613 m a. s. l; Fig. 1).

Etymology.

We discovered a new species in Chayu County that we named Murina chayuensis sp. nov. We propose the common English name “ Chayu Tube-Nosed Bat ” and the Chinese name “ chá yú guǎn bí fú (察隅管鼻蝠). ”

Diagnosis.

The new species is a medium-sized bat in the genus Murina (FA: 33.49–36.51 mm; Table 2 and Suppl. material 1: table S 1). Dorsal fur overall displays a tan color, with a few reddish-brown guard hairs. Dorsal fur has two color bands: black at the base and tan at the tip (Fig. 3 A, B). Ventral fur overall is pale, with two color bands, a dark base covering approximately two-thirds and a whitish tip covering approximately one-third (Fig. 3 C). The plagiopatagium is almost attached to the base of the claw (Fig. 3 D). The skull is domed (Fig. 4 C). The sagittal crest is absent, and the lambdoid crest is weakly developed (Fig. 4 A, C). The first upper incisor (I 2) is obscured by the second upper incisor (I 3) in lateral view (Fig. 4 C). The mesostyles of the first and second upper molars (M 1 and M 2) are well developed, with distinct cusps, and there is a W-shaped indentation on the outer side of the molars (Fig. 4 B). The basal area of the second upper premolar (P 4) is comparable to that of the upper canine (C 1), whereas the basal area of the first upper premolar (P 2) is approximately two-thirds that of P 4 (Fig. 4 B). The basal area of the lower M 1 and M 2 talonids is two-thirds of their respective trigonids, and the M 3 talonid is half of its trigonid (Fig. 4 D, E).

In the phylogenetic analyses (Fig. 2), all specimens of Murina chayuensis sp. nov. formed a clade and a distinct lineage sister to M. pluvialis with a posterior probability of 1, indicating that Murina chayuensis sp. nov. and M. pluvialis have differentiated but share a close phylogenetic relationship. However, the genetic distance between Murina chayuensis sp. nov. and M. pluvialis was 0.09, a value that is greater than those between M. fanjingshanensis and M. bicolor (0.08), between M. liboensis and M. cyclotis (0.08), between M. suilla and M. florium (0.08), and between M. eleryi and M. gracilis (0.08) (Table 1). Therefore, the validity of Murina chayuensis sp. nov. as a distinct species is established.

Description.

Murina chayuensis sp. nov. possesses a “ cyclotis - type ” dentition, characterized by the I 3 obscuring the I 2, with the basal area of P 2 being two-thirds or more than that of P 4 (Corbet and Hill 1992; Koopman, 1994; Francis et al. 2010; Son et al. 2015). There is black facial hair surrounding the mouth and eyes (Fig. 3 A). There is a rounded auricle with no visible incision on the posterior edge (Fig. 3 A). On the dorsal surface, the hair color displays two bands, being black at the base and tan at the tip, with a few reddish-brown guard hairs (Fig. 3 A, B). The upper surfaces of the uropatagium, hind limbs, and feet are densely covered in uniformly tan hairs. Short golden hairs occur on the dorsum of the forearms and thumbs but not on the metacarpals. On the ventral surface, the hairs are also bicolored, dark brown at the base and whitish at the tip (Fig. 3 C). The plagiopatagium is attached to the base of the claw (Fig. 3 D).

The skull is medium-sized, with a GTL of 15.75–16.83 mm. The CM 3 L is 5.14–6.06 mm, which is 0.31–0.37 of the GTL (Table 2 and Suppl. material 1: table S 1). The rostrum is flat, and the braincase is domed (Fig. 4 C), with a relatively high braincase (BCH / BCW: ‾ x = 0.98; sd = 0.07; range = 0.87–1.06; n = 5; Table 2 and Suppl. material 1: table S 1). The interorbital region is deeply concave (Fig. 4 A). The forehead is slowly and smoothly rising from the rostrum to the braincase (Fig. 4 C). The zygoma is not strong without a dorsal process (Fig. 4 C). The prepalatal emargination is equal in depth and width, ending at the level of middle of the upper canine (C 1) (Fig. 4 A, B). The postpalatal emargination is width over depth (Fig. 4 B). A pair of basisphenoid pits are well defined, tear-drop shaped, and deep. (Fig. 4 B). The sagittal crest is absent, and the lambdoid crest is weakly developed (Fig. 4 A, C). The maxillary toothrows are convergent anteriorly (C 1 C 1 W / M 1 M 1 W: ‾ x = 0.69; sd = 0.02; range = 0.68–0.73; n = 5). The dental formula is I 2 / 3 C 1 / 1 P 2 / 2 M 3 / 3 = 34 (Fig. 4 B, D). The I 2 is largely obscured by I 3 in the side view (Fig. 4 C). P 2 is shorter than P 4; P 4 is approximately two-thirds of C 1, and P 2 is half of C 1 in height (Fig. 4 C). The basal area of P 4 is comparable to that of C 1 (Fig. 4 B). The paracones of the first and second upper molars (M 1 and M 2) are higher than their respective metacones. The third upper molar (M 3) retains only the paracone, parastyle, and protocone. The mesostyles of M 1 and M 2 are well developed, with distinct cusps. There is a W-shaped indentation on the labial sides of M 1 and M 2 (Fig. 4 B, C).

The mandible is delicate, with 10.22–11.55 mm of ML (Table 2 and Suppl. material 1: table S 1). The CM 3 L is 5.23–6.67 mm, which is 0.48–0.61 of ML (Table 2 and Suppl. material 1: table S 1). C 1 is higher than the lower first and second premolars (P 2 and P 4) (Fig. 4 E). P 2 and P 4 are subequal in height (Fig. 4 E). The basal area of P 2 is approximately two-thirds that of P 4 (Fig. 4 D). The lower first and second molars (M 1 and M 2) possess the structural type of nyctalodonty (Fig. 4 D). The entoconids of M 1 and M 2 are developed, with distinct cusps (Fig. 4 D). The basal area of the lower M 1 and M 2 talonids is two-third their respective trigonids, and the M 3 talonid is half of its trigonid (Fig. 4 D, E).

Comparisons with other taxa.

Murina chayuensis sp. nov. possesses “ cyclotis - type ” dentition. Therefore, it is readily distinguished from all species with the “ suilla - type ” dentition. Within all recognized species that have “ cyclotis - type ” dentition, M. liboensis and M. rozendaali are much smaller and can be easily distinguished from the new species (FA lower than 33.5 mm; Table 2). M. harrisoni, M. tiensa, M. cyclotis, M. fionae, M. guilleni, and M. peninsularis either possess unicolored pale fur or indistinct color bands on the ventral side (vs. distinct bicolor; Fig. 3 C), and they possess a developed sagittal crest (vs. absent; Figs 4 A, C, 5 B – E, I, L). Compared with Murina chayuensis sp. nov., M. harrisoni and M. tiensa also have larger skulls, longer CM 3 L and CM 3 L (Table 2), and a flatter braincase (vs. domed; Figs 4 C, 5 E, L). In addition, M. cyclotis, M. fionae, M. guilleni, and M. peninsularis lack mesostyles of M 1 and M 2 (vs. developed; Figs 4 B, 5 B – D, I). Of the above species, only M. cyclotis occurs in the southeastern QTP and adjacent areas (Fig. 1); this species can also be distinguished from Murina chayuensis sp. nov. by smaller FA (Table 2) and more developed P 2 (basal area: P 2 and P 4 are equal in M. cyclotis vs. P 2 is two-thirds of P 4 in Murina chayuensis sp. nov.; Figs 4 B, 5 B).

Other Murina species possess “ cyclotis - type ” dentition that is distributed in the southeastern QTP, including M. huttonii and M. pluvialis. The ear of M. huttonii is longer at 16.20–17.40 mm (vs. 13.72–14.82 mm; Table 2); the interfemoral membrane is extensively covered with reddish-brown hairs (vs. absent); and the skull is longer, with GTL 17.90–18.40 mm (vs. 15.75–16.83 mm; Table 2). Furthermore, the prepalatal emargination is shallower, closing to the junction of C 1 and P 2 (vs. middle of C 1; Figs 4 B, 5 F); the talonids of M 1 and M 2 are only slightly less than their respective trigonids in length (vs. two-thirds; Fig. 4 D). M. pluvialis as a sister taxon to M. chayuensis sp. nov. (Fig. 2), and these two species are similar in body size (Table 2). However, M. pluvialis has bright red dorsal fur without shiny guard hairs and silvery gray hair ventrally, clearly distinguishing it from the new species (vs. tan in the dorsal and whitish in the ventral hair, with the presence of reddish-brown guard hairs; Fig. 3 A – C); the sagittal and lambdoid crests are more developed (vs. absent and weak; Figs 4 A, C, 5 J). Furthermore, the crown area between P 2 and P 4 has a distinct gap (vs. indistinct; Figs 4 C, 5 J); the mesostyles of M 1 and M 2 are reduced (vs. well developed; Figs 4 B, 5 J); and the indentation in the labial side is more U-shaped from the ventral view (vs. W-shaped; Figs 4 B, 5 J). In addition, the talonids of M 1 and M 2 are equal to their respective trigonids in length (vs. two-thirds; Figs 4 D, E, 5 J).

M. lorelieae and M. annamitica are similar to Murina chayuensis sp. nov. in fur color and cranial morphology. However, both species have a shorter FA (Table 2), and the prepalatal emargination is shallower, ending at the level of the junction of C 1 and P 2 (vs. middle of C 1; Figs 4 A, B, 5 A, H). In addition, M. annamitica shows slate gray basal fur dorsally (vs. black; Fig. 3 B), and P 2 is equal to P 4 in height (vs. two-thirds; Figs 4 C, 5 A). Despite the lack of M. lorelieae in the phylogenetic analysis, it is also possible to distinguish Murina chayuensis sp. nov. by its dorsal fur having three color bands (vs. two color bands; Fig. 3 B). The braincase is also more inflated, rising more abruptly from the rostrum (vs. slowly and smoothly rising; Figs 4 C, 5 H), and the lambdoidal is absent (vs. present; Figs 4 A, C, 5 H).

Distribution and ecology.

To date, Murina chayuensis sp. nov. has only been found in Xiachayu Town, Chayu County, Xizang, China. The specimens were captured in harp traps set in mixed coniferous-broad-leaved forest at an altitude of approximately 1500–1600 m. This forest is near Xiachayu Town and local farms, where we also collected six species from five genera: Murina sp 2, M. aff. huttonii, Harpiola isodon, Rhinolophus ferrumequinum, Pipistrellus sp., and Myotis sp.