Theloderma khoii Ninh & Nguyen & Nguyen & Hoang & Siliyavong & Nguyen & Ziegler 2022, sp. nov.

Theloderma khoii sp. nov.

urn:lsid:zoobank.org:act: 491C280C-F0CA-475E-8DC9-377603DCA558

Figs 2–3

Diagnosis

Theloderma khoii sp. nov. shows the diagnostic characters of the genus Theloderma, for instance a distinct tympanum, round canthus rostralis, bony ridges from canthus rostralis to occiput absent, and skin of head not co-ossified to the skull, and also molecular analyses revealed it to be nested within Theloderma. The new species is distinguished from its congeners and other small rhacophorid species by a combination of the following characters: 1) large-sized frog of the genus Theloderma (SVL 52.2 mm in a single male, 59.4 mm in a single female); 2) head length and width equal; 3) vomerine teeth present; 4) snout pointed and truncated (SNL/SVL 16.3% in male; 16.0% in female); 5) eye large, eye diameter about a half of snout length (ED/SNL 54.60% in male; 58.9% in female), spinules on upper eyelid; 6) tibiotarsal articulation reaching to the posterior border of the eye or the tip of the snout; 7) dorsal skin very rough, with large irregular gland ridges and warts, ventral surface granular; 8) fingers rudimentary webbed, toes almost four-fifths webbed, tips of all digits dilated but all considerably smaller than tympanum; 9) dorsal surface mossy green or olive mottled with dark magenta; 10) lateral and ventral surfaces black with irregular lemon yellow pattern and some white granules; 11) male with large nuptial pads and an inner vocal sac.

Etymology

The specific epithet is in honor of Professor Dr Le Vu Khoi of the VNU Hanoi University of Science, Ha Noi, Vietnam, in recognition of his great support of teaching, mentoring, research and conservation work in Vietnam. As common names we suggest Khoi’s Mossy Frog (English) and Ếch cây sần khôi (Vietnamese).

Type material

Holotype VIETNAM • adult ♂; northern Vietnam, Ha Giang Province, Quan Ba District, in the karst forest near Tung Vai Commune; 1641 m a.s.l; 8 Jun. 2020; H.Q. Nguyen leg.; VNMN 012757.

Paratype VIETNAM • adult ♀; same collection data as for holotype; VNMN 012758.

Description

Holotype

SIZE. Large, body distinctly flattened (SVL 52.2 mm).

HEAD. Very strongly depressed, length and width equal (HL 19.7 mm, HW 19.7 mm), snout pointed and truncated, snout length double the diameter of eye (SNL 8.5 mm, ED 4.7 mm).

CANTHUS ROSTRALIS. Oval, loreal region very oblique, slightly concave; interorbital distance wider than internarial distance and upper eyelid width (IOD 6.0 mm, IN 3.7 mm, UEW 4.5 mm); distance between anterior corners of eyes (DAE 10.1 mm) about 59.8% distance between posterior corners of eyes (DPE 16.3 mm).

NOSTRIL. Oval, inside rather enlarged tubercle on tip of snout, nostrils nearer to tip of snout than to eyes (NS 3.1 mm, EN 6.1 mm).

PUPIL. Circular.

TYMPANUM. Distinct, diameter less than eye diameter and slightly larger than width of third finger disc (TYD 3.7 mm), tympanum separated from eye by distance (TYE) 65.0% of tympanum length (TYD).

PINEAL OCELLUS. Absent; conical tubercles on eyelid, smaller than those in the back.

SUPRATYMPANIC FOLD. Distinct, interrupted, extending from behind eye to beyond level of axilla, composed of large irregular glandular ridges.

VOMERINE TEETH. Arranged in two small oblique groups between choanae and widely separated from each other.

TONGUE. Large, accounting for almost half of mouth, heart-shaped, dorsal surface smooth, notched and free posterior.

FORELIMBS. Moderately strong and long (FLL 13.2 mm, HAL 15.1 mm, 54.3% of SVL), much shorter than hindlimbs (FLL 87.5% of HAL); relative length of fingers: I <II <IV <III; tips of fingers dilated into

large, rounded and flattened discs, with grooves separating dorsum of discs from venter; disc of finger III approximately two times width of finger III (fd3/fw3 219.2%) but smaller than tympanum diameter (fd3/TYD 83.1%); subarticular tubercles large and distinct, with indistinct supernumerary tubercles; formula of subarticular tubercles: 1, 1, 2, 2; well-developed nuptial pad on lateral side of thumb; outer side of fourth finger fringed, outer edge of fourth finger distinctly serrated; webbing between fingers slightly developed, about 50% between base of finger up to proximal subarticular tubercles (Fig. 3).

HINDLIMBS. Strong and long, tibia length about five times greater than tibia width (TbL 27.3 mm, TbW 5.65 mm, TbL/TbW 4.6), tibia longer than thigh length and foot length (TbL/FeL 107%; TbL/ FoL 108%), tibio-tarsal articulation reaching posterior edge of snout when hindlimbs pressed forward as opposed to eye; relative length of toes I <II <V <III <IV; toes with rounded discs, tips of toes dilated into flattened discs with grooves that separate dorsum from venter, smaller than discs on fingers; webbing formula I(1/3) – (1)II(0) – (1/2)III(0) – (1)IV(1) – (1/3)V (Fig. 3); large subarticular tubercles roundish: 1, 1, 2, 3, 2; large inner metatarsal tubercle oval and raised (IMT 2.7 mm), outer metatarsal tubercle absent; with small warts on inner aspect of metatarsal area; outer side of fifth toe fringed, outer edge of fringe with five distinct serrations.

SKIN TEXTURE IN LIFE. Dorsal surface of head, dorsum, arms and legs above very rough, with large irregular glandular ridges ordered symmetrically in middle vertebral region; a large, distinct horn gland behind head in X-shape; on top of each supraorbital 3–4 enlarged glands, distinctly conical; lateral parts of body become granular; large conical tubercles on back of thighs near vent; throat and chest with some small blurred pattern; belly and ventral surface and underside of thigh with thickened flat granules or warts on groin; axillary region and underside of tibia smooth; surroundings of tympanum with small tubercles, with 4–5 enlarged tubercles posteriorly.

COLORATION IN LIFE. Dorsal surface mossy-green or light-olive mixed with mossy-green, resembling moss; tips of skin ridges and tubercles reddish-brown; flank with clearly shaped dark brown pattern, ventrally joining a yellowish-green band; dorsal surfaces of forelimbs and hindlimbs with army-green bands, and some irregular patches on webbing; both finger and toe discs green, in center deep olive; nuptial pad ivory; throat and chest dark-brown with yellowish-green warts; belly has black shape of irregular size with yellowish-green pattern and some cream warts; pupil black, iris yellowish-green with irregular black reticulation; tympanum dark-olive (Fig. 2).

COLORATION IN PRESERVATIVE. In ethanol, dorsal surfaces of head, dorsum, and upper part of flanks dark indigo with brown markings and blotches; tympanum light brown; forelimb, dorsal surface of thigh, tibia and foot black with lights bands, posterior part of thigh below vent dark-grey with large ivory bands; chin and throat light-grey with small ivory spots; chest and belly dark to black, with cream areas on chest (Fig. 3).

Variation of paratype

Male smaller than female, with single vocal sac and nuptial pads. For measurements of the type series see Table 3.

Comparison with other species

We compared Theloderma khoii sp. nov. with other members of the genus Theloderma based on morphological specimen examination (see Appendix 1) and data obtained from the literature (e.g., Tschudi 1838; Boulenger 1903; Smith 1924; Ahl 1927, 1931; Bourret 1937, 1942; Liu & Hu 1962; Taylor 1962; Chanda 1994; Inger et al. 1999; Chanard 2003; Bain & Nguyen 2004; Stuart & Heatwole 2004; Orlov & Ho 2005; Orlov et al. 2006, 2012; McLeod & Norhayati 2007; Bain et al. 2009; Chan & Norhayati 2009; Fei et al. 2009, 2012; Jiang et al. 2009; Kunz et al. 2010; Rowley et al. 2011; Nguyen et al. 2014).

Species of Theloderma inhabiting Indochina, Sumatra, southern China and eastern India can be assigned to three different size groups (Dever 2017): small species (SVL<35 mm), such as T. albopunctatum (Liu & Hu, 1962); T. annae Nguyen, Pham, Nguyen, Ngo & Ziegler, 2016; T. asperum (Boulenger, 1886); T. auratum Poyarkov, Kropachev, Gogoleva & Orlov, 2018; T. baibungense Jiang, Fei & Huang, 2009; T. lacustrinum Sivongxay, Davankham, Phimmachak, Phoumixay & Stuart, 2016; T. laeve (Smith, 1924); T. lateriticum Bain, Nguyen & Doan, 2009; T. licin McLeod & Ahmad, 2007; T. nebulosum and T. palliatum Rowley, Le, Hoang, Dau & Cao, 2011; T. petilum (Stuart & Heatwole, 2004); T. pyaukkya Dever, 2017; T. rhododiscus (Liu & Hu, 1926); T. (Stelladerma in Poyarkov et al. 2015) stellatum Taylor, 1926; T. (Stelladerma in Poyarkov et al. 2015) vietnamense (Poyarkov et al., 2015); and T. truongsonense (Orlov & Ho, 2005); medium-sized species with SVL of 40–45 mm, T. horridum (Boulenger, 1903); T. moloch (Annandale, 1912); T. phrynoderma (Ahl, 1927); T. nagalandense and T. ryabovi Orlov, Dutta, Ghate & Kent, 2006; and T. schmardana (Kelaart, 1853); large-sized species with SVL 48–75 mm (Orlov 1997), including T. bicolor (Bourret, 1937); T. corticale (Boulenger, 1903); T. gordoni Taylor, 1962; T. leporosum Tschudi, 1838; and Theloderma khoii sp. nov.

Compared to T. bicolor, another large-sized group member in Vietnam, Theloderma khoii sp. nov. can be distinguished by its coloration pattern: the lateral part from the axilla to groin is black with an irregular yellowish-green pattern in T. bicolor vs flank pattern with clear brown-dark speckles, ventrally joining the yellowish-green band in Theloderma khoii sp. nov.; a comparatively lighter belly pattern, consisting of irregular blackish brown speckles with whitish pattern in T. bicolor vs belly irregular black with yellowish-green pattern and some cream warts, and the presence of few smaller bluish spots on the throat, in Theloderma khoii sp. nov. (Fig. 4); by the comparatively dark-colored posterior part of the thighs, consisting of black blotches and irregular light-green or olive reticulations (vs black with yellowgreenish bands and a few red-brown warts in Theloderma khoii sp. nov.; Fig. 4); and foot webbing well-developed: I(0) – (1)II(0) – (1/2)III(0) – (1)IV(1) – (0)V (vs I(1/3) – (1)II(0) – (1/2)III(0) – (1) IV(1) – (1/3)V in Theloderma khoii sp. nov.; Fig. 4). Theloderma khoii sp. nov. (Bourret 1937; Hou et al. 2017) differs from T. corticale by its shorter body size: SVL 52.2 mm in male and 59.4 mm in female in Theloderma khoii sp. nov. vs SVL up to 67 mm in T. corticale; by colour pattern: a much lighter belly pattern, yellow-lemon with irregular small black patterns and creamy warts (vs dark belly pattern, blackish ground color with thin yellowish-green pattern and some cream warts in Theloderma khoii sp. nov.); by skin texture: the absence of enlarged warts in the scapular area (vs large irregular prominent warts on dorsum, forming large groups at the base of the head and scapular area in Theloderma khoii sp. nov.); by the head being slightly wider than long (vs head length and width equal in Theloderma khoii sp. nov.); and foot webbing well developed: webbing formula: I(0) – (1 + 12)II(0) – (1)III(0) – (1) IV(1) – (0)V (vs I(1/3) – (1)II(0) – (1/2)III(0) – (1)IV(1) – (1/3)V in Theloderma khoii sp. nov.

Theloderma khoii sp. nov differs from T. gordoni by its coloration pattern: dorsal surface mossy-green or light-olive mixed with mossy-green, resembling moss; ventral yellowish-green band in Theloderma khoii sp. nov. vs dorsum dark brown or coffee with some clusters light brown or orange on enlarged gland ridges; ventral surface dark blue with numerous irregular grayish white patterns and speckles in T. gordoni. Tympanum and tympanic fold distinct in Theloderma khoii sp. nov. vs tympanum and tympanic fold invisible in T. gordoni; head width equal to head length in Theloderma khoii sp. nov. vs head width greater than head length in T. gordoni (Qui et al. 2018).

Ecological notes

Theloderma khoii sp. nov. appears to be closely associated with karstic environments. Specimens were found at night between 19:00 and 23:30 h near cave entrances and in valleys surrounded by limestone cliffs, about 5–6 m from water sources (Fig. 5). Advertisement calls, eggs and tadpoles of the species have not been recorded during our field surveys. The main habitat at the type locality was secondary karst forest of medium and small hardwoods mixed with shrubs and vines. One specimen was found on a leaf, about 0.5–1.2 m above the ground, the other specimen was collected on a limestone cliff, about 0.5–1.2 m above the ground. The air temperature at the time of collection ranged from 18.3 to 23.2 oC and relative humidity from 91 to 100%. In Tung Vai, several species of Theloderma have been recorded, viz. T. albopunctatum (Liu & Hu, 1962), T. gordoni (Taylor, 1962), T. lateriticum (Bain, Nguyen & Doan, 2009), and T. rhododiscus (Liu & Hu, 1962), but all were found in tree holes filled with water or on tree leaves near streams in the valleys. Other tree frogs that were found at the same site were Polypedates sp. (of the P. megacephalus Hallowell, 1861 species complex), Zhangixalus duboisi (Ohler, Marquis, Swan & Grosjean, 2000), Z. jodiae Nguyen, Ninh, Orlov, Nguyen & Ziegler, 2020, Z. franki Ninh, Nguyen, Orlov, Nguyen & Ziegler, 2020, Z. pachyproctus Yu, Hui, Hou, Wu, Rao & Yang, 2019 and Kurixalus sp.

Distribution

Theloderma khoii sp. nov. is currently known only from the type locality in Ha Giang Province, northeastern Vietnam (Fig. 6). The species was recorded at elevations between 1320 and 1750 m a.s.l.

Conservation status

The range of the new species is not expected to extend outside of Mount Tung Vai and it is expected to be found in evergreen forests of Yunnan Province, southern China. However, the actual distributional range should be the focus of further studies. Currently, we assume that the new species is restricted geographically, likely having an Extent Of Occurrence (EOO) of only <1000 km 2. The new species likely occurs in one threat-defined location, which has been characterized as an area with a continuing decline in the quality of its habitat due to deforestation (Meyfroidt et al. 2013). Therefore, Theloderma khoii sp. nov. likely qualifies as Endangered (EN) B1ab(iii) in accordance with the categories and criteria of the IUCN Red List of Threatened Species (IUCN 2012).