Oreolalax adelphos Nguyen, Tapley, Kane, Tran, Cui & Rowley, 2024, sp. nov.

Oreolalax adelphos sp. nov. Figs. 4–7 Holotype. Adult male (ITBCZ 3619; field tag LNT1144) encountered on a path through bamboo forest on Mount Po Ma Lung, Ban Lang Commune, Phong Tho District, Lai Chau Province, Vietnam (N22 37.581 E103 29.104; 2959 m elevation; Figs 2 & 3.). Collected at 19:53 h on August 10, 2023 by Luan Thanh Nguyen, Chao Van Dat, Ly Manh Ha, and Hoang Van Hung. Paratypes. Female (ITBCZ 3620; field tag LNT1145) encountered on a path through bamboo forest on Mount Po Ma Lung, Ban Lang Commune, Phong Tho District, Lai Chau Province, Vietnam (N22 37.538 E103 29.112; 2920 m elevation) and an adult female (ITBCZ 3621; field tag LNT1146) encountered on a path through bamboo forest on Mount Po Ma Lung, Phong, Ban Lang Commune, Phong Tho District, Lai Chau Province, Vietnam, (N22 37.476 E103 29.148; 2914 m elevation). Both collected at 20:30 h on August 10, 2023 by Luan Thanh Nguyen, Chao Van Dat, Ly Manh Ha, and Hoang Van Hung. Etymology. Specific epithet ‘ adelphos ’ the masculine adjective of the transliterated Greek word meaning brother, in reference to the fact that this is the second Oreolalax species known from Vietnam and that the two species are sympatric at one site. Suggested vernacular name. Mount Po Ma Lung toothed toad (English), Cóc răng pờ ma lung (Vietnamese). Diagnosis. Oreolalax adelphos sp. nov. is placed in the genus Oreolalax based on its molecular phylogenetic position and the following morphological characters: prominent maxillary teeth; a rough dorsal surface with scattered large warts, covered with oval black spots; vertical pupil; and an oval tongue, notched posteriorly (Myers & Leviton 1962; Delorme et al. 2006; Fei & Ye 2016). The new species can be diagnosed from congeneric species by the combination of the following characters: (1) SVL of adult male 38.0 mm, N= 1; adult female 46.2 mm, N= 1; (2) narrow supratympanic fold; (3) no visible tympanum; (4) head longer than wide; (5) vocal sac absent; (6) absence of subarticular tubercles on hands; (7) basal interdigital webbing on hind feet; (8) ventral surface mottled with grey and creamy white; (9) dorsal surface of head and body covered in rounded, evenly spaced and similar sized tubercles; (10) presence of dark bars on limbs; (11) greyish white and creamy white spots on the flanks, and (12) a bicoloured iris. Description of holotype. Small sized (SVL 38.0 mm); head longer than wide, head rounded anteriorly; snout rounded in profile, protrudes slightly beyond lower jaw; loreal region concave; nares oval and positioned laterally, canthus rostralis distinct, interorbital area flat; tympanum not visible, narrow supratympanic fold extends from behind eye, terminates above axilla; ridges on head lacking; eyes large, eye diameter smaller than snout length; pupil vertical; vomerine teeth and ridges absent, maxillary teeth present; tongue free at back and posteriorly notched; vocal sac absent. Forelimbs long and gracile; lower arm thicker than upper arm; fingers long and slender, tips of fingers rounded, finger length: II<I<IV<III, fingers lacking distinct tubercles, fringes, and interdigital webbing; inner metacarpal tubercle distinct large and rounded, palmar tubercle distinct and rounded, smaller than inner metacarpal tubercle; hind limbs, long and gracile; toes with basal interdigital webbing and narrow fringes, lacking distinct tubercles, relative toe length: I<II<V<III<IV; toe tips rounded, without discs; inner metatarsal tubercle small and rounded; outer metatarsal tubercle absent. Dorsal surfaces of head, body and limbs densely covered with rounded, evenly spaced, and similar sized tubercles; sparse scattering of very small tubercles on upper eyelid and lateral sides of head; large tubercles on flanks, less rounded than those on dorsal surfaces; crest of supratympanic fold covered in rounded tubercles; no tubercles with black tipped asperities; throat smooth, although some small rounded tubercles clustered directly below commissure of jaw; chest, belly, and ventral surfaces of limbs smooth; chest lacking small black spines. Colour of holotype in life: Head and dorsal surface of body greyish brown with numerous, evenly spaced brown-black spots, black spots typically covering tubercles; numerous creamy grey spots, smaller in diameter than brown-black spots but also covering tubercles; flanks greyish brown with greyish white and creamy white spots which are larger on flanks than on dorsal surface; dorsal surface of upper arms greyish brown with two brown-black bars and few creamy grey spots, lower arm greyish brown with four brown-black bars; dorsal surfaces of fingers cream with brown-black bars; dorsal surface of hind limbs dark brown, anterior surface of thigh with dark bars, posterior surface of thighs with small greyish-white spots; dorsal surface of lower leg with brown-black bars; dorsal surfaces of fingers cream with brown-black bars; throat, chest, belly mottled with grey and creamy white; iris bicolored with black reticulations, metallic silver on lower half, with a hint of copper in the upper half. Colour of holotype in preservative: Head, dorsal surfaces of body and limbs dark brown, black; flanks with greyish white spots; dorsal surfaces of fingers grey with black bars; throat, chest, belly mottled with dark and light grey. Variation. Ventral surface of ITBCZ 3621 is mottled with cream and grey; tibia length is greater than femur length in ITBCZ 3621 (versus femur length greater than tibia length in ITBCZ 3620 and ITBCZ 3619). See Table 3 for measurements of all individuals in the type series. Sex determination and secondary sexual characters: No evidence of secondary sexual characters. Sex determined by dissection and assessment of gonads or ovaries. Large testes present in ITBCZ 3619. Small eggs present in ITBCZ 3621. No eggs observed in ITBCZ 3620. Natural history: All individuals were associated with a high elevation bamboo forest with scattered Rhododendron (Fig. 3A–B). There was rain in the morning before the survey and the air temperature was 15.5 °C at the time of collection. Ambient humidity was 100%. The three individuals were encountered at night on the forest floor about 400 m away from the nearest stream. During the surveys, males were not heard calling and the females we collected were not heavily gravid. Tadpoles were not observed. A single spider was found in the digestive tract of the adult female specimen (ITBCZ 3621). Oreolalax adelphos sp. nov. is sympatric with O. sterlingae. Distribution and conservation status: Oreolalax adelphos sp. nov. is currently known from a single location at elevations between 2914 and 2920 m, near the summit of Mount Po Ma Lung in the Hoang Lien Range (Figs. 2 & 3). All individuals were collected within 100 m of the border with China. It is almost certain that the species also occurs in Jinping County, Yunnan Province, China. The species’ EOO is currently predicted to be 19.8 km 2 (Fig. 2C). The habitat of this species at the collection site is relatively intact. However, the forest in which this species occurs is being negatively impacted by fuelwood collection for the tourism industry. At elevations below 2300 m asl, the forest is being degraded to establish cardamom plantations. Not enough is currently known about the range of this species. If this species were to be restricted to elevations above 2500 m on Mount Po Ma Lung, and the habitat were to be increasingly degraded due to fuelwood collection this species could qualify for being assessed as Critically Endangered B1ab(iii) in accordance with the IUCN Red List of Threatened Species categories and criteria (see IUCN 2012). However, there is currently only limited data available on this species and so it likely qualifies for being assessed as Data Deficient in accordance with the IUCN Red List of Threatened Species categories and criteria (see IUCN 2012). Comparisons: Oreolalax adelphos sp. nov. can be distinguished from all congeneric species on the basis of morphology and for species where comparable sequences exist, molecular data. The following comparisons are based on one adult male and two adult females of Oreolalax adelphos sp. nov. The SVL of the third specimen (ITBCZ 3620) is not included in the comparisons as sexual maturity of this female was not ascertained when the specimen was dissected, and it could be a subadult. Oreolalax adelphos sp. nov. differs from O. chuanbeiensis by having a smaller adult male size, SVL 38.0 mm (versus 46.7–56.0 mm, N =13, in O. chuanbeiensis; Hou et al. 2020), a smaller adult female size SVL 46.2 mm (versus 55.0–59.0 mm, N =3, mm in O. chuanbeiensis; Fei & Ye 2016), interdigital toe webbing basal (versus ⅓ webbed in O. chuanbeiensis; Fei & Ye 2016), and a mottled belly (versus immaculate in O. chuanbeiensis). Oreolalax adelphos sp. nov. differs from O. granulosus by having a smaller adult male size, SVL 38.0 mm (versus 48.6–61.0 mm in O. granulosus; Fei & Ye 2016), a smaller adult female size SVL 46.2 mm (versus 47.4– 60.0 mm in O. granulosus; Fei & Ye 2016), and a grey and creamy white mottled belly (versus yellowish white, without spots or with light grey, fine spots in O. granulosus; Fei et al. 2012).Species SVL adult male (mm) SVL adult female Tympanum visible? Vocal sac Interdigital toe webbing Belly pattern Skin texture on belly Tubercles on dorsum Dark bars on hindlimbs Dark triangular marking between eyes RefOreolalax adelphossp. nov.38.0 (N=1) 46.2 (N=1) No Absent Basal Mottled Smooth Rounded, evenly spaced, similar sized tubercles Present Absent This studyO. chuanbeiensis46.7–56.0 55.0–59.0 No Absent 1/3 webbed Immaculate Smooth Covered in spiny tubercles Present Absent 5, 6, (N=13) (N=3) 7O. granulosus48.6–61.0 47.4–60.0 No Absent 1/2 – 2/3 Immaculate Smooth Covered in small spiny Present Absent 5, 6 (N=?) (N=?) webbed or with small tubercles spotsO. jingdongensis49.3–60.3 48.7–56.5 No Absent 1/3 webbed Grey spots Smooth Covered in large tubercles with t