Megophrys (Xenophrys) maosonensis Bourret 1937

Megophrys (Xenophrys) maosonensis

Figs. 3E and 8

Molecular data: A 16S sequence was generated from a tissue sample obtained from the single tadpole (VNMN010904). Uncorrected p -distance between the tadpole in this study and a M. maosonensis specimen also collected in the rough proximity of one of the type specimens; Sa Pa District, Lao Cai Province, Vietnam (GenBank accession number KX 811786) was 0.0 %.

Collection site: The following tadpole description is based on two specimens at Gosner stage 25 (VNMN010904 and HLNP 2018090900015). The specimens were found feeding in a 8 m wide stream in disturbed evergreen forest on Mount Fansipan, Hoang Lien National Park, Cat Cat river, Sa Pa District, Lao Cai Province, Vietnam (22.3214°N 103.8264°E, 1244 m asl; Figs. 1 and 2D), on 9 September 2018 by Luan Nguyen, Chung Nguyen and Luong Hoang.

Morphology: The body is elongated and slender; the nares are oval and are approximately equal in distance from the eyes and the snout, the rims of the nares are serrated and raised from the body wall, the internarial distance is less than the interorbital distance; the eyes are positioned dorsolaterally, the pupils are round; the spiracle is sinistral and the spiracular tube protrudes from one third of the way along the body, anterior to maximal trunk width and opens laterally; the tail length is 76.5–77.9% of the total length; the dorsal tail fin inserts behind the body-tail junction, the dorsal fin is low, particularly towards the proximal half of the tail length; the basal tail width is 51.2–61.0%, of the maximal trunk width; the tail tip is narrowly rounded; the oral disc is subterminal and antero-dorsal; the lateral corners fold medially and turn upward when not fully extended (and in preservative), the mean width of the umbelliform oral disc makes up 63.4–68.3% of the maximal width of the trunk; in life, the maximal BW is 73.2% (n =1)the maximal width of the fully extended ODW and the width of the umbelliform oral disc exceeds the maximal width of the trunk; the lower lip is bi-triangular shaped; marginal papillae are absent; five rows of submarginal papillae are present on the upper lip when they are counted medially at the maximal width of the oral disc; these are longitudinally oblong shaped and become substantially smaller in the outermost row; four rows of longitudinally oblong submarginal papillae are present on the lower lip when they are counted medially at the maximal width of the oral disc; these are regularly positioned and become smaller on the outermost row the lower lip is deeper than the upper lip; labial teeth are absent; the upper jaw sheath is serrated and has a medial notch; the lower jaw sheath lacks a medial notch. See Table 1 for measurements.

Colour in life: (Fig. 8) Dorsally, the head and body are brown with dark brown speckles which become increasingly dense towards the posterior half of the body; a dark brown bar runs from each nare to the anterior edge of the eye; there are obvious pale neuromasts; the oral disc is translucent orange brown with darker brown submarginal papillae; the dorsal apex of the tail muscle on the anterior half of the tail is orange brown and forms a saddle which is speckled with dark brown, the lower margins of the orange brown saddle fade to cream bordered by a dark brown band which runs half way along the tail length on the lateral surface; at the point where the tail meets the body there is an area of dense dark brown flecks which form a thin line which extends from the body-tail junction and runs along the midline of the lateral tail surface; the dorsal and ventral tail fins are opaque, beige brown with a few dark brown speckles; the ventral surface is a translucent cream with and speckled with metallic grey blue; the lower lip is bordered by a “V” shaped area of dark stippling when viewed from the ventral surface; the sclera of the eye is broad and black with green-gold flecks; the pupil is black and round; the iris orange and speckled with black dots.

Colour in preservative: (Fig. 3E) The body is grey with darker speckles; the oral disc is a translucent grey with dark brown submarginal papillae; the dorsal and ventral fins are opaque, pale grey with few visible darker speckles; the ventral surface is dark grey.

Variation: The tadpole of M. maosonensis at Stages 37–39 was described previously by Fei et al. (2009; see Table 1 for measurements) as M. major Boulenger; a species now only definitively known from northeast India (Mahony et al. 2018), although species identity was not apparently supported with molecular data in Fei et al. (2009). The line drawing depicts a tadpole with a very pointed tail tip, the specimens from the Hoang Lien Range have a narrowly rounded tail tip (Fig. 8). Robust comparison cannot be made with the description of Fei et al. (2009) as the tadpoles were of a much later stage (37–39) than those collected in the Hoang Lien Range (Stage 25).