Doi Soi Malai crocodile newt (Tylototriton soimalai), Salamandridae from Mae Tuen Wildlife Sanctuary, Thailand

NEWS - Doi Soi Malai crocodile newt (Tylototriton soimalai sp. nov.) from Mae Tuen Wildlife Sanctuary, Tak Province, northwestern Thailand, is described based on molecular and morphological evidence and is the seventh recorded species of the genus Tylototriton reported in Thailand.

Morphologically T. soimalai is distinct from other species with a head longer than wide; snout blunt or truncated; sagittal ridge on head narrow, short and distinct; dorsolateral bony ridges on head distinct and rough; parotoids distinct.

Vertebral ridges prominent, broad and unsegmented; 14-16 distinct rib nodules, rounded and isolated but posterior nodules connected; forelimb and hindlimb tips overlap when pressed along the body. Body background color is black, while markings are orange.

Molecular analysis indicates T. soimalai is a distinct lineage and sister to T. uyenoi with a genetic sequence divergence of 4.1% based on mitochondrial NADH dehydrogenase subunit 2 gene. The new species is currently restricted to the pine forests of the Doi Soi Malai hills.

T. soimalai is a member of the subgenus Tylototriton that can be distinguished from T. anguliceps, T. phukhaensis, T. kachinorum, and T. shanorum by having a narrow, short, and distinct sagittal ridge (vs. prominent in T. anguliceps; narrow, long, and distinct in T. phukhaensis; very faint and barely distinct in T. kachinorum; absent in T. shanorum).

Distinguished from T. verrucosus and T. podichthys by having a rough dorsolateral bony ridge (vs. smooth in T. verrucosus; very rough in T. podichthys); from T. zaimeng by having an inverted V-shape of the vomerine tooth series (vs. bell-shaped in T. zaimeng).

Differs from T. panwaensis in having unsegmented dorsal horns (vs. weakly segmented in T. panwaensis); from T. himalayanus in the absence of grooves on both sides of the caudal peduncle (vs. present in T. himalayanus); from T. shanjing in the absence of sharp contrast between orange crown and black nape (vs. sharp contrast in T. shanjing).

Differs from T. yangi in having uniformly orange parotoids (vs. black except for the posterior tip of the parotoids, which are orange in T. yangi); from T. kweichowensis in having isolated pale markings on the rib nodules (vs. connected markings forming a continuous pale dorsolateral line in T. kweichowensis).

Differs from T. ngarsuensis in having orange markings on the parotoids, dorsal horns, rib nodules, and legs (vs. dark brown, almost black in T. ngarsuensis); from T. houi by having orange markings on the head, body, legs and tail (vs. extensive orange-red markings in T. houi); from T. pulcherrimus by the absence of the pale spots located ventrolaterally and on the sides of the body (vs. present in T. pulcherrimus).

The new species was discovered during the day, at around 12:00 when the adult male came to the surface and both larvae lived in an isolated mud puddle along the road to the summit of Doi Soi Malai during the rainy season, which is the mating season for Tylototriton species.

The puddle had murky water and a muddy sedimentary bottom. The surrounding area consists of evergreen hill forest. The puddle was about 1000 cm long, 500 cm wide and a maximum depth of 35 cm. No fish were observed.

The type locality is a popular destination for mountain biking and 4x4 road trips, especially in the period after the end of the rainy season, from October onwards, when this activity extends to the summit of Doi Soi Malai. This could have a negative impact on the population of this new species, especially during the larval stage.

The breeding season takes place around late April to August during the rainy season. Aquatic larvae of Tylototriton inhabit the breeding water for several months and undergo complete metamorphosis before the larvae start moving onto land.

Larvae were found in water bodies from August to November in T. panhai, August to December in T. uyenoi, December in T. verrucosus, and December to March in T. anguliceps. Therefore, the breeding sites should not be disturbed by anthropogenic activities.

The researchers recommend that T. soimalai sp. nov. should be listed as Endangered (EN) under the IUCN Red List criteria B1ab(iii)+2ab(iii) and a conservation plan is urgently needed.

Original research

Pomchote P, Peerachidacho P, Khonsue W, Sapewisut P, Hernandez A, Phalaraksh C, Siriput P, Nishikawa K (2024). The seventh species of the newt genus Tylototriton in Thailand: a new species (Urodela, Salamandridae) from Tak Province, northwestern Thailand. ZooKeys 1215: 185-208, DOI:10.3897/zookeys.1215.116624

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