Description
Tylototriton ngarsuensis is a newt with a relatively large body size and proportionately small head. The snout-vent length is 102.3 mm in the only female specimen and 74.9 - 76.4 mm in three male specimens. The ratio of head length to snout-vent length is 0.22 - 0.26. Adults have well-developed cephalic and vertebral ridges. They have rough skin and possess small, glandular warts across the dorsal and ventral surfaces. Additionally, they have prominent dorsolateral bony ridges on the head. The vertebral ridge is low and wide. They have around 15 rib nodules, but these are indistinct and sometimes absent medially. There are four fingers and five toes with no webbing. The tail is laterally compressed and tapers posteriorly with a sharp narrow dorsal fin and a blunt acuminate tip (Grismer et al. 2018). For more description please see Grismer et al. 2018.

DIAGNOSIS:

Tylototriton ngarsuensis is generally differentiated from other species of Tylotriton by the following characters: it is larger but has a proportionately short head, the rib nodule morphology is very distinct, and it has an overall dark coloration that differs from the lighter and sometimes orange coloration of close relatives. It also is differentiated genetically (Grismer et al. 2018).

From its closest relative, T. shanorum has smaller females (87.9 mm snout-vent length vs. 102.3 mm) and relatively longer heads in males (head to snout-vent length ratio = 0.29 - 0.32 vs. 0.22 - 0.26). In T. ngarsuensis, the diameter of rib nodules is uniquely larger than the eye and the glandular, vertebral tubercular ridge is much thicker than in other species of Tylotriton. Tylototriton ngarsuensis is mostly dark, near black-brown, which differs from red-brown T. shanorum. The undersides, including the palms, soles, and subcaudal region, are dark-brown and not dull yellow as in T. shanorum (Grismer et al. 2018).

Coloration also differentiates T. ngarsuensis from other Tylotriton: T. podicthys is orange on the limbs and lateral sides of the tail; T. anguliceps has an orange head, limbs, tail, parotoids, rib nodules and vertebral ridge; T. uyenoi and T. pulcherrima have orange limbs, tail, parotoids, rib nodules and vertebral ridge; T. shanjing has an orange crown on its head and orange digits; and T. himalayanus has cream-colored ventral surfaces. Finally, T. ngarsuensis differs from the remaining species of Tylotriton morphologically: T. taliangensis lack rib nodules, and T. kweichowensis and T. pseudoverrucosus have connected rib nodules. Behaviorally, the T. ngarsuensis differs from all congeners in having a later breeding season (Grismer et al. 2018).

COLORATION:

In life, the skin is dark-brown to black, with the labial regions, palms, soles, vent, and subcaudal regions being a lighter brown (Grismer et al. 2018).

VARIATION:

The main variation is in adult body size, with the female holotype measuring much larger than the male paratypes. However, there is also slight variation in the darkness of their coloration and potential sexual dimorphism in relative leg lengths, with males having longer relative limbs than females (Grismer et al. 2018).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Myanmar

View distribution map in BerkeleyMapper.

This species was first discovered in Baw Hto Chang, a small stream that travels through Ngar Su Village near Ywangan, Shan State, Myanmar. As of 2023, the species is still only documented from this stream, although locals anecdotally attest to their presence in other nearby streams. Streams in this region are shallow and slow moving in a forest environment. Their distribution is thought to be limited to the forest-covered areas of the stream, like other Tylototriton (Grismer et al. 2018).

Life History, Abundance, Activity, and Special Behaviors
During the cold, dry winter, the newts are assumed to estivate in a narrow band of forest near Baw Hto Chang stream. The species becomes active, migrating to the stream, at the beginning of the monsoon season in May or June and can often be found wandering into homes. During the breeding season, adult salamanders have been found, in the late evening, walking on sand at the stream bottom, one meter deep, near vegetation (Grismer et al. 2018).

Other Tylototriton species breed from April to July or June to September. However, gravid female T. ngarsuensis were found in October, indicating a later or more prolonged breeding period (Grismer et al. 2018).

Larva
Gilled larvae at Grosse stage 44 had a snout-vent range of 10 - 33 mm (Grismer et al. 2018).

Larvae typically reside in shallower areas of the stream, near the shore beneath leaves or other cover (Grismer et al. 2018).

Trends and Threats
Tylototriton ngarsuensis has a limited range and is potentially threatened by habitat loss and harvesting for the pet trade and traditional medicines (Grismer et al. 2018). Myanmar experiences general forest loss due to expanding agriculture (Sodhi et al. 2009). As the species has been reported to inhabit streams specifically in forests, this habitat loss likely places pressure on the species. Additionally, during the migration period, people from Yangon, a nearby city, hire locals to collect individuals for traditional medicine and the pet trade (Grismer et al. 2018).

Relation to Humans
These salamanders are collected each year by locals for indigenous medicines and for the pet trade (Grismer et al. 2018).

Possible reasons for amphibian decline

General habitat alteration and loss
Intentional mortality (over-harvesting, pet trade or collecting)

Comments

PHYLOGENETIC RELATIONSHIPS:

References
Dufrensnes, C., and Hernandez, A. (2022). Towards completing the crocodile newts’ puzzle with all-inclusive phylogeographic resources. Zoological Journal of the Linnean Society 197(3), 620–640. [link]

Grismer, L. L., Wood, Jr P. L., Quah, E. S. H., Thura, M. K., Espinoza, R. E., Grismer, M. S., Murdoch, M. L., and Lin, A. 2018. A new species of Crocodile Newt Tylototriton (Caudata: Salamandridae) from Shan State, Myanmar (Burma). Zootaxa 4500, 553–573. [link]

Sodhi, N. S., Lee, T. M., Koh, L. P., and Brook, B. W. (2009). A meta-analysis of the impact of anthropogenic forest disturbance on Southeast Asia's biotas. Biotropica, 41(1), 103–109. [link]

Species Account Citation: AmphibiaWeb 2024 Tylototriton ngarsuensis: Ywangan Crocodile Newt <https://amphibiaweb.org/species/8930> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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