Paraxenodermus borneensis, Deepak & Lalronunga & Lalhmingliani & Das & Narayanan & Das & Gower, 2021

Deepak, V., Lalronunga, Samuel, Lalhmingliani, Esther, Das, Abhijit, Narayanan, Surya, Das, Indraneil & Gower, David J., 2021, Phylogenetic relationships of xenodermid snakes (Squamata: Serpentes: Xenodermidae), with the description of a new genus, Vertebrate Zoology 71, pp. 747-762 : 747

Paraxenodermus borneensis sp. nov.

Figs 3E-F , 4 & 5

Stoliczkaia borneensis Boulenger 1899: 452

Stoliczkaia borneensis - de Rooij 1917: 45

Stoliczkaia borneensis - de Haas 1950: 530

Stoliczkaia borneensis - Haile 1958: 766

Stoliczkaia borneensis - Stuebing: 1991: 329

Stoliczkia borneensis - Manthey and Grossmann 1997: 394

Stoliczkia borneensis - Malkmus et al. 2002

Stoliczkia borneensis - Das 2006a: 9

Stoliczkia borneensis - Das 2006b: 500-501

Stoliczkia borneensis - Das 2012 :153

Stoliczkia borneensis - Das 2018: 151, 169

Stoliczkia borneensis - Stuebing et al. 2014: 79

Stoliczkia borneensis - Wallach et al. 2014: 689

Stoliczkia borneensis - Boundy 2020: 172

Stoliczkia borneensis - Lalronunga et al. 2021: 569-580

Diagnosis.

This genus can be diagnosed based on the combination of the following features: (1) maxillary teeth small and subequal, (2) head very distinct from (much wider than) ‘neck’, with large shields on dorsal aspect, (3) posterior one-third of the head and posterior temporal region covered with small scales like those of the anterior of the body, (4) numerous small scales between parietal and supralabial shields immediately behind eye, (5) a row of 4-6 small scales between the frontal and prefrontal shields, (6) 10-11 supralabials, (7) nostril in a large concave nasal, (8) body slender and somewhat laterally compressed, (9) ventrals large, and (10) dorsum with numerous dorsolateral and middorsal pale blotches, venter pale with brown patches and subcaudals dark grey.

Comparison to other xenodermid genera.

Morphologically Paraxenodermus borneensis differs from all other xenodermid snakes by a combination of the following characters: presence of head shields (absent in Xenodermus javanicus , other than at snout tip), approximately one-third of the head covered with small scales similar to dorsal scales on the anterior of the body (versus head scales distinct from body scales in Achalinus , Fimbrios and Parafimbrios ), head much wider than ‘neck’ (versus head indistinct from neck in Fimbrios , Parafimbrios and Achalinus ) and presence of a row of small scales between frontal and prefrontal scales (absent in Stoliczkia ).

Distribution.

The new genus is restricted to the island of Borneo and so far, reported from the Kinabalu Massif ( Boulenger 1899) and the contiguous Crocker Range, both in Sabah, in the northeastern part of Borneo ( Das 2006a), as well as in the isolated Gunung Murud ( Das 2006b), in Sarawak State. https://www.inaturalist.org/observations?taxon_id=28573). Information is not available for the holotype, but all other reported individuals were found late at night, moving slowly on rocky banks of streams at elevations of 950-2,100 m above sea level ( Das 2006a).

Variation.

The two examined specimens of Paraxenodermus borneensis , the holotype BMNH 1946.1.15.58 and UNIMAS 8002, differ slightly in the number of small scales lying between the frontal and prefrontals, being six and four, respectively. We counted six small scales in this position in images of a live individual on the internet (https://www.inaturalist.org/taxa/28573). UNIMAS 8002 also differs from BMNH 1946.1.15.58 in having a two more ventrals (208 versus 206) and five additional subcaudals (128 versus 123), and in being smaller (713 mm versus 789 mm total length).

Etymology.

The generic name Paraxenodermus is composed of the modern Latin generic name Xenodermus and the Latin adjective par (paris), meaning, among other possibilities, "similar to".

Figures

Figure 3. Line drawings of Stoliczkia khasiensis (A, B), Stoliczkia vanhnuailianai (C, D) and Paraxenodermus borneensis (E, F) based on ZSIK 14945, BNHS 3656 and BMNH 1946.1.15.58 respectively. Genus characteristics are highlighted in different colours: 1) some supralabials in contact with eye in Stoliczkia, separated by circumorbital scales in Paraxenodermus; 2) fewer supra- and infralabials in Stoliczkia than in Paraxenodermus; 3) single prefrontal in Stoliczkia versus 2 - 3 in Paraxenodermus, 4) fewer scales between parietal and supralabials immediately behind eye in Stoliczkia than in Paraxenodermus, and 5) small row of scales between frontal and prefrontals absent in Stoliczkia, present in Paraxenodermus. Note small scales behind the temporals are indicative rather than precisely accurate. Pale grey coloured areas are bare skin exposed between scales. Illustrations by V. Deepak and Surya Narayanan. Scale bars = 10 mm.

Figure 4. Holotype of Paraxenodermus borneensis (Boulenger, 1899), BMNH 1946.1.15.58. Photographs by Kevin Webb. Scale bar increments in mm.

Figure 5. Paraxenodermus borneensis in life (ZRC 2.5731), from Crocker Range, Sabah, in the north-western Borneo. Sequences for this specimen was published in Vidal and Hedges (2002) and used in this study. Photograph by Indraneil Das.