Dendrelaphis anthracina, Kraus, 2025

Kraus, Fred, 2025, New species of snakes of the genus Dendrelaphis (Squamata: Colubridae) from the Milne Bay Islands, Papua New Guinea, Zootaxa 5618 (4), pp. 451-480 : 464-468

publication ID	https://doi.org/10.11646/zootaxa.5618.4.1
publication LSID	lsid:zoobank.org:pub:D5D78E88-9801-4307-8763-6B70872DEB7E
DOI	https://doi.org/10.5281/zenodo.15295625
persistent identifier	https://treatment.plazi.org/id/5C0DC869-AD48-D656-E7B1-FD0D05E8FD43
treatment provided by	Plazi
scientific name	Dendrelaphis anthracina
status	sp. nov.

Treatment

Dendrelaphis anthracina sp. nov.

urn:lsid:zoobank.org:act:6DC3A2DE-EA17-4636-A636-02B33EADEE5D

Figs. 2C, D View FIGURE 2 , 7 View FIGURE 7 , 8A View FIGURE 8

Dendrelaphis papuensis McDowell 1984 View in CoL —7–9.

Holotype. BPBM 20838 About BPBM (field number FK 9812 ), adult male, obtained from local collectors by F. Kraus, Vutha, on far side of ridge due west of Camp 1, 11.4918° S, 153.3846° E, ~ 80 m a.s.l., Sudest Island, Milne Bay Province, Papua New Guinea. GoogleMaps

Paratypes (n = 5). Papua New Guinea: Milne Bay Province: Sudest Island: Araeda , 11.4362° S, 153.4301° E, 1–20 m a.s.l. ( BPBM 20837 About BPBM ) GoogleMaps ; Rambuso , 0–100 m a.s.l. ( AMNH 76648 About AMNH ) ; west slope Mt. Rio , 250–350 m a.s.l. ( AMNH 76655–57 About AMNH ) .

Diagnosis. A large species of Dendrelaphis (adult SVL up to 960 mm, tail up to 460 mm; TL/SVL = 0.31–0.33); eye approximately equal in diameter to eye-naris distance (EY/EN = 0.92–1.00, mean = 0.95); ventrals 178–188 in four males, 187 in two females; subcaudals 134–139 in four males, 140–142 in two females; hemipenis without a terminal awn, ornamented proximally with a few whorls of large spines; dorsum and most of venter uniformly black; supralabials white on lower third to half, black dorsally; infralabials and chin uniformly white or white with few black flecks.

Comparisons with other species. The complete melanization of adults distinguishes Dendrelaphis anthracina sp. nov. from all other Melanesian members of the genus. It further differs from all other species except D. papuensis and D. roseni sp. nov. in having a region of large spines around the proximal third of the hemipenis. From D. papuensis , D. anthracina sp. nov. further differs in its slightly greater number of subcaudals (134–142 vs. 120–133 in D. papuensis ); smaller eye (EY/EN = 0.92–1.00, mean = 0.95 vs. 0.92–1.11, mean = 1.01 in D. papuensis ); narrower snout (EN/SWnares = 0.79–0.95, mean = 0.84 vs. 0.72–0.87, mean = 0.79, respectively, in D. papuensis ); and wider frontal scale (FW/SWnares = 0.76–0.85, mean = 0.81 versus 0.57–0.87, mean = 0.76 in D. papuensis ). From D. roseni sp. nov., D. anthracina sp. nov. further differs in its smaller eye (EY/EN = 0.92–1.00, mean = 0.95 vs. 0.98–1.22, mean = 1.13 in D. roseni sp. nov.), uniformly black dorsum (vs. first scale row yellow or tan and vertebral scale row with series of brown spots anteriorly in D. roseni sp. nov.) and venter (vs. black posteriorly and yellow or tan anteriorly in living D. roseni sp. nov.), chin and labials glossy white (vs. matte white heavily marked with gray in D. roseni ), and supralabials white on the lower third to half and black on upper half to two-thirds, with a sharp demarcation between the two (vs. supralabials white and heavily dusted or stained with black throughout in D. roseni sp. nov.).

Description of the holotype. Adult male, hemipenes everted. Dorsal scale rows 14-13-11, reduction to 13 rows at ventral 9 and to 11 rows at ventral 100; all scales smooth. Vertebral scales hexagonal, remainder narrowly rhomboidal and oblique to body axis, paravertebral row wider. Rostral half again as wide as high; internasals, frontal, supraoculars, and parietals longer than wide; prefrontals wider than long; lateral extension of parietal contacts upper postocular; nasals divided by large nares, with short dorsal suture extending from anterior of naris to internasal on both sides, short ventral suture extending from anterior of naris to first supralabial on both sides; loreal single, elongate; preocular single, higher than long; postoculars two, upper larger; anterior temporals two, upper larger than lower on right, reversed on left; posterior temporals 3 (R) and 6 (L) ( Fig. 7 View FIGURE 7 ). Supralabials 9, 5th and 6th below eye; infralabials 10, 5 (R) and 6 (L) contact anterior genials. Posterior genials in contact with infralabials 5 and 6 (R) and 6 and 7 (L), separated along their posterior half by pair of intergenials; single lateral gular separates posterior genials from infralabial 7 (R) or 8 (L). Many small tubercles present in the rostral, nasals, internasals, prefrontals, loreals, preoculars, frontal, supraoculars, parietals, mental, infralabials, and genials; shallow pits present on loreals, preoculars, postoculars, temporals, supralabials, and lateral edge of parietals.

Vertebral scales hexagonal; remaining dorsal scales oblique. Dorsal scales on tail in nine rows at level of cloaca, six rows at second ventral, four rows at midtail, and two rows near tip. Ventrals 182; cloacal scale divided; subcaudals 136; ventrals and subcaudals each with a ventrolateral ridge.

Total length 1420 mm; snout-vent length 960 mm; tail length 460 mm, tail complete; mass 215 g in life.

Hemipenis unilobed, widest at one-third length of organ from base, narrower distal to that. Base of organ nude and with small pleats, followed distally by a short zone of small spicules, this followed distally by a zone of large spines starting approximately 25–33% along organ, these spines smaller distally than proximally; terminal half of hemipenis densely covered with small spicules ( Fig. 8A View FIGURE 8 ). Sulcus spermaticus narrow, unforked, arising from junction of base with tail, continuing more or less straight to terminus or organ, not diverging to left or right. Left side of sulcus spermaticus with large nude semi-circular patch at junction where large spines meet the terminal spicules, this nude field margined all around by a raised spiculose lip or shelf identical to that bordering the sulcus spermaticus. Hemipenis crowned with a small inverted, spiculose pocket.

Dorsal ground color in preservative uniform black ( Fig. 2C View FIGURE 2 ); supralabials black dorsally, white ventrally; infralabials and genials white, narrowly margined with black on infralabials 3, 5, and 6 (R) and infralabials 1, 4, and 5 (L) ( Fig. 2D View FIGURE 2 ). First three ventrals white marked with black, next four ventrals black marked with white, remainder black like dorsum, slightly paler than dorsum on tail; ventrolateral ridges narrowly corneous brown. Iris black.

Variation. Available specimens vary from 470–960 mm SVL and 699–1420 mm total length, and mensural ratios of potential interest fall within very tight ranges ( Table 3 View TABLE 3 ). Numbers of ventrals and subcaudals also fall within narrow ranges ( Table 3 View TABLE 3 ), and there is no obvious difference in these counts between the sexes. Number of loreals on each side is uniformly one, though temporals vary from 5–8, with most snakes having six or seven. Supralabials vary from 8–10 on each side; typically supralabials 5 and 6 subtend the eye, but sometimes supralabials 4 and 5 touch the eye instead. Infralabials are uniformly ten on each side. Everted hemipenes available only for the holotype.

The dorsum is uniformly black in all specimens except BPBM 20837, which is dark brown; there is never a trace of an anterior vertebral stripe nor a postocular stripe. The venter is uniformly black with a glossy white chin in all specimens, except BPBM 20837 (SVL = 896 mm), which is dark brown instead of black. AMNH 76656 has white markings on the first 14 subcaudals, and AMNH 76657 has them on the first 25 ventrals. These are the two smallest specimens (SVL = 631 mm and 470 mm, respectively), suggesting that there may be some degree of posterior-to-anterior ventral melanization during ontogeny. The infralabials and gulars are uniformly white in most specimens, but AMNH 76656 has a few tiny black flecks on some of these scales, and AMNH 76648 (SVL = 942 mm) has some small black spots posterior to the gulars. In all specimens, the lower third to half of the supralabials is uniformly white and the upper half to two-thirds solid black, with a sharp demarcation between the two.

Etymology. The species name is a feminine Latin adjective meaning “coal black” in recognition of its shiny black coloration.

Range. As currently known, this species is restricted to Sudest Island ( Fig. 4 View FIGURE 4 ) but may eventually be found on smaller islands of the Calvados Chain, which are contained within the fringing reef that demarcated the larger Sudest Island during glacial periods.

Ecology. We saw several uncaptured individuals active during daytime in primary or disturbed secondary rainforest, especially in the vicinity of streams, but like other Dendrelaphis , animals are difficult to capture. Specimens were taken both from the coastal villages of Araeda (BPBM 20837) and Rambuso (AMNH 76648) as well as from inland rainforest (AMNH 76655–57, BPBM 20838). However, prior to human occupation, Sudest was entirely forested, so this species would appear to have a wide ecological tolerance ranging from rainforest to villages and gardens established by humans. When found, BPBM 20837 was located on the ground adjacent to a stream and wrapped around a goshawk that had apparently attacked it and had been rendered immobile by the snake’s enveloping defensive reaction.

Remarks. Contrary to the description of the hemipenes provide by McDowell (1984) on the basis of examining dissected, uneverted organs, I do not find the terminal half of the organ to be calyculate, nor do I find a transverse ridge separating the large basal spines from the distal field of small spicules. Instead, I find a small, semi-circular nude patch on the left side of the sulcus spermaticus, with a raised ridge flared out to cover the margin of this patch, but it does not form a continuous ridge around the organ by any means ( Fig. 8A View FIGURE 8 ). I presume this difference in our observations reflects the difficulty of determining hemipenial morphology accurately when in the uneverted position.