Dendrelaphis melanarkys Kraus, 2025, sp. nov.
Creators: name: Kraus, Fred
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Squamata
Colubridae
Dendrelaphis
Dendrelaphis melanarkys

description: Dendrelaphis melanarkys sp. nov.
urn:lsid:zoobank.org:act: F19FCB0C-132A-4814-BD33-02CDDB65E484
Figs. 2E, F, 3C, 8B, 9
Dendrelaphis papuensis McDowell 1984 —8–9.
Holotype. BPBM 20845 (field number FK 10302), adult male, F. Kraus, along Rupu R., 11.3354° S, 154.2247° E, 280 m a.s.l., Rossel Island, Milne Bay Province, Papua New Guinea.
Paratypes (n = 20). Papua New Guinea: Milne Bay Province: Rossel Island: same locality as holotype (BPBM 20849); Gobubob, ~ 1 km NNW Camp 3, 11.3354° S, 154.2223° E, 275 m a.s.l. (BPBM 20844, 20851); 11.3327° S, 154.2248° E, 156 m a.s.l. (BPBM 20846–48); above Mission station at Jinjo, 11.3179° S, 154.2353° E (BPBM 20850); Cheme, 11.3231° S, 154.2428° E, 5 m a.s.l. (BPBM 20852); Jinjo, 11.315° S, 154.236° E, 0–100 m a.s.l. (AMNH 76661–66); Abaleti, 11.394° S, 154.198° E 0–50 m a.s.l. (AMNH 76672–76); no specific data (AMNH 89362).
Diagnosis. A large species of Dendrelaphis (adult SVL up to 1055 mm, tail up to 440 mm; TL/SVL = 0.26– 0.33); eye approximately equal in diameter to eye-naris distance (EY/EN = 0.93–1.22, mean = 1.00); ventrals 187– 191 in seven males, 181–202 in 12 females (two juveniles are too small to sex); subcaudals 143–147 in four males with complete tails, 127–142 in nine females with complete tails; hemipenis without a terminal awn, ornamented proximally with a few whorls of large spines; dorsum in life bluish bronze, each scale margined in black, without a vertebral stripe; venter bluish gray or bluish yellow; labials and chin yellow suffused or dusted with bluish gray or brown; a black postocular stripe widens and extends down the anterior neck to separate the dark dorsum from the paler venter.
Comparisons with other species. The large spines around the proximal end of the hemipenis distinguish Dendrelaphis melanarkys sp. nov. from all other Melanesian members of the genus except D. papuensis, D. roseni sp. nov., and D. anthracina sp. nov. It differs from D. papuensis and D. roseni sp. nov. in lacking the anterior vertebral stripe of those species and in having the dorsal scales each margined in black; it further lacks the uniformly tan dorsum of D. papuensis and the dorsal and ventral melanization seen in D. roseni sp. nov. Dendrelaphis melanarkys sp. nov. differs from D. anthracina sp. nov. in its bluish-bronze dorsum, bluish-gray or bluish-yellow venter, and presence of a black postocular stripe that widens on the anterior neck; D. anthracina sp. nov. is uniformly black above and below and lacks a postocular stripe. D. melanarkys sp. nov. further differs from these species in having more ventrals (187–191, mean = 189.7 in seven males, 181–202, mean = 195.2 in 11 female D. melanarkys sp. nov. vs. 179–185 in five male, mean = 182.4 and 184–187, mean = 185.0 in four female D. roseni sp. nov.; 182– 190, mean = 185.2 in six female D. papuensis, and 178–188, mean = 182 in four male and 187 in two female D. anthracina sp. nov.).
Description of the holotype. Adult male, hemipenes everted. Dorsal scale rows 15-13-11, reduced to 13 rows at ventral 16, reduced to 11 rows at ventral 108; 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 posterior 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 on right, lower larger on left; anterior temporals one on right, two on left, upper larger than lower; posterior temporals 5 (R) and 6 (L) (Fig. 9). Supralabials 8, 4th and 5th below eye; infralabials 10, 5 contact anterior genials. Posterior genials in contact with infralabials 5 and 6, separated along their posterior half by pair of intergenials; single lateral gular separates posterior genials from infralabial 7. Many small tubercles present in the rostral, nasals, internasals, prefrontals, loreals, preoculars, supralabials, mental, infralabials, and genials; shallow pits present on loreals, preoculars, postoculars, temporals, supralabials 2–5, and postoculars.
Vertebral scales hexagonal; remaining dorsal scales oblique. Dorsal scales on tail in six rows at second ventral, four rows at midtail, and two rows near tip. Ventrals 191; cloacal scale divided; subcaudals 147; ventrals and subcaudals each with a ventrolateral ridge.
Total length 1047 mm; snout-vent length 705 mm; tail length 342 mm, tail complete; mass 51.8 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. 8B). Sulcus spermaticus narrow, unforked, arising from junction of base with tail, continuing more or less straight to terminus of 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 bluish gray with vague cream mottling in each scale; dorsal scales margined in black dorsally and posteriorly, giving appearance of diagonal narrow black lines running anteroventrally from vertebral scale row. Vertebral scales with white margins on the two anterolateral margins, black on the other margins. Top and sides of head medium brown; supralabials and infralabials yellow with sparse blue-gray dusting; wide black postocular stripe runs behind eye to corner of jaw, expanding in width to include three lateral scale rows to ventral 10, after which becoming broken and narrower, finally ending between ventrals 31–39. Chin, throat, and anterior venter yellow cream changing to blue gray infused with pale yellow cream posteriorly. Under tail paler blue gray than adjacent dorsum. Each ventral with narrow black streak on posterior half to two-thirds of each ventrolateral ridge. Iris black with some silver dorsally.
Variation. Available adult and subadult specimens vary from 431–1055 mm SVL and 605–1494 mm total length; the three juveniles (BPBM 20844, 20849, AMNH 89362) have SVL = 317 mm, 348 mm, and 286 mm and total lengths of 455 mm, 498 mm, and 410 mm, respectively. Mensural ratios of potential interest differ little between the sexes, though there is a suggestion that males may possibly have slightly larger eyes (Table 4). Females appear to have slightly more ventrals and slightly fewer subcaudals than males, though the difference is not great (Table 4). Hemipenes on six of the paratypes do not differ from those seen in the holotype.
In all specimens there is no trace of a vertebral stripe, with the vertebral scale row the same color as the remaining dorsal scales. The juveniles have a bold anterolateral row of black blotches on each side behind the postocular stripe that continues down the neck; in adults these disappear or become obscure with additional melanization of the intervening areas in the largest adults, though they are still evident in smaller adults. In juveniles, the black margining to the dorsal scales is evident anteriorly but disappears posteriorly; all recently collected adults have an obvious network of black margining to the dorsal scales across the entire dorsal surface (Fig. 2E), though in half of the sample of AMNH specimens, which were collected in 1956, this black margining is no longer evident. The black margining is strongest on the anterior and posterior margins of each scale, imparting an overall appearance of narrow, diagonal black stripes across the dorsum (Fig. 3C). The black postocular stripe is evident in all recently collected specimens, is clearly evident in five of the AMNH specimens from 1956, but is not clearly present in the seven remaining specimens from that older collection. Ventral color in recently collected adults is uniformly bluish yellow (Fig. 2F), but some of the specimens from 1956 have each scale either pale gray or yellow anteriorly and darker gray posteriorly; ventrals of the two juveniles are yellow anteriorly and blue gray posterior to the neck. In recent specimens, the supralabials are typically yellow with brown on the upper portions of the anterior supralabials and black on the same areas of the posterior scales, but are yellow suffused or heavily dusted with brown or gray in the AMNH collection, except for AMNH 76664 and 89362, which are uniformly cream. Infralabials and gulars are typically yellow suffused with some blue gray, except that juveniles BPBM 20844 (SVL = 317 mm) and AMNH 89362 (SVL = 286 mm) are uniformly pale yellow and cream, respectively.
Color in life. Paratype BPBM 20844 was recorded as “Dorsum olive green with black lateral stripe and series of black spots on neck. Series of blue-white lateral spots forming a row of vague diagonal bands on anterior half of body. Iris burnt orange. Supralabials, chin, and throat yellow, changing to olive brown approximately one-fifth way down venter.” The holotype (Fig. 3C) was the same but with the entire venter pale yellow-gray, the light spots obviously just interstitial skin, and the tongue dark. BPBM 10446 was noted as having the iris orange and the tongue black; BPBM 20847 and 20848 had the iris orange brown.
Etymology. The species name is a compound feminine noun in apposition from the Greek melan -, meaning “black”, and the Greek arkys, meaning “net”. It refers to the pattern of black margining on the dorsal scales.
Range. As currently known, this species is restricted to Rossel Island (Fig. 4). There are a few tiny islets within the fringing reef around Rossel Island that might also be found to contain this species.
Ecology. Most of the specimens I obtained came from an area of well-developed secondary rainforest around 280 m a.s.l. that was the site of the former village of Bibikea, which the Australian government forcibly relocated to the coast at the end of World War II. Furthermore, the cyclone of 1993 created an areally extensive landslide from above to below this region that ran from ca. 250–600 m a.s.l. The canopy in this area was 25–30 m high, and the undergrowth was moderate but not dense; palms, pandanus, and ferns were common. Other specimens came from gardens or secondary forest around the villages of Cheme and Jinjo; presumably the AMNH specimens from Abaleti and Jinjo came from similar disturbed forest, as reported by Brass (1959).
Remarks. As remarked for Dendrelaphis anthracina sp. nov. above, my observations on everted hemipenes do not reveal 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 (Fig. 8B), contrary to the report of McDowell (1984) based on dissection of uneverted organs.
description: Published as part of Kraus, Fred, 2025, New species of snakes of the genus Dendrelaphis (Squamata: Colubridae) from the Milne Bay Islands, Papua New Guinea, pp. 451-480 in Zootaxa 5618 (4) on pages 468-471, DOI: 10.11646/zootaxa.5618.4.1, http://zenodo.org/record/15218844