Dendrelaphis atra, 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 : 472-476

Dendrelaphis atra sp. nov.

urn:lsid:zoobank.org:act:C16CE36C-8493-4FE1-B314-2F6E8C37C6DF

Figs. 3D , 8C , 10 , 11

Dendrelaphis salomonis McDowell 1984 —5, 8.

Holotype. BPBM 17277 (field number FK 6959 ), adult male, F. Kraus, Bwaga Bwaga ridge camp: 10.6740° S, 152.6828° E, 440–480 m, Misima Island , Milne Bay Province, Papua New Guinea.

Paratypes (n = 13). Papua New Guinea: Milne Bay Province: Misima Island : same location as holotype ( BPBM 17234 ) ; vicinity of Liak , 10.659° S, 152.694° E, 1–80 m a.s.l. ( BPBM 17276 ) ; along Nulia River, Liak , 10.661° S, 152.685° E, 1–40 m a.s.l. ( BPBM 17235 ) ; Narian, near mouth of Cornwall Creek , 4 km W Bwagaoia, 0–15 m a.s.l. ( AMNH 76691–94 ) ; Misima Mine site, 10.6914° S, 152.7958° E, 30 m a.s.l. ( SAMA R69248 ) ; 10.6644° S, 152.8017° E, 290 m a.s.l. ( SAMA R69901 ) ; 10.6642° S, 152.7981° E, 270 m a.s.l. ( SAMA R69903 , R69906 , R69911 ) ; 10.6742° S, 152.8133° E, 215 m a.s.l. ( SAMA R69915 ) .

Diagnosis. A moderately large species of Dendrelaphis (adult SVL up to 907 mm, tail up to 390 mm; TL/ SVL = 0.31–0.34); adult eye approximately equal in diameter to eye-naris distance (EY/EN = 0.87–1.11, mean = 1.01); ventrals 177–187 in six males, 182–193 in eight females; subcaudals 124–137 in six males, 121–141 in five females; hemipenis with a transverse ridge approximately halfway along its length and a terminal papilla but no awn, ornamented with small spines below the transverse ridge and calyculate above that; dorsum and venter of adults uniformly black (juveniles and subadults may be brown or gray suffused with black or with each scale margined in black); supralabials white heavily dusted or stained with black; infralabials and chin white heavily dusted or stained with black.

Comparisons with other species. The complete melanization of adults distinguishes Dendrelaphis atra sp. nov. from all other Melanesian members of the genus except D. anthracina sp. nov. From that species it is distinguished by its hemipenis that lacks the large proximal spines of D. anthracina sp. nov., has a transverse ridge that encircles the entire organ (vs. ridge forms a semicircle on the left side of the sulcus in D. anthracina sp. nov.), and is calyculate distally (vs. with many small spines in D. anthracina sp. nov.). It further differs from that species in details of its color pattern: the dorsum is matte black (vs. glossy black in D. anthracina sp. nov.), and the labials and chin are matte white heavily dusted or stained with black (vs. uniformly glossy white with only a few black markings in D. anthracina sp. nov.). Dendrelaphis roseni sp. nov. is also highly melanized as adults but differs from D. atra sp. nov. in retaining a pale vertebral stripe or vestige of such a stripe, and it has the first dorsal scale row on the anterior body cream whereas D. atra sp. nov. is completely black on all dorsal scale rows. Dendrelaphis calligastra has the same hemipenial structure as D. atra sp. nov. and may be a close relative. However, as noted above, the highly melanized coloration of adult D. atra sp. nov. distinguishes that species from D. calligastra , and all stages of D. calligastra have a distinct black postocular stripe, which is only vaguely suggested by dark pigment along the upper sutures of the supralabials with the postoculars and temporals in juvenile D. atra sp. nov.

Description of the holotype. Adult female. Dorsal scale rows 13-13-11, reduction to 11 rows at ventral 105; all scales smooth. Vertebral scales hexagonal; paravertebral scales elongated, semi-hexagonal; remainder narrowly rhomboidal and oblique to body axis. 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 left, and from posterior of naris to first supralabial on right; loreal single, elongate; preocular single, higher than long; postoculars two, upper larger; anterior temporals two, upper shorter than lower; posterior temporals 4 (R) and 5 (L) ( Fig. 10 ). Supralabials 8, 4th and 5th below eye; infralabials 9, 4 (R) and 5 (L) 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, mental, infralabials, and genials; shallow pits present on loreals, preoculars, postoculars, temporals, supralabials, and lateral edge of parietals. Ventrals 186; cloacal scale divided; subcaudals 91+; ventrals and subcaudals each with a ventrolateral ridge. Dorsal scales on tail in nine rows at level of cloaca, six rows at third ventral, four rows at midtail, and four rows near tip.

Total length 1245 mm; snout-vent length 907 mm; tail length 338 mm, tip missing; mass 87.5 g in life.

Dorsal ground color in preservative uniform black; head black; white heavily marked with black on supralabials, infralabials, chin, and first six ventrals; venter black otherwise; ventrals on anterior third of body have some little amount of white on ventrolateral ridges. Iris black.

Hemipenis (taken from paratype SAMA 69248). Hemipenis unilobed with transverse ridge at approximately half its length that is small on the asulcate side and which expands into a large shelf on the sulcate side; organ capped with terminal papilla ( Fig. 8C ). Sulcus spermaticus narrow, unforked, arising from anteromedial side of base, crossing transverse ridge, and then diverging medially to end just below terminal papilla; lips of sulcus closely adpressed along entire length. Hemipenis widest at transverse ridge, from which it narrows considerably towards terminal papilla. Base of organ nude, then with many small spines to the level of the transverse ridge; above ridge calyculate, with tiny spicules mixed among the calyces.

Variation. Available adult specimens vary from 610–1055 mm SVL and 887–1245 mm total length; the one juvenile ( BPBM 17234 ) and apparent subadult ( SAMA R69915 ) have SVL = 247 mm and 454 mm and total lengths of 356 mm and 677 mm, respectively. Mensural ratios of potential interest differ little between the sexes, though the smallest specimen ( BPBM 17234 ) has a relatively wider snout than do the adults ( Table 5 ). Females trend toward having slightly more ventrals than males, though there is no apparent difference in numbers of subcaudals between the sexes ( Table 5 ). Variation in other scale counts is minimal. Everted hemipenes are available only for the paratype described above.

In all specimens there is no trace of a vertebral stripe, with the vertebral scale row being the same color as the remining dorsal scales. All larger adults (> 690 mm SVL) are uniformly black dorsally ( Fig. 11A ); the sole juvenile ( SVL = 247 mm) is gray brown; two specimens of intermediate size ( SVL = 454 and 610 mm) are gray or brown with each scale margined in black ( Fig. 11C ); and a third, slightly larger, specimen 681 mm) is gray with each scale heavily suffused with black. Two of these smallest specimens ( BPBM 17234 , SVL = 247 mm; BPBM 17235 , SVL = 610 mm) have the margin between the posterior supralabials and the lower temporals darker, imparting the impression of a vague, narrow postocular line, though it is not as wide as seen in D. calligastra nor in other species characterized by a postocular stripe; that of BPBM 17235 is the best developed. Similarly, the venter of all larger adults is uniform black with a white chin ( Fig. 11B ); the juvenile is lighter gray brown ventrally; the two specimens of SVL = 454 and 610 mm are blue-gray or pale gray-brown with black spots, streaks, or flecks ( Fig. 11D ); and the slightly larger specimen of 658 mm SVL is gray heavily suffused with black. Clearly, this species undergoes progressive ontogenetic melanization both dorsally and ventrally. Similar melanization occurs progressively on the chin and labials, with smaller specimens having less black: SAMA R69915 ( SVL = 454 mm) has uniformly cream gulars and infralabials, and the supralabials are cream narrowly margined dorsally with black; the smaller BPBM 17234 ( SVL = 247 mm) has cream supralabials though the gulars and infralabials are heavily dusted with black. All adults have labials and gulars white heavily dusted or stained with black, and AMNH 76691 even has the supralabials uniformly black, and AMNH 76693–94 have them almost entirely black.

Color in life. As seen in photos of the holotype, adults are uniform black in life with labials and chin white dusted with black ( Fig. 3D ).

Etymology. The species name is a feminine Latin adjective meaning “black”.

Range. Restricted to Misima Island ( Fig. 4 ).

Ecology. Two of my specimens came from the general area of a village at sea level and two from rainforest along a ridge at 440 m elevation. The four AMNH specimens also came from the vicinity of a village near sea level. The SAMA specimens came from a mix of remnant primary rainforest, secondary forest, gardens, and severely degraded human-modified habitats at a mine site, including alongside a building.

Figures

FIGURE 3. Portraits in life of (A) Dendrelaphis papuensis, NHM 2013.275, Edevu, 9.2130° S, 147.3097° E, Central Province, PNG; (B) D. roseni sp. nov., BPBM 39678, holotype, Woodlark Island, Milne Bay Province, PNG; (C) D. melanarkys sp. nov., BPBM 20845, holotype, Rossel Island, Milne Bay Province, PNG; (D) D. atra sp. nov., BPBM 17277, holotype, Misima Island, Milne Bay Province, PNG. Photo credits: (A) M. O’Shea, remainder F. Kraus.

FIGURE 4. Map of the Milne Bay region of Papua New Guinea showing collecting localities for species treated herein. Solid circle = type locality for Dendrelaphis papuensis, shaded circles = additional specimens examined for D. papuensis, open circles = photographs verified for D. papuensis, solid square = type locality for D. roseni sp. nov., star = type locality for D. anthracina sp. nov., solid triangle = type locality for D. melanarkys sp. nov., diamond = type locality for D. atra sp. nov.

FIGURE 8. Sulcate views of hemipenes of (A) Dendrelaphis anthracina sp. nov., BPBM 20838; (B) D. melanarkys sp. nov., BPBM 20845; and (C) D. atra sp. nov., SAMA R69248. Scale bar = 5 mm.

FIGURE 10. Dorsal, ventral, and lateral views of head of holotype of Dendrelaphis atra sp. nov., BPBM 17277.

FIGURE 11. Dorsal and ventral views of Dendrelaphis atra from Misima Island, Milne Bay Province, PNG. (A, B) Adult holotype, BPBM 17277, SVL = 907 mm; (C, D) subadult, BPBM 17235, SVL = 610 mm, showing ontogenetic differences in degree of melanization. Scale bars = 2 cm.