Dendrelaphis roseni, 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 : 459-464

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.15295623
persistent identifier	https://treatment.plazi.org/id/5C0DC869-AD4D-D64A-E7B1-FA0301FCFD43
treatment provided by	Plazi
scientific name	Dendrelaphis roseni
status	sp. nov.

Treatment

Dendrelaphis roseni sp. nov.

urn:lsid:zoobank.org:act:575993EB-9DEA-4CEE-A812-2D6556BE1E4A

Figs. 3B View FIGURE 3 , 5 View FIGURE 5 , 6 View FIGURE 6

Dendrelaphis papuensis McDowell 1984 View in CoL —8–9.

Holotype. BPBM 39678 About BPBM (field number FK 14930 ), adult female, obtained from villagers by F. Kraus, Kulumadau, 9.08° S, 152.72° E, 100 m a.s.l. Woodlark Island , Milne Bay Province, Papua New Guinea. GoogleMaps

Paratypes (n = 8). Papua New Guinea: Milne Bay Province: Woodlark Island: Kulumadau ( AMNH 76615–18 About AMNH , 76625 About AMNH ) ; Guasopa , 9.16° S, 152.98° E, 5 m a.s.l. ( BPBM 17891–92 About BPBM ) GoogleMaps ; vicinity of Talpos River , 9.16° S, 152.78° E, 100 m a.s.l. ( BPBM 17893 About BPBM ) GoogleMaps .

Diagnosis. A moderately sized species of Dendrelaphis (SVL up to 728 mm, tail up to 318 mm; TL/SVL = 0.32–0.33 in five adults with complete tails); eye approximately equal in diameter to eye-naris distance (EY/EN = 0.98–1.22, mean = 1.13); ventrals 179–185 in five males, 184–187 in four females; subcaudals 131–135 in two males, 132–145 in three females; hemipenis without a terminal awn, ornamented proximally with a few whorls of large spines; black bars absent from neck; body brown dorsally and ventrally in juveniles changing to dark gray or black in adults; before turning entirely black, paler anterior vertebral stripe present that is margined in black; supralabials white heavily stained with black throughout; infralabials and chin white heavily suffused with black; anteriormost 2–6 ventrals mostly white, stained with some black; subcaudals black centrally, ventrolateral ridges of subcaudals white.

Comparisons with other species. The pale anterior vertebral stripe and the large basal spines on the hemipenes distinguish Dendrelaphis roseni sp. nov. from all other Melanesian members of the genus except D. papuensis . From that species, D. roseni sp. nov. differs in its larger eye (EY/EN = 0.98–1.22, mean = 1.13 vs. 0.92–1.11, mean = 1.01 in D. papuensis ); dorsum and venter gray in juveniles changing to black in adults (vs. tan in D. papuensis ), thereby encroaching on and reducing contrast with the pale vertebral stripe (vs. stripe distinct throughout life in D. papuensis ); absence of a black postocular stripe (vs. present in D. papuensis ); labials and chin white stained/ suffused with black (vs. cream or yellow in D. papuensis ); and subcaudals black with white ventrolateral ridges (vs. tan in D. papuensis ).

The ontogenetic melanization of animals such that most adults are dark gray or black distinguishes D. roseni from all other Melanesian species of the genus, all of which are brown or green above and white, yellow or brown below.

Dendrelaphis roseni sp. nov. further differs from D. lineolatus and D. striolatus in lacking black bars on the neck; from D. lorentzii in lacking dark speckling on the head, in having more ventrals (179–187 vs. 156–181 in D. lorentzii ), and having an eye subequal to or larger in size to the EN distance (vs. eye much smaller than EN distance in D. lorentzii ); from D. gastrostictus and D. calligastra in lacking any indication of a dark postocular stripe in most adults, and further from D. gastrostictus in lacking dense black spotting on the venter; from D. keiensis in having fewer ventrals (179–187 vs. 211–213 in D. keiensis ) and a longer tail (TL/SVL = 0.32–0.33 vs. 0.29–0.30 in D. keiensis ), and from D. calligastra , D. macrops and D. punctulatus in lacking a terminal awn on the hemipenis (vs. present in those species), and the hemipenis having a few whorls of large spines proximally (vs. with numerous tiny spines proximally in those species).

Description of the holotype. Adult female. Dorsal scale rows 15-13-11, reduction to 13 rows occurs at the level of Ventral 10 and to 11 rows at Ventral 112; 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 and ventral sutures extending from anterior of naris to internasal and first supralabial, respectively; two loreals on each side, all longer than high; preocular single, higher than long; postoculars two, upper larger; anterior temporals two, upper shorter than lower on right but reverse on left; posterior temporals 4 (R) and 3 (L) ( Fig. 5 View FIGURE 5 ). Supralabials 8, 5th and 6th (R) or 4th and 5th (L) below eye; infralabials 9 (right) and 10 (left), five 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, postoculars, temporals, supralabials, mental, infralabials, and genials; absent from the frontal, supraoculars, and parietals.

Vertebral scales hexagonal; remaining dorsal scales oblique. Dorsal scales on tail in six rows at level of cloaca, four rows at midtail, and two rows near tip. Ventrals 184; cloacal scale divided; subcaudals 95+; ventrals and subcaudals each with a ventrolateral ridge.

Total length 999 mm; snout-vent length 728 mm; tail length 271 mm, tip missing; mass 83.3 g in life.

Dorsal ground color in preservative largely black except scales of vertebral row with white spot in each ( Fig. 6A View FIGURE 6 ), and first and second rows white marked with black to ~ventral 70, with amount of white decreasing and amount of black increasing posteriorly ( Fig. 6B View FIGURE 6 ); white markings also intrude into the black on scale rows 3–6 from ventral 32 to ~ventral 70. Head black except supralabials, mental, and infralabials white heavily marked with black; genials uniformly white. Throat and anterior ventrals white marked with black, gradually darkening posteriorly, becoming largely black by ventral 75. Ventrolateral ridges of each ventral and subcaudal with white longitudinal line, faintest just anterior to cloaca. Iris black.

Variation. One unusual feature of this species is that the number of loreals varies, usually being one, as is seen in all other Dendrelaphis I have examined. But the holotype as well as BPBM 17891 About BPBM have two loreals on each side, one above the other; and BPBM 17892 About BPBM has two loreals on the right side and one on the left. Supralabials vary from 8–9 ( Table 2 View TABLE 2 ), with the fourth and fifth usually entering the eye, though the fifth and sixth do on one side of three specimens. Infralabials are usually nine or ten but are 11 on the right side of BPBM 17893 About BPBM . There is no evidence of sexual dimorphism in subcaudal counts (but only two males and three females had complete tails), though ventrals may be slightly greater in females (184–187) than males (179–185) ( Table 2 View TABLE 2 ).

The smallest specimen ( BPBM 17893 About BPBM , SVL = 230 mm) is light brown above and below and has a vague suggestion of the beginning of a dark postocular stripe, with the dorsal margins of the lower temporals being dusted with darker brown than the adjacent scales; the supralabials of this specimen are yellow with a few brown flecks. Larger specimens may be brown dorsally with each scale margined in black (e.g., BPBM 17891–92 About BPBM , Fig. 6C, E View FIGURE 6 ) but are usually dark gray ( AMNH 76618 About AMNH ) or black (all others). Degree of melanization seems to vary individually, and this is most evident on the venter, which may be uniformly black (but with a white chin/throat), as seen in the holotype ( SVL = 728 mm, Fig. 6B View FIGURE 6 ) and in AMNH 76616 About AMNH ( SVL = 672 mm), but can also be gray mottled with black or with the posterior margin of each scale black (e.g., AMNH 76615 About AMNH , 76617–18 About AMNH , 76625 About AMNH , SVL = 509, 675, 597, and 658 mm, respectively). Two BPBM specimens are more anomalous in this regard: BPBM 17891 About BPBM ( SVL = 534 mm, Fig. 6D View FIGURE 6 ) is yellow cream with a few short black streaks, and BPBM 17892 About BPBM ( SVL = 675 mm, Fig. 6F View FIGURE 6 ) is pale yellow with a blue cast and is mottled with black posteriorly. These specimens are also among the few with a dark postocular stripe. The pale anterior vertebral stripe is evident in all specimens but is reduced by encroaching melanization to a series of vertebral spots in AMNH 76616–17 About AMNH and 76625. AMNH 76618 About AMNH is gray above with a darker postocular stripe evident.

Color in life. The holotype ( Fig. 3B View FIGURE 3 ) was recorded as “Jet black above except that anterior dorsal row 1 yellow and black, darkening to tan and black and then solid black posteriorly. A brown spot present on each vertebral scale anteriorly but turning to solid black posteriorly at ~ midbody. Chin white marked with black; ventrals yellow marked with black anteriorly, changing to tan and black and then solid black posteriorly except that the ventral [ventrolateral] keels and subcaudal [ventrolateral] keels each have a cream longitudinal streak, giving to the ventral side a series of cream dashes on each side. Iris white above the pupil, otherwise black. Tongue black.”

Etymology. This species is a genitive honorific for my late friend, snake ecologist and conservationist Philip Clark Rosen.

Range. This species is restricted to Woodlark Island ( Fig. 4 View FIGURE 4 ).

Ecology. I have no specifics on the ecology of this species, though most specimens were taken from the villages of Kulumadau (holotype, AMNH series) or Guasopa ( BPBM 17891–92 About BPBM ); only BPBM 17893 About BPBM came from rainforest. However, prior to human occupation, Woodlark was entirely forested, so this species would appear to thrive in either rainforest or villages and gardens established by humans.

Remarks. Melanization in this species clearly proceeds ontogenetically from posterior to anterior, but there is individual variation in its rate of development. The least melanized specimens still have black developing in the center of the subcaudals and on the margins of the posterior ventrals; specimens with more melanization have black mottling on the rear of the venter, and the most melanized have the venter entirely black posteriorly and either black or dark gray anteriorly. The adults with the least melanized patterns (BPBM 17891–92) came from the far east of Woodlark, whereas the darker specimens came from 30 km west of there. Possibly these color differences reflect geographic variation on the island, but sample sizes are too small to infer that with any confidence.