Gerrhopilus persephone, Kraus, 2017

Kraus, Fred, 2017, New Species of Blindsnakes (Squamata: Gerrhopilidae) from the offshore islands of Papua New Guinea, Zootaxa 4299 (1), pp. 75-94 : 84-89

Gerrhopilus persephone sp. nov.

Figs. 3 A, B, 4, 5A, B, C

Holotype. Immature female, UMMZ 242536 (field number FK 16708), collected by F. Francisco on 10 September 2013 in forest near Normanby Mining Camp, above Awaiara Bay (10.0592° S, 151.0722° E, 620 m a.s.l.), Normanby Island, D’Entrecasteux Archipelago, Milne Bay Province, Papua New Guinea.

Diagnosis. This species belongs to Gerrhopilus based on the presence of head glands in the centers of the anterior head shields in addition to their anterior margins ( McDowell 1974; Wallach 1996b). A small, thin species of Gerrhopilus having the unique combination of head glands evenly and densely dispersed among the anterior head scales but absent from the centers of the ocular and subocular scales and from all supralabials except the third, a rostrate snout with a transverse keel on the ventral margin of the rostral that lies dorsal to the rictus, angle of preoral snout in lateral aspect inclined at a 25° angle to the horizontal, distinct pupil in the eye, longitudinal scale rows 26/24/22, mid-dorsal scales between the rostral and tail spine 780, supralabial imbrication pattern T-V, subocular scale one, presubocular scale absent, subcaudal scales 32, and L/W ratio 82. Refer to Table 1 for additional diagnostic qualitative and quantitative features.

Comparisons. Gerrhopilus persephone may be distinguished from all other members of this genus except G. addisoni , G. depressiceps , G. eurydice , and G. mcdowelli in having a transverse keel on the ventral margin of the rostral, which gives the snout a beaked appearance in lateral aspect, and in having a posterior reduction of four longitudinal scale rows from head to vent. From all of these species G. persephone is distinct in its greater number of mid-dorsal scale rows (780 vs. 627 in G. addisoni , 649–664 in G. depressiceps , 601–647 in G. eurydice , and 431– 464 in G. mcdowelli ). Gerrhopilus persephone may be further distinguished from G. addisoni , G. depressiceps , and G. eurydice by having 26 scale rows around the body just posterior to the head (vs. 24 in G. addisoni , G. depressiceps , and G. eurydice ) and having the angle of the pre-oral snout in lateral aspect being inclined at a 25° angle to the horizontal (vs. horizontal in G. addisoni , G. depressiceps , and G. eurydice ) so that the tip of the rostral keel lies dorsal to the rictus (vs. ventral to the rictus in G. addisoni , G. depressiceps , and G. eurydice ). Gerrhopilus persephone may be further distinguished from G. mcdowelli by its greater length (254 mm vs. 94–199 in G. mcdowelli ), narrower body (total length/mid-body width = 82 in G. persephone vs. 44–53 in G. mcdowelli ), glands absent in supralabials, except for a single row along dorsal margin of third supralabial (vs. glands present in all supralabials in G. mcdowelli ), greater number of subcaudal scales (32 vs. 17–25 in G. mcdowelli ), snout profile rounded in dorsal view (vs. pointed in G. mcdowelli ), and rostral keel pointing directly downward (vs. anteroventrally in G. mcdowelli ).

Description of holotype. Female. L = 254 mm, SVL = 247 mm, TL = 7.1 mm, HW = 3.3 mm, NW = 3.1 mm, SN = 2.3 mm, SW = 2.7 mm, PSN = 1.2 mm, RW = 2.10 mm, EW = 0.45 mm, W = 3.1 mm, VW = 3.1 mm, TW = 2.7 mm, L/W 82, M = 1.65 g (in life). Snout acutely rounded in dorsal view, rounded but with ventrally directed transverse keel in lateral view, giving rostral a beaked appearance; keel deepest medially, keratinized. Pre-oral snout inclined at 25° angle from horizontal; keel lying dorsal to rictus. Rostral large (0.45 head width), oval in shape, posterior border extending halfway between eye and naris, posterior margin convex; ventral surface papillose, sides slightly diverging anteriorly, slightly concave behind the keel. Nasals separated dorsally by prefrontal ( Fig. 3 A); superior nasal large, with slightly sinuous posterior margin, crescentic dorsally, acutely rounded ventrally ( Fig. 3 B). External naris compressed, oval shaped, oriented obliquely, close to rostral; superior nasal suture complete, extending anterodorsally at ~45° angle from naris to rostral; inferior nasal suture complete, contacting second supralabial just posterior to latter’s contact with first supralabial. Prefrontal, frontal, supraoculars, parietals, and interparietal all subequal in size. Preocular large, triangular; larger than ocular but smaller than superior nasal. Ocular large, smaller than preocular, extending dorsally well above preocular, extending ventrally to ~2/3 depth of preocular, bordered posteroventrally by subocular of less than half its size. Eye with distinct round pupil and iris, situated at widest point of ocular and approximately midway along its height, anterior 40% covered by preocular plate in lateral view. Three postoculars bordering ocular and subocular between parietal and fourth supralabial. Four supralabials, third the largest, all except first with long axis oblique to long axis of body, first an irregular tetrahedron. Supralabial imbrication pattern T-V, posterior border of second supralabial overlaps anteroventral margin of preocular, that of third supralabial overlaps anteroventral margin of subocular. Mental hexagonal, wider than long, projecting slightly beyond curve of lower jaw and fitting into notch on upper lip when mouth is closed. Infralabials two on each side.

Longitudinal scale rows 26 anteriorly, reducing to 24 by ventrolateral loss of two rows 10–11 mm behind tip of rostral and to 22 by ventrolateral loss of two additional rows 14 mm anterior to vent; mid-dorsal scale rows between rostral and tail tip 780; subcaudals 32; dorsocaudals 29, apical region without spine, covered by three small plates. The irregular shape of these plates suggests mutilation of the tail, and a spine may have been originally present.

Rostral, superior nasals, preoculars, oculars, prefrontal, supraoculars, and third supralabial with head glands; these glands in the centers of the supraoculars, restricted to three glands on oculars posteroventral to eyes, restricted to dorsal margin of third supralabial, but arrayed along both anterior margins and throughout centers of the other scales. Superior nasals with 17 (right) and 14 (left) glands along anterior margin and>70 throughout remainder of each of these scales. Preoculars with 15 (right) and 17 (left) glands along anterior margins and ~47 (right) and ~56 (left) in remainder of these scales, these uncertain numbers due to ambiguous fusion among and poor pigmentation around some of these glands.

In preservative, dorsum pale brown, with little difference between dorsal and ventral surfaces, which lightens ventrally only gradually; each scale darker anteriorly. Head glands, ventral portion of rostral, supralabials, and lower jaw and chin unpigmented; ventral keel of rostral dark brown. Iris black, pupil pale gray.

Color in life. Washed with pale pink and blue, with the pink predominating anteriorly but with most of the snake appearing pale bluish ( Fig. 4 ). The eye was black and distinct, and there is no sign of incipient ecdysis in the preserved specimen, so I presume this is a reflection of the snake’s usual color and not an instance of the blueing that precedes shedding.

Osteology. As for other scolecophidians, atlas divided into three bones: pair of neural arches not articulating with each other or with succeeding axis, and relatively well-developed ventral hypocentrum. Axis posterior to atlas, broader than long, with two well-developed hypapophyses, followed by further 282 vertebrae.

Nasal region quite inflated; naris formed at junction of nasal, prefrontal, premaxilla, and septomaxilla; neither nasals nor premaxillae contribute to formation of rostral keel. Nasals paired, joining with ventrolateral prefrontals to form nasal capsule, rounded in dorsal profile; nasals divided dorsally from each other for approximately twothirds of their length by frontals, with median plate anteriorly and dorsally forming incomplete internasal septum; anterodorsal surfaces of nasals irregularly concave on either side of central ridge running posteriorly along each, containing two or more foramina; dorsolateral surfaces of nasals poorly ossified. Premaxillae fused, broadly articulating with nasals just ventral to latter’s anteriormost margin, broadly articulating along concave margin with septomaxillae posteriorly, with two foramina on each side. Septomaxillae fused anteriorly but separated posteriorly. Vomers small, lying posterior to septomaxillae but details of articulation uncertain. Prefrontal articulating anterodorsally with nasal, posterodorsally with frontal, and ventrally with septomaxilla; posterolateral surface of prefrontal poorly ossified. Each frontal with sinuous posterior margin articulating with parietal, with ventrolaterally descending process extending posterior to anterior margin of parietal and articulating along basisphenoid; these dorsoventral processes widely separated from each other by intervening basisphenoid. Parietals large, paired, longer medially than laterally ( Fig. 5 A, C). Prootic, exoccipital, and supraoccipital fused into single bone on each side; each with deeply sinuous articulation with parietal anteriorly and dorsally, joining basioccipital ventrally and basisphenoid anteroventrally, articulating with atlas posteriorly; these paired bones meet ventrally, excluding basioccipital from contact with atlas. Most cranial bones unsutured with each other, but contact between basisphenoid and basioccipital closely sutured along largely straight articulation ( Fig. 5 B).

Maxilla triangular, free of bones of nasal region, its widened, tooth-bearing margin oriented transversely; three mature teeth on right maxilla, two replacement teeth forming adjacent to these. Pterygoid long, thin; anterior end posteroventral to palatine, posterior end ventral to quadrate; free from contact with any other bone. Palatine short, extending transversely from above vomer to maxilla; a short ventrolateral process midway along palatine, lying near anterior end of pterygoid. Independent ectopterygoid absent.

Quadrate relatively elongate, flattened, extending anteriorly from posterolateral surface of exoccipital to mandible; adductor process closer to mandibular than otic end. Supratemporal absent. Retroarticular process of mandible short, extending approximately one-quarter length of quadrate. Coronoid tall, pointedly triangular, concave on anterior and posterior margins. Dentary without teeth, articulating with mandible, splenial, and coronoid posteriorly. Splenial narrow splint, approximately same length as dentary, underlying coronoid.

Etymology. The specific epithet is the name of the Greek goddess―daughter of Zeus and Demeter―who was abducted by Hades , Greek god of the underworld, and forced to reside underground for a portion of each year. It is a proper noun in apposition.

Distribution and natural history. Known only from central Normanby Island in the D’Entrecasteaux Archipelago, off the southeastern tip of New Guinea ( Fig. 2 ). It likely occurs across the entire island, based on the extensive habitat present across Normanby, but it remains to be determined whether it also resides on other islands of this archipelago, which are only separated by narrow marine passages.

The holotype was collected while climbing a tree trunk at night in primary foothill rainforest having a canopy height of ca. 30 m. The collector reported to me that he has seen other blindsnakes on Normanby Island ―presumably the same species―engaged in the same activity at night.

Figures

FIGURE 2. Map of Papua New Guinea, showing the two known localities for Gerrhopilus depressiceps (circles) and type localities for Gerrhopilus addisoni (triangle), Gerrhopilus eurydice (square), Gerrhopilus persephone (star), and Gerrhopilus lestes (diamond). The demarcated northern portion of Papua New Guinea is the former German New Guinea from which the holotype of Typhlops depressiceps presumably came; the irregular solid line running through northwestern Papua New Guinea shows the course of the Sepik River, along which the holotype of Typhlops monochrus was presumably obtained.

FIGURE 3. Dorsal (A) and lateral (B) views of the head of the holotype of Gerrhopilus persephone holotype (UMMZ 242536); dorsal (C) and lateral (D) views of the head of the holotype of Gerrhopilus lestes holotype (BPBM 11904) showing the collar of dark color across the head. Scale bars = 2 mm.

FIGURE 4. Portrait in life of the holotype of Gerrhopilus persephone (UMMZ 242536).

FIGURE 5. Dorsal (A), ventral (B), and lateral (C) radiographs of the skull of the holotype of Gerrhopilus persephone (UMMZ 242536). Scale bar = 2 mm.