Gerrhopilus inornatus (Boulenger, 1888)

Kraus, Fred, 2023, A revision of Gerrhopilus inornatus (Squamata: Gerrhopilidae) reveals a multi-species complex, Zootaxa 5231 (1), pp. 1-23 : 3-6

Gerrhopilus inornatus

Figs. 1A, B

Typhlops inornatus Boulenger, 1888: 384 .

Gerrhopilus inornatus Vidal, Wynn, Donnellan & Hedges, 2010: 560 in Vidal et al. 2010.

Holotype. BMNH 1946.1 .11.80, collected by H.O. Forbes at “Sogere Camp” [Sogeri, 530 m a.s.l.], Central Province , Papua New Guinea.

Diagnosis. A Gerrhopilus species characterized by the unique combination of having a rounded snout in lateral view; LSR = 20 at midbody; TSR = 374–375; loreal absent; supralabial imbrication pattern T-V; subocular scale one; presubocular scale absent; a sharp, protruding tail spine that is white; 2–3 glands in the prefrontal, 2–3 in the supraocular, 0–6 in the ocular, 22–24 in the preocular, 0 in the frontal, 0–2 in the subocular; L/W = 36.4–47.8; TL/SVL = 0.026 in one female and 0.030 in one male; and a uniformly dark venter. Its size is small for this species group ( Table 1 ).

Comparisons with other species. Gerrhopilus inornatus is distinguished from G. fredparkeri , G. hades , and G. suturalis in having 20 longitudinal scale rows at midbody (vs 16 in G. fredparkeri and 18 in G. hades and G. suturalis ). It is further distinguished from G. fredparkeri in its lower number of transverse scale rows (374–375 vs 539 in G. fredparkeri ), from G. hades in having 20–22 longitudinal scale rows behind the head (vs 18 in G. hades ) and more and smaller glands in the center of the preocular (22–24 vs 10–11 in G. hades ), and from G. suturalis in having a single postocular on each side of the head (vs two in G. suturalis ) and lacking a presubocular (vs present in G. suturalis ).

Redescription of the holotype. Female, with ventral cut ~70% of way down body; body soft around ventral cut. L = 177 mm, SVL = 172.5 mm, TL = 4.5 mm, HW = 3.7 mm, SN = 1.9 mm, SW = 3.0 mm, PSN = 1.0 mm, RW = 1.5 mm, EW = 0.3 mm, W = 3.7 mm, VW = 3.6 mm, TW = 3.2 mm, L/W = 47.8, TL/SVL = 0.026. Head slightly wider than neck. Snout rounded in dorsal and lateral views. Snout anterior to lower jaw angled slightly ventrally. Rostral moderately large (RW/HW = 0.41), oval dorsally, lateral margins convex, posterior border extending approximately half way between naris and eye, posterior margin straight; ventrally surface papillose, with sides slightly diverging anteriorly and posterior margin straight. Nasals separated dorsally by prefrontal ( Fig. 1A ); superior nasal large, with slightly sinuous posterior margin, concave dorsally, convex ventrally ( Fig. 1B ). External naris semicircular, oriented obliquely, close to rostral, anterior half covered by inferior nasal; superior nasal suture extending anterodorsally from naris to rostral; inferior nasal suture complete, contacting second supralabial well posterior to latter’s contact with first supralabial. Prefrontal, frontal, and supraoculars subequal in size, larger than parietals and interparietal, which are also 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 obscure, with indistinct margin and small pupil, situated above widest point of ocular and approximately midway along its height, anterior half covered by preocular plate in lateral view. Four postoculars bordering ocular and subocular between parietal and fourth supralabial. Four supralabials, third the largest, all with long axis oblique to long axis of body, first approximately rectangular. Supralabial imbrication pattern T-V, posterior border of second supralabial overlaps anteroventral margin of preocular, that of third supralabial overlaps anteroventral margin of subocular and ends at level of rear margin of preocular. 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, second much longer.

Longitudinal scale rows 22 behind head, 20 at midbody, and 20 anterior to vent; transverse scale rows 375, six intercalary scales along vertebral row; subcaudals 12; dorsocaudals 15; apical region with sharp, transverse, slightly downturned spine that extends well past last scales.

Rostral, nasals, and preoculars densely covered in pale glands; oculars with 2 (R) and 0 (L) glands, preoculars with 22 (R) and 23 (L), supraoculars with 2 (R) and 3 (L), prefrontal with 2; frontal and suboculars without glands.

In preservative, 136–137 years after its preservation, dorsum dark brown (black in life, cf. Boulenger, 1888), gradually fading laterally to slightly paler brown on venter; no sharp distinction between dorsal and ventral coloration; each dorsal scale uniformly dark; each ventral scale slightly darker anteriorly. Anterior third of rostral, area around nares, first two supralabials, mental, and center of throat to five scales behind mental pale straw yellow; third and fourth supralabials pale straw yellow with brown along dorsal margins. Head glands pale straw yellow; tail spine and adjacent scales white, spine with corneus brown tip. Iris dark gray, obscure; pupil pale gray.

Variation. The sole additional specimen ( USNM 213488 ) differs from the holotype in being male, slightly shorter (L = 171 mm, SVL = 166 mm, TL = 5 mm, Table 1 ), relatively wider (W = 4.7 mm, L/W = 36.4), with a longer tail (TL/SVL = 0.030), and in having 20-20-20 longitudinal scale rows, with no reduction from the head to midbody. It has 374 transverse scale rows, ten intercalary scales, 17 subcaudals, 16 dorsocaudals, the third supralabial extending posterior to the posterior margin of the preocular, the eye half covered by the preocular, oculars with 6 ( R) and 2 (L) glands, preocular with 22 ( R) and 24 (L), supraoculars with 2 on each side, prefrontal with 3, frontal with 0, and suboculars with 2 glands on each side. It is obvious that variation between these two specimens is minimal. The pale straw yellow on the chin extends to four scales behind mental; base of the tail spine is black, and the tip is white .

Distribution. Known only from Sogeri (9.42° S, 147.42° E) and from 4 km N of Sogeri at McDonald’s Corner, 9.3849° S, 147.427° E ( Fig. 2 ). Given the imprecision of named 19 th Century collecting localities, these are effectively the same location.

Ecology. USNM 213488 was collected under tin in a rubber plantation of very mature trees, near a stream.The native habitat around Sogeri is now highly disturbed but would have been lower-elevation hill forest, as still can be found in nearby Varirata National Park ( Fig. 3A ).

Remarks. The holotype of G. inornatus was originally catalogued as BMNH 88.3.21.6 and noted as collected by and purchased from H.O. Forbes, who maintained a camp at Sogeri from October 1885 to April 1886 ( Forbes 1888), during which period the specimen would have been collected. The USNM specimen was collected by C. Ross on 25 March 1978. The holotype was described by Boulenger (1888), within three years of its collection, as uniformly black. Twenty-nine years later de Rooij (1917) noted the specimen to be black above and a little lighter below, showing the typical pattern of fading I have seen in snakes of this complex..

Subsequent to the original description, the holotype was reported on only by de Rooij (1917). The second specimen (USNM 213488) was, however, examined by Wallach (1996). All subsequent treatments of Gerrhopilus inornatus have been based on specimens from some of the species described below.

Figures

FIGURE 1. Dorsal and lateral views of heads for members of the Gerrhopilus inornatus Group having 20 midbody scale rows. A, B holotype of Gerrhopilus inornatus (BMNH 1946.1.11.80); C, D holotype of Gerrhopilus slapcinskyi (BPBM 18944).

FIGURE 2. Map of southern Papua New Guinea showing collecting localities for Gerrhopilus inornatus (star), G. flavinotatus (diamond), G. lorealis (hexagon), G. papuanorum (square), G. polyadenus (open circles), G. slapcinskyi (filled circle), and G. wallachi (triangle).

FIGURE 3. Habitats for members of the Gerrhopilus inornatus Group. A Forest at Varirata National Park, very near the type locality of G. inornatus (photo M. O’Shea); B the hills around Bunisi and Siyomu from which G. papuanorum was collected (photo F. Kraus).