Gerrhopilus polyadenus, Kraus, 2023

Kraus, Fred, 2023, A revision of Gerrhopilus inornatus (Squamata: Gerrhopilidae) reveals a multi-species complex, Zootaxa 5231 (1), pp. 1-23 : 9-12

Gerrhopilus polyadenus sp. nov.

Figs. 4C, D

Typhlops inornatus de Rooij 1917: 14 .

Gerrhopilus inornatus Pyron & Wallach 2014: 79 .

Holotype. BMNH 1901.11 .27.10, collected at Mt Albert Edward , Papua New Guinea by H.S. Rohu.

Paratype. MCZ 140728 , collected at Sangara [8.76° S, 148.18° E], 120 m a.s.l., Oro Province, Papua New Guinea .

Diagnosis. A Gerrhopilus species characterized by the unique combination of having a rounded snout in lateral view; LSR = 22 at midbody; TSR = 320; loreal absent; supralabial imbrication pattern T-V; subocular scale one; presubocular scale absent; a sharp, protruding tail spine that is dark brown with a white or corneous-brown tip; 29 glands in the prefrontal, 8–9 in the supraocular, 22–23 in the ocular, 46–50 in the preocular, 6 in the frontal, 16 in each subocular; L/W = 36.2–36.3; TL/SVL = 0.028 –0.036; dorsum and venter uniformly pale brown with a contrasting dark-brown patch around tail spine. Its size is moderate for this species group ( Table 1 ).

Comparisons with other species. Gerrhopilus polyadenus is distinguished from G. fredparkeri , G. hades , G. inornatus , G. slapcinskyi , and G. suturalis in having 22 longitudinal scale rows at midbody (vs 16 in G. fredparkeri , 18 in G. hades and G. suturalis , and 20 in G. inornatus and G. slapcinskyi ). It is further distinguished from G. fredparkeri and G. inornatus in having fewer transverse scale rows (294–320 vs 539 in G. fredparkeri and 374–375 in G. inornatus ); from G. hades in having 22 longitudinal scale rows behind the head (vs 18 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 ). Gerrhopilus polyadenus is readily distinguished from G. inornatus , G. slapcinskyi , and G. papuanorum by its pale-brown color (dark brown or black in the other species), dark-brown scales around the tail spine (area black or white in the other species), and much greater number of glands in the ocular (11–23 vs 0–6 in G. inornatus , 4–9 in G. slapcinskyi , and 0–3 in G. papuanorum ), preocular (42–50 vs 22–24 in G. inornatus , 35–39 in G. slapcinskyi , and 18–28 in G. papuanorum ), prefrontal (11–29 vs 2–3 in G. inornatus , 1–2 in G. slapcinskyi , and 1–5 in G. papuanorum ), supraocular (5–9 vs 2–3 in G. inornatus , 0–3 in G. slapcinskyi , and 0–4 in G. papuanorum ), and subocular (5–16 vs 0–2 in G. inornatus , 3–4 in G. slapcinskyi , and 0–2 in G. papuanorum ). It is further distinguished from G. papuanorum by its stouter habitus (L/W = 36.2–36.3 vs 51.2–53.5 in G. papuanorum ) and longer tail (TL/SVL = 0.028 –0.036 vs 0.021 –0.026 in G. papuanorum ).

Description of the holotype. Female. L = 199 mm, SVL = 193.5 mm, TL = 5.5 mm, HW = 10.1 mm, SN = 5.5 mm, SW = 8.6 mm, PSN = 2.4 mm, RW = 3.7 mm, EW = 0.8 mm, W = 10.6 mm, VW = 8.7 mm, TW = 7.2 mm, L/W = 39.0, TL/SVL = 0.028. Head slightly wider than neck. Snout rounded in dorsal and lateral views. Snout anterior to lower jaw horizontal, parallel to body axis. Rostral rather narrow (RW/HW = 0.36), 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. 4C ); superior nasal large, with slightly sinuous posterior margin, concave dorsally, convex ventrally ( Fig. 4D ). 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 just posterior to latter’s contact with first supralabial. Prefrontal larger than supraoculars, which are larger than parietals and interparietal, which are subequal in size. Frontal fused with both parietals. 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 approximately two-thirds its size. Eye distinct, with pale pupil, situated at widest point of ocular and approximately midway along its height, anterior 1/4 (R) or 1/3 (L) covered by preocular plate in lateral view. Four 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 approximately square. 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 extends posterior to 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 uniformly 22 behind head, at midbody, and anterior to vent; transverse scale rows between rostral and tail tip 320, six intercalary scales along vertebral row; subcaudals 16; dorsocaudals 16; apical region with blunt spine that barely extends past last scales.

Rostral, nasals, and preoculars densely covered in large pale glands; oculars with 22 (R) and 23 (L) glands, preoculars with 50 (R) and 46 (L), supraoculars with 8 (R) and 9 (L), prefrontal with 29; frontal with 6, and suboculars with 16.

In preservative, ~121 years after preservation, dorsum faded medium brown, gradually fading laterally to paler brown on venter; no sharp distinction between dorsal and ventral coloration; each dorsal scale uniformly dark; each ventral scale slightly darker anteriorly. Anterior half of rostral, area around nares, first supralabial, mental, and center of throat to six scales behind mental pale straw yellow; second, third, and fourth supralabials pale straw yellow with brown along dorsal margins. Head glands pale straw yellow; tail spine and adjacent scales dark brown (darker than rest of body), spine with white tip. Iris dark gray; pupil pale gray.

Variation. The paratype is an immature female and differs from the holotype in being shorter (L = 138 mm, SVL = 133 mm, TL = 5 mm, Table 1 ), the same relative width (W = 3.8 mm, L/W = 36.3), and with a longer tail (TL/SVL = 0.038). It has 294 transverse scale rows, 15 subcaudals and dorsocaudals, and fewer head glands than the holotype, with 11 (R) and 16 (L) glands in the oculars, 42 (R) and 43 (L) in the preoculars, 5 (R) and 6 (L) in the supraoculars, 11 in the prefrontal, 0 in the frontal, and 5 (R) and 8 (L) in the subocular. It has a sharp, protruding tail spine that is longer than that in the holotype; base of spine and adjacent scales dark brown, but the tip of the spine is corneous brown.

Etymology. The specific epithet is a masculine Latinized compound adjective, from the Greek poly-, meaning many, and adeno, meaning gland.

Distribution. Known from the type locality at an unspecified location on Mt Albert Edward and from the nearby lowlands of Oro Province, Papua New Guinea ( Fig. 2 ).

Remarks. The BMNH catalogue for the holotype states that it was purchased from Mr. H.S. Rohu of Stepney, a district on the east end of London. This catalogue states that the specimen came from “not less than 6000 ft. ” on the Albert Edward Range, but this information is doubtful for two reasons. First, Wichmann (1912: 754) states that Rohu’s expedition up Mt Albert Edward reached no farther than a height of 6000 ft. (“...dort bis in die Höhe von 6000 feet gelangte.). Wichmann does not state the source of his information, but he may have been in direct correspondence with Rohu on the matter. Rohu was an overseer on the Tamata Station, along the Mambare River ( Administrator, British New Guinea 1902), which lies on the northern versant in what is now Oro Province, PNG. He quit service at Tamata Station on 18 October, 1900, and his expedition would thus have occurred in late 1900 or the first part of 1901 in order for the specimens to have reached BMNH in time to be catalogued in late November, 1901. Mt Albert Edward is one of the higher peaks of the Owen Stanley Range; it now lies largely within Central Province, PNG, but straddles the division between the northern and southern versants of the Owen Stanley Mts. Given Rohu’s residence at Tamata Station, I presume he made his ascent from the east (Oro Province), which is consistent with the paratype being from Sangara, 50–60 km S of the Mambare River in the same province. Inasmuch as the paratype came from an elevation of approximately 120 m a.s.l., I presume that the holotype did not, in fact, come from as high as “not less than” 6000 ft. (1830 m), as stated in the BMNH catalogue, and that Wichmann’s (1912) account is correct. Second, the BMNH accession of Rohu’s herpetological material includes 24 specimens of 15 species. Of these, at least four (e.g., Cornufer papuensis , Emoia jakati , Palaia pulchra , Prasinohaema semoni ) are lowland species that are not found as high as 1800 m a.s.l., much less occurring “not less than that elevation”. Several of the other species are also predominantly lowland inhabitants though they may attain elevations as high as 1800 m a.s.l. Hence, the exact elevational provenance of the holotype is uncertain, but it seems to have been collected at a relatively low elevation. Zweifel (1979) makes this same inference that the reported elevation for the syntypes of Palaia pulchra , collected by Rohu on the same expedition, is erroneous.

The holotype of this species was examined and referred to Typhlops inornatus by de Rooij (1917), who, however, did not remark on the differences between this specimen and the holotype of G. inornatus . The paratype was examined by Wallach (1996) and Pyron & Wallach (2014), who listed it as Typhlops inornatus .

Figures

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 4. Dorsal and lateral views of heads for members of the Gerrhopilus inornatus Group having 22 midbody scale rows and uniformly dark venters. A, B holotype of Gerrhopilus papuanorum (BPBM 17236); C, D holotype of Gerrhopilus polyadenus (BMNH 1901.11.27.10).