Stegonotus reticulatus ( Boulenger, 1895:31 )

Kaiser, Christine M., Kaiser, Hinrich & O’Shea, Mark, 2018, The taxonomic history of Indo-Papuan groundsnakes, genus Stegonotus Duméril et al., 1854 (Colubridae), with some taxonomic revisions and the designation of a neotype for S. parvus (Meyer, 1874), Zootaxa 4512 (1), pp. 1-73 : 43

Stegonotus reticulatus ( Boulenger, 1895:31)

Taxonomic status. Stegonotus reticulatus has heretofore been considered as a synonym of S. cucullatus . We use the following characteristics to differentiate this species from S. cucullatus (whose characteristics we provide in parentheses): (1) IL G = 4 (5); (2) the length of the internasal suture is ḵ 50% of internasal width (the rostral invades the internasal area and nearly separates the internasals); (3) the suture separating the prefrontals and the frontal lies posterior to or is level with the anterior edge of the eyes (anterior to eyes); (4) the chin area is separated from true ventral scales (gastrosteges) by only one scale in the ventral midline (two scales); and (5) the absence of any specimens with the characteristic reticulated scale pattern from the Bird’s Head Peninsula, the type locality of S. cucullatus . Based on these differences, and based on the uncertainty surrounding the species cucullatus (see above), we hereby remove this strikingly-patterned species from the synonymy of S. cucullatus .

Synonyms. None.

Original name. Stegonotus reticulatus Boulenger, 1895:31 . In naming this form, Boulenger (1895) used the term reticulatus (Latin = net-like) descriptively, in reference to the striking dorsal patterning found in these animals. The pattern itself comprises darkened edges around all dorsal scales, producing a netlike surface coloration. The species description was presented in English.

Syntypes. BMNH 1946.1.14.87–88 ( Fig. 24 ), formerly BMNH 95.4.26.50–51, an adult female and an adult male, respectively.

Type locality. “Fergusson Island, D’Entrecasteaux Group, British New Guinea ” [Milne Bay Province, Papua New Guinea; ca. 9.54°S, 150.67°E].

Collection. These specimens were also collected by A.S. Meek (see the account of S. guentheri above).

Key characteristics of the type specimens. (1) BMNH 1946.1.14.87: 890 (880) mm SVL + 250 (238) mm TL = 1140 (1118) mm TTL. V ♀ = 201 (201), SC ♀ = 78 (78), SCR ♀ = 0.28 (0.28), D = O-17-O (17-17-15), SL E = 4+5 (4+5), SL = 8 (8), IL = O (9), IL G = 4 or 5 (4). (2) BMNH 1946.1.14.88: 1080 (1124) mm SVL + O (broken tail) mm TL = O (O) mm TTL. V ♂ = 203 (204), SC ♂ = O (O), SCR ♂ = O (O), D = O-17-O (17-17-15), SL E = 4+5 (4+5), SL = 8 (8), IL = O (9), IL G = 4 or 5 (4).

Key characteristics of the species. We have been able to examine 144 specimens (34 ♀♀, 82 ♂♂, 28 unsexed) of S. reticulatus from all mainland provinces of Papua New Guinea with the exception of Enga and Morobe Provinces. We have so far located a single specimen from Indonesian New Guinea, from Padaido Island, a small island off the eastern coast of Biak Island, Schouten Islands, Papua Province, Indonesia (USNM 119549). Characteristics of S. reticulatus include V ♀ = 186–215 (202 ± 8.2), V ♂ = 188–230 (208 ± 7.7); SC ♀ = 73–88 (82 ± 4.3), SC ♂ = 71–92 (83 ± 5.2); SCR ♀ = 0.29, SCR ♂ = 0.29; D = 17-17-15 (100%); SL E = 4+5 (n = 140, 97%) or 3+4 (n = 4, 4%); SL = 7 (n = 3, 2%), 8 (n = 81, 56%), or 9 (n = 42%); IL = 9 (n = 61, 42%) or 10 (n = 83, 58%); IL G = 4 (100%).

Whereas males tend to have more ventrals and more subcaudals than females on average, these differences are not statistically significant and there does not appear to be any sexual dimorphism in these counts. We note that, compared with other well-defined species of Stegonotus , the ranges of ventrals and subcaudals in S. reticulatus are rather large (ranges of 29 and 42 ventrals, and 15 and 21 subcaudals in females and males, respectively), and the relatively large standard deviation values may indicate that there could be cryptic taxa hidden in this widely distributed morphotype.

Comment. In order to stabilize the nomenclature of S. reticulatus , we hereby designate BMNH 1946.1.14.87 ( Fig. 24 A–E; Table 1), the female specimen, as the lectotype of this species (Code, Article 74.7). This specimen is the only syntype with a complete tail, and given the importance of the number of subcaudal scales in diagnoses of species in the genus Stegonotus , it is relevant to ascertain that this characteristic can be fully evaluated. This designation renders BMNH 1946.1 .14.88, the male syntype with a broken tail, as a paralectotype.

Even though specimen data for S. reticulatus are sufficient to separate the reticulated morphotype from S. cucullatus , it remains unclear whether the specimens we examined represent more than one species. It does appear as if the species is found primarily along the northern versant of New Guinea’s Central Cordillera, with some specimens also encountered in the southeastern lowlands. However, it is uncertain to what degree the number of captured specimens of a particular phenotype is due to greater survey efforts as opposed to natural distribution patterns. The reticulated morphotype appears to be the most widely distributed Stegonotus species, and some individuals are also known from Australia, where they are relatively rare (Rick Shine, pers. comm.).

Figures

FIGURE 24. Type specimens of Stegonotus reticulatus Boulenger, 1895. Photos include views of the entire body of the lectotype BMNH 1946.1.14.87, an adult female (TTL = 1118 mm) in (A) dorsal and (B) ventral views, and of the specimen’s head in (C) dorsal, (D) right lateral, and (E) ventral views. The body of the adult male paralectotype BMNH 1946.1.14.88 is shown in (F) dorsal and (G) ventral views, and the specimen’s head in (H) dorsal, (I) right lateral, and (J) ventral views.