Stegonotus modestus ( Schlegel, 1837:119 )

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 : 9-12

Stegonotus modestus ( Schlegel, 1837:119)

Taxonomic status. Valid.

Synonyms. Lycodon lividum Duméril et al., 1854 ; Ablabes greineri Bleeker, 1860a ; Coronella rosenbergii Bleeker, 1860b ; Coluber holochrous Boulenger, 1863 ; Lycodon aruensis Doria, 1874 .

Original name. Lycodon modestus Schlegel, 1837:119 . In the second volume of his expansive treatise on snakes, Hermann Schlegel (1804–1884; Fig. 3A ), then employed as assistant to the director of the Rijksmuseum van Natuurlijke Historie in Leiden, The Netherlands (RMNH), described this taxon as a member of the genus Lycodon . The Latin species epithet means “moderate” in English and was perhaps used to indicate that this was a fairly nondescript form compared to some of the other members of the genus Lycodon , as then recognized. The species description was presented in Dutch. The image of Schlegel ( Fig. 3A ; public domain) is from a lithograph by the Belgian illustrator Abraham Jacobus Wendel (1826–1915).

5. There is no uniform terminology for the scales covering the chin region of a snake’s head. An informal literature survey revealed that the terms “genials” and “chin shields” have been used widely throughout the historical and recent literature. Ruane et al. (2017) recently used the term “inframaxillary” for these scales, a term we find most commonly used by 19 th Century authors. We prefer the term “genials” for two reasons. (1) Any scale in the chin region of a snake’s head is strictly a chin shield (or chin scale, or chin plate), and this term may therefore be ambiguous—especially should a translation to another language be necessary. (2) The term “inframaxillary” relates the position of a visible external feature (the scale) to an invisible internal one (the bone). We believe this is not optimal, especially considering that the skull of many snakes is very kinetic and the position of the maxillary bone can shift.

Holotype. RMNH. RENA 324 ( Fig. 4 ; Table 1), an adult male.

Type locality. “Amboine” [ Ambon Island, Maluku Province, Indonesia].

Collection. The specimen was collected by Salomon Müller (1804–1864), a key member of the Dutch expeditions to the East Indies under the umbrella of the Natuurkundige Commissie voor Nederlandsch-Indië [Natural History Commission for the Dutch Indies]. He appears to have been a productive collector in the Indonesian archipelago in the time from 1826–37 ( Steenis-Kruseman 1950), and he distinguished himself among the Dutch explorers of the time by surviving his travels and returning to his homeland. Müller settled down as a scientist to work on his collection until the Commission was disbanded in 1850 and he retired. It is curious, given Müller’s contributions to natural history, that no photograph or other illustrations of him appear to exist (Charles Klaver, in litt.). The time frame of the specimen’s collection is given by the schedule of the corvette Triton and the schooner Iris , which arrived on Ambon on 5 September and departed on 7 October 1828 ( Macklot 1829), to drop off the members of the Commissie, including Müller, at Kupang on Timor on 14 October 1828 ( Macklot 1829; Steenis-Kruseman 1950). Thus, the specimen must have been collected between 5 September and 7 October 1828 ( Müller 1857).

Key characteristics of the holotype. 700 (656) mm SVL + 210 (206) mm TL = 910 (862) mm TTL. V ♂ = 200 (198), SC ♂ = 84 (83), SCR ♂ = 0.30 (0.30), D = O-17-O (17-17-15), SL E = O (3+4), SL = O (7), IL = O (8), IL G = O (4). Based on its SCR of 0.30 the holotype falls well outside the SCR values for females (see below) and can there-fore be identified as a male .

Key characteristics of the species. We were able to examine 18 specimens of S. modestus that were collected on the three major islands to which we are restricting the distribution of the species (see below). Of these, eight (4 ♀♀, 4 ♂♂) were collected on Ambon, six on Buru (6 ♂♂), and four on Seram (4 ♂♂). These include the holotypes of Ablabes greineri , Coluber holochrous , and Coronella rosenbergii (see individual accounts for each of these species below). Characteristics include V ♀ = 190–198 (194 ± 3.5), V ♂ = 195–206 (202 ± 3.3); SC ♀ = 58–68 (63 ± 4.4), SC ♂ = 78–94 (84 ± 4.5); SCR ♀ = 0.24, SCR ♂ = 0.29; D = 17-17-15 (100%); SL E = 3+4 (n = 16, 89%) or rarely 4+5 (n = 2, 11%); SL = 7 (n = 11, 61%) or 8 (n = 7, 39%); IL = 8 (n = 10, 59%), 9 (n = 6, 35%), or 10 (n = 1, 6%); IL G = 4 (100%).

In this species, there exists some sexual dimorphism with respect to V and SC counts, with females having values of V <200 and with males possessing slightly higher counts (but overlapping with some females). There is no overlap in values of SCR, with values for females ranging from 0.23–0.26 and for males from 0.28–0.31. Thus, males of S. modestus have slightly longer tails than females.

Comments. An important characteristic for the identification of this species is the incomplete light-colored band that marks the posterior extent of the head. This neck band is bisected by one or two brown scales mediodorsally, and it is two or three light scales wide along the lateral side of the body. The band is sometimes faint but present in a majority of specimens (89%) and living individuals. This Maluku Island regional endemic appears to be the only species of Stegonotus featuring this characteristic type of band in adults. We consider the species confirmed only for Ambon, Buru, and Seram, but we see no reason why it would not also occur on some of the associated smaller islands in the northern part of Maluku Province, Indonesia (e.g., Boano, Haruku, Kelang, Maripa, Saparua). De Lang (2013) cited a personal communication regarding the presence of this species on the Tanimbar Islands, Maluku Province, Indonesia, but we have not found any record of actual specimens from there. Given our concept of S. modestus as a central Moluccan regional endemic, a population of Stegonotus in the nearly 400 km distant Tanimbar Islands could, with high probability, be a separate species.

As a consequence of restricting the terra typica of this species to the islands listed above, Lycodon lividum from Semau Island (ca. 800 km to the southwest) and Lycodon aruensis from the Aru Islands (ca. 500 km to the southeast) need to be removed from the synonymy of S. modestus (see their individual accounts below for a review of their taxonomic status). An additional, unfortunate consequence of a more restricted type locality for S. modestus is that most of the specimen identifications and assumptions regarding the identity and distribution of this species, such as those made by McDowell (1972) and Ruane et al. (2017), are now shown to be incorrect. In fact, McDowell (1972) already pointed out that even within the purported members of S. modestus in Papua New Guinea alone three distinct forms existed, leading him to present the species name as “ S. modestus ” (in quotation marks) and lamenting the unreliability of commonly used morphological data. The molecular data of Ruane et al. (2017: Fig. 3 ) also clearly indicated a taxonomic division in these forms, and their data identified a distinct population of Stegonotus in north-central New Guinea. However, these authors erred in applying the name S. modestus to that population.

Figures

FIGURE 3. Selected 19 th Century authors and collectors of Stegonotus species. (A) Hermann Schlegel (1804–1884), author of the species name modestus. (B) André Marie Constant Duméril (1774–1860), co-author with (C) and (D) of the genus name Stegonotus and the species names cucullatus, lividus, and muelleri. (C) Gabriel Bibron (1806–1848). (D) Auguste Henri André Duméril (1812–1870). (E) René-Primevère Lesson (1794–1849), co-collector (with Prosper Garnot; no image available) of the L. cucullatum holotype. (F) Pieter van Oort (1804–1834), co-collector (with Salomon Müller and Heinrich Macklot; no images available) of the L. lividum syntypes. (G) Pieter Bleeker (1819–1878), author of the species names greineri (and perhaps collector of its holotype) and rosenbergii. (H) Hermann von Rosenberg (1817–1888), collector of the Coronella rosenbergii holotype and the person for whom the species was named. (I) Wilhelm Karl Hartwig Peters (1815–1883), author of the species name samarensis. (J) Fedor Jagor (1816–1900), collector of the Spilotes samarensis holotype. (K) Albert Karl Ludwig Gotthilf Günther (1830–1914), author of the genus name Zamenophis as well as the species names holochrous, batjanensis, and australis. The species Stegonotus guentheri was named in Günther’s honor. (L) Adolf Bernhard Meyer (1840–1911), author of the species names magnus and parvus and collector of the type material.

FIGURE 4. Holotype of Stegonotus modestus (Schlegel, 1837), RMNH.RENA 324, an adult male from Ambon Island, Maluku Province, Indonesia. Shown are the entire specimen (TTL = 862 mm) in (A) dorsal and (B) ventral views, and its head in (C) dorsal, (D) right lateral, and (E) ventral views.