Stegonotus ayamaru, Kaiser & O’Shea & Kaiser, 2019

Kaiser, Christine M., O’Shea, Mark & Kaiser, Hinrich, 2019, A new species of Indo-Papuan groundsnake, genus Stegonotus Duméril et al., 1854 (Serpentes, Colubridae), from the Bird’s Head Peninsula of West Papua, Indonesia, with comments on differentiating morphological characters, Zootaxa 4590 (2), pp. 201-230 : 208-222

Stegonotus ayamaru sp. nov.

Ayamaru Groundsnake

( Figs. 4 , 5 , 6A, 6 A’, 7A, 7A’, Table 2 )

Holotype. RMNH. RENA 31199 , an adult male from “Komara” [Kamro], Aitinyo District , Maybrat Regency, West Papua Province, Indonesia (1.5103°S, 132.3763°E; elevation ca. 140 m; Fig. 1 ). The type locality is a village of the Ayamaru people inhabiting the central Bird’s Head Peninsula, situated in lowland primary rainforest. The specimen was collected in February 1953 by the Reverend Herbert Marcus (1883–1961) and his wife Mieneke Marcus-van den Nieuwenhuizen 5 (1911–2009). In addition to the village name, the original specimen label also gives the local name for the specific collection site as “apan bebach,” but this appears to be a local designation and we were unable to determine its precise locality. In order to determine the detailed locality of the village listed as “Komara,” we located the name on Map SA 53-1 ( Army Map Service 1942), the most likely map of the area available to missionaries in the 1950s. On this map, there is a village listed under the name Komara 6, which we confirmed as the correct locality based on the accounts of the missionaries (Marcus-van den Nieuwenhuizen 2009). The map in Elmberg (1968: Fig. 2 ) reflects this arrangement and indicates that Komara was a village with school activity, making it a very likely residence for missionaries. This location is now known as Kamro. The initial identification of the specimen as S. batjanensis was done by Dr. Maria S. (“Riet”) Knaap-van Meeuwen (born 1936) in March 1962.

Diagnosis. Stegonotus ayamaru appears to be a relatively small-sized (SVL of only known specimen = 493 mm) member of the genus with a relatively long tail (SCR ♂ = 0.37). It can be distinguished from all other known Stegonotus by the following combination of characters: (1) rostral extending onto the dorsal part of the head and not intruding into the internasal area, resulting in a relatively long internasal suture (character state: gull wing +; Fig. 3C ); (2) area of prefrontals 1.5 times that of the internasals, internasal suture two-thirds the length of the prefrontal suture ( Fig. 7A ); (3) frontal clearly pentagonal with well-formed corners and a slightly convex anterior suture; (4) AE lies behind the anterior end of frontal ( Fig. 7 A’); (5) length of frontal equal to that of the parietal suture; (6) PF / ¿ 90° ( Fig. 7 A’); (7) AP / = 135° with lateral ray directed laterally ( Fig. 7 A’); (8) three temporal scales touching the parietals, the lengths of the two anterior temporals combined equaling the length of the posterior temporal, temporal formula 2+2+3; (9) three neck scales contacting parietals (10) loreal two-thirds as long as wide; (11) a single preocular with dimensions similar to those of the loreal, curving around the anterior border of the eye ( Fig. 5 B’); (12) seven supralabials, three (SL3–5) touching the eye; SL5 projecting forward from behind the eye to form a narrow contact zone with the eye ( Figs. 5B , B’, 6A’); (13) eight infralabials, four (IL1–4) touching the anterior genial, two-thirds of IL 4 in contact with the anterior genial ( Fig. 5 D’); (14) four chin scales separating the posterior genial and the anteriormost gastrostege; (15) 17-17-15 dorsals; 181 ventrals, 105 paired subcaudals; (16) cloacal plate entire; (17) color in preservative (65 years post-collection): dorsum Maroon (29) fading laterally to Hazel (26), head Maroon with areas on the frontal and parietals that are a lighter color (Hazel); nasals Light Buff (2) with some darker areas (Hazel); venter Light Buff ( Figs. 4 , 5 ). On the ventral surface, the anterior to medial portions of the subcaudals are Hazel, creating a dark tail ( Fig. 4C ).

Comparisons. In the comparisons that follow, characteristics of S. ayamaru are listed in parentheses. Species names are followed by the number of specimens used to determine ranges of continuous characters. Since the only known specimen of S. ayamaru is a male, we limit our comparisons of characteristics with potential sexual dimorphism (see Kaiser et al. 2018a) to male specimens; gender is indicated throughout by subscripted male (♂) and female (♀) symbols for ease of reference. A listing of those characters most relevant for interspecies comparisons is provided in Table 2 .

5. The Reverend Herbert F. Marcus was a Dutch Mennonite (Doopsgezind in Dutch) missionary in the Vogelkop Peninsula of Dutch New Guinea in the 1950s. His wife Mieneke Marcus-van den Nieuwenhuizen served as a government physician in support of the missionary work.

6. There is an obvious difficulty with the identification of towns whose names are so similar in writing and pronunciation, a problem compounded by local customs. It is, for example, quite possible that entire villages move, either to farm new areas or to escape bouts of illness or death (or due to spiritual concerns), with the new village at a different location given the same name as the old one. In this case, we have relied specifically on the collectors’ account (Marcus-van den Nieuwenhuizen 2009) as it matches the contemporary map. This situation is compounded by the presence in southern New Guinea (Papua Province, Indonesia) of the Kamoro people ( Muller 2004).

Stegonotus admiraltiensis (n = 1) differs from S. ayamaru by scale counts of V ♂ = 208 (181), SC ♂ = 98 (105), SCR ♂ = 0.32 (0.37), D = 17-19-15 (17-17-15), SL = 8 (7), SL E = 4+5 (3+4+5), IL = 9 or 10 (8), and IL G = 6 (4). Additional differences include: (1) the rostral of S. admiraltiensis is clearly visible on the dorsal surface of the head, where it forms a shallow V ( Fig. 3D ) when viewed from above (gull wing +); (2) the rostral intrudes upon the internasal space, shortening the internasal suture (does not extend into internasal space, internasal suture not impacted); (3) InS = ½ PfS (InS = ¾ PfS); (4) the lateral ray of AP / is directed posterolaterally (laterally); (5) FL is slightly shorter than ParS (FL = ParS); (6) two temporals contact the parietals (3); and (7) two neck scales contact the parietals (3). The closest known locality for S. admiraltiensis is on Manus Island, Papua New Guinea ( PNG), ca. 1600 km by air from the type locality of S. ayamaru .

Stegonotus aruensis (n = 1) differs by scale counts of V ♂ = 190 (181) and SL E = 3+4 (3+4+5). Additional differences include (1) the rostral of S. aruensis is not visible on the dorsal surface of the head ( Fig. 3A ) (gull wing +); (2) InS = ¾ PfS (InS = ¾ PfS); (3) the lateral ray of AP / is directed posterolaterally (laterally); and (4) FL = % ParS (FL = ParS). The closest known locality for S. aruensis is in the Aru Islands, Maluku Province, Indonesia, ca. 500 km by air from the type locality of S. ayamaru .

Stegonotus australis (n = 21) differs by scale counts of V ♂ = 191–220 (181), SC ♂ = 74–88 (105), SCR ♂ = 0.25–0.29 (0.37), SL E = 4+5 (3+4+5); SL = 8 or 9 (7); IL = 9 or 10 (8), and IL G = 5 (4). Additional differences include (1) the rostral of S. australis is clearly visible on the dorsal surface of the head, where it forms a shallow V when viewed from above (gull wing +); (2) the rostral intrudes upon the internasal space, shortening the internasal suture (does not extend into the internasal space, internasal suture not impacted); (3) InS = ⅓ PfS (InS = ¾ PfS); (4) the lateral ray of AP / is directed posterolaterally (laterally); (5) FL is slightly shorter than ParS (FL = ParS); and (6) two temporals contact the parietals (3). The closest known locality for S. australis is in northern Queensland, Australia, ca. 1500 km by air from the type locality of S. ayamaru .

Stegonotus batjanensis (n = 15) differs by scale counts of V ♂ = 221–236 (181), SC ♂ = 78–89 (105), SCR ♂ = 0.25–0.29 (0.37), SL = 8, or rarely 7 (7), IL = 9, rarely 8 or 10 (8), and IL G = 5 (4). In addition, (1) in S. batjanensis SL3 projects posteriorly towards the eye to form a narrow contact zone ( Fig. 6B , B’) (SL5 projects anteriorly towards the eye; Fig. 6A , A’); (2) the rostral of S. batjanensis is clearly visible on the dorsal surface of the head, where it forms a shallow V when viewed from above (gull wing +); (3) the rostral intrudes upon the internasal space, shortening the internasal suture (does not extend into internasal space, internasal suture not impacted); (4) InS = ¼ PfS (InS = ¾ PfS); (5) AE lies in front of the anterior edge of the frontal (AE lies behind anterior edge of the frontal); (6) FL is slightly shorter than ParS (FL = ParS); (7) one, rarely two, neck scales contact the parietals (3); and (8) a distinctive color pattern is present (no distinctive color pattern). The closest known locality for S. batjanensis is on Halmahera Island, North Maluku Province, Indonesia, ca. 500 km by air from the type locality of S. ayamaru .

Stegonotus borneensis (n = 1) is a geographically distant species from Borneo, an island to the west of Wallace’s Line, with scale counts differing in V ♂ = 196 (181), SC ♂ = 78 (105), SCR ♂ = 0.28 (0.37), SL E = 4+5 (3+4+5), SL = 9 (7), IL = 10 (8), and IL G = 5 (4). Additional differences include (1) InS = ¼ PfS (InS = ¾ PfS); (2) the lateral ray of AP / is directed posterolaterally (laterally); (3) FL = % ParS (FL = ParS); and (4) two temporals contact the parietals (3). The closest known locality for S. borneensis is in northern Borneo, Sabah State, Malaysia, ca. 1900 km by air from the type locality of S. ayamaru .

Stegonotus cucullatus (n = 3) differs by scale counts of V ♂ = 205–216 (181), SC ♂ = 84–95 (105), SCR ♂ = 0.29–0.31 (0.37), SL E = 4+5 (3+4+5), SL = 8 (7), IL = 9 or 10 (8), and IL G = 5 (4). Additional differences include (1) the rostral of S. cucullatus is clearly visible on the dorsal surface of the head, where it forms a deep V ( Fig. 3E ) when viewed from above (gull wing +); (2) the rostral intrudes upon the internasal space, shortening the internasal suture (does not extend into internasal space, internasal suture not impacted); (3) InS = ¼ PfS (InS = ¾ PfS); (4) AE lies at the same level as the anterior end of the frontal (AE lies behind the anterior edge of the frontal); (5) FL = ¾ ParS (FL = ParS); and (6) two temporals are in contact with the parietals (3). The closest known locality for S. cucullatus is in Manokwari, West Papua, Indonesia, ca. 200 km by air from the type locality of S. ayamaru .

Stegonotus derooijae (n = 1) differs by scale counts of SC ♂ = 94 (105), SL E = 3+4 (3+4+5), and IL G = 5 (4). Additional differences include (1) AE lies at the same level as the anterior end of the frontal (AE lies behind the anterior edge of the frontal); (2) PF / is <90° (¿ 90); and (3) three to five neck scales contact the parietals (3). The closest known locality for S. derooijae is on Salawati Island, Raja Ampat Archipelago, West Papua Province, Indonesia, ca. 200 km by air from the type locality of S. ayamaru .

Stegonotus diehli (n = 1; juvenile, sex unknown) differs by scale counts of SC? = 82 (SC ♂ = 105), SCR? = 0.31 (SC ♂ = 0.37), D = 15-15-15 (17-17-15), and SL E 3+4 (3+4+5). Additional differences include (1) the rostral of S. diehli is barely visible on the dorsal surface of the head, where it forms a gull wing ( Fig. 3B ) when viewed from above (gull wing +); (2) InS = ½ PfS (InS = ¾ PfS); (3) PF / <90° (¿ 90°); and (4) four neck scales contact the parietals (3). The closest known locality for S. diehli is Bogadjim, Madang Province, PNG, ca. 1500 km by air from the type locality of S. ayamaru .

Stegonotus dorsalis (n = 1) differs by scale counts of V ♂ = 208 (181), SC ♂ = 88 (105), SCR ♂ = 0.30 (0.37), D = 15-15-15 (17-17-15), SL E 4+5 (3+4+5), SL = 8 (7), IL = 10 (8); and IL G = 5 (4). Additional differences include (1) the rostral of S. dorsalis is clearly visible on the dorsal surface of the head, where it forms a deep V when viewed from above (gull wing +); (2) the rostral intrudes upon the internasal space, shortening the internasal suture (does not extend into internasal space, internasal suture not impacted); (3) InS = ¼ PfS (InS = ¾ PfS); (4) AE lies at the same level as the anterior end of the frontal (AE lies behind the anterior edge of the frontal); (5) FL = % ParS (FL = ParS); and (6) three neck scales contact the parietals, two of them enlarged (3, equally sized). The closest known locality for S. dorsalis is in Madang Province, PNG, ca. 4.2280°S, 144.9333°E (see Kaiser et al. 2018a), ca. 1400 km by air from the type locality of S. ayamaru .

Stegonotus florensis (n = 1) differs by scale counts of V ♂ = 230 (181), SC ♂ = 82 unpaired (105, paired), SCR ♂ = 0.26 (0.37), D = 21-21-19 (17-17-15), SL = 8 or 9 (7), IL = 10 (8), and IL G = 5 (4). Additional differences include (1) the rostral of S. florensis is clearly visible on the dorsal surface of the head, where it forms a shallow V when viewed from above (gull wing +); (2) the rostral intrudes upon the internasal space, shortening the internasal suture (does not extend into internasal space, internasal suture not impacted); (3) InS = ½ PfS (InS = ¾ PfS); (4) AE lies at the same level as the anterior end of the frontal (AE lies behind anterior edge of the frontal); (5) the lateral ray of AP / is directed posterolaterally (laterally); (6) FL is slightly shorter than ParS (FL = ParS); (7) PF / <90° (¿ 90°); and (8) a distinctive color pattern is present (no distinctive color pattern). The closest known locality for S. florensis is on Flores Island, East Nusa Tenggara Province, Indonesia, ca. 1400 km by air from the type locality of S. ayamaru .

Stegonotus guentheri (n = 29) differs by scale counts of V ♂ = 185–198 (181), SC ♂ = 64–80 (105), SCR ♂ = 0.25–0.29 (0.37), D = 15-15-13 (17-17-15), SL E 4+5, or rarely 3+4 (3+4+5), SL = 8, or rarely 7 (7), IL = 9, or rarely 8 or 10 (8), and IL G = 5 (4). Additional differences include (1) InS = ½ PfS (InS = ¾ PfS); and (2) FL is slightly shorter than ParS (FL = ParS). The closest known locality for S. guentheri is on Fergusson Island, Milne Bay Province, PNG, ca. 2100 km by air from the type locality of S. ayamaru .

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Stegonotus heterurus (n = 13) differs by scale counts of V ♂ = 179–198 (181), SC ♂ = 76–88 unpaired (105 paired), SCR ♂ = 0.29–0.32 (0.37), and SL E = 3+4 (3+4+5). Additional differences include (1) the rostral of S. heterurus is generally clearly visible on the dorsal surface of the head, where it forms a shallow V when viewed from above (gull wing +); (2) the rostral intrudes upon the internasal space, shortening the internasal suture (does not extend into internasal space, internasal suture not impacted); (3) InS = ½ –½ PfS (InS = ¾ PfS); (4) AE lies at the same level as the anterior end of the frontal (AE lies behind anterior edge of the frontal); (5) the lateral ray of AP / is directed posterolaterally (laterally); (6) FL = % ParS (FL = ParS); and (7) PF / <90° (¿ 90°). The closest known locality for S. heterurus is Duke of York Island, East New Britain Province, PNG, ca. 2200 km by air from the type locality of S. ayamaru .

Stegonotus iridis (n = 6) differs by scale counts of V ♂ = 198–211 (181), SC ♂ = 78–88 (105), SCR ♂ = 0.28–0.30 (0.37), SL E 4+5 (3+4+5), SL = 8 (7), IL = 9 or 10 (8), and IL G = 5 (4). Additional differences include (1) the rostral of S. iridis is clearly visible on the dorsal surface of the head, where it forms a deep V when viewed from above (gull wing +); (2) the rostral intrudes upon the internasal space, shortening the internasal suture (does not extend into internasal space, internasal suture not impacted); (3) InS = ½ PfS (InS = ¾ PfS); (4) AE lies at the same level as the anterior end of the frontal (AE lies behind anterior edge of the frontal); (5) FL = % ParS (FL = ParS); and (6) a distinctive color pattern is present (no distinctive color pattern). The closest known locality for S. iridis is on Salawati Island, Raja Ampat Archipelago, West Papua Province, Indonesia, ca. 200 km by air from the type locality of S. ayamaru .

Stegonotus keyensis (n = 4) differs by scale counts of V ♂ = 200–207 (181), SC ♂ = 70–80 (105), SCR ♂ = 0.26–0.28 (0.37), SL E = 4+5 (3+4+5), SL = 8, or rarely 9 (7), IL = 8, 9, or rarely 10 (8), and IL G = 5 (4). Additional differences include (1) the rostral of S. keyensis is barely visible on the dorsal surface of the head, where it forms a gull wing when viewed from above (gull wing +); (2) InS = ¼ PfS (InS = ¾ PfS); (3) AE lies at the same level as the anterior end of the frontal (AE lies behind anterior edge of the frontal); (4) FL = ¼ ParS (FL = ParS); (5) two temporals contact the parietals (3); and (6) five (rarely 3) neck scales contact the parietals (3). The closest known locality for S. keyensis is in the Kei Islands, Maluku Province, Indonesia, ca. 400 km by air from the type locality of S. ayamaru .

Stegonotus lividus (n = 2, female specimens) differs by scale counts of V ♀ = 197–199 (V ♂ = 181), SC ♀ = 67–68 (SC ♂ = 105), SCR ♀ = 0.25 (SCR ♂ = 0.37), and SL E = 3+4 (3+4+5). Additional differences include (1) InS = ½ PfS (InS = ¾ PfS); (2) AE lies at the same level as the anterior end of the frontal (AE lies behind anterior edge of the frontal); (3) PF / <90° (¿ 90°); and (4) two or four neck scales contact the parietals (3). The closest known locality for S. lividus is on Semau Island, East Nusa Tenggara Province, Indonesia, ca. 1350 km by air from the type locality of S. ayamaru .

Stegonotus melanolabiatus (n = 5) differs by scale counts of V ♂ = 190–201 (181), SC ♂ = 93–100 (105), SCR ♂ = 0.32–0.34 (0.37), SL E = 3+4 (3+4+5), and IL G = 5 (4) Additional differences include (1) the rostral of S. melanolabiatus is barely visible on the dorsal surface of the head, where it forms a gull wing when viewed from above (gull wing +); (2) InS = ½ PfS (InS = ¾ PfS); (3) AE lies at the same level as the anterior end of the frontal (AE lies behind anterior edge of the frontal); (4) the lateral ray of AP / is directed posterolaterally (laterally); and (5) FL = ¼ ParS (FL = ParS). The closest known locality for S. melanolabiatus is at Bobole, Hela Province, PNG ( Ruane et al. 2017), ca. 1300 km by air from the type locality of S. ayamaru .

Stegonotus modestus (n = 14) differs by scale counts of V ♂ = 195–206 (181), SC ♂ = 78–94 (105), SCR ♂ = 0.28–0.31 (0.37), and SL E = 3+4, rarely 4+5 (3+4+5). Additional differences include (1) InS = ½ PfS (InS = ¾ PfS); (2) AE lies at the same level as the anterior end of the frontal (AE lies behind anterior edge of the frontal); (3) the lateral ray of AP / is directed posterolaterally (laterally); (4) FL is slightly shorter than ParS (FL = ParS); and (5) almost all known specimens of S. modestus have a distinctive, incomplete, light-colored band that marks the end of the head (no neck band). The closest known locality for S. modestus is on Seram Island, Maluku Province, Indonesia, ca. 250 km by air from the type locality of S. ayamaru .

Stegonotus muelleri (n = 18) is from the south-central Philippine Islands and differs by scale counts of V ♂ = 226–241 (181), D = 19-17-15 (17-17-15), SC ♂ = 85–108, SCR ♂ = 0.26–0.31 (0.37), SL E = 4+5 (3+4+5), SL = 8, or rarely 9 (7), and IL = 10, or rarely 9 (8). Additional differences include (1) InS = ½ PfS (InS = ¾ PfS); (2) the lateral ray of AP / is directed posterolaterally (laterally); and (3) FL = % ParS (FL = ParS). The closest known locality for S. muelleri is on the Philippine island of Mindanao, ca. 1200 km by air from the type locality of S. ayamaru .

Stegonotus parvus (n = 1; numeric data are from the original species description 7, specimen destroyed) differs by scale counts of V ♂ = 177 (181), SC ♂ = 100 (105), and SL E = 3+4 (3+4+5). Additional differences include (1) the rostral of S. parvus is not visible on the dorsal surface of the head (gull wing +); (2) InS = ½ PfS (InS = ¾ PfS); (3) the lateral ray of AP / is directed posterolaterally (laterally); (4) FL = % ParS (FL = ParS); (5) PF / <90° (¿ 90°); and (6) four neck scales contact the parietals (3). The closest known locality for S. parvus is on Yapen Island, Papua Province, Indonesia, ca. 400 km by air from the type locality of S. ayamaru .

Stegonotus poechi (n = 1, a female specimen) differs by scale counts of V ♀ = 200 (181), D = 19-19-17 (17-17- 15), SL E = 4+5+6 (3+4+5), SL = 9 (7), and IL = 10 (8). Additional differences include (1) the rostral of S. poechi is clearly visible on the dorsal surface of the head, where it forms a U ( Fig. 3F ) when viewed from above (gull wing +); (2) the rostral intrudes upon the internasal space, somewhat shortening the internasal suture (does not extend into internasal space, internasal suture not impacted); (3) InS = ½ PfS (InS = ¾ PfS); (4) the lateral ray of AP / directed posterolaterally (laterally); and (5) PF / <90° (¿ 90). The closest known locality for S. poechi is in Madang Province, PNG, ca. 4.2280°S, 144.9333°E (see Kaiser et al. 2018a), ca. 1400 km by air from the type locality of S. ayamaru .

Stegonotus reticulatus (n = 82) differs in counts of V ♂ = 188–230 (181), SC ♂ = 71–92 (105), SCR ♂ = 0.26–0.33 (0.37), SL E = 4+5, rarely 3+4 (3+4+5), SL = 8 or 9, or rarely 7 (7), and IL = 9 or 10 (8). Additional differences include (1) InS = ½ PfS (InS = ¾ PfS); (2) AE lies at the same level as the anterior end of the frontal (AE lies behind anterior edge of the frontal); (3) FL is slightly shorter than ParS (FL = ParS); (4) two temporals contact the parietals (3); and (5) there is a very prominent color pattern in S. reticulatus , where each dorsal scale has dark posterior edging to produce a reticulated pattern (no distinctive color pattern). The closest known locality for S. reticulatus is along the Ok Ma Road in Western Province, PNG, ca. 1100 km by air from the type locality of S. ayamaru . We have also examined a specimen (USNM 119549) from the Padaido Islands, Papua Province, Indonesia (ca. 500 km by air from the type locality of S. ayamaru ), whose color pattern approximates that of S. reticulatus . With all other specimens of S. reticulatus occurring in localities south of New Guinea’s mountainous spine or along its southern versant, we set this specimen aside for further examination as S. cf. reticulatus .

Stegonotus sutteri (n = 2) differs in counts of V ♂ = 210–230 (181), D = 21-21-19 (17-17-15), SC ♂ = 83 unpaired (105, paired), SCR ♂ = 0.27 (0.37), SL = 9 (7), and IL = 9 or 10 (8). Additional differences include (1) the rostral of S. sutteri is barely visible on the dorsal surface of the head, where it forms a gull wing when viewed from above (gull wing +); (2) InS = ½ PfS (InS = ¾ PfS); (3) the lateral ray of AP / is directed posterolaterally (laterally); and (4) FL = % ParS (FL = ParS). The closest known locality for S. sutteri is on Sumba Island, ca. 1600 km by air from the type locality of S. ayamaru .

Description of the holotype – metrics (in mm) and pholidosis. An adult male; length 493 SVL + 217 TL = 710 TTL, TL 30.5% of TTL; head distinct from body; snout rounded in dorsal view, angled in lateral view, mouth subterminal. Rostral barely extending onto the dorsal part of the head and not intruding into the internasal area (character state: gull wing +; Figs. 3C , 5A, B ). Internasals nearly as long as wide, with InS = ¾ PfS. Prefrontals slightly wider than long and about 1.5 times the area of the internasals; PfS = ¼ ESL. Frontal pentagonal with wellformed corners and a slightly convex anterior suture; AE lies behind anterior edge of the frontal; FL = ParS ( Fig. 5A ); PF / = 98°. Supraoculars relatively large and triangular, projecting beyond anterior and posterior extent of the eye. Parietals angular, about twice as long as wide; AP / = 135°, with lateral ray directed laterally. Three temporals touching the parietals, the lengths of the two anterior temporals combined equal the length of the posterior temporal; temporal formula 2+2+3; three neck scales in contact with the parietals.

Nasal slightly larger than loreal, half as tall as wide, its widest point on the posterior border; naris one-third the length and half the height of the nasal; loreal two-thirds as long as wide; a single preocular of similar dimensions as the loreal, curving around the anterior border of the eye; two postoculars, the lower scale the size of the upper. Seven supralabials; SL3–5 touching the eye, SL5 projecting forward from behind the eye to form a narrow contact zone with the eye ( Fig. 5B , B’); relative areas of supralabials 5> 6> 4> 3 = 7> 2 = 1, SL4 about half the size of

7. Based on the high value of SCR (0.36, the second-highest in the genus), Kaiser et al. (2018a) determined that the syntype used for the numeric description by Meyer (1874) was a male. The neotype of S. parvus (RMNH 46844) proposed by Kaiser et al. (2018a) is female, so it does not allow for direct numeric comparisons to the male holotype of S. ayamaru . We used the neotype to determine characters other than those that might be sexually dimorphic.

SL5 ( Fig. 6 A’). Eye length 75% of eye–naris distance; pupil round; internarial distance 62% of interorbital distance. Eight infralabials; IL1–4 contacting anterior genials, with two-thirds of the medial border of IL 4 in contact with the anterior genial; four scales separate the posterior genial and the anteriormost gastrostege; length of mental groove one-third of ventral head length ( Fig. 5 D’). Dorsals in 17-17-15 rows, 181 ventrals, cloacal plate entire, 105 paired subcaudals, SCR ♂ = 0.37.

Description of the holotype – coloration in preservative (65 years after collection). Dorsum Maroon (29), possibly with a more deeply colored middorsal area, color fading laterally to Hazel (26). Head Maroon with Hazel areas on the frontal and parietals and extending over most of the rostral and all preoculars, postoculars, and temporals ( Fig. 5A ). Much of the supralabials colored Hazel ( Fig. 5B, C ), with posterior edges on SL2, 3, and 5 of a lighter color, Light Buff (2). Nasals Light Buff with their anterior third as well as a small area on the posterior border of the nostril colored Hazel. Infralabials Hazel with posterior edges of IL2–6 and all of IL7 Light Buff ( Fig. 5D ). Venter colored Light Buff, well demarcated in color from the lateral areas. The ventral area of the tail is dark because the anteromedial parts of the subcaudals are darkly colored in Hazel ( Fig. 4C ).

Natural history. Members of the genus Stegonotus are widely distributed geographically in the Indo- Australian archipelago and occupy habitats ranging from swamps and lowland tropical forests (e.g., S. modestus ) to montane dipterocarp forests (e.g., S. borneensis in Sabah). They are able to adapt to disturbed areas, such as gardens and coconut plantations (e.g., Karin et al. 2018: S. keyensis ), and they may display arboreality in epiphytes or even in honeycombed ant plants (Myrmecodia) ( O’Shea 1996; Greer 1997). These snakes are known to consume a variety of small vertebrates, particularly small lizards and reptile eggs ( Brown et al. 2002; Trembath et al. 2009). Given that there is only a single specimen, there is no specific information about this species. It was collected in moist lowland rainforest.

Etymology. The species name ayamaru is a noun in apposition. It references the Ayamaru people of Maybrat Regency, West Papua, Indonesian New Guinea and their homonymic language. We select this name not only to indicate the type locality but also to highlight the Ayamaru people’s struggle to protect their forests and waterways from exploitation. The Ayamaru Lakes are a case in point. One of the several endemic fishes in the lake ( Melanotaenia boesemani ) has been over-collected and is currently listed as Endangered on the IUCN Red List ( Allen 1996). West Papua was recently declared a conservation province ( Anonymous 2018), and it is hoped that this will have a long-term, positive effect on regional development.

Figures

FIGURE 1. Map of the Banda Sea (dark blue area in the center of the map, showing significant deep-water sea floor topography), adjacent bodies of water, and surrounding landmasses in the eastern part of Wallacea. The yellow buttons indicate type localities for species of the genus Stegonotus, with yellow lines encircling the estimated distributions of these taxa. Included are S. sutteri on Sumba (1); S. florensis on Flores (2); S. lividus on Semau (3); S. modestus on Ambon (4); S. batjanensis on Bacan (5); S. iridis on Batanta (6); S. derooijae on Salawati (7); S. keyensis in the Kei Islands (8); S. aruensis in the Aru Islands (9); S. cucullatus near Manokwari, West Papua (10); Lycodon magnus, a synonym of S. cucullatus, on Supiori (11); and S. parvus on Yapen (12). The insert (A) provides a close-up of the area in the south-central Bird’s Head Peninsula, West Papua Province, Indonesian New Guinea, near the type locality of S. ayamaru sp. nov. Buttons indicate the type locality (red), and two locations of note (white), including the town of Teminabuan (1), Lake Ayamaru (2), and Kamro Village (3).

FIGURE 2. Characters used to assess the head scale pattern for species in the genus Stegonotus. (A) Positions of head scales, sutures, and measurements, including internasals (IN) and the internasal suture (InS), prefrontals (PF) and the prefrontal suture (PfS), the frontal (F) with its length (FL) and width (FW), the supraoculars (SO), and the parietals (P) with the parietal suture (ParS). (B) Positions of the posterior frontal angle (PF /), the anterior parietal angle (AP /) and its lateral ray (yellow line), and the anterior eye line (AE; white line). The underlying specimen is the holotype of Stegonotus ayamaru sp. nov. (RMNH.RENA 31199).

FIGURE 3. Six conditions of the rostral scale when viewed from above in species of Stegonotus. (A) Not visible. The body of the scale is not visible, and only its tip may show. Pictured is the holotype of S. aruensis (MSNG 30186). (B) Gull wing. The rostral scale is barely visible, and its suture with the internasals forms slightly curved edges that come to a medial point. Pictured is the holotype of S. sutteri (NMBA 14872). (C) Gull wing +. The rostral scale is more visible than in (B). Pictured is the holotype of S. ayamaru sp. nov. (RMNH.RENA 31199). (D) Shallow V. The suture between rostral and internasals forms an obtuse angle (>> 90°) with straight or nearly straight rays (i.e., not curved into a gull-wing shape). Pictured is the holotype of S. florensis (ZMA 11080). (E) Deep V. The point of the rostral comes up far onto the dorsal surface of the head and lies between the nostrils. It forms an angle close to 90°. Pictured is a specimen of S. cucullatus (RMNH.RENA 47736). (F) U-shaped. The rostral does not have a point on the dorsal surface of the head but the edge of the suture is rounded. Pictured is the holotype of S. poechi (NMW 23406).

FIGURE 4. Holotype of Stegonotus ayamaru sp. nov. (RMNH.RENA 31199) in (A) dorsal and (B) ventral views. (C) Enlargement of the subcaudal region to show the extent of dark patterning.

FIGURE 5. Head of Stegonotus ayamaru sp. nov. (holotype, RMNH 31199) in both photographs (left column) and line drawings (right column). Shown are dorsal (A, A’), right lateral (B, B’), left lateral (C, C’), and ventral (D, D’) views. Scale abbreviations are as in Fig. 2, with the addition of rostral (R), nasals (N), loreals (L), preoculars (PR), postoculars (PO), anterior temporals (AT), posterior temporals (PT), supralabials (SL), infralabials (IL), mental (M), anterior genials (AG), posterior genials (PG), and ventrals (V).

FIGURE 6 (A–D). Right lateral views of four species of Stegonotus as photographs (upper images) and line drawings (lower images), illustrating the position of supralabial scales (SL) and the eye. (A, A’) S. ayamaru sp. nov. (holotype, RMNH.RENA 31199), showing SL = 7 and a 3+4+5 pattern with SL5 projecting forward from a position behind the eye to form a narrow contact zone with the eye. (B, B’) S. batjanensis (holotype, BMNH 1946.1.11.36), showing SL = 8 and a 3+4+5 pattern with SL3 projection backwards from a position in front of the eye to form a narrow contact zone with the eye. (C, C’) S. florensis (holotype, ZMA 11080), showing SL = 9 and a 3+4+5 pattern similar to S. batjanensis. In this specimen, SL5 displays a developmental aberration on both sides of the head by being divided into two scales (as indicated by red stippling). (D, D’) S. sutteri (holotype, NMBA 14872), showing SL = 9 and a 3+4+5 pattern similar to S. batjanensis and S. florensis.

FIGURE 7 (A–D). Dorsal head views of four species of Stegonotus, shown to illustrate the position of measurements, sutures, and angles as explained in Fig. 2. The placement of AE in A’–H’ documents the position of the eyes relative to the anterior border of the frontal. The yellow line in A’–H’ shows the lateral ray of AP /. (A, A’) S. ayamaru sp. nov. (holotype, RMNH.RENA 31199). (B, B’) S. batjanensis (holotype, BMNH 1946.1.11.36). (C, C’) S. florensis (holotype, ZMA 11080). (D, D’) S. sutteri (holotype, NMBA 14872), showing a forward extension of the anterior border of the frontal.