Stegonotus nancuro, Kaiser & Kaiser & Mecke & O’Shea, 2021

Kaiser, Hinrich, Kaiser, Christine M., Mecke, Sven & O’Shea, Mark, 2021, A new species of Stegonotus (Serpentes: Colubridae) from the remnant coastal forests of southern Timor-Leste, Zootaxa 5027 (4), pp. 489-514 : 495-507

Stegonotus nancuro sp. nov.

Timor Groundsnake (EN), Ular Tanah Timor (ID), Samea Metan 7 (TET), Sohai Meta (Mambai), Timor-Schiefernatter (DE)

( Figs. 3–9 , Table 1)

Holotype ( Figs. 3 , 4 , 9 ). USNM 580549 is an adult female from a coastal strip of land locally known as Nancuro, ca. 6.5 km south of Natarbora Village, Barique Suco , Manatuto Municipality (9.0345°S, 126.0769°E, elevation 18 m; Fig. 1 ). The snake was spotted moving on the ground in moist coastal forest by Caitlin Sanchez , chased into a rotting tree by Sven Mecke and Hinrich Kaiser , and retrieved from the soft mulch inside the tree by Mark O’Shea on 3 July 2012.

Paratypes ( Figs. 5–9 ). USNM 579383 is an adult male, collected on 22 January 2011 . MCZ R-192767 is an adult male, collected on 7 August 2014 . USNM 580550 is a juvenile male, collected on 3 July 2012 . All paratypes were collected by Hinrich Kaiser and Mark O’Shea at the same locality as the holotype .

Referred specimen. One specimen ( USNM 579384 ), presumably an adult male based on its size and scale characteristics, was collected on 12 November 2010 near Betano , Manufahi Municipality, Timor-Leste (9.1875°S, 125.7016°E, elevation 20 m) by Luis Lemos de Araujo. The specimen could not be sexed directly due to its state of preservation (dried out, hardened tail) .

Diagnosis. In the following character list, readers may wish to refer to the illustrations of different head views in photographs and line drawings ( Figs. 2 , 3 ) for a better understanding of our descriptions. Stegonotus nancuro (maximum known SVL = 684 mm) is a medium-sized member of the genus Stegonotus with a relatively short tail (TL = 0.20% of TTL; mean SCR ♂ = 0.27 ± 0.004, SCR ♀ = 0.23). It can be distinguished from other species of Stegonotus by a combination of the following characters: (1) rostral extending onto the dorsal part of the head but not intruding into the internasal area, resulting in a long internasal suture (character state: gull wing +); (2) area of prefrontals 2.5 times that of the internasals, internasal suture ⅓–½ times the length of the prefrontal suture (mean snout-scale ratio = 0.47 ± 0.08); (3) frontal pentagonal, with usually well-formed corners and a slightly convex anterior edge; (4) AE line behind (60%) or at the same level (40%) of the anterior end of the frontal; (5) length of the frontal slightly shorter or equal to the parietal suture (mean frontal-parietal ratio = 0.90 ± 0.03); (6) prefrontal suture one-fifth the length of external skull length (mean head-scale ratio = 0.18 ± 0.02) (7) PF∠ <90° (mean = 79 ± 5.0°);

7 The names for this species in Tetun and Mambai, important languages of Timor-Leste, are taken from Lemos de Araujo (2010).

(8) LR AP directed laterally; (9) loreal two-thirds longer than wide (mean loreal scale ratio = 0.69 ± 0.02); (10) labial scale formula 73+4 | 94; (11) IL 4 nearly three times as large as IL 3, one-half of IL 4 in contact with the anterior genial; (12) five gulars separating the posterior genial and the anteriormost ventral ( Fig. 3D , D’); (13) 17-17-15 dorsals; 197–207 ventrals in males (mean = 203 ± 4), 206 ventrals in the single known female; 71–75 paired subcaudals in males (mean = 74 ± 2), 61 in the female; (14) cloacal plate entire; (15) color in life and in preservative is light brown to grayish brown dorsally with an immaculate cream-colored venter, but with non-uniform coloration on each individual dorsal scale and along the body (see “Coloration in life” below for details). The brown dorsal color extends onto the ventral side only on the mental scale and IL 1–3, with coloration on other infralabial scales, if present, becoming progressively diffuse posteriorly. On the head, the darkest brown color covers SL 1–2 and diminishes dorsally along the supralabial scale row.

Comparisons. The following series of comparisons includes taxa from the geographic region we consider relevant to an analysis of Wallacean island taxa. Thus, we omit extralimital species of Stegonotus from New Guinea and its close offshore islands, as well as from Borneo and the Philippines. Throughout this section, characteristics of S. nancuro are listed in parentheses. The number of specimens used to determine ranges of continuous characters follows the name of each species. When the species is known not to be sexually dimorphic (see Kaiser et al. 2018a), data for the sexes are combined and no subscript is used. A listing of characteristics most relevant for interspecies comparisons, including means and standard deviations, is provided in Table 1.

Stegonotus aruensis (Doria, 1874) (n = 1♀ 2♂) has a lower ventral scale count in females of V ♀ = 191 (206) and a significantly lower (t = 3.96, p <0.01) ventral scale count in males of V ♂ = 179–190 (197–207). The subcaudal count of SC ♀ = 78 (61) in females is higher, and this difference is statistically significant (t = 7.26, p <0.001) in males, where SC ♂ = 102–103 (71–75). Values for SCR ♂ = 0.35–0.36 (0.26–0.27) and SCR ♀ = 0.29 (0.23) are also higher in S. aruensis . Additional differences include (1) the rostral of S. aruensis is not visible on the dorsal surface of the head (gull wing +); (2) SSR = ¾ (⅓–½); (3) PF∠ ≥ 90° (<90°); and (4) four gulars (five) separate the poste- rior genials from the first ventral. The closest known locality for S. aruensis is in the Aru Islands, Maluku Province, Indonesia, ca. 800 km by air from the type locality of S. nancuro .

Stegonotus australis (Günther, 1872) (n = 11♀, 22♂) males have ventral scale counts that overlap those of S. nancuro at V ♂ = 191–221 (197–207), but the statistical distribution of these counts is significantly different (t = 2.23, p <0.05). In females, V ♀ = 197–215, which overlaps with the value for the single S. nancuro female (206). Subcaudal numbers in female S. australis are much higher at SC ♀ = 77–87 (61) and in males they are significantly different (t = –3.45, p <0.05), with SC ♂ = 77–93 (71–75). In S. australis , the labial scale formula is 84+5 | 105 or less frequently 94+5 | 95 (73+4 | 94). In addition, (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 internasal space, internasal suture not impacted); (3) LR AP directed posterolaterally (laterally); (4) FPR = 0.87 ± 0.05 (0.90 ± 0.06); (5) PF∠> 90° (≤ 90°); and (6) a uniform dark brown or black ground color (color shifting from dark brown to lighter brown laterally and on each scale). The closest known locality for S. australis is near Darwin in the Northern Territory, Australia, ca. 620 km by air from the type locality of S. nancuro .

Stegonotus batjanensis (Günther, 1865) (n = 9♀, 15♂) males have significantly (t = –10.82, p <0.00001) more ventrals with V ♂ = 221–236 (197–207) and significantly (t = 6.68, p <0.00001) more subcaudals with SC ♂ = 78–89 (71–75), as well as a higher number of subcaudals in females of SC ♀ = 80–90 (61), with no overlap in either set of scales. The ventral count in females of S. batjanensis at V ♀ = 203–216, overlaps with the count in the S. nancuro female (206). In S. batjanensis , the labial scale formula is 83+4+5 | 105 and rarely 73+4+5 | 95 (73+4 | 94). In addition, (1) 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 +); (2) the rostral intrudes upon the internasal space, shortening the internasal suture (does not extend into internasal space, internasal suture not impacted); (3) SSR = ¼ (⅓–½); (4) AE lies in front of the anterior edge of the frontal (AE lies behind or at the same level as the anterior edge of the frontal); (5) PF∠ ≥ 90° (<90°); (6) four gulars separate the posterior genials from the first ventral (five); and (7) a distinctive pattern of contrasting pale markings is present on the anterior part of the body, where the pale color forms laterodorsal blotches on the dark brown or black ground color (the coloration is nearly uniform, no contrasting pale markings but the color shifts from dark brown to lighter brown laterally and on each scale). The closest known locality for S. batjanensis is on Obi Island, North Maluku Province, Indonesia, ca. 830 km by air from the type locality of S. nancuro .

Stegonotus florensis (De Rooij, 1917) (n = 1♀, 1♂) has 21-21-19 dorsals (17-17-15), higher ventral scale counts of V ♀ = 217 (206) and V ♂ = 230 (197–207), SC ♀ = 65, unpaired (61, paired) and SC ♂ = 82, unpaired (71–75, paired), and a labial scale formula of 83+4+5 | 105 or 93+4+5 | 105 (73+4 | 94). 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) AE lies at the same level as the anterior end of the frontal ( AE lies behind or at the same level as the anterior edge of the frontal); (4) LR AP directed posterolaterally (laterally); and (5) a distinctive color pattern that includes a yellowish head, spotted with brown, and with a brown lateral streak from the naris through the orbit to the angle of the jaw (head coloration nearly uniform). The closest known locality for S. florensis is on Flores Island, East Nusa Tenggara Province, Indonesia, ca. 350 km by air from the type locality of S. nancuro .

Stegonotus keyensis (Doria, 1874) (n = 4♀, 4♂) has a lower ventral scale count of V ♀ = 188–200 (206). Values for V ♂ = 200–207 (197–207), SC ♀ = 59–68 (61), and SC ♂ = 70–80 (71–75) all overlap. This species differs by a labial scale formula of 94+5 | 105 and rarely 83+4 | 95 (73+4 | 94). Additional differences include (1) SSR = ⅕ (⅓–½); (2) PF∠ ≥ 90° (<90°); (3) FPR = 0.77 ± 0.05 (0.90 ± 0.06); and (4) four gulars separate the posterior genials from the first ventral (five). The closest known locality for S. keyensis is in the Kei Islands, Maluku Province, Indonesia, ca. 800 km by air from the type locality of S. nancuro .

Stegonotus lividus (Duméril et al., 1854) (n = 2♀, 1♂) has a lower ventral scale count in females of V ♀ = 197–199 (206) and a higher subcaudal count of SC ♀ = 67–68 (61). Even though the value of V ♂ = 196 (197–207) does not overlap, it is too small a difference to be considered diagnostic given the small sample size. This species also has a slightly larger SCR ♀ of 0.25 (0.23). Additional differences between the species include (1) nares distinctly smaller than nasal width, medially positioned in the nasals, directed dorsally (nearly as wide as nasal, positioned anteromedially, directed laterally); (2) mean PF∠ 76° (mean PF∠ 85 ± 2.2°); FPR = 1.03 ± 0.11 (0.90 ± 0.06); (3) posterior genial ⅕ longer than anterior genial (same length); (4) IL 4 twice the size of IL 3 ( IL 4 nearly three times the size of IL 3 ); (5) six gulars separate the posterior genials from the first ventral (five); and (6) dorsal coloration lead-gray with a violet-blue sheen, ventral coloration yellowish (light brown to grayish brown dorsally with an immaculate cream-colored venter). The closest known locality for S. lividus is on Semau Island, East Nusa Tenggara Province, Indonesia, ca. 310 km by air from the type locality of S. nancuro . Details of the single male paralectotype ( MNHN 3414 ) and the taxonomy of the species were recently provided by Kaiser et al. (2021) .

Stegonotus modestus (Schlegel, 1837) (n = 4♀, 14♂) differs significantly (t = 4.47, p <0.0005 from S. nancuro by a scale count of SC ♂ = 78–94 (71–75) and by a ventral scale count in females of V ♀ = 190–198 (206). In addition, SCR ♂ = 0.28–0.31 (0.26–0.27) is also significantly different (t = 4.57, p <0.0005) and does not overlap. Other differences include (1) LR AP directed posterolaterally (laterally); (2) PF∠ ≥ 90° (<90°); (3) three or four gulars separate the posterior genials from the first ventral (five); and (4) almost all known specimens of S. modestus have a distinctive, incomplete, light-colored band that marks the nape of the neck (no neck band). The closest known locality for S. modestus is on Buru Island, Maluku Province, Indonesia, ca. 580 km by air from the type locality of S. nancuro .

Stegonotus sutteri Forcart, 1953 (n = 1♀, 2♂) differs significantly (t = 2.51, p <0.05) in non-overlapping counts of V ♂ = 210–230 (197–207), as well as in the number of dorsals at 21-21-19 (17-17-15), SC ♀ = 76, unpaired (61, paired) and SC ♂ = 83, unpaired (71–75, paired), labial scale formula 93+4+5 | 105 and rarely 93+4+5 | 95 (73+4 | 94). Additional differences include (1) the rostral in 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) posterolaterally directed LR AP (laterally); (3) FPR = 0.84 ± 0.01 (FPR = 0.90 ± 0.06); and (4) a distinctive dark line running from the nostril to the neck (no such line). The closest known locality for S. sutteri is on Sumba Island, ca. 580 km by air from the type locality of S. nancuro .

Description of the holotype (USNM 580549)—metrics (in mm) and pholidosis. An adult female with length measurements of 618 SVL + 151 TL = 769 TTL, TL = 20% of TTL; head broad and 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 +; Fig. 3A, B , B’). Internasals as long as wide, with SSR = 0.46. Prefrontals slightly longer than wide, their area about 2.5 times that of the internasals; HSR = 0.23. Frontal pentagonal with slightly rounded to well-formed corners and a convex anterior suture; AE lies behind the anterior edge of the frontal; FPR = 0.91, indicating that the frontal length is nearly equal to the length of the parietal suture ( Fig. 3 A’); PF∠ = 88°. Supraoculars are triangular and large, projecting beyond both the anterior and posterior border of the eye. Parietals angular and twice as long as wide; LR AP directed laterally.

Nasals large, 1.5 times longer than the loreal, half as high as wide, with their widest point on their posterior border; naris one-third the length and two-fifths the height of the nasal; loreal two-thirds as long as wide; two preoculars of similar size, about half the length of the loreal; two postoculars, the lower slightly smaller than the upper. Seven supralabials; SL 3+4 touching the eye, relative areas of supralabials 5> 6> 4> 3> 7> 2> 1, SL 4 about half the size of SL 5 ( Fig. 3 B’). Eye length 70% of eye–naris distance; pupil oval; internarial distance 65% of interorbital distance. Nine infralabials, IL 1–4 touching the anterior genials, IL 4 nearly three times as large as IL 3, with one-half of the medial border of IL 4 touching the anterior genial ( Fig. 3 D’); five gulars between the posterior genials and anteriormost ventral; length of mental groove one-quarter of VHL ( Fig. 3 D’). Dorsals in 17-17-15 rows, 206 ventrals, cloacal plate entire, 61 paired subcaudals, SCR ♀ = 0.23.

Coloration in life. Stegonotus nancuro has an unusual color pattern that shows a significant amount of detail in the interplay between warm brown and cream tones, both on each scale as well as in a dorsal–ventral direction. Along the body, the coloration is darkest in the area along the vertebral scale row. The vertebral scale row and one scale row on either side of it comprise scales, whose coloration is nearly uniform and on which the gradation from darker brown to lighter brown is hardly noticeable. In a lateral direction along the sides of the body (i.e., from the vertebral row to the lowest dorsal row), the gradient of color change from brown to cream becomes more and more pronounced, and the lowest lateral scale row is colored light brown to cream. Only the posterior part of the tail is uniformly brown above.

Each of the largely rhomboid body scales has its own specific patterning. As part of this pattern, the anteriormost area of a scale (the “nucleus” from which the pattern extends) is characterized by the darkest brown coloration. From this nucleus, the color gradually diminishes in intensity in an outward and posteriad direction (e.g., Fig. 9D, F ). Thus, the posterior edges of most body scales tend to be almost completely without pigmentation and reflect the ventral coloration. This pattern also shifts in a dorsal-to-lateral direction, with the brown becoming lighter and the dorsally deep brown color of the nucleus becoming more diffuse.

Variation. There are only few differences between the holotype (USNM 580549) and the three paratypes (USNM 579383, 580550, MCZ R-192767; Appendix 2). Most notably, there is a strong indication for the presence of sexual dimorphism in subcaudal scale counts. Whereas the female holotype has 61 subcaudals, males have a nonoverlapping range of 71–74 subcaudals, with the female value well outside the range of two standard deviations. Even though the sample size for the species is small (n = 5) we are confident based on our experience with other species of Stegonotus that this difference in count and the concomitant values for the subcaudal ratio (0.26–0.27 in males, 0.23 in the female) constitutes a sexually dimorphic characteristic. Paratype MCZ R-192767 has the lowest ventral count of the type series (197) compared to 203 and 204 in the two other paratypes. The AE line lies behind the anterior edge of the frontal, except in USNM 579383, where it lies at the same level. Paratype USNM 579383 has the greatest snout-scale ratio (0.46) compared to the other two paratypes (MCZ R-192767, USNM 580550) and the holotype (0.40, 0.45, and 0.43, respectively), with none reaching 0.50. The ratio of frontal width to frontal length is highest in the holotype at 82%, compared to the three paratypes at 72–74%. One specimen (USNM 579384), whose sex could not be determined directly due to a dried out and hardened tail, has similar ventral and subcaudal counts as the other, male specimens, and we therefore consider it most likely that this specimen is also a male. Nevertheless, since its sex is still undetermined, this specimen was omitted from the analysis of characters that might be sexually dimorphic. The juvenile paratype, USNM 580550, has larger eyes relative to overall head size and a slightly darker, more grayish brown coloration than the other specimens. This specimen also has an aberrant supralabial count of 8L 9R, which is due to the apparent fragmentation of an anterior supralabial (SL 2 or SL 3) on both sides and of SL 5 on its right side. This alters the value of SL E to 4+5. Fragmentation of these scales also occasionally occurs in some other Stegonotus species (e.g., S. guentheri , S. modestus , S. reticulatus ; Kaiser et al. 2018a).

......continued on the next page Habitat. The type locality of Stegonotus nancuro ( Fig. 10 ) consists primarily of lowland tropical forest on sandy soils, considered a moist deciduous forest by Monk et al. (1997) and a lowland alluvial forest by Trainor et al. (2007). It is one of the last forested coastal lowland areas on Timor, and this forest and its surroundings (locally known as “Sungai Clere”) was identified as an Important Bird and Biodiversity Area according to the criteria developed by BirdLife International ( Monk et al. 1997; Trainor et al. 2007). Even though the surroundings are relatively dry during the months of July and August, when most of the specimens were collected, the forest itself is quite humid throughout the year, and during rainy periods many areas of standing water and muddy substrate form. The forested area adjacent to the beach (“beach forest” according to Trainor et al. 2007; Fig. 10B ) is generally more scrubby and drier than areas only 50–100 m further inland ( Fig. 10A, C ), where some portions of the ground become inundated during heavy rains. Further inland, the forest shifts dramatically to a wide stretch of grassland, with grasses reaching heights of well over 2 m ( Fig. 10D ). In the Betano area, where USNM 579384 was collected, the habitat is remarkably similar and localized flooding, due to rain or high water levels of the Rio Caraulun, may occur.

Natural history. Very little is known about the natural history of this species. Of the four live specimens encountered at the type locality, the three adult individuals were active during the daytime and seen traveling across the forest floor. Two were captured with relative ease and calmed quickly after attempting defensive strikes. A third (the holotype) sought shelter deep inside a rotting log, from which it was extracted by hand from within the sawdust-like interior. A juvenile specimen (paratype USNM 580550) was encountered while removing bark from a standing, rotting tree, as it sheltered underneath the bark in a tight, circular coil. We also recovered two sloughed skins of this species at the type locality (USNM Field Series 255398–99), one from a height of 1.5 m above ground in a tree near the beach and the other inside a decaying tree stump. The snake found near Betano, ca. 40 km by air distance to the west of the type locality, was discovered as it rested during the day in a rotting, 6-m tall tree that remained upright on muddy soil ( Lemos de Araujo 2010). The only other snakes reported to date from the southern coastal areas include the Timor Bronzeback, Dendrelaphis inornatus timoriensis ( Smith, 1927) , the Reticulated Python, Malayopython reticulatus (Schneider, 1801) , the Lesser Sunda Racer, Coelognathus subradiatus (Schlegel, 1837) , and the Island Pitviper, Trimeresurus insularis Kramer, 1977 . The pitviper may be a potential predator for small individuals of S. nancuro , given that Reilly et al. (2016) reported that a pitviper had consumed a pipesnake ( Cylindrophis boulengeri Roux, 1911 ). Skinks, such as Carlia sp. , Eutropis multifasciata (Kuhl, 1820) , Lamprolepis smaragdina (Lesson, 1829) , Sphenomorphus melanopogon (Duméril & Bibron, 1839) , or Sphenomorphus sp. , and geckos, including Gehyra mutilata (Wiegmann, 1834) , Gekko gecko (Linnaeus, 1758) , or Hemidactylus frenatus Duméril & Bibron, 1836 , are abundant, and may represent a possible food source; we have examined other species of Stegonotus from New Guinea (e.g., AMS 148822 from Papua Province, Indonesia; AMNH 59087 from Central Province, Papua New Guinea) with skinks in their stomachs.

Etymology. The species name is a noun in apposition. We choose this name to recognize the beautiful area known locally as “Nancuro” on the southernmost tip of Manatuto Municipality, where most of the specimens were collected. Efforts to protect this area as the Nancuro Nature Reserve were initiated in 2011 by His Excellency José Ramos-Horta, then the President of Timor-Leste. We hope that the presence of a new and unique serpent in this area may provide a renewed motivation to set aside this area for the benefit of future generations. The term nancuro is a composite noun used in Tetum, the lingua franca of Timor-Leste, and signifies a place where fish are caught. Specifically, nan means meat or fish and curo is the process of catching something with a round net.

Figures

FIGURE 1. Distribution of Stegonotus species in south-central Wallacea. Islands relevant to this study occupy a geographic area that stretches from some of the northern Moluccas in the northeast to Timor and Sumba Islands in the southwest. Species distribution is color-coded and islands with confirmed species records are numbered. These include S. batjanensis (encircled in yellow), found on Morotai (1), Halmahera (2), Ternate (3), Tidore (4), Kasiruta (5), Bacan (6), and Obi (7); S. modestus (green), on Seram (8), Buru (9), and Ambon (10); S. keyensis (blue), endemic to the Kei Islands (11); S. aruensis (purple), endemic to the Aru Islands (12); S. florensis (orange), endemic to Flores Island (13); S. sutteri (brown), endemic to Sumba Island (14); and S. lividus (teal), with its type locality on Semau Island (15). In the map of Timor-Leste (inset), the two localities from where S. nancuro sp. nov. is known include the type locality (red star) and a coastal forest near Betano, Samé Municipality (red circle). The globe shows the position of the depicted region relative to Australia and mainland Asia.

FIGURE 2. Schematic dorsal head views of USNM 580549, the holotype of Stegonotus nancuro sp. nov., shown to illustrate the pattern of head scales and other important characters. Scale labels in (A) include internasals (IN), internasal suture (InS – distance between Points 1 and 2), prefrontals (PF), prefrontal suture (PfS – distance between Points 3 and 4), frontal (F), frontal length (FL – distance between Points 4 and 5), frontal width (FW), supraoculars (SO), postoculars (PO), parietals (P), external skull length (ESL – distance between Points 3 and 8), and parietal suture (ParS – distance between Points 5 and 8). The numbers 1–8 in (B) represent key reference points for measurements and angles as follows: (1) anteriormost internasal contact point; (2) posteriormost internasal contact point; (3) anteriormost prefrontal contact point; (4) posteriormost prefrontal contact point and anteriormost point on the frontal; (5) point on the frontal, where the posterior edge of the frontal meets the parietal suture; (6) the two points on either side of the head where frontal, parietal, and supraocular meet; (7) the two points on either side of the head where parietal, supraocular, and postocular meet; and (8) posteriormost parietal contact point. The posterior frontal angle (PF∠) is produced by a vertex at Point 5 with rays extending from Point 5 through Point 6 on either side of the head. The anterior parietal angle (AP∠) is produced by a vertex at Point 6 and two rays, one extending from Point 6 through Point 5 and the other from Point 6 through Point 7. The ray including Points 6 and 7 is the lateral ray, and its orientation relative to the midline of the head is of diagnostic value. The yellow line in (B) shows our method of evaluating the lateral ray, which can be oriented laterally (angle of the yellow line with the midline of the head = 90° ± 10°) or posterolaterally (the angle of the red line with the midline of the head <80°). The white anterior eye line (AE) intersects the anteriormost points of the eyes and is assessed by its position in relation to the anterior frontal suture (“behind,” “same level,” or “in front of”).

FIGURE 3. Head of USNM 580549, the holotype of Stegonotus nancuro sp. nov., displayed as 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. Scales shown in (A’) include internasals (IN), prefrontals (PF), frontal (F), supraoculars (SO), and parietals (P). Scales in (B’) include rostral (R), internasal (IN), prefrontal (PF), nasals (N), loreal (L), preoculars (PR), postoculars (PO), frontal (F), supraocular (SO), parietal (P), anterior temporals (AT), posterior temporals (PT), numbered supralabials (SL), mental (M), and numbered infralabials (IL). Scales in (D’) include rostral (R), numbered supralabials (SL), mental (M), numbered infralabials (IL), anterior genials (AG), posterior genials (PG), gulars (G) with Roman numerals, and ventrals (V).

FIGURE 4. Holotype of Stegonotus nancuro sp. nov. (USNM 580549) in (A) dorsal and (B) ventral views.

FIGURE 5. Whole body views of the paratypes of Stegonotus nancuro sp. nov., including dorsal and ventral views of USNM 579383 (A, B), MCZ R-192767 (C, D), and USNM 580550 (E, F). Images not to scale.

FIGURE 6. Dorsal head views of the paratypes of Stegonotus nancuro sp. nov., shown as both photographs and line drawings. Shown are USNM 579383 (A, A’), MCZ R-192767 (B, B’), and USNM 580550 (C, C’). The juvenile paratype (C, C’) shows noticeable differences in head proportions, with eyes larger and more protruding relative to head size than in the other specimens. Scale proportions appear almost identical to those of the adults. Images not to scale.

FIGURE 7. Ventral head views of the paratypes of Stegonotus nancuro sp. nov., shown as both photographs and line drawings. Shown are USNM 579383 (A, A’), MCZ R-192767 (B, B’), and USNM 580550 (C, C’). Images not to scale.

FIGURE 8. Lateral head views of the paratypes of Stegonotus nancuro sp. nov., shown as both photographs and line drawings in left and right aspects, in the left and right image columns, respectively. Shown are USNM 579383 (A, A’, B, B’), MCZ R- 192767 (C, C’, D, D’), and USNM 580550 (E, E’, F, F’). The juvenile paratype has a noticeably different head shape from the eyes forward, with a snout that is shorter relative to eye size than in the other specimens. Images not to scale.

FIGURE 9. Photographs of four live individuals of Stegonotus nancuro sp. nov. to show color variation. Each snake is shown in full body view (left column) with a close-up of the anterior body (right column). The unusual color scheme, in which there is a gradation of brown to cream in both individual scales as well as along the lateral side of the body, is clearly visible. Shown are the holotype, USNM 580549 (A, B), the two adult paratypes, USNM 579383 (C, D) and MCZ R-192767 (E, F), and the juvenile paratype, USNM 580550 (G, H). It is noteworthy that the juvenile shows differences in both head morphology (by the large eyes relative to overall head size) and coloration (a slightly darker, grayer overall color regimen).

FIGURE 10. Habitat of Stegonotus nancuro sp. nov. in the Nancuro area, Manatuto Municipality, Timor-Leste. (A) Typical tropical moist forest habitat, showing a humus substrate, dense growth, and decaying logs. (B) Near the beach (the bright area at right in the image), there are few larger trees and a thick, shrubby undergrowth. (C) Access road into the Nancuro area, showing the dense vegetation and undergrowth. (D) The edge of the grassland, showing the height of the grasses against one of the expedition vehicles.