Phrynonax sexcarinatus ( Wagler, 1824 ) Revalidated

Lopes, Leonardo V. & Passos, Paulo, 2023, Taxonomic status of the enigmatic Natrix sexcarinata Wagler, 1824 (Serpentes: Colubridae: Colubrinae), Zootaxa 5244 (2), pp. 123-144 : 134-138

Phrynonax sexcarinatus ( Wagler, 1824) Revalidated

Ahaetulla polylepis Peters, 1867 . (Type locality: Suriname; holotype ZMB 5899 ).

Spilotes fasciatus Peters, 1869 . (Type locality: Maroni River , Suriname; holotype ZMB 6455 ).

Phrynonax atriceps Werner, 1913 . (Type locality: unknown; holotype formerly housed at ZMH but lost, according to Hallermann 1998).

Neotype. Adult female, MNRJ 20302 , collected by Emiliane Pereira Gonçalves and team between November 13 and December 08, 2006, Porto Trombetas (01°28’01.3”S, 56°22’46.0”W; ca. 40 m above sea level; asl hereafter), municipality of Oriximiná, state of Pará, Brazil. By present designation (see remarks). No tissue sample from this specimen was preserved ( Fig. 8 ).

Diagnosis and Definition. Phrynonax sexcarinatus can be distinguished from all congeners by a unique combination of the following characters: dorsal scale rows usually keeled in adult specimens, except for the first series, usually smooth; dorsal scale rows usually 21/23/15; postoculars usually two; temporal formula usually 2+2; supralabials usually eight, fourth to sixth contacting the orbit; infralabials usually 13, the first eight contacting the first pair of chinshields; maxillary teeth 11–19; ventral scales 196–211 in females, 186–215 in males; subcaudal scales 95–142 in females, 110–139 in males; color in preservative (70% ethanol), adults presenting the dorsum of the head brown, supralabials and gular region cream, ventral surface of the body cream anteriorly, darkening to brown posteriorly, ventral surface of the tail brown, dorsum of the body and tail uniform brown; color in preservative (70% ethanol), juveniles with the dorsum of the head beige with scattered brown spots or blotches, supralabials and infralabials cream with brown vertical bars on the posterior edges, a cream gular region, dorsum of the body and tail beige with transverse dark blotches, ventral surface of the body creamish-white anteriorly, darkening posteriorly to beige, belly with scattered dark brown spots or blotches concentrated on the posterior of the body, ventral surface of the tail beige speckled with dark brown spots; maximum SVL 1128 mm in females, 1200 mm in males; relative tail length 32.7–46.7% SVL in females, 34.2–45.7% SVL in males.

Comparison. Phrynonax sexcarinatus differs from all congeners (in parenthesis) due to a uniform brown dorsal color pattern in adults (vs. brown dorsum with dark brown paravertebral bands and dorsal scales with scattered yellow spots or blotches on the vertebral region in Ph. poecilonotus , dorsum orange or reddish with yellow stripes in Ph. shropshirei , and dorsum reticulated with yellow and black in Ph. lyoni [= Ph. polylepis sensu Uetz et al. 2022 ]). Phrynonax sexcarinatus differs from Spilotes species (sensu Jadin et al. 2013; in parenthesis) by presenting a maximum SVL of approximately 1200 mm (vs. maximum SVL of over 2500 mm), hemipenis unilobed, unicapitate with evident capitular constriction, and two insertion points of the hemipenis retractor muscle on the hemipenial apice (vs. a noncapitate hemipenis and a single insertion point for the hemipenis retractor muscle); differs from Spilotes pullatus by usually having 23 dorsal scale rows on the midbody (vs. 16–18 dorsal scale rows at midbody), usually 14–16 maxillary teeth (vs. usually 20 maxillary teeth), adults with a uniform brown coloration (vs. adults never uniform brown), hemipenis with the apical portion of the capitulum rounded, spines similar in size and spaced with the exception of the most basal, which are smaller, and calyces on the asulcate side similar to the sulcate side (vs. hemipenis with the apical capitulum portion of triangular with lateral and apical bulbs, spines increasing in size from the base to distal region of hemipenial body, and very deep calyces on the asulcate side); differs from Spilotes sulphureus by the absence of the subocular scale, usually two postocular, temporals usually 2+2, usually seven rows of keeled dorsal scale rows (vs. subocular usually present, usually three postoculars, temporals usually 1+2, only the paraventral rows without keels), hemipenis with apical portion of the capitulum rounded, hemipenial body covered with spines on both sides of the organ and hemipenial spines approximately half the size of the spine in S. sulphureus (vs. hemipenis with the apical portion of the capitulum triangular with lateral bulbs, hemipenial body with spines restricted to the lateral side on the sulcate side of the organ and hemipenial spines approximately twice the size of the spine in P. sexcarinatus ).

Neotype Description. Adult female; SVL 1128 mm, CL 446 mm, HL 44.7/ 45.3 mm (left/right, hereafter), HW 24.6 mm; rostro–orbital distance 13.9/ 14.5 mm, naso–orbital distance 8.4/9.0 mm, interocular distance 16.6 mm, internasal distance 9.5 mm; rostral 7.6 mm width, 4.4 mm high; internasals, divided, 5.8/ 5.7 mm long, 3.3/ 3.3 mm wide; prefrontals, divide, 7.5/ 7.5 mm wide, 5.9/ 6.4 mm length; frontal 8.7 mm wide, 10.0 mm long; supraocular 6.3/ 6.3 mm wide, 11.1/ 11.1 mm long; parietal 9.5/ 9.8 mm wide, 11.6/ 11.8 mm long; LL 3.6/ 4.6 mm, LH 2.2/ 2.2 mm; preocular 1.5/ 2.9 mm long, 6.0/ 5.5 mm high; symphysial 3.1 mm long, 5.6 mm wide; anterior chinshields 10.3/ 10.5 mm long, 4.9/ 5.2 mm wide; eye diameter 7.3/ 7.2 mm; preocular 1/1; postocular 2/3; temporal formula 2+2/3+2; supralabials nine, fourth to sixth contacting the orbit; infralabials 14, eight first infralabials contacting the first pair of chin shields; first pair of infralabials in contact behind the symphysial; anterior dorsal scales 22, with almost no keeled scale rows; dorsal scales on the midbody 23, with seven keeled scale rows; posterior dorsal scales 15, with five keeled scale rows; two apical pits separated from each other by the midline (= keel); ventral scales 201; cloacal shield whole; subcaudal scales divided in 123/124 series; terminal spine present; maxillary teeth on the right side 16.

Dorsum of the head uniformly brown; gular region and supralabials cream; supralabials and infralabials with some inconspicuous brown vertical bars on the posterior edges of the posterior supralabials; dorsum of the body and tail uniformly brown; ventral surface of the body cream-yellow anteriorly, gradually darkening to beige or a light brown ground color posteriorly; belly anteriorly presenting some brown spots or blotches concentrated on the lateral region of the ventral scales; ventral surface of the tail completely brown ( Fig. 8 ).

Morphological Variation. Prefrontals divided (n = 117) or whole (n = 1); frontal in contact (n = 124 sides) or not contacting (n = 104 sides) the preocular scale; single nasal (n = 91 sides), divided (n = 71 sides), with the division visible at the top (n = 41 sides) or at the bottom (n = 15 sides); preocular one (n = 227 sides) or two (n = 7 sides); postoculars two (n = 220 sides) or three (n = 12 sides); temporal formula 1+1 (n = 6 sides), 1+2 (n = 14 sides), 2+1 (n = 6 sides), 2+2 (n = 145 sides), 2+3 (n = 17 sides), 3+2 (n = 11 sides), 3+3 (n = 4 sides) with some specimens displaying a unusual pattern (n = 31 sides); supralabials 6 (n = 2 sides), 7 (n = 14 sides), 8 (n = 150 sides), 9 (n = 67 sides) or 10 (n = 3 sides); 3–4 th supralabials contacting the orbit (n = 2 sides), 3–5 th (n = 12 sides), 4–5 th (n = 9 sides), 4–6 th (n = 200 sides), 4–7 th (n = 1 side), 5–6 th (n = 3 sides) or 5–7 th (n = 7 sides); infralabials 10 (n = 1 side), 11 (n = 6 sides), 12 (n = 54 sides), 13 (n = 98 sides), 14 (n = 61 sides), 15 (n = 13 sides) or 16 (n = 1 side); infralabial pairs contacting the anterior chin shields 5 th (n = 5 sides), 6 th (n = 11 sides), 7 th (n = 86 sides), 8 th (n = 122 sides) or 9 th (n = 10 sides); anterior dorsal scale rows 20 (n = 1), 21 (n = 85), 22 (n = 18), 23 (n = 24) or 24 (n = 1); midbody dorsal scale rows 15 (n = 4), 16 (n = 5), 17 (n = 15), 18 (n = 39), 19 (n = 9), 20 (n = 24), 21 (n = 26), 22 (n = 25), 23 (n = 53), 24 (n = 4) or 25 (n = 3); posterior dorsal scale rows 13 (n = 15), 14 (n = 24), 15 (n = 95), 16 (n = 1) or 18 (n = 1); absent anterior dorsal scale rows with keels in females (n = 39), 1 (n = 3), 2 (n = 1) or 15 (n = 1); absent anterior dorsal scale rows with keels in males (n = 29), 1 (n = 15), 2 (n = 1), 3 (n = 6) or 5 (n = 1); absent midbody dorsal scale rows with keels in females (n = 1), 1 (n = 3), 2 (n = 1), 3 (n = 7), 4 (n = 6), 5 (n = 20), 6 (n = 3), 7 (n = 4) or 17 (n = 1); absent midbody dorsal scale rows with keels in males (n = 4), 2 (n = 1), 4 (n = 5), 5 (n = 12), 6 (n = 9), 7 (n = 12), 9 (n = 1), 10 (n = 3), 11 (n = 2), 13 (n = 1), 14 (n = 1), 15 (n = 1) or 17 (n = 1); absent posterior dorsal scale rows with keels in females (n = 3), 1 (n = 1), 2 (n = 2), 3 (n = 8), 4 (n = 4), 5 (n = 19), 6 (n = 2), 7 (n = 6) or 11 (n = 1); absent posterior dorsal scale rows with keels in males (n = 3), 3 (n = 1), 4 (n = 5), 5 (n = 10), 6 (n = 9), 7 (n = 12), 8 (n = 5), 10 (n = 3), 11 (n = 2) or 12 (n = 1); subcaudals divided (n = 69) or mostly divided and some while (n = 38); maxillary teeth 11 (n = 1), 13 (n = 4), 14 (n = 9), 15 (n = 10), 16 (n = 10), 17 (n = 15), 18 (n = 8) or 19 (n = 4); apical pits absent (n = 12), 1 (n = 10), 2 (n = 101) or 3 (n = 1), usually with one on each side of the midline keel (n = 86); without keels (n = 10) or with keels (n = 105); ventrals 196–211 in females (mean = 201.0, SD = 3.0, n = 45), 186–215 in males (mean = 195.2, SD = 5.0, n = 51); subcaudals 95–142 in females (mean = 125.4, SD = 7.8, n = 46), 110–139 in males (mean = 125.2, SD = 6.7, n = 47); loreal scale present (n = 111) or absent (n = 4); LH 0.9–3.0 mm (mean = 2.1, SD = 0.4, n = 88) in females; LH 0.7–2.0 mm (mean = 1.9, SD = 0.5, n = 100) in males, 1.4–4.6 (mean = 3.0, SD = 0.6, n = 88) in females; LL 0.9–4.0 (mean = 2.6, SD = 0.7, n = 100) in males; SVL 361.0–1128.0 mm (mean = 837.8, SD = 18.1, n = 46) in females, 239.0–1200.0 mm (mean = 70.4, SD = 21.8, n = 54) in males; CL (% SVL) 32.7–46.7% (mean = 38.5, SD = 2.7, n = 46) in females, 34.2–45.7% (mean = 39.2, SD = 2.7; n = 53) in males. Color Pattern A (n = 2; SVL mean: 44.1), B (n = 27; SVL mean: 91.4) or Color Pattern C (n = 8; SVL mean: 83.8) in females; Color Pattern A (n = 5; SVL mean: 38.8), Color Pattern B (n = 18; SVL mean: 83.1) or Color Pattern C (n = 21; SVL mean: 72.2) in males. All values include juveniles and adults.

Color in life. Juveniles displaying a brown dorsum with reddish transverse blotches; blotches may be more or less conspicuous and surrounded by some black pigmentation; dorsum of the head brown covered with reddish spots or blotches; supralabials and infralabial may display the same color as the dorsal stains in the body or be brown. Adults uniform greenish brown; supralabials and the anterior belly region yellowish ( Fig. 3 ).

Hemipenial Morphology. The fully everted and maximally expanded hemipenes renders unilobed, unicapitate, and unicalyculate organs; capitulum slightly bulbous and rounded in the distal region; distal region of the capitulum with two insertion points of the musculus retractor hemipenis magnus; evident capitular constriction; capitulum with papillate calyces; calyces restricted to the sides and proximal region of the capitulum; central region of the capitulum naked; asulcate side with the naked capitular region smaller than in the sulcate side; centrolinear sulcus spermaticus; smooth intrasulcar region; subelliptic hemipenial body, narrower than the capitular region of the organ; distal region of the hemipenial body covered by spines on both sides of the organ; similarly sized and spaced spines, except the most basal, which are smaller; proximal region of the hemipenial body naked ( Fig. 9 ).

Distribution. From the island of Trinidad Island on the Caribbean Coast (ca., 10º N) to La Guardia, in Bolivia (ca., 18º S), in the east of the Andes from Gualaquiza in Ecuador (ca., 78ºW) to Junco do Maranh„o, in Brazil (ca., 46ºW). Phrynonax sexcarinatus’ distribution follows the Tropical and Subtropical Moist Broadleaf Forests domains ( Olson et al. 2001), ranging from 1–1538 m elevations (see Nogueira et al. 2019: plate 143 [as P. polylepis ]).

Remarks. The ICZN (1999: 84-85) lists seven qualifying conditions for a neotype designation detailed in Article 75. Criterion (i) is fulfilled because both the taxonomic status and the type locality are unclear, as detailed above. Criterion (ii) is fulfilled concerning the diagnosis and comparisons. Criterion (iii) is fulfilled by comparing the data from this study with the characters described by Wagler (1824) in detail. Criterion (iv) is fulfilled insofar as Franzen & Glaw (2007) declare that the holotype was lost during World War II and we confirmed this information (see above). Criterion (v) is also fulfilled by comparing data from this study to the characters described by Wagler (1824), considering it is the only source of information on Natrix sexcarinata . Criterion (vi) is fulfilled, and we reinforce that we chose a neotype close to the Amazon River, in agreement with the original description. Criterion (vii) is fulfilled, because the neotype is deposited at the MNRJ.

Figures

FIGURE 3. General view of Phrynonax polylepis in life from Parauapebas, in the state of Pará (A); Sinop, in the state of Mato Grosso (B); from Bujari, in the state of Acre (C); and Belterra, in the state of Pará (D), all in Brazil. Color PatternA is depicted in Figures A–B, while Color Pattern B is depicted in figures C–D. Modified images from original photographs by Fábio Giordano (A), Antonino Gonçalves Medina (B), Martin Acosta (C), and Miguel A. Casado (D). All photos are available at <https://www. inaturalist.org/home>.

FIGURE 8. Dorsal (A), ventral (B) and lateral (C) views of the head and dorsal (D) and ventral (E) views of the body of the Phrynonax sexcarinatus (MNRJ 20302) neotype from Porto Trombetas, Oriximiná municipality, in the state of Pará, Brazil. Specimens measured 1128 mm snout-vent length and 446 mm tail length.

FIGURE 9. Aulcate (A) and asulcate (B) sides of the hemipenis of the Phrynonax sexcarinatus (MNRJ 18023) specimen from the Carajás National Forest, Parauapebas municipality, in the state of Pará, Brazil. Scale = 1 cm.