Sibon vieirai, Arteaga & Batista, 2023

Arteaga, Alejandro & Batista, Abel, 2023, A consolidated phylogeny of snail-eating snakes (Serpentes, Dipsadini), with the description of five new species from Colombia, Ecuador, and Panama, ZooKeys 1143, pp. 1-49 : 1

Sibon vieirai sp. nov.

Figs 4d , 9 , 10b-d , 11a, b Proposed standard English name: Vieira’s Snail-eating Snake Proposed standard Spanish name: Culebra caracolera de Jose Vieira

Type material.

Holotype: ZSFQ 5071 (Figs 9 , 10d , 11b ), adult male collected by Jose Vieira, Frank Pichardo, and Matteo Espinosa on 28 February 2021 at Tundaloma Lodge, Esmeraldas Province, Ecuador (1.18166, -78.74945; 74 m a.s.l.).

Paratypes: MZUA.RE.0328, adult male collected at Jauneche, Los Ríos province, Ecuador (-1.33333, -79.58333; 41 m a.s.l.). MZUTI 4810, adult female collected by Jaime Culebras on 14 February 2016 at Bosque Privado El Jardín de los Sueños, Cotopaxi province, Ecuador (-0.83142, -79.21337; 349 m a.s.l.). ZSFQ 5070, adult male collected by Alejandro Arteaga and Jose Vieira on 12 March 2018 at La Primavera, Carchi province, Ecuador (0.79502, -78.21763; 1228 m a.s.l.). MZUTI 3911, juvenile male collected by Jaime Culebras on 11 November 2014 at Itapoa Reserve, Esmeraldas Province, Ecuador (0.51307, -79.13401; 321 m a.s.l.). MZUTI 5342, adult male collected by Jorge Vaca on 27 May 2017 at Reserva Jama Coaque, Manabí province, Ecuador (-0.11556, -80.12472; 299 m a.s.l.). ZSFQ 5073, adult male collected by Jose Vieira on 23 August 2020 at Hacienda Cerro Chico, Los Ríos province, Ecuador (-0.63862, -79.42585; 141 m a.s.l.). USNM 285499, juvenile male collected by Roy McDiarmid on 1 January 1979 at Centro Científico Río Palenque, Los Ríos province, Ecuador (-0.58333, -79.36667; 173 m a.s.l.). USNM 285501, adult male collected by Roy McDiarmid on 10 March 1979 at Hacienda Cerro Chico, Los Ríos province, Ecuador (-0.63862, -79.42585; 141 m a.s.l.). USNM 283534, adult of undetermined sex collected on 6 June 1981 at Rancho Santa Teresita, Santo Domingo de los Tsáchilas province, Ecuador (-0.25277, -79.37946; 288 m a.s.l.). USNM 285498, adult of undetermined sex collected by Roy McDiarmid on 23 May 1976 at Centro Científico Río Palenque, Los Ríos province, Ecuador (-0.58333, -79.36667; 173 m a.s.l.). USNM 285500, adult of undetermined sex collected by Roy McDiarmid on 2 February 1976 at Centro Científico Río Palenque, Los Ríos province, Ecuador (-0.58333, -79.36667; 173 m a.s.l.). MZUA.RE.0174, adult female collected at Macul, Los Ríos province, Ecuador (-1.1298, -79.65731; 65 m a.s.l.).

Diagnosis.

Sibon vieirai sp. nov. is placed in the genus Sibon based on phylogenetic evidence (Fig. 1a ) and on having the penultimate supralabial conspicuously higher than all other supralabials. The species is diagnosed based on the following combination of characters: (1) 15/15/15 smooth dorsals with enlarged vertebral row (1.4-3 × as wide as adjacent rows); (2) loreal and prefrontal in contact with orbit; (3) 7-8 supralabials with, usually, 4th, 5th, and occasionally 6th contacting orbit; (4) 9-10 infralabials with 1st to 6th in contact with chinshields, first pair of infralabials in contact behind symphysial; (5) 183-195 ventrals in males, 178-189 in females; (6) 95-105 divided subcaudals in males, 78-92 in females; (7) dorsal background color slate gray to brownish gray with faint blackish blotches or incomplete bands bordered by a series of white dots, fine blackish and white speckling in the interspaces (Figs 4d , 9a , 10b-d ), ventral surfaces white with encroachment from the dorsal blackish blotches and with or without fine black speckles in-between the blotches (Fig. 9b ), dorsal aspect of head black with fine white speckles, throat white with various amounts of black markings that form a checkerboard pattern (Fig. 11a, b ), iris pale gray finely variegated with black; (8) 363-542 mm SVL in males, 352-544 mm in females; (9) 127-224 mm TL in males, 113-170 mm in females.

Comparisons.

Sibon vieirai sp. nov. is most similar to S. leucomelas , from which it differs primarily on the basis of coloration (differences summarized under Table 3 ). In S. vieirai sp. nov. (Figs 4d , 10b-d ), the complete black and pale dorsal bands typical of S. leucomelas (Fig. 10a ) are usually absent. Instead, the white “bands” are formed by series of white spots and the black bands are faint and incomplete. The color of the pale “bands” also differs between species: rosy white in S. Sibon leucomelas and white in S. vieirai sp. nov. (Fig. 10 ). In S. vieirai sp. nov the throat has a checkerboard pattern of black and white markings whereas in S. leucomelas it is entirely black with fine white speckling (Fig. 11 ). Overall, specimens assignable to S. leucomelas have a greater number of ventral scales than Sibon vieirai sp. nov. in both males and females, although there is overlap in the counts (Table 3 ). Sibon vieirai sp. nov. differs from S. bevridgelyi by having white (instead of golden yellow) dorsal markings on a primarily gray (instead of rusty brown to deep maroon) background color. Arteaga at al. (2018) presented an in-depth comparison between S. bevridgelyi and Sibon vieirai sp. nov. (reported as S. nebulatus from Ecuador).

Description of holotype.

Adult male, SVL 515 mm, tail length 199 mm (38.6% SVL); head length 20.7 mm (4.0% SVL) from tip of snout to angle of jaw; head width 11.6 mm (55% head length) taken at broadest point; snout-orbit distance 4.9 mm; head distinct from neck; snout short, blunt in dorsal outline and rounded in profile; rostral 3.8 mm wide, higher than broad; internasals 2.1 mm wide, broader than long; prefrontals 3.4 mm wide, slightly broader than long, entering orbit; supraocular 3.6 mm long, longer than broad; frontal 4.3 mm long, with a rounded triangular shape, in contact with prefrontals, supraoculars, and parietals; parietals 6.4 mm long, longer than broad; nasal divided, in contact with two supralabials, loreal, prefrontal, internasal, and rostral; loreal 2.3 mm long, longer than high, entering the orbit; eye diameter 3.9 mm; pupil semi-elliptical; no preocular; two postoculars; temporals 1+2; seven supralabials with 4th and 5th contacting orbit; symphysial precluded from contacting chinshields by first pair of infralabials; nine infralabials with 1st-6th contacting chinshields; two pairs of chinshields longer than wide; dorsal scales in 15/15/15 rows, smooth, without apical pits; 195 ventrals; 105 divided subcaudals; cloacal plate entire.

Natural history.

Specimens of Sibon vieirai sp. nov. have been found in old growth to heavily disturbed evergreen lowland/foothill forests as well as in rural gardens and plantations. Active snakes have been seen at night foraging at ground level or on vegetation up to 3 m above the ground. One snake was spotted as it emerged from under a pile of logs at sunset. Based on our own field experience, individuals appear to be more active when it is raining or drizzling. In the field in Ecuador, specimens of S. vieirai sp. nov. have been observed feeding on slugs and snails. A female from Hostería Selva Virgen, Pichincha province, Ecuador laid a clutch of four eggs.

Distribution.

Sibon vieirai sp. nov. is known from at least 95 localities (listed in Suppl. material 2) along the Chocoan lowlands and adjacent foothills of the Andes in northwestern Ecuador and southwestern Colombia. Previous records of S. nebulatus from the rainforests of northwestern Ecuador as well as those of the Pacific lowlands of Colombia in Nariño department almost surely correspond to this new species. Sibon vieirai sp. nov. occurs over an estimated 58,551 km2 area and has been recorded at elevations 5-1803 m above sea level (Fig. 12 ).

Etymology.

The specific epithet Sibon vieirai is a patronym honoring Jose Vieira, a Venezuelan biologist and wildlife photographer who created the Ex-Situ project, a free-access photo bank depicting Latin American fauna on a white background. Jose Vieira’s photos have been crucial in illustrating field guides about herpetofauna, educational posters, and research publications. Most of the images in this work were created by Jose Vieira. Additionally, after nearly six years of active collaboration with one of us (AA), it has become evident that Jose is one of the most tireless and focused young field biologists ever to sample the jungles of the tropics, a work ethic that has resulted in the generation of photo and museum vouchers for hundreds of poorly studied species of herpetofauna, including the holotype of this new Sibon .

Conservation status.

We consider Sibon vieirai sp. nov. to be included in the Least Concern category following IUCN Red List criteria ( IUCN 2001) because the species is distributed over a region of the Chocó biome that holds large areas of continuous unspoiled forest. Based on the species distribution model presented in Fig. 12 in combination with maps of vegetation cover of Colombia ( IDEAM 2014) and Ecuador ( MAE 2012), we estimate that more than half (~ 51%) of the species’ forest habitat is still standing. Unfortunately, vast areas of the Chocó rainforest in western Ecuador have already been converted to pastures ( Myers et al. 2000). However, S. vieirai sp. nov. occurs over an area greater than 50,000 km2 and is presumably not declining fast enough to qualify for a threatened category.

Figures

Figure 1. Phylogenetic relationships within Dipsadini inferred using a Bayesian inference and derived from analysis of DNA gene fragments 12 S, 16 S, COI, CYTB, ND 4, DNAH 3, and NT 3. Support values on intra-specific branches are not shown for clarity. Voucher numbers for sequences are indicated for each terminal. Black dots indicate clades with posterior probability values from 95 - 100 %. Grey dots indicate values from 70 - 94 %. White dots indicate values from 50 - 69 % (values <50 % not shown). Colored clades correspond to the species' distribution presented in the maps. New or redefined species are indicated in bold type.

Figure 4. Photographs of some species of Sibon and Dipsas in life a S. canopy sp. nov. from El Valle de Anton, Cocle province, Panama b S. irmelindicaprioae sp. nov. holotype MHCH 3143 from Puerto Indio, Darien province, Panama c S. marleyae sp. nov. from Verdecanande, Esmeraldas Province, Ecuador d S. vieirai sp. nov. from Mashpi Amagusa Reserve, Pichincha province, Ecuador e Dipsas sp. from Cerro Gaital, Cocle province, Panama f D. welborni sp. nov. ZSFQ 5060 from Via a Nuevo Paraiso, Zamora Chinchipe province, Ecuador.

Figure 9. Adult male holotype of Sibon vieirai sp. nov. ZSFQ 5071 in a dorsal and b ventral view.

Figure 10. Photographs of species of the Sibon nebulatus leucomelas complex in life a S. leucomelas from Morromico Reserve, Choco department, Colombia b S. vieirai sp. nov. ZSFQ 5073 from Hacienda Cerro Chico, Los Rios province, Ecuador c S. vieirai sp. nov. from Tundaloma Lodge, Esmeraldas Province, Ecuador d S. vieirai sp. nov. holotype ZSFQ 5071 from Tundaloma Lodge, Esmeraldas Province, Ecuador.

Figure 11. Differences in throat color pattern between species of the Sibon nebulatus leucomelas complex a S. vieirai sp. nov. ZSFQ 5073 from Hacienda Cerro Chico, Los Rios province, Ecuador b S. vieirai sp. nov. holotype ZSFQ 5071 from Tundaloma Lodge, Esmeraldas Province, Ecuador c S. leucomelas CZI-R 075 from Represa Murrapal, Valle del Cauca department, Colombia d S. leucomelas CZI-R 029 from Campamento Yatacue, Valle del Cauca department, Colombia.

Figure 12. Distribution of species of Sibon previously subsumed under S. nebulatus leucomelas. Black symbols represent type localities; white symbols other localities listed in Suppl. material 2. Colored areas show the extent of suitable environmental conditions for each species.