Sibon irmelindicaprioae, 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 irmelindicaprioae sp. nov.

Figs 2a, b , 3 , 4b , 5c Proposed standard English name: DiCaprio’s Snail-eating Snake Proposed standard Spanish name: Culebra caracolera de DiCaprio

Type material.

Holotype: MHCH 3143 (Figs 3 , 4b ), adult male collected by Abel Batista and Milan Vesely, on 29 September 2011 at Cerro Bailarín, Pavarandó, Comarca Emberá-Wounaan, Panama (7.69385, -78.04267; 852 m a.s.l.).

Paratypes: MHCH 3145, adult female collected by Abel Batista and Milan Vesely on 26 September 2012 at Ambroya, Panama province, Panama (8.91680, -78.61779; 484 m a.s.l.). MHCH 3146, adult male collected by Abel Batista on 16 November 2012 at Cerro Garra Garra, Pavarandó, Comarca Emberá-Wounaan, Panama (7.76400, -78.10063; 655 m a.s.l.). MHCH 3111, adult male collected by Abel Batista, Madian Miranda, Orlando Garcés, Rogemif Fuentes on 15 October 2016 at Chucantí, Darién province, Panama (8.79773, -78.46225; 1295 m a.s.l.). MHCH 3120, adult male collected by Abel Batista, Madian Miranda, Michelle Quiroz, Marcos Ponce on 18 June 2015 at Pirré, Darién province, Panama (7.99695, -77.71040; 550 m a.s.l.). COLZOOCH-H 0792, adult male collected by Jhon Tailor Rengifo Mosquera on 6 March 2005 at El Afirmado, Chocó department, Colombia (5.64190, -77.07550; 216 m a.s.l.).

Diagnosis.

Sibon irmelindicaprioae 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 (1.5 × as wide as adjacent rows); (2) loreal and prefrontal in contact with orbit; (3) 7-9 supralabials with, usually, 5th and 6th contacting orbit; (4) 8-10 infralabials with 3rd-7th in contact with chinshields, first pair of infralabials not in contact behind symphysial due to presence of postmentals; (5) 187-196 ventrals in males, 174 in the single female; (6) 110-128 divided subcaudals in males, 117 in the single female; (7) dorsal background color olive with maroon lateral body blotches or irregular bands (2-6 dorsal scales long) and a reddish tint along the vertebral line (Figs 2a, b , 4b ), ventral surfaces yellowish white with encroachment from the dorsal maroon blotches and with smaller blackish speckles and marks in-between the blotches, dorsal aspect of head variegated with a mixture of pinkish to maroon and pale olive yellow speckles (Fig. 5c ), throat yellowish white with brownish blotches and spots, iris pale olive brown to rich dark brown; (8) 292-387 mm SVL in males, 402 mm in the single female; (9) 123-193 mm TL in males, 204 mm in the single female.

Comparisons.

Sibon irmelindicaprioae sp. nov. is compared to other species of Sibon previously subsumed under S. annulatus sensu lato (differences summarized in Table 2 ). From S. annulatus sensu stricto, the new species differs in having the dorsal body bands faint and broken along the vertebral line (Figs 2a, b , 4b ) and by having a finely variegated pattern on the dorsal surface of the head (Fig. 5c ), whereas in S. annulatus the dorsal bands reach over all dorsal and lateral surfaces and extend comparably far onto the ventral surfaces (Figs 2d, e ) and the head pattern consists of symmetrical broad blotches (Fig. 5a ). Sibon irmelindicaprioae sp. nov. differs from S. canopy sp. nov. by having two (instead of one) postmental scales, a higher number of infralabials (8-10 instead of 6-10), a higher number of ventrals in males (187-196 instead of 180-189), a finely variegated pattern on the dorsal surface of the head (instead of broad irregular blotches; Fig. 5 ), and by lacking reddish spots enclosed in the dorsal olive interspaces (Figs 2 , 4 ). Sibon irmelindicaprioae sp. nov. differs from S. marleyae sp. nov. by having a finely variegated pattern on the dorsal surface of the head (instead of having irregular/symmetrical broad blotches; see Fig. 5 ), distinct dorsal bands (instead of bands usually broken along the vertebral line), and a higher number (over 177) of ventrals in females.

Description of holotype.

Adult male, SVL 387 mm, tail length 193 mm (49% SVL); head length 14.3 mm (3.7% SVL) from tip of snout to angle of jaw; head width 9.0 mm (88% head length) taken at broadest point; snout-orbit distance 2.3 mm; head distinct from neck; snout short, blunt in dorsal outline and rounded in profile; rostral 1.8 mm wide, higher than broad; internasals 1.8 mm wide, broader than long; prefrontals 2.3 mm wide, longer than broad, entering orbit; supraocular 3.6 mm long, longer than broad; frontal 3.7 mm long, pentagonal and with an inward-bent anterior border, in contact with prefrontals, supraoculars, and parietals; parietals 5.8 mm long, longer than broad; nasal divided, in contact with first two supralabials, loreal, prefrontal, internasal, and rostral; loreal 1.4 mm long, longer than high, entering the orbit; eye diameter 3.7 mm; pupil semi-elliptical; no preocular; two postoculars; temporals 1+3 on the right side, 2+3 on the left side; eight supralabials with 5th and 6th contacting orbit on the right side, eight supralabials with 5th and 6th contacting orbit on the left side; symphysial precluded from contacting chinshields by a pair of postmentals; ten infralabials, 3rd-7th contacting chinshields; two pair of chinshields longer than wide; dorsal scales in 15/15/15 rows, smooth, without apical pits; 193 ventrals; 128 paired subcaudals; cloacal plate single.

Natural history.

Specimens of Sibon irmelindicaprioae sp. nov. have been found at night foraging on shrubs, trees, and palm fronds 200-300 cm above the ground in old-growth to moderately disturbed evergreen lowland/foothill forests. Snakes of this species are docile and never attempt to bite. When threatened, individuals may hide the head among body coils and produce a musky and distasteful odor.

Distribution.

Sibon irmelindicaprioae sp. nov. is known from 16 localities (listed in Suppl. material 2) in the Chocó region of eastern Panama and northwestern Colombia, with an isolated population on the western slopes of the Cordillera Oriental of Colombia. The species occurs over an estimated area of 62,241 km2 and has been recorded at elevations 346-1295 m above sea level (Fig. 6 ). Since the population on the Cordillera Oriental is isolated from the remaining populations and individuals in this area occur at higher elevations and have a different dorsal color pattern, we provisionally assign them to S. irmelindicaprioae sp. nov. pending more comprehensive genetic analyses.

Etymology.

The specific epithet Sibon irmelindicaprioae is a patronym honoring Irmelin DiCaprio (1945-present), mother of Leonardo DiCaprio, long-time advocate and supporter of biodiversity conservation around the world.

Conservation status.

We consider Sibon irmelindicaprioae sp. nov. to be included in the Near Threatened category following IUCN Red List criteria ( IUCN 2001) because the species is distributed over a region that holds large areas of continuous unspoiled forest. Based on the species distribution model presented in Fig. 6 in combination with maps of vegetation cover of Colombia ( IDEAM 2014) and Panama ( CATHALAC 2011), we estimate that more than half (~ 54%) of the species’ forest habitat is still standing. Unfortunately, vast areas of the Chocó rainforest in northern Colombia and towards central Panama have already been converted to pastures ( Myers et al. 2000). However, S. irmelindicaprioae 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 2. Photographs of some species of Sibon in life a S. irmelindicaprioae sp. nov. MHCH 3269 from Chucanti Reserve, Darien province, Panama b S. irmelindicaprioae sp. nov. from Morromico Reserve, Choco department, Colombia c S. canopy sp. nov. from Cerro Gaital, Cocle province, Panama d, e S. annulatus from Centro Manu, Limon province, Costa Rica f S. ayerbeorum ZSFQ 5066 from Canande Biological Reserve, Esmeraldas Province, Ecuador g S. marleyae sp. nov. holotype ZSFQ 5065 from Verdecanande, Esmeraldas Province, Ecuador h S. marleyae sp. nov. ZSFQ 5068 from Verdecanande, Esmeraldas Province, Ecuador i S. marleyae sp. nov. neonate from Verdecanande, Esmeraldas Province, Ecuador.

Figure 3. Adult male holotype of Sibon irmelindicaprioae sp. nov. MHCH 3143 in lateral views a right and b left side.

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 5. Differences in head morphology between species of Sibon previously subsumed under S. annulatus a S. annulatus MHCH 1982 from Bonyic, Bocas del Toro province, Panama b S. canopy sp. nov. holotype MHCH 3110 from Cerro Gaital, Cocle province, Panama c S. irmelindicaprioae sp. nov. MHCH 3120 from Pirre, Darien province, Panama d S. marleyae sp. nov. holotype ZSFQ 5065 from Verdecanande, Esmeraldas Province, Ecuador.

Figure 6. Distribution of species of Sibon previously subsumed under S. annulatus. 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.