Dipsas welborni, Arteaga & Batista, 2023
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publication ID |
https://dx.doi.org/10.3897/zookeys.1143.93601 |
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publication LSID |
lsid:zoobank.org:pub:8889CB19-B159-4D07-881C-7A87B033BCF3 |
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persistent identifier |
https://treatment.plazi.org/id/8F1C3963-FB25-4C98-81E9-714727A4CCEF |
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taxon LSID |
lsid:zoobank.org:act:8F1C3963-FB25-4C98-81E9-714727A4CCEF |
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treatment provided by |
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scientific name |
Dipsas welborni |
| status |
sp. nov. |
Dipsas welborni sp. nov.
Figs 4f View Figure 4 , 13 View Figure 13 , 14a View Figure 14 , 15a Proposed standard English name: Welborn’s Snail-eating Snake Proposed standard Spanish name: Culebra caracolera de Welborn View Figure 15
Type material.
Holotype: MZUTI 3663 (Figs 13 View Figure 13 , 15a View Figure 15 ), adult male collected on 2 July 2014 at Reserva Maycu, Zamora Chinchipe province, Ecuador (-4.20719, -78.63987; 960 m a.s.l.).
Paratypes: MZUA.RE.0261, adult male collected at Nangaritza, Zamora Chinchipe province, Ecuador (-4.43169, -78.63869; 996 m a.s.l.). DHMECN 11197, juvenile male collected by Raquel Betancourt and Miguel Alcoser on 18 September 2012 at Concesión ECSA, Zamora Chinchipe province, Ecuador (-3.57245, -78.46982; 790 m a.s.l.). ZSFQ 5060 (Figs 4f View Figure 4 , 14a View Figure 14 ), female collected by Alejandro Arteaga and Amanda Quezada at Maycu Reserve, Zamora Chinchipe province, Ecuador (-4.26395, -78.64483; 1078 m a.s.l.).
Diagnosis.
Dipsas welborni sp. nov. is placed in the genus Dipsas based on phylogenetic evidence (Fig. 1b View Figure 1 ) and the absence of a labial that is noticeably higher than other labials. The species is diagnosed based on the following combination of characters: (1) 13/13/13 smooth dorsals with enlarged vertebral row (1.8-2.1 × as wide as adjacent rows); (2) loreal and a preocular in contact with orbit; (3) 7-8 supralabials with 4th, 5th, and occasionally 6th, contacting orbit; (4) 8-9 infralabials with 1st to 5th or to 6th in contact with chinshields, one pair of infralabials in contact behind symphysial; (5) 181-193 ventrals in males, 177-179 in females; (6) 107-116 divided subcaudals in males, 105-106 in females; (7) dorsal color consisting of 21-26 dark brown to blackish body blotches (8-13 dorsal scales long anteriorly and 2-5 dorsal scales long posteriorly) separated from each other by narrow (2-3 dorsal scales long) pale brown interspaces that become white towards the lower lateral side, ventral surfaces white with encroachment from the dorsal dark brown blotches and with smaller brownish marks in-between the blotches, dorsal aspect of head dark reddish brown with fine bright yellow (juveniles) to light brown (adults; Fig. 15a View Figure 15 ) reticulations, throat white, iris pale brown; (8) 491-542 mm SVL in males, 321-595 mm in females; (9) 190-279 mm TL in males, 132-281 mm in females.
Comparisons.
Dipsas welborni sp. nov. differs from the majority of its congeners by having dorsal scales arranged in 13/13/13 rows, loreal entering the orbit, and dorsum of head strongly vermiculated. The new species is most similar to D. vermiculata , from which it differs on the basis of the following characters of coloration and lepidosis (Fig. 14 View Figure 14 ; Table 4 View Table 4 ). In D. welborni sp. nov., there are two prefrontal scales (partially fused in ZSFQ 5060) whereas in all specimens of D. vermiculata examined (Suppl. material 1) as well as the four Ecuadorian specimens reported in Peters (1960), the prefrontals are fused into a single scale (Fig. 15 View Figure 15 ). Females of Dipsas welborni sp. nov. have more ventrals (177-179) and subcaudals (105-106) than those of D. vermiculata (173-174 ventrals and 99-103 subcaudals). Females of the new species attain a larger body size than those of D. vermiculata (Table 4 View Table 4 ), and males of the former also have more rows of spines on the asulcate surface of the hemipenis body (the hemipenis of D. vermiculata is depicted in Vera-Pérez 2020 whereas the organs of four males of D. welborni sp. nov. are depicted in Pazmiño-Otamendi et al. 2020). Finally, the two species further differ in the background color of the ventral surfaces: always white in D. welborni sp. nov. (Fig. 13b View Figure 13 ), and usually yellow or occasionally pale yellowish white in D. vermiculata .
Description of holotype.
Adult male, SVL 542 mm, tail length 195 mm (incomplete); head length 16.4 mm (3.0% SVL) from tip of snout to angle of jaw; head width 10.2 mm (62% head length) taken at broadest point; snout-orbit distance 3.8 mm; head distinct from neck; snout short, blunt in dorsal outline and rounded in profile; rostral 2.4 mm wide, higher than broad; internasals 1.8 mm wide, broader than long; prefrontals 2.7 mm wide, longer than broad, not entering orbit; supraocular 3.8 mm long, longer than broad; frontal 4.1 mm long, hexagonal and with angled anterior border, in contact with prefrontals, supraoculars, and parietals; parietals 5.5 mm long, longer than broad; nasal divided, in contact with two supralabials, loreal, prefrontal, internasal, and rostral; loreal 2.1 mm long, longer than high, entering the orbit; eye diameter 3.4 mm; pupil semi-elliptical; one small preocular above loreal; two postoculars; temporals 2+2; seven supralabials with 4th-5th contacting orbit; symphysial precluded from contacting chinshields by first pair of infralabials; nine infralabials with 1st to 5th contacting chinshields; three pairs of chinshields, first longer than wide; dorsal scales in 13/13/13 rows, smooth, without apical pits; 185 ventrals; 80+ divided subcaudals; cloacal plate entire.
Natural history.
Specimens of Dipsas welborni sp. nov. have been found foraging on vegetation 20-350 cm above the ground in old-growth to moderately disturbed evergreen montane forests. Snakes of this species are docile and never attempt to bite. When threatened, individuals may flatten their body and expand their head to simulate a triangular shape as well as produce a musky and distasteful odor.
Distribution.
Dipsas welborni sp. nov. is known from 26 localities (listed in Suppl. material 2) along the Cordillera del Cóndor in southeastern Ecuador (provinces Morona Santiago and Zamora Chinchipe) and northern Peru (Amazonas department). The species occurs over an estimated area of 10,521 km2 and has been recorded at elevations 853-1843 m above sea level (Fig. 16 View Figure 16 ). One locality, Etseketai Entse, Amazonas department, Peru, is in the Río Cenepa valley at ~ 245 m above sea level. Since this locality is much lower in elevation than other localities in the Cordillera del Cóndor, it is likely that the specimens collected there (USNM 316599-600) were actually found on the neighboring mountain ridges.
Etymology.
The specific epithet Dipsas welborni is a patronym honoring David Welborn, a lifelong champion of ecosystem and species conservation who supports and serves on several nonprofit boards dedicated to the environment. David retired from the board of Nature and Culture International in 2021 after 18 years of service, including four as board chairman. Nature and Culture International, a non-profit organization, has conserved more than 9 million hectares of tropical Latin American ecosystems, including key habitat in the Maycu Reserve of southeastern Ecuador, where Dipsas welborni sp. nov. was discovered.
Conservation status.
We consider Dipsas welborni sp. nov. to be in the Near Threatened category following IUCN Red List criteria ( IUCN 2001) because the species is distributed over a region of the Amazonian slopes of the Andes that holds large areas of continuous unspoiled forest. Based on the species distribution model presented in Fig. 16 View Figure 16 in combination with the most recent maps of vegetation cover of the Amazon basin ( MapBiomas Amazonía 2022), we estimate that the majority (~ 76%) of the species’ forest habitat in Ecuador is still standing. Unfortunately, vast areas of the Cordillera del Cóndor, notably on the Ecuadorian part of the species’ range, are being cleared to make room for large-scale opencast mining operations ( Chicaiza 2010; Valencia et al. 2017). However, since D. welborni sp. nov. occurs over an area greater than 10,000 km2, the species does not qualify for a threatened category.
Presence of Sibon ayerbeorum in Ecuador and Valle del Cauca, Colombia
We expand the distribution of Sibon ayerbeorum , a species previously known only from departments Cauca ( Vera-Pérez 2019), Chocó ( Echavarría-Rentería and Medina-Rangel 2021), and Risaralda ( Bonilla and Moya 2021) in Colombia. We examined three additional specimens (listed in Suppl. material 1) at Colección Zoológica de la Universidad ICESI (labeled CZI) and at ZSFQ that represent, respectively, new records for Valle del Cauca department in Colombia and Esmeraldas province in Ecuador. CZI-R063 is a juvenile male collected by Santiago Orozco on 17 August 2019 at La Loca, Valle del Cauca department, Colombia (3.57656, -76.88029; 658 m a.s.l.). CZI-R067 is a juvenile male collected by Santiago Orozco on 30 August 2019 at La Riqueza, Valle del Cauca department, Colombia (3.59874, -76.89184; 621 m a.s.l.). ZSFQ 5066 (Fig. 2f View Figure 2 ) is a juvenile male collected by Jose Vieira, Daniela Franco, and Alex Mora on 4 December 2019 at Reserva Biológica Canandé, Esmeraldas Province, Ecuador (0.49531, -79.17832; 560 m a.s.l.). These specimens agree in coloration and lepidosis with the description of S. ayerbeorum presented in Vera-Pérez 2019 (expanded in Echavarría-Rentería and Medina-Rangel 2021), most notably in having a much lower (fewer than 160) number of ventral scales than any other sympatric Sibon species, vertebral scale row not noticeably wider than adjacent rows, postmentals absent, dorsal coloration green to grayish brown with black-bordered reddish markings, and ventral coloration consisting of a checkerboard pattern of yellowish white markings interspersed with blackish markings. We also report an individual of S. ayerbeorum photographed (https://www.inaturalist.org/photos/179847493; DHMECN 14936) by Mateo Vega on July 21, 2019 at Comunidad El Baboso, Carchi province, Ecuador (0.89972, -78.44797; 803 m). We did not examine this specimen, but the photograph agrees in coloration with the variation reported for this species in Vera-Pérez (2019) and Echavarría-Rentería and Medina-Rangel (2021). The updated distribution of S. ayerbeorum is shown in Fig. 17 View Figure 17 and includes both published records as well as new localities reported here (summarized in Suppl. material 2).
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