Imantodes chocoensis, Torres-Carvajal, Omar, Yanez-Munoz, Mario H., Quirola, Diego, Eric N. Smith, & Almendariz, Ana, 2012

Torres-Carvajal, Omar, Yanez-Munoz, Mario H., Quirola, Diego, Eric N. Smith, & Almendariz, Ana, 2012, A new species of blunt-headed vine snake (Colubridae, Imantodes) from the Choco region of Ecuador, ZooKeys 244, pp. 91-110 : 93-99

Imantodes chocoensis sp. n.

Holotype.

- QCAZ 7984 (Figs. 1, 2), an adult male from 4 km N Durango, 1.0283°N, 78.5950°W (DD), 253 m, Provincia Esmeraldas, Ecuador, collected on 24 April 2007 by E. Carrillo-Ponce, I. G. Tapia, and E. E.Tapia.

Paratypes (6).

- ECUADOR: Provincia Carchi: DHMECN 6753, Río San Juan, 1.1858°N, 78.5006°W (DD), 243 m, collected on 12 September 2009 by M. Yánez-Muñoz, L. Oyagata, and M. Altamirano; DHMECN 6757, Sendero Awa, 1.1643°N, 78.5071°W (DD), 257 m, collected on 16 September 2009 by M. Yánez-Muñoz, L. Oyagata, and M. Altamirano. Provincia Esmeraldas: UTA R-60205, San Lorenzo-Santa Rita, 1.0321°N, 78.7138°W (DD), 115 m, collected on 21 March 2008 by M. Alcoser, R. Betancourt, P. Loaiza L., L. Oyagata, S. Ramírez J., J. W. Streicher, C. Tobar, and E. N. Smith; QCAZ 7978, same collection data as holotype; QCAZ 10185, 4 km W Alto Tambo, 0.91241°N, 78.5809°W (DD), collected on 18 December 2009 by S. Poe, L. Gray, and I. Latella; QCAZ 10710, Playa de Oro, Estero Pote and Estero Angostura, lower part of Cotacachi Cayapas Ecological Reserve, 0.8285°N, 78.7220°W (DD), collected on 27 November 1994 by E. Toral-Contreras, V. Ortiz, and F. Nogales.

Diagnosis.

Imantodes chocoensis differs from all other known congeners in lacking a loreal scale. It can be further distinguished from its sister species (see Phylogenetic relationships) Imantodes lentiferus by having 17 longitudinal rows of dorsal scales at midbody and at nearly one head length anterior to the cloaca (15 in Imantodes lentiferus ), more ventrals (t = 7.27, P <0.001), more subcaudals (t = -4.31, P <0.001), more postoculars (2-3, mean = 2.43 ± 0.51; 1-2, mean = 1.81 ± 0.39 in Imantodes lentiferus ), more infralabials (12-15, mean = 13.21 ± 0.80; 9-12, mean = 10.68 ± 0.60 in Imantodes lentiferus ), and smaller dark blotches on dorsum (Fig. 3). Among other species of Imantodes known from Ecuador, the new species differs further from Imantodes inornatus (N = 2-3) in having more ventrals (t = 6.74, P <0.001), more subcaudals (t = -5.05, P = 0.002), more infralabials (9-11, mean 10.00 ± 0.89 in Imantodes inornatus ), a longer head (head length/width 1.54-1.71, mean = 1.63 ± 0.07 in Imantodes chocoensis sp. n.; 1.29-1.61, mean = 1.45 ± 0.16 in Imantodes inornatus ), and dark blotches on dorsum (dark spots and flecks in Imantodes inornatus ; Fig. 3). The new species can also be distinguished from Imantodes cenchoa by having a single anal scale (vrs. two), fewer ventrals (t = 7.73, P <0.001), fewer subcaudals (t = -4.04, P <0.001), more infralabials (7-12, mean 9.92 ± 0.85 in Imantodes cenchoa ), and dorsal dark blotches that include two or fewer vertebral scales and do not extend laterally onto ventrals (blotches are larger in Imantodes cenchoa and extend onto lateral tips of ventrals; Fig. 3). Scale counts and measurements of species of Imantodes from Ecuador are presented in Table 2.

Description of holotype.

Male (Figs. 1, 2); SVL = 66.30 mm; tail length = 30.40 mm; head width = 7.98 mm; head length = 13.26 mm; head height = 5.37 mm.

Short, blunt head 1.7 times longer than broad and 2.5 times longer than deep; head abruptly distinct from neck, three times wider than thinnest part of neck and also slightly wider than greatest width of body; eye large and protuberant, occupying 27% of length of head, with elliptical pupil visible from anterior, lateral, dorsal, and ventral aspects; rostral 1.6 times wider than high, concave in anterior view, and narrowly visible from above; paired prefrontals extending anteroventrally to level of center of eye, each in contact with its mate and with frontal, supraocular, preocular, nasal, and internasal; frontal pentagonal, 1.6 times longer than wide (greatest width), and about 1.2 times longer than distance from its anterior edge to tip of snout; supraocular anteriorly narrow and posteriorly nearly as wide as greatest frontal width; broad parietals, about 1.3 times longer than wide; interparietal suture 1.2 times longer than length of frontal, and 1.4 times longer than distance from frontal to tip of snout; nasal plate single, centrally pierced by large naris (0.79 mm in diameter), in contact with rostral anteriorly, internasal dorsally, prefrontal posterodorsally, preocular posteriorly, and first and second supralabials ventrally; loreal absent; one large and high preocular; two postoculars (an extra tiny scale on left side ventrally), the lower somewhat less than half the size of the upper; temporals 2+2+3; supralabials 9, first and second in contact with nasal, fourth in contact with preocular, and fourth to seventh bordering the orbit; infralabials 13, with first six in contact with anterior genial, and sixth to eighth touching posterior genial; first pair of infralabials in contact medially behind mental; anterior and posterior genials nearly equal in length; gular scales with posterolateral apical pit.

Body higher than wide, rounded ventrolaterally; dorsal scales smooth, juxtaposed or subimbricate; dorsal body scales in 17 rows throughout; scales of vertebral row conspicuously enlarged, 2.5 times wider than adjacent dorsals, with concave posterior margins; ventrals 242; anal plate single; subcaudals 161.

Color in preservative of holotype (Figs 1, 2). Dorsal background light brown, with a longitudinal series of 63 dark brown middorsal blotches from head to cloaca; dark middorsal blotches longer anteriorly, 2-3 vertebral scales long, than posteriorly, 1-2 vertebral scales long, and extending laterally 1-3 (anteriorly) or more (posteriorly) dorsal scale rows, but never reaching ventral scales; each dark middorsal blotch irregularly bordered anteriorly and posteriorly by thin cream line; ventral aspect of body yellowish cream with dark brown spots and flecks; ventral aspect of tail yellowish cream with spots concentrating midventrally; dorsal surface of head light brown with several dark brown spots and two short dark stripes extending from posterior aspect of parietals to a point just posterior to head; ventral surface of head whitish cream.

Hemipenes (Fig. 4). The right hemipenis of the paratype DHMECN 6753 of Imantodes chocoensis was removed, fully everted and expanded (Fig. 4). The organ is bulbous and relatively long, 11.2 mm in length, and when adpressed to the outside of the tail it extends from the cloaca to the sixth subcaudal scale. The organ is longer than wide (width 46% of length), unilobed, symmetrical, calyculate, capitate, and arched towards the sulcal side. The sulcus spermaticus is simple, linear, semicentripetal, and thin, demarcated by thick bordering tissue at the base, particularly at the anterior border, and ending on the surface of the capitulum facing medially. The capitulum is ornamented with papillated calyces, spinulated proximally. The capitulum, approximately 45% the length of the hemipenis, is slightly demarcated by a groove, more prominent on the sulcal side and joining the sulcus spematicus. In the asulcate side the base of the capitulum has more prominent spines. Truncus covered by large spines, on the sulcate and asulcate and surfaces, 23 in total, 13 to the right of the sulcus spermaticus and 10 to the left, and has a few rows of small spines, two at the base on the asulcate side and two to three rows just right of the sulcus spermaticus.

Variation.

Intraspecific variation in scale counts and measurements in Imantodes chocoensis sp. n. is presented in Table 2. Color in life of paratypes UTA R-60205 and DHMECN 6753 (Fig. 5) is similar to color in preservative of holotype; iris copper brown. Middorsal blotches from head to cloaca vary between 55-66; one specimen (UTA R-60205) had one middorsal blotch covering five vertebral scales.

Distribution and ecology.

Imantodes chocoensis inhabits Chocoan rainforests on the Pacific coast in northern Ecuador (Fig. 6). It occurs in lowland evergreen forest ( Cerón et al. 1999) at elevations of 115-260 m in the provinces of Carchi and Esmeraldas. This new species has been collected in sympatry with Imantodes cenchoa in Esmeraldas, and most likely also shares its distribution with Imantodes inornatus . Other colubrid snakes collected in Tobar Donoso (Carchi) are Chironius grandisquamis , Clelia clelia , Dendrophidion clarkii , Leptophis ahaetulla , Mastigodryas sp., Ninia atrata , Oxyrhopus petola , Pseustes shropshirei , Sibon nebulatus , Synophis bicolor , Tantilla melanocephala , and Xenodon rabdocephalus . The known localities of Imantodes chocoensis lie in close proximity to the Ecuador-Colombia border and we expect for it to be found in neighboring Colombia.

Etymology.

The specific epithet chocoensis is an adjective derived from Chocó, the very humid tropical region comprising the Pacific coast of northern Ecuador, Colombia and Panama ( Morrone 2001). This region is part of the 274,597 km2 Tumbes-Chocó-Magdalena hotspot as defined by Conservation International, which includes more than 320 species of reptiles.

Phylogenetic relationships.

Selected models of evolution for sampled fragments of ND4 and cyt-b genes were HKY+I+G and TPM2uf+I+G, respectively. The resulting 50% majority rule consensus tree (Fig. 7) supports strongly (PP=1) a sister taxon relationship between Imantodes chocoensis sp. n. and Imantodes lentiferus , as well as the exclusivity ( Rieppel 2010) of both species. Similarly, Imantodes inornatus and Imantodes cenchoa are recovered as exclusive clades with strong support (PP=1). Noteworthy the Imantodes cenchoa clade includes samples from Guatemala, Costa Rica, Panama, Brasil, and Colombia, Ecuador and Peru on both sides of the Andes. In agreement with previous hypotheses, Imantodes gemmistratus is paraphyletic; of three samples included in this study, one from Guatemala is sister to the Imantodes cenchoa clade with strong support (PP=1), whereas the other two, from Mexico, are weakly supported as sister to the Imantodes chocoensis sp. n. and Imantodes lentiferus clade.