Rhadinaea nuchalis

description

Description of holotype (Figs 1, 2). Male; adult; head length = 12.2 mm, snout-vent length (SVL) = 275 mm, tail length = 104 mm. Head distinct from neck; snout long, contained 2.5 times in head length, rounded from above, projecting anteriorly beyond lower jaw; rostral broader than high, portion visible from above 0.6 times as long as its distance from frontal, 0.5 times as long as internasal common suture, upper edge slightly above level of upper margin of nostrils; internasals broader than long (width / length = 1.5), rounded laterally, contacting anterior and posterior nasals laterally, length and common suture ca. 0.8 and 0.4 times as long as prefrontal common suture, respectively; prefrontal contacting postnasal and loreal laterally, length ca. 0.3 times length of snout, common suture ca. 0.5 times frontal length; frontal longer than broad (width / length = 3.6 / 2.3), angulate posteriorly; supraocular large, contacting prefrontal, frontal, parietal, and upper postocular broadly, length ca. 1.3 times length of horizontal diameter of eye, 1.3 / 1.3 times as long as loreal, ventral margin projecting anteriorly and posteriorly beyond margins of orbit; parietals 1.6 times longer t

A new rare species of the Rhadinaeadecorata group from the Sierra Madre del Sur of Guerrero, Mexico (Squamata, Colubridae)

diagnosis

Diagnosis. A colubrid snake of the Rhadinaea decorata group (sensu Myers 1974) that may be distinguished from all other members of the genus Rhadinaea by the following combination of character states: eight supralabials; 149 - 151 ventrals in males; 63 - 77 subcaudals in males; presence of two large pale nuchal blotches, forming an incomplete collar that occupies two scales laterally and bissected along the dorsal midline; postocular pale marking consisting of a well-defined and narrow line beginning anteriorly behind the upper posterior margin of the eye and extending posteriorly nearly horizontally until connecting with the nuchal blotches; and ground color of the flanks extending to the lateral portion of the ventrals.

A new rare species of the Rhadinaeadecorata group from the Sierra Madre del Sur of Guerrero, Mexico (Squamata, Colubridae)

distribution

Distribution and ecology. Rhadinaea nuchalis sp. n. is known only at intermediate elevations from the vicinity of El Molote in the western portion of the Sierra Madre del Sur of Guerrero. The species appears to be allopatric with the other species of the R. decorata group. The closest Rhadinaea record to R. nuchalis is that of R. omiltemana from El Tambor, Coyuca de Benitez, Guerrero, approximately 8 km E in straight line from the type locality of R. nuchalis (Palacios-Aguilar et al. 2016). The second closest record is that of R. taeniata from 1.5 mi N San Vicente de Jesus, Guerrero, about 18 km SSW in straight line from the type locality of R. nuchalis (Myers 1974). Other close records are those of R. omiltemana from Omiltemi and Asoleadero, R. hesperia from Acahuizotla and Chilpancingo, and R. taeniata from Chilpancingo, all in Guerrero (Fig. 6). All the three are about 72 km, straight line, from the type locality of R. nuchalis The closest records of species in the R. decorata group, excluding those of R. hesperia, to the type locality of R. nuchalis are those of R. myersi from Malinaltepec, Guerrero, and southwestern Oaxaca (Garcia-Vazquez et al. 2006); and those of R. macdouga

A new rare species of the Rhadinaeadecorata group from the Sierra Madre del Sur of Guerrero, Mexico (Squamata, Colubridae)

etymology

Etymology. The specific name nuchalis comes from the Latin nucha, meaning nape. It makes reference to the large nuchal blotches present in the new species.

A new rare species of the Rhadinaeadecorata group from the Sierra Madre del Sur of Guerrero, Mexico (Squamata, Colubridae)