First records of the Chihuahuan Black-headed Snake , Tantilla wilcoxi Stejneger , 1902 ( Squamata : Colubridae ) , in the Mexican state of Jalisco

Based on three specimens, we document the occurrence of Tantilla wilcoxi in the Mexican state of Jalisco. This species was found at two localities, 2.9 km apart, both in the ecotone between xerophytic scrub and oak forest in the arid plains of the municipality of Ojuelos de Jalisco in the northeastern portion of the state.

The genus Tantilla is comprised of 62 species distributed in North, Central, and South America; it is the second largest snake genus in the Western Hemisphere (Wilson and Mata-Silva 2014).In Mexico 30 species occur, making this country the center of diversity for the genus (Wilson and Mata-Silva 2014).Tantilla wilcoxi is a small snake reaching 36 cm total length.It has a black head bordered posteriorly by a white collar; the color of the dorsum is light brown or yellowish brown and the belly is white gradually becoming bright orange posteriorly (Liner 1983).This primarily Mexican species has been previously recorded from the states of Aguascalientes, Chihuahua, Coahuila, Durango, Nuevo León, San Luis Potosí, Sinaloa, Sonora, and Zacatecas, between elevations of 914 and 2438 m (Liner 1983;Vázquez-Díaz and Quintero-Díaz 2005;Enderson et al. 2009;Váldez-Lares et al. 2013;Wilson and Mata-Silva 2014).A disjunct population occurs in the United States in extreme southern Arizona, which includes the holotype of the species collected from Fort Huachuca, Cochise County.
Currently 124 species of reptiles have been listed for the state of Jalisco, comprised by one crocodile, nine turtles, 44 lizards, and 70 snakes (Uetz and Hošek 2014).However, the reptilian fauna of the northeastern portion of the state still remains relatively unknown.We are only aware of one published herpetofaunal inventory near the plains of the municipality of Ojuelos de Jalisco (Riojas-López and Mellink 2006).Herein we present locality data for three specimens of Tantilla wilcoxi collected during herpetological surveys on the arid plains of the municipality of Ojuelos de Jalisco.Institutional acronyms are those listed in Sabaj-Pérez ( 2013), with the addition of La Sierra University Digital Photo Collection (LSUDPC).
During a field trip on July 2009, we (RACM, JCAM and ZYGS) found an adult specimen of T. wilcoxi in a rock crevice in the foothills of Mesa Las Preñadas plateau, municipality of Ojuelos de Jalisco, ca. 3 km SW of Las Negritas, Asientos, Aguascalientes (21.962267°N, 101.891364°W, WGS84; 2,200 m elevation).Four years later on July 2013, CMGB returned to the same locality and found an adult male of T. wilcoxi (Figure 1) at ca. 12:30 h inactive beneath a Sotol plant (Dasylirion acrotrichum) along with a lizard Sceloporus spinosus.However, because we mistakenly assigned this locality to the state of Aguascalientes rather than Jalisco, while we were doing the herpetological surveys, we released both specimens immediately after photos were taken.Photo vouchers were subsequently submitted to the La Sierra University Digital Photo Collection (LSUDPC 8018 and 8019).Four species of Tantilla are known otherwise from the state of Jalisco, including T. bocourti, T. calamarina, T. cascadae, On a third specimen found by RACM and GEQD on February 2014 we realized the locality does lie within the state of Jalisco and, therefore, all the collected specimens represent new state records.The third specimen of T. wilcoxi was caught around 12:20 h under a rock next to a Lechuguilla plant (Agave filifera) in the same foothills of Mesa Las Preñadas plateau (21.937229°N, 101.884915°W, WGS84; 2337 m elevation); it is a juvenile measuring 11.8 cm in snout-vent length, and 15.0 cm in total length with a weight upon capture of 0.83 g (Figure 2).It was deposited in Universidad Autónoma de Aguascalientes Colección de Vertebrados (voucher UAACV-R 264) and identified by the collection manager J. Jesús Sigala Rodríguez.The vegetation in the foothills of Mesa Las Preñadas plateau consists of an ecotone between xerophytic scrub forest and oak forest, represented by associations of xeric plant species such as Prosopis laevigata, Ferocactus histrix, Opuntia streptacantha, Dasylirion acroctrichum, Agave filifera, Yucca filifera, and Dodonaea viscosa, with interspersed Quercus resinosa and Q. potosina oaks (Rosales-Carrillo 2008).
Together the new records fill a distributional gap for Tantilla wilcoxi between the states of San Luis Potosí and Aguascalientes (Figure 3).The three specimens found are from two localities 2.9 km from each other, and together extend the range of this species ca.38 km (in a straight line) southeast from Tepezala, Aguascalientes, 71 km (in a straight line) southwest from 1.5 mi (by road) east San Luis Potosí  and T. ceboruca (Wilson and Mata-Silva 2014).The last three species, all members of the calamarina group, can be distinguished easily from T. wilcoxi in having a dorsal body pattern consisting of dark stripes on a paler background, in contrast with the body dorsal pattern of T. wilcoxi consisting of light brown or yellowish brown without stripes.In addition, members of the calamarina group have a head pattern consisting of a pair of pale parietal spots, whereas T. wilcoxi presents a distinct black or dark brown head cap extending posteriorly to end abruptly near the tips of the parietals followed by a white nape band two scales wide.Tantilla wilcoxi more closely resembles T. bocourti, but the two can be readily distinguished from one another by the non-overlapping number of ventral scales (135-161 in the former and 164-195 in the latter), (Liner 1983;Wilson and Mata-Silva 2014).With the addition of T. wilcoxi, the number of recorded reptiles for the state of Jalisco increases to 125 species (Uetz and Hošek 2014).

Figure 3 .
Figure 3. Collecting localities for Tantilla wilcoxi across its southeastern geographic distribution in México; red circles represent the new records for Jalisco state, and black circles additional recorded localities.The hatched area represents the distribution of T. wilcoxi according to the IUCN Red List of Threatened Species (Hammerson et al. 2007).