Conopsis nasus Günther 1858

Goyenechea, Irene & Flores-Villela, Oscar, 2006, Taxonomic summary of Conopsis, Günther, 1858 (Serpentes: Colubridae), Zootaxa 1271, pp. 1-27 : 13-14

Conopsis nasus Günther 1858 .

Conopsis nasus Günther, 1858:6 –7.

Oxyrhina (Exorhina) maculata Jan, 1862:54 . Oxyrhina maculata anomala Dugès, 1869:144 . Conopsis maculatus Cope, 1884:162 .

Contia nasus Boulenger, 1894:268 –269.

Conopsis [ nasus nasus ] Cuesta Terrón, 1930:176. Conopsis nasus heliae Cuesta Terrón, 1930:175 –176. Conopsis nasus labialis Tanner, 1961:15 . nov. sin. Gyalopion atavus Leviton and Banta, 1961:2 .

Type specimen: BMNH lost; neotype BMNH 83.4.16.38.

Type locality: Milpas, Durango.

Diagnosis: This snake is characterized by the following combination of characters: fused prefrontals and internasals; upper labials 7, 6 lower labials (some populations with reduced number of these scales); light cinnamon dorsal coloration; with a vertebral line of hexagonal spots that may be bordered by two paravertebral rows of spots. Ventrally it is yellowish, with intercalated black dots. It differs from C. megalodon , the only species with which it could be mistaken, by the light cinnamon dorsal coloration, its larger body size (SVL: 100–320 mm in C. nasus and 107–250 mm in C. megalodon ), and by its distributional range in the Mesa Central, which does not overlap with C. megalodon .

Description: A species with fused prefrontals and internasals; a loreal; a pointed rostral; nasal pierced by nostril on each side of head; a preocular and two postoculars; hexagonal frontal, contacting internasals; temporal formula 1+2; 7 or 6 upper labials and 6 lower labials; 2 or 2.5 upper labials before eye; genial shields separated by one or two scales; a mean of 123.3 ventrals (116–138), and 31.6 subcaudals (20–43); 17 rows of smooth scales at midbody; dorsum light cinnamon or beige, with vertebral line of hexagonal spots; venter yellowish, with intercalated black dots.

Measurements: Adult specimens of Conopsis nasus average 202.1 mm snout­vent length (100–320 mm), 238.1 mm in total length (120–385 mm), body diameter 7.6 mm.

Variation: Of all specimens examined only two had prefrontals and internasals divided. Loreals present on both sides of head (75.6%), absent (15.6%), or absent on one side of head (8.7%). Upper labials usually 7 (84.5%), 6 (8.6%), or less than 6 (6.9%). The latter percentage corresponds to a population in Chihuahua. Lower labials 7 (34.5%), 6 (48.3%), or less than 6 (17.2%). Upper labials before eye 3 (13.7%), 2.5 (75.8%) or 2 (10.3%). First pair of genial shields separated by one (51.6%) or two scales (48.4%). Dorsal coloration is cinnamon (44.8%), beige (21%), brown (25%), dark brown (7.7%), or olive green (1.7%); with a vertebral row of hexagonal spots bordered by two paravertebral rows of smaller dots (73.3%), a vertebral row of hexagonal spots on the first third of body and on the other two thirds a tessellated pattern (15.4%), or a vertebral row of hexagonal spots over a light vertebral band (12.9%, variation found in some juveniles). Ventral coloration creamy (87.9%), yellow (9.5%), whitish (1.8%) or gray (0.8%). The venter with dark scattered spots (60.3 %), a row of paired dots (28.05 %), large dots forming a band (1.6%), dots in half circle (2.5%), dots on the external edge of each ventral scale (3.3%), or immaculate (4.1%).

Distribution: Conopsis nasus is distributed in north­central Mexico (fig. 7); it has been collected in the states of Chihuahua, Aguascalientes, Distrito Federal, Durango, Guanajuato, Hidalgo, Jalisco, Estado de Mexico, Michoacan, Morelos, Puebla, Queretaro, San Luis Potosi, Sinaloa, Tlaxcala, Veracruz and Zacatecas, from 1515 to 2950 m, in xerophilous underbrush, oak, pine, and fir forest. It is usually under rocks or logs during every month of the year, being more abundant from June to September.