Liebmann's Earth Runner

description

Chersodromus liebmanni Reinhardt, 1861, Vidensk. Meddel. Naturhist. Foren. Kjöbenhavn 2: 243. Holotype: ZMUC 60561. Type-locality: “ Mexico. ” Restricted to Cuautlapan, Veracruz, Mexico, by Smith & Taylor (1950: 347), and to Mirador, Veracruz, Mexico by Smith & Braestrup (1963: 240). Chersodromus nigricans Reinhardt, 1861 Vidensk. Meddel. Naturhist. Foren. Kjöbenhavn 2: 245. Holotype: ZMUC 60562. Type locality: “ Mexico. ” Restricted to Cuautlapan, Veracruz, Mexico, by Smith & Taylor (1950: 347), and to Mirador, Veracruz, Mexico by Smith & Braetrup (1963: 240). Opisthiodon torquatus Peters, 1861, Monatsber. königl. Akad. Wiss. Berlin. 1861: 461. Holotype: Berlin Museum. Type locality: Huanusco [= Huatusco], Veracruz. Dirosema collare Werner 1900, Zool. Anz. 23: 197. Holotype: Not traced. Type-locality: Mexico.

Taxonomic review of the rare Mexican snake genus Chersodromus (Serpentes: Dipsadidae), with the description of two new species

description

Description. Small, slender snake; head moderately wider than the neck. Adults commonly reaching 250 – 330 mm in total length with the largest known male 310 mm, and the largest female 330 mm. Tail comprises 16 – 22 % of total length in males, 15 – 18 % in females. Prefrontals fused into a single, large scale. Supraoculars fused with postoculars. Frontal relatively broad and nasals divided. Small internasals 1 / 1, loreals 1 / 1, extending from the postnasal to the anterior edge of eye (no preoculars). No discrete postoculars are present (fused with supraocular). temporals 1 + 2 (rarely 1 + 1 owing to fusion of secondary series), supralabials 6 – 7 (usually 7) with 3 – 4 entering orbit, infralabials 6 – 8 (usually 7) with 1 – 4 contacting anterior chinshields (5 usually narrowly). Mental broader than long, first pair of infralabials not in contact along ventral midline. Anterior chinshields large with posterior pair of chinshields about one-third to onehalf the size and anterior pair. Dorsal scales keeled in 17 - 17 - 17 rows, rarely reduced by one either anteriorly or posteriorly. Preventrals 2 (rarely 1), ventrals 121 – 136 in males and 126 – 140 in females; divided subcaudals 32

Taxonomic review of the rare Mexican snake genus Chersodromus (Serpentes: Dipsadidae), with the description of two new species

diagnosis

Diagnosis. Chersodromus liebmanni can be distinguished from all Mexican species of snakes by having combination of prefrontals fused into single scale; postocular fused with supraocular; dorsal scales keeled in 17 rows at midbody, unreduced posteriorly; supralabials 7, third and fourth entering orbit; infralabials 7 – 8, usually 1 – 5 contacting anterior chinshields (5 narrowly); mental contacting anterior chinshields; venter cream colored. This species may be distinguished from all species of Chersodromus, except C. rubriventris, by having the postocular fused with supraocular; from C. rubriventris by having 17 scales around body (vs. 15), ventral surface uniformly cream (vs. bright orange) (Table 1). Ninia diademata Baird & Girard (1853) might be confused with this species, and they are sympatric at some localities in Oaxaca and Veracruz. Ninia diademata differs from Chersodromus in having paired prefrontals shields, 19 strongly keeled dorsal scale rows, and two postoculars, larger body size (reaching at least 330 cm TL), and more slender tail.

Taxonomic review of the rare Mexican snake genus Chersodromus (Serpentes: Dipsadidae), with the description of two new species

distribution

Distribution and habitat. Inhabiting the Atlantic foothills and versant of west-central Veracruz in the Orizaba region southward through the Sierra Zongolica to Sierra Negra in southeast Puebla and the Sierra Mixe in northern Oaxaca (Fig. 1). Chersodromus liebmanni inhabits upper rain forest and cloud forest (Fig. 3 B) between 1000 – 1800 m above sea level (asl hereafter). Several specimens have been collected in agricultural fields and shade coffee plantations.

Taxonomic review of the rare Mexican snake genus Chersodromus (Serpentes: Dipsadidae), with the description of two new species