27 



residing east of this valley is T. gracilis, which occurs in extreme southwestern Illinois. Four 

 species are endemic (36.4%) to the United States {T. coronata, T. cucullata, T. oolitica, and 

 T. relicta). 



Mexico is the region inhabited by the largest number of species in the genus, i.e., twenty-seven 

 (Table 1). Seven of these 27 species also occur in the United States {T. atriceps, T. gracilis, T. 

 hobartsmithi, T. nigriceps, T. planiceps, T. wilcoxi, and T. yaquia). Tantilla cucullata is the 

 only species occurring west of the Mississippi River Valley that has not been recorded in 

 Mexico, although it occurs just to the north of the Rio Grande Valley in the Big Bend and 

 Trans-Pecos regions of western Texas. Fourteen species in the genus are endemic (51.9%) to 

 Mexico (7. bocourti, T. briggsi, T. calamarina, T. cascadae, T. coronadoi, T. deppei,T. 

 flavilineata, T.johnsoni, T. oaxacae, T. shawi, T. slavensi, T. striata, T. tayrae, and T. 

 triseriata). 



Nineteen species of Tantilla reside in Central America (Table 1). Six of these species are 

 shared with Mexico {T. cuniculator, T. impema, T. moesta, T. rubra, T. schistose, and T. 

 vulcani). Most of these species have made relatively small inroads into either Mexico or 

 Central America. Only T. schistosa inhabits a significant range on either side of the Mexican- 

 Central American border. Nine species of Tantilla are endemic (47.4%) to Central America {T. 

 albiceps, T bairdi, T. brevicauda, Tjani, T lempira, T taeniata, T. tecta, T tritaeniata, and 

 T. vermiformis). 



South America is home to twelve species of Tantilla (Table 1). Four of these species also 

 occur in Central America (71 alticola, T melanocephala, T reticulata, and T supracincta). 

 Only one of these species {T. melanocephala) is broadly distributed in South America, and it is 

 the most broadly distributed species of Tantilla. Eight species are endemic (66.7%o) to South 

 America {T. andinista, T. capistrata, T. equatoriana, T. insulamontana, T miyatai, T nigra, 

 T petersi, and T. semicincta). 



Tantilla, thus, is only one of twelve snake genera that are widely distributed enough to occur 

 from the United States to South America (the other eleven are Coniophanes, Crotalus, 

 Drymarchon, Drymobius, Lampropeltis, Leptodeira, Leptotyphlops, Masticophis, Micrurus, 

 Oxybelis, and Rhadinaea). 



