A new species of the calamarina group of the colubrid snake genus Tantilla(Reptilia : Squamata) from Guerrero, Mexico, with a review of and key to members of the group

A new species of Tantilla of the calamarina group, T. sertula, is described from the Pacific coastal plain of southwestern Guerrero, Mexico. It belong s to a clade that contains T. calamarina, T. cascadae, T. coronadoi, T. dep pei, and T. vermiformis. All these species are endemic to Mexico, except fo r T. vermiformis, which is distributed along the Pacific coastal plain from El Salvador to northwestern Costa Rica. The new species appears to be the sister species of T. cascadae. Members of the calamarina group are highly a dapted to fossoriality.