Three additional species of garter snake were identified in a 2005 research paper. In their paper, “Species limits within the Mexican garter snakes of the Thamnophis godmani complex,” published in no. 79 of the Occasional Papers of the Museum of Natural Science and available as a PDF online, Douglas Rossman and Frank Burbrink argue that four populations of garter snake in central Mexico previously identified as Godman’s Garter Snake, Thamnophis godmani, are in fact four distinct species. This conclusion is based on the fact that the four populations are apparently isolated and morphologically distinct from one another. New, then, are Thamnophis bogerti and lineri, from the Mexican state of Oaxaca, and Thamnophis conanti, from the Puebla-Veracruz border. Entries in the Species Guide for these three species are forthcoming. Thanks to Stefan Allen for the tip.