New Garter Snake Species Discovered in MexicoThamnophis ahumadai sp. nov. holotype (INIRENA 2933) from the vicinity of Cumbre de Guadalupe, in the Municipio de Cuautla, Jalisco, Mexico. Photo by Christoph I. Grünwald, María del Carmen G. Mendoza-Portilla, Iván Ahumada-Carrillo, and Ginny N. Weatherman

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New Garter Snake Species Discovered in Mexico

The researchers recommend that Thamnophis ahumadai sp. nov be listed as Endangered under IUCN criterion

The snake is currently only known to exist in two small high elevation highland areas of Jalisco, known as the Jaliscan Transverse Range Pine-Oak Woodland and Jaliscan Sierra Madre del Sur Mixed Temperate Woodland.

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A new garter snake species has been discovered in Jalisco, Mexico that is morphologically unique from that assigned to Thamnophis scalaris, also from Jalisco. Both are each other’s closest relatives, and both fall within the researchers’ Mexican Clade of the phylogenetic tree.

The holotype of the new species, Ahumada’s Alpine Garter Snake (Thamnophis ahumadai sp. nov) was found residing under a log, near a pond in a marshy meadow, according to researchers Christoph I. Grünwald, María del Carmen G. Mendoza-Portilla, Iván Ahumada-Carrillo, and Ginny N. Weatherman. It was found August 23, 2019.

The researchers say Thamnophis ahumadai is small for a garter snake. The male holotype measures 565 mm snout to vent length and 705 mm total length. It differs from T. scalaris, according to the study, in that it has 19-17-17 dorsal scale rows, a shorter tail length in males; a black nuchal blotch versus a brown nuchal blotch in T. scalaris, two rows of dark brown or black dorsal blotches versus one row of large brown dorsal blotches in T. scalaris.

The snake is named after Iván Trinidad Ahumada-Carrillo, who continues to make significant contributions to herpetology and herpetofauna of Jalisco and Zacatecas, Mexico.


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The snake is currently only known to exist in two small high elevation highland areas of Jalisco, known as the Jaliscan Transverse Range Pine-Oak Woodland and Jaliscan Sierra Madre del Sur Mixed Temperate Woodland.

The researchers recommend that Thamnophis ahumadai sp. nov be listed as Endangered under IUCN criterion based on the logging, farming and other habitat destruction that occurs in the snake’s natural range.

The complete paper, “A new species of Thamnophis (Serpentes, Colubridae) from Jalisco, Mexico, with a discussion on the phylogeny, taxonomy, and distribution of snakes related to Thamnophis scalaris” can be read on the OGH Herpetozoa website.