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| Yakacoatl tlalli Cisneros-Bernal, Palacios-Aguilar, Hernández-Jiménez, Smith, Flores-Villela, Hernández-Morales, Loyola & Campillo-García, 2025 |
Abstract
The colubrid snake tribe Sonorini, which is largely composed of semifossorial and fossorial species, has undergone a series of taxonomic changes in the last few decades. New species have been added, multiple genera have been synonymized, and phylogenetic relationships have been tested using molecular systematics. Our field explorations of the dry Balsas Basin within the Mexican state of Puebla recently resulted in the procurement of two specimens of an unknown Sonorini species. Based on an integrative methodology of genetic and morphological data, we conclude that these specimens represent a hitherto unnamed genus and species, which we describe herein. This new genus is closely related to the other monotypic, Mexican endemic genera Pseudoficimia and Sympholis, but is easily diagnosable from them.
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| the head of the holotype of Yakacoatl tlalli (MZFC-HE 37100) Dorsal (A), lateral (B), and ventral (C) views. Scale bar represents millimeters. |
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| Location of the Yakacoatl tlalli type locality (red dot, A). Rural construction where the holotype (MZFC-HE 37100) was found (B); typical vegetation at the type locality (C). Photographs of the type locality were taken by Oscar Olivares Loyola, shape files used to construct the map were obtained from INEGI (Instituto Nacional de Estadística y Geografía, Mexico). |
Yakacoatl gen. nov.
Diagnosis.—This genus differs from all the other Western Hemisphere colubrids by the following set of characters: 1) smooth dorsal scales arranged in 17-17-17 rows, 2) an upturned rostral scale in contact with the internasals, 3) 154–156 ventral scales in known males; 4) 35–36 paired subcaudals scales; 5) short, thick supranasal bones; 6) absence of a supraoccipital keel; 7) 12 maxillary teeth, with rear teeth enlarged and faintly grooved; 8) hemipenis subcylindrical with slightly protruding lobes, a single sulcus spermaticus, body covered with spines and spinules, and lacking calyces.
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Etymology.—From the Nahuatl words yacatl meaning nose, and coatl meaning snake, in reference to the pronounced rostral scale that resembles a pointed nose in the species. Of feminine gender.
Yakacoatl tlalli sp. nov.
Etymology.—The specific epithet tlalli, comes from the Nahuatl word for land or earth. This naming choice alludes to the presumed fossorial habits of Yakacoatl tlalli, inferred from its morphology and the known behavior of other Sonorini genera.
Antonio Y. Cisneros-Bernal, Ricardo Palacios-Aguilar, Carlos Hernández-Jiménez, Eric N. Smith, Oscar Flores-Villela, Cristian Hernández-Morales, Oscar Olivares Loyola and Gustavo Campillo-García. 2025. Sticking our nose into the Sonorini tribe: A New Genus and Species of Snake (Squamata: Colubridae: Sonorini) from the Balsas Basin of Mexico. PLoS One. 20(12): e0337187. DOI: doi.org/10.1371/journal.pone.0337187 [December 10, 2025]
