Background and Aims: Pachyphytum (Crassulaceae) is a genus with 26 species endemic to Mexico. During explorations in the Sierra de Puruagua, Guanajuato, a population of Pachyphytum with distinctive characteristics was discovered. The aims of this study were to describe P. theodactylum as a new species to science, present a distribution map, assess its conservation status and provide a key to the Pachyphytum taxa in Guanajuato. Methods: Flowering specimens were collected for morphological analysis and data were compared with the most similar species. The collections were prepared as herbarium specimens and will be deposited in the IBUG and ZON herbaria. Its conservation status was assessed using GeoCAT and IUCN criteria. The distribution map was generated in QGIS with georeferenced herbarium coordinates projected on a layer of the biogeographic provinces of Mexico. The identification key was elaborated based on specialized literature. Key results: Pachyphytum theodactylum is described as a new species morphologically similar to P. garciae, distinguished primarily by its longer and wider stems, elliptic-lanceolate peduncle bracts with acute apex, longer pedicels, sepals with pink and olive coloration and acute apex, shorter antesepalous stamens, and pink styles. It is assessed as a Critically Endangered (CR) species. Conclusions: The description of Pachyphytum theodactylum raises the number of endemic species of the genus in Mexico to 27. Given its vulnerability, conservation measures are recommended.
HERNÁNDEZ-CAMPOS et al. (Thu,) studied this question.