Reopening the case of the enigmatic record hitherto referred to as the Mayan shrew, Cryptotis mayensis (Mammalia, Soricidae)

Abstract

The Mayan small-eared shrew, Cryptotis mayensis, is endemic to the Yucatán Peninsula, with records from México, Belize, and Guatemala. For half a century, skull fragments from dozens of individuals found in pellets of the barn owl (Tyto furcata) in Guerrero, Mexico, previously identified as the Mayan shrew, have intrigued taxonomists and biogeographers. A previous robust analysis of current and fossil C. mayensis dentary samples, including those from Guerrero, showed a high morphometric similarity between them. Given that these owl pellet remains are located 1,000 km from the known distribution of C. mayensis in the Yucatán Peninsula, this has raised the hypothesis that they are not an isolated population of C. mayensis but rather an as-yet-undescribed species. By integrating new specimens of C. mayensis from the Yucatán Península and Guerrero, as well as Cryptotis lacandonensis, the sister species of C. mayensis, we reanalyzed the morphological attributes. In addition, we used paleodistribution estimates to investigate the possible isolation of the records previously referred to as C. mayensis in Guerrero, Mexico. Multivariate analyses of morphological data from the cranium and dentary revealed high similarity in size among the three samples analyzed, especially between C. mayensis sensu stricto and Cryptotis from Guerrero. Paleodistribution models suggest that the population of Guerrero has remained in long-term isolation from the populations of the Yucatan Peninsula due to a very large area with unsuitable conditions for the connectivity of the shrew population during the last glacial-interglacial cycle. It is possible that the Guerrero population is an independent lineage, despite its morphological similarity to C. mayensis sensu stricto; however, genetic evidence to confirm this is essential.