Paleophylogeography of Notiosorex desert shrews with description of a new species.

This article focuses on the taxonomy, phylogeny, and paleophylogeography of the North American desert shrew genus *Notiosorex*, which is uniquely adapted to arid and semiarid environments. Using geometric morphometric analyses of cranial and mandibular characters from extant and fossil specimens, the study identifies a new species, *Notiosorex carrawayae*, from the Altiplano Mexicano, distinct from but closely related to *N. villai*. Phylogenetic reconstructions rooted in fossil data suggest that *Notiosorex* originated in the Late Miocene (~5–7 million years ago) in the Sonoran Desert region and subsequently diversified and dispersed southward, with speciation driven largely by geographic barriers such as mountain ranges and rivers. The research integrates morphological and fossil evidence to clarify species boundaries, evolutionary history, and biogeographic patterns within the genus, highlighting the complex speciation processes in desert-adapted shrews.