A new species of small-eared shrew in the Cryptotis thomasi species group from Costa Rica (Mammalia: Eulipotyphla: Soricidae)

Abstract

We describe a new species of small-eared shrew, genus Cryptotis Pomel, 1848 (Eulipotyphla: Soricidae), from a single specimen found dead in 1973 near the community of Monteverde in the Tilarán highlands of northwestern Costa Rica in 1973. The new species is distinguished from all other North, Central, and South American species of Cryptotis by a combination of its large size; long tail; large, distinctly proportioned skull; lack of bulbous dentition; deep sigmoid notch on the mandible; and long, distinctive humerus. Morphologically, the new species belongs to the C. thomasi group of small-eared shrews, a clade that is more typically distributed in the Andes Cordillera and other highland regions of northern South America. The new Costa Rican species and the Panamanian endemic C. endersi Setzer, 1950 are the only two members of this species group known to occur in Central America. Like most other members of the C. thomasi group for which the postcranial skeleton has been studied, the new species tends be more ambulatory (rather than semi-fossorial) when compared with other members of the genus. Our survey efforts over several years failed to locate a population of the new species, and we discuss its conservation status in light of its limited potential distribution in the Tilarán highlands and the significant climatic change that has been documented in the Monteverde region during the past four decades.