Primer registro fósil del gasterópodo Cincinnatia (Hydrobiidae: Nymphophilinae) en México

The first record of fossil shells of the freshwater gastropod genus Cincinnatia Pilsbry, 1891 found in fluvial sediments of the late Pleistocene in the Acatita Valley, Coahuila, Mexico, is described. Morphology and discriminant analysis indicate that the fossil material correspond to Cincinnatia integra (Say, 1821), an extant species with a disjunct distribution between the eastern part of United States of America and southern Canada and a small area near Pánuco River, San Luis Potosí, Mexico. The new findings mark the westernmost limit of the original distribution of Cincinnatia and suggest a north-south connection between both areas in the original extension of C. integra, today separated according to the records by more than 700 km, since the late Pleistocene to sub-recent times. Considering that northern Mexico to date is under-sampled for the Hydrobiidae, there is a high probability of finding live populations of Cincinnatia in this region and in other aquatic habitats in the northern part of the states of Coahuila, Nuevo León, and Tamaulipas.