Resumen

CZAJA, Alexander; ESTRADA-RODRIGUEZ, José Luis; ROMERO-MENDEZ, Ulises  y  ORONA-ESPINO, Anselmo. Two new subfossil species of springsnails (Hydrobiidae: Pyrgulopsis) from North Mexico and their relation with extant species from Cuatrociénegas. Bol. Soc. Geol. Mex [online]. 2017, vol.69, n.1, pp.199-208. ISSN 1405-3322.

We describe two new species of the genus Pyrgulopsis Call and Pilsbry from subfossil spring deposits of Viesca, Coahuila, in the northern part of Mexico. The first species, P. paleominckleyi sp. nov., has trochiform shells with flat whorls and bulbous shoulders. Extant endemic species Pyrgulopsis minckleyi (Taylor) displayssimilar shell features - this species was originally described as Nymphophilus minckleyi Taylor from the spring complex of the Cuatrociénegas valley, Coahuila. Some specimens of P. paleominckleyi sp. nov. show wing-like shoulders that have never been observed among fossil or extant members of the genus. In addition, shells of the second new species from Viesca, P. paleoacarinatus are similar to P. acarinatus, which is other endemic Pyrgulopsisspecies from Cuatrociénegas. We suppose that both sub-fossil springsnails of Viesca are sister species or, likely, direct precursors of the two extant endemic springsnails from Cuatrociénegas valley.

Palabras llave : Pyrgulopsis; new species; sub-fossil; North Mexico; Viesca; Cuatrociénegas.