A NEW SPECIES OF EREMOPYRGUS (HYDROBIIDAE: COCHLIOPINAE) FROM THE CHIHUAHUAN DESERT, MEXICO

Abstract

A new species of hydrobiid gastropod, Eremopyrgus elegans, is described from northwestern Chihuahua state, Mexico. This new species inhabits a single spring more than 1000 km south-southeast of waters occupied by its sole congener (E. eganensis), which lives in east-central Nevada. Eremopyrgus elegans differs from its congener in its narrower shell, larger number of shell whorls, tilted shell apex, location of glandular lobe on the outer edge of the penis, presence of a terminal penial papilla, and 12 additional anatomical features. Although well differentiated, these two species share an unique type of glandular penial lobe and distinctive female genitalic organs, and their monophyly within the Cochliopinae is supported by a phylogenetic analysis based on a partial sequence of the mitochondrial COI gene. Our phylogenetic analysis depicts Eremopyrgus as sister to Zetekina, which is distributed along the Pacific Coast of southern Central America. We conjecture that the broadly disjunct distribution of Eremopyrgus, which cuts across the structural grain of western North America, may reflect the trace of a prior inland ‘invasion’ by coastal progenitors.