Fluminicola, CARPENTER, 1864

Hershler, Robert, Liu, Hsiu-Ping, Frest, Terrence J. & Johannes, Edward J., 2007, Extensive diversification of pebblesnails (Lithoglyphidae: Fluminicola) in the upper Sacramento River basin, northwestern USA, Zoological Journal of the Linnean Society 149 (3), pp. 371-422 : 385-386

GENUS FLUMINICOLA CARPENTER, 1864

Fluminicola Carpenter, 1864: 676 . Type species Paludina nuttalliana Lea, 1838 , by original designation.

Fluminicola shares with other members of the family Lithoglyphidae (fide Wilke et al., 2001) a distinctive combination of a flattened, blade-like penis lacking glands and a female capsule gland with an enclosed ventral channel ( Radoman, 1983; Thompson, 1984; Hershler & Thompson, 1990). Hershler & Frest (1996) provided a morphology-based phylogenetic analysis that resolved a ‘ Fluminicola clade’ that was more closely related to eastern North American Somatogyrus than to divergent F. virens . However, because the phylogenetic placement of the type species of Fluminicola ( Paludina nuttalliana Lea, 1838 ) is unknown (this snail has never been anatomically studied and is probably extinct), the genus continues to be broadly envisaged as a paraphyletic unit consisting of F. virens and all other regional lithoglyphids ( Hershler & Frest, 1996). A detailed description of Fluminicola was provided by Hershler & Frest (1996) and does not need to be repeated or emended here.

The fauna of the upper Sacramento River basin described below may be referred to as the ‘ Fluminicola clade’ (see above) as they share the two synapomorphies of this unit – an elongate pedal commissure and a sickle-shaped or elongate penis that lacks an eversible, terminal papilla ( Hershler & Frest, 1996). Variation in reproductive morphology, which has often been useful in taxonomic studies of freshwater rissooidean snails, proved to be relatively minor among the members of this fauna ( Figs 6, 7) and most of the new species described below are instead diagnosed by shell or radular features. Species are treated in the text below in approximately the order of their distribution within the upper Sacramento River basin.