This species was reported in Utah by Call (1884) as Anodonta nuttalliana, the name under which he synonymized A. nuttalliana, A. wahlametensis, and A. californiensis.
As currently recognized, this species is monotypic.
Status in Utah
At least 2 extant occurrences are known in Utah (see Clarke 1993), possibly as many as 6. This species was historically reported from Utah and Millard counties (Henderson 1936). There has been a recent report of fresh shells from Rich and Tooele counties and shells of unspecified age (and thus not mapped) from northwestern Box Elder County (Clarke 1993).
Abundance at most Utah localities is unreported, but Clarke (1993) stated that this species "occurs abundantly" at "Reddin Spring [sic]".
Pesticides in agricultural run-off, habitat degradation by cattle, and water diversion are the most immediate threats.
This species is apparently declining in Utah; historical populations in the Raft River (Box Elder County), Utah Lake (Utah County), and Bear Lake (Rich County) are possibly extirpated (see Clarke 1993).
Inventory is needed, particularly in drainages in the Great Basin, as is continued monitoring of known populations.
Considerable confusion exists concerning this and other floaters (Anodonta) in Utah. How many species of floaters occur or historically have occurred in this state is uncertain, and whether reported Utah specimens of floaters have been correctly identified is questionable. The most comprehensive work on Utah mollusks, by Chamberlin and Jones (1929), discussed 4 nominal species of floaters and provided specific localities, from the earlier literature as well as new records, for 3 of the 4 species; only for Anodonta californiensis did Chamberlin and Jones (1929) have no specific Utah localities, commenting: "We have not recognized it in material known to us."
Habitats Utilized in Utah
Clarke (1993) found very different habitat profiles at two localities. At one, this species "occurs abundantly at depths of about 6 to 12 inches, among watercress, on a muddy bottom in two small ponds joined together by a ditch." The other locality was a creek "5 to 15 feet wide, up to 18 inches deep, with a bottom of gravel and sand in flowing areas and mud in pools, and with abundant Myriophyllum and Spirogyra."