Scientific Name: Alasmidonta undulata

Classification:  State Threatened

Photo Credit: NCWRC




NOTE: Hover over the bold words for definitions or see the Glossary.

Say described this species in 1817. The shell is inflated with umbos extending well above the hinge line. A tightly curved ventral margin makes the length to height ratio roughly equal. The periostracum may be yellow to golden brown with rays, turning dark brown or black with age. There is one chunky pseudocardinal tooth in the right valve, two in the left valve. The lateral teeth are vestigial. Nacre color is bluish-white with an occasional salmon or pink wash.


Shell Anatomy

Distribution by County: Pee Dee River Basin: Montgomery Co. (Little River Subbasin); Cape Fear River Basin: Moore Co. (Deep River), Chatham Co. (Rocky River Subbasin); Neuse River Basin: Person Co. (Flat River Subbasin), Durham Co. (Flat River Subbasin), Orange Co. (Eno River Subbasin), Wake Co. (Crabtree, Middle, and Swift creek subbasins, Little River Subbasin), Johnston Co. (Middle, Swift, and Mill creek subbasins, Little River Subbasin), Nash Co. (Moccasin and Turkey creek subbasins), Wilson Co. (Turkey and Contentnea creek subbasins), Jones Co. (Trent River Subbasin); Tar River Basin: Granville Co. (Tar River and Shelton Creek subbasins), Vance Co. (Tabbs and Ruin creek subbasins), Franklin Co. (Fox, Crooked, Cedar, and Sandy creek subbasins), Nash Co. (Swift and Stony creek subbasins), Halifax Co. (Rocky Swamp, and Little Fishing Cr. subbasins), Edgecombe Co. (Swift Creek Subbasin and Tar River); Roanoke River Basin: Halifax and Northampton counties (Roanoke River); Chowan River Basin: Hertford and Gates counties (Chowan River) NOTE: All headwater areas that flow into these occupied habitats should receive special management.


This species demonstrates no particular habitat preference across its range, having been collected from silt/sand in slower moving waters, gravel/sand in riffles and runs, and from crevices in bedrock.

The triangle floater may be found gravid throughout the year (Ortmann 1919); however, in North Carolina it is only found gravid during the cooler months of the year. At this time, no fish hosts have been identified for this species.


General Life History For Mussels