Somatogyrus humerosus

**Atlas Pebblesnail (Somatogyrus humerosus)** The Atlas Pebblesnail is a minute freshwater gastropod mollusk, measuring approximately 2-3 millimeters in length. This tiny snail features a distinctive conical shell with pronounced spiral ridges and a characteristic shoulder-like projection that gives the species its name. Like other pebblesnails, it feeds on algae and organic detritus, playing a role in nutrient cycling within its aquatic ecosystem. This species is endemic to Alabama, with its range historically limited to specific spring systems in the Tennessee River drainage. The Atlas Pebblesnail inhabits cool, clear spring waters and spring-fed streams, requiring stable water temperatures and high dissolved oxygen levels. It typically occurs in areas with limestone substrates where groundwater emerges. The species faces critical threats from habitat modification and groundwater depletion. Spring development, water diversions, and increased groundwater pumping have altered or eliminated many of the pristine spring environments essential for its survival. Sedimentation from land-use changes and potential contamination from agricultural and urban runoff further degrade water quality in remaining habitats. Conservation efforts focus primarily on habitat protection and water quality monitoring in known spring systems. Some sites receive protection through land acquisition or management agreements, though comprehensive population surveys remain limited due to the species' small size and specialized habitat requirements. The current outlook for the Atlas Pebblesnail remains uncertain. With its extremely restricted range and ongoing habitat pressures, the species continues to face significant extinction risk. The lack of comprehensive population data makes it difficult to assess whether current conservation measures are sufficient to ensure long-term survival.