Shell solid, heavy, inflated. Strongly inequivalve in juveniles, less so in adults. Highly variable in shape, shell thickness and convexity of the valves. Height/length ratio = 0.69-0.88, width/length = 0.53-0.84 (Cesari and Pellizzato, 1985). Umbonal area smooth and dark in juvenile specimens. Sculpture of 31 to 34 radial ribs with a mean value of 32.6 ± 1.0 ribs (Morello and Solustri, 2001). Taxodont hinge. Internal ventral margin strongly crenulate. Periostracum persistent.
shell white; a velvety, dark brown to black periostracum present near the margins.
common size :
70-75 and up to 80 mm in length, up to 61 mm in height.
Easy to distinguish because of its valves being different in size. However, as in other Anadara, the shells become equivalve with age (Rinaldi, 1994b). Can be confused with A. diluvii (Lamarck, 1805), which differs in the number of radial ribs: 31-34 in A. inaequivalvis versus 26-28 in A. polii and the bigger size (A. diluvii does not exceed 50 mm in length). Differences from A. demiri.
BIOLOGY / ECOLOGY
Species eurytherm, euryhaline, that can withstand extreme conditions. Comparative biometric studies in marine and lagoonal populations revealed that under extreme conditions of salinity and temperature (in lagoons) the shell is more fragile - weight about 14% less - than in marine environments and the population density limited (Lazzari and Rinaldi, 1994). Maximum occurrence corresponds to areas with salinity 30‰ and sandy seabeds (Mizzan, 1999).
brackish lagoons in the Adriatic. From inshore brackish waters down to 30 m on sand, on rocks; mud and sand with Zostera nana and Cymodocea nodosa.