Venerida, Gray, 1854

Simone, Luiz Ricardo L., 2024, New species, misidentifications and problematic taxonomy of some Atlantic South American marine mollusks: a review, Papéis Avulsos de Zoologia 64, pp. 1-104 : 89

Order Venerida Family Veneridae

Subfamily Petricolinae

Choristodon typicum Jonas, 1844 revalidated

Choristodon typicum Jonas, 1844: 185 .

Type locality: insulam St.Thomas.

Remarks: Choristodon typicum , formerly recognized as Petricola typica and Rupellaria typica , has recently been synonymized with the Pacific species Choristodon robustus (Sowerby I, 1834) by, e.g., Coan & Valentich-Scott (2012), MolluscaBase (2023), and Passos et al. (2024). Despite being considered sibling species, three factors suggest that this synonymy can be disregarded. Firstly, the southern region of South America does not host occurrences of C. typicum , making gene flow between both sides of the Americas impossible. In the Atlantic coast, for instance, the southernmost detected occurrence of C. typicum is in Santa Catarina, Brazil, significantly distant from the south curve to the Pacific region of the mainland. Secondly, Choristodon exhibits variable shell characteristics, making it challenging to identify secure conchological attributes justifying their separation. However, the Atlantic C. typicum generally displays a larger size and a coarser radial sculpture compared to the Pacific C. robustus , which tends to have a more delicate sculpture. Thirdly, the presence of C. typicum shells in pre-Columbian deposits, albeit rare, indicates that the species is not of anthropogenic introduction. Therefore, until a more robust database supports the improbable synonymy, Choristodon typicum will be maintained as a distinct taxon.