bivalvierna

Bivalvierna is a proposed but not universally accepted taxonomic grouping within the phylum Mollusca. This classification attempts to group together all mollusks that possess a shell composed of two hinged valves. The most prominent and widely recognized members of this proposed clade are the bivalves, a class of marine and freshwater mollusks that includes familiar creatures like oysters, clams, mussels, and scallops. However, the concept of Bivalvierna may also extend to include other, less commonly considered, groups with bivalve-like shells or evolutionary origins.

The term "Bivalvierna" is not a formally established rank in standard zoological taxonomy. Instead, it often appears in discussions of molluscan phylogeny and evolutionary relationships. Proponents of this grouping suggest that the development of a two-part shell is a key evolutionary innovation and that organisms sharing this characteristic, even if not strictly classified as bivalves in the traditional sense, might share a common ancestry related to this shell morphology. Research into molluscan evolution continues to refine our understanding of these relationships, and the validity and precise composition of Bivalvierna remain subjects of ongoing scientific debate and investigation.