Species Synonymies in the Deep-Sea Wood-Boring Bivalve Genus Xyloredo (Mollusca: Xylophagaidae)

Sequences of specimens of the xylophagaid genus Xyloredo revealed minimal molecular divergence among ten specimens from the North and South Atlantic and the northeast and southwest Pacific Oceans. Although genetically identical, the valves of two New Zealand specimens differ dramatically, likely due to their three-fold size difference. Comparable size differences among the type series of X. nooi, X. naceli and X. ingolfia and their disjunct distributions may have contributed to their recognition as distinct species; the species are synonymized here as Xyloredo nooi. The flattened umbonal-ventral ridge, the fold inside the posterior shell, the two elongate calcified strips of the mesoplax embedded in a periostracal anterior adductor cover and a two-parted siphon with the simple, separate openings are unique to members of Xyloredo. Molecular sequencing of the Japanese X. teramachii is needed to test if it is distinct.