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The oyster traditionally referred to as Booneostrea subucula (Jousseaume in Lamy, 1925) exemplifies persistent generic instability in Ostreinae, driven by misidentified type material and debated synonymies spanning multiple genera, subfamilies and even families. We reassessed the identity of Ostrea subucula and the validity of Booneostrea Harry, 1985 using an integrative approach that combined shell morphology, anatomy and multilocus phylogenetic data. Phylogenetic analyses reveal two deeply divergent, reciprocally monophyletic lineages. The Western Indian Ocean lineage corresponds to O. subucula sensu stricto and ranges from Rodrigues to Yemen and Oman. By contrast, the northern Arabian–Persian Gulf lineage represents a distinct species, here described as Ostrea sorosubucula sp. nov. Despite substantial genetic divergence, morphological differences are subtle, mainly in the adductor muscle scar. Re-examination of historical material reveals that the type concept of Booneostrea is based on misidentified or now-untraceable shells. Ostrea subucula and Ostrea setoensis Habe, 1958 are morphologically and genetically distinct, and O. subucula does not conform to the shell features historically used to define Booneostrea. We conclude that Booneostrea cannot be applied in a taxonomically consistent and meaningful way and should be treated as a nomen dubium. By resolving this long-standing confusion and documenting an endemic Gulf lineage, this study significantly contributes to stabilising generic concepts in Ostreinae and demonstrates the power of integrating molecular and morphological evidence in oyster systematics. ZooBank: urn:lsid:zoobank.org:pub:ECDB3E11-0C17-4EE9-A253-36EC59B28DD8
Salvi et al. (Fri,) studied this question.