A new species of the genus Yoldiella (Bivalvia, Protobranchia, Yoldiidae) from Haima Cold Seep, South China Sea, China

Abstract

In present study, a previously unidentified but frequently encountered species of deep-sea protobranch, Yoldiella haimaensissp. nov., is described new to science from the Haima Cold Seep on the northwestern slope of the South China Sea. A morphological analysis confirmed that this species belongs to a previously undescribed species of the genus Yoldiella A.E. Verrill & K.J. Bush, 1897. It differs morphologically from other known species within the genus in its shell shape, degree of inflation, beaks, and number of hinge teeth. Furthermore, we sequenced three gene segments of Y. haimaensissp. nov., comprising a nuclear ribosomal gene (18S rRNA), a nuclear protein-coding gene (histone H3), and a mitochondrial gene (cytochrome c oxidase subunit I, COI). Our phylogenetic analysis performed on the superfamily Nuculanoidea and family Yoldiidae indicates that the genus Yoldiella is non-monophyletic, and the widely recognized families within the superfamily Nuculanoidea are also not monophyletic. Our results provide molecular insights into the Protobranchia and highlight the necessity for further samples and data to revise the classification of families and genera within the superfamily using an integrative approach that combines morphological analysis and molecular data.