Bathyaustriella Thionipta, a New Lucinid Bivalve From a Hydrothermal Vent on the Kermadec Ridge, New Zealand and Its Relationship to Shallow-Water Taxa (Bivalvia: Lucinidae)

Bathyaustriella thionipta, a new species from water depths of 480—500 m on the Macauley Caldera, Kermadec Ridge, is the first record of a member of the chemoautotrophic bivalve family Lucinidae from an active hydrothermal vent. The new species and genus is morphologically similar to the shallow‐water, mangrove mud‐inhabiting Austriellacorrugata from the central Indo‐West Pacific region. Sequences of18S and 28S rRNA genes confirm its position close to Austriella within a clade of shallow‐water lucinids. Features of B. thionipta include the extremely large gill, the vacuolated foot, two coiled, lobate structures arising from the anterior body wall and a very thick periostracum. Its probable close relationship to shallow‐water lucinids lends support to an hypothesis proposing the onshore to offshore derivation of deep‐sea and vent faunas.