Life in a sea urchin esophagus: a new endosymbiotic bivalve (Galeommatida, Galeommatoidea) from abyssal depths off southern Australia

During a large deep-sea survey off the southern coast of Australia, an unusual galeommatid bivalve was discovered living in the esophagus of the abyssal irregular urchin Carnarechinus clypeatus (Agassiz, 1879). We have determined that the bivalve, found from approximately 4000–5000 m depth, is a new species in the poorly documented genus Vaticinaria Dall, 1901. We reinstate the genus Vaticinaria and compare it with other genera that have been associated with it in the literature. We herein describe Vaticinaria gulicola sp. nov ., as well as document its anatomy and unusual commensal relationship with its host. We further place the new species in a reconstructed phylogenetic tree of Galeommatoidea.