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Here, we report on 33 molluscan species from Miocene ’Calcari a Lucina’ hydrocarbon-seep deposits in northern Italy. Three new species are described: the chilodontaid gastropod Putzeysia diversii sp. nov., the lucinid bivalve Miltha (sensu lato) romaniae sp. nov., and Sisonia ultimoi sp. nov., a heterodont bivalve of uncertain taxonomic affinity. Fourteen species are described in open nomenclature. The common but enigmatic gastropod species Phasianema taurocrassa is here suggested to belong to the seguenzioid genus Cataegis. Most gastropod species are inhabitants of the deep-sea floor in general, and are not restricted (obligate) to sites of hydrocarbon-seepage. The gastropod Putzeysia diversii sp. nov. and the bivalve Sisonia ultimoi sp. nov. are the geologically oldest members of their genera known to date. While the genus Putzeysia is geographically restricted to the NE Atlantic Ocean and the Mediterranean Sea, Sisonia ultimoi sp. nov. represents another link of the Miocene Mediterranean seep fauna to that of the central Indo-West Pacific Ocean.
A new species of Apseudidae is described from a submarine canyon in the Mediterranean Sea, Leviapseudes tethys sp. nov. The species was sampled at 600 m depth on deep muddy sand. The new species is characterized by the presence of processes on both sides of the rostrum, a pinnate seta on the inner distal margin of the maxillipedal endite, smooth distal spines of the labium palp, two spines on the cheliped basis, three ventral spines on pereopod 1 basis and an unarticulated pleopod exopod. This is the second species and the third record of the genus in the Mediterranean Sea, and raises the number of tanaid species known from the deep Mediterranean Sea to a total of 16. The diagnosis of the genus is amended in light of the new data and re-evaluation of previous works. The new species presents a set of characters that provide novel insights to understanding the diversity and taxonomy of the Leviapseudinae, as well as their geographic distribution. Finally, a list of all deep-sea Tanaidacea known in the Mediterranean Sea is provided.
Dorvilleids belonging to Ophryotrocha Claparède & Mecznikow, 1869 are known from deep-sea hydrothermal vents in the Pacific, Atlantic, Indian and Southern Oceans. However, how they colonized and diversified in these ecosystems has not been assessed in detail. Here, a collection of Pacific hydrothermal vent Ophryotrocha was examined using morphology and DNA markers (COI, 16S and H3). Five new species were revealed, largely expanding the diversity of the group at this habitat type. They are Ophryotrocha charlottae sp. nov., O. kailae sp. nov., O. marinae sp. nov., O. pruittae sp. nov. from eastern Pacific, and O. bohnorum sp. nov. from the western Pacific. Phylogenetic analyses based on the concatenated alignments of all three genes suggest vent habitants have been colonized several times independently within Ophryotrocha. One clade of six vent species was recovered, indicative of diversification following a colonization of hydrothermal vents, likely in the eastern Pacific. An Indian Ocean species, O. jiaolongi, was nested inside this clade and was closely related to one of the new species from the Gulf of California, diverging from it by less than 4% on COI.