10 April 2018 Hanging on — lucinid bivalve survivors from the Paleocene and Eocene in the western Indian Ocean (Bivalvia: Lucinidae)
John D. Taylor, Emily A. Glover
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Rare species of three long-lived lucinid genera, GibbolucinaCossmann, 1904, BarbierellaChavan, 1938 and Retrolucina n. gen., with origins in the Paleocene and Eocene of western Tethys, are present in the Mozambique Channel area of the southwestern Indian Ocean but absent elsewhere in the Indo-West Pacific. A new species, Gibbolucina zelee n. sp., is described from the Banc de la Zélée and western Madagascar that resembles Miocene species from western France. Since their origin in the Paleocene to the present day Barbierella species have always been rare. New records and images, including syntypes, are provided for Barbierella louisensis (Viader, 1951) from Mauritius and the Mozambique Channel, with Barbierella scitulaOliver & Abou-Zeid, 1986 from the Red Sea regarded as synonym. A new genus, Retrolucina n. gen., is proposed with the living Lucina voorhoeveiDeshayes, 1857 (usually called Eomiltha voorhoevei) as type species and also including Lucina defranceiDeshayes, 1857, a strikingly similar species from the Eocene of the Paris Basin. Retrolucina n. gen. differs from EomilthaCossmann, 1912 in shape, sculpture and hinge characters. MonitiloraIredale, 1930, another genus of Paleocene or earlier origins, includes a few living species in the Indo-West Pacific and is now identified from Mozambique with Monitilora sepes (Barnard, 1964) (formerly Phacoides sepesBarnard, 1964). It is suggested that Gibbolucina, Barbierella and Retrolucina n. gen. species became isolated in the western Indian Ocean following the closure of the Tethyan Seaway in the early Miocene while their congeners in western Tethys became extinct. The survival of these rare genera, with restricted geographical ranges and seemingly small populations, runs counter to current ideas concerning long-term extinction risk.

© Publications scientifiques du Muséum national d'Histoire naturelle, Paris.
John D. Taylor and Emily A. Glover "Hanging on — lucinid bivalve survivors from the Paleocene and Eocene in the western Indian Ocean (Bivalvia: Lucinidae)," Zoosystema 40(2), 123-142, (10 April 2018). https://doi.org/10.5252/zoosystema2018v40a7
Received: 27 September 2017; Accepted: 12 December 2017; Published: 10 April 2018

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Mozambique Channel
new combination
new genus
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