Evolution of Janthina and Recluzia (Mollusca: Gastropoda: Epitoniidae)
Abstract
Fossil and living neustonic gastropods referred previously to Janthinidae are revised and included in Epitoniidae. Species recognized in Janthina Röding, 1798 (= Iodes, Iodina and Amethistina Mörch, 1860, Hartungia Bronn, 1861, Heligmope Tate, 1893, Violetta Iredale, 1929, Parajanthina Tomida & Itoigawa, 1982, and Kaneconcha Kaim, Tucholke & Warén, 2012) are J. typica (Bronn), Messinian–early Piacenzian (latest Miocene–early late Pliocene), c. 7–3.0 Ma (New Zealand, southern Australia, Japan, Morocco, dredged off Brazil, Madeira, Gran Canaria I., Selvagem Grande I., and Santa Maria I., Azores); J. krejcii sp. nov., Zanclean (early Pliocene), c. 4.8–4.3 Ma (Santa Maria I.); J. chavani (Ludbrook), late Piacenzian–early Calabrian (latest Pliocene–early Pleistocene), 3.0–c. 1.7 Ma or later (New Zealand, southern Australia, Japan, mid-Atlantic ridge); J. globosa Swainson, living, and two late Pliocene–early Pleistocene records (Jamaica, Philippines); and J. exigua Lamarck, J. janthina (Linnaeus), J. pallida Thompson, and J. umbilicata d’Orbigny, all Holocene only. Janthina evolved from a benthic epitoniid resembling Alora during Messinian (late Miocene) time, and feeds mainly on colonial cnidarians (Physalia, Velella, Porpita). The extinction of Janthina typica and origination of J. chavani at 3.0 Ma (end of the Pliocene climatic optimum) potentially is useful for world Pliocene correlation. The two Recluzia species, R. johnii (Holten) and R. lutea (Bennett), feed on floating Minyadidae anemones. Recluzia has no fossil record and evolved independently during Holocene time from a benthic epitoniid resembling Alexania and Surrepifungium. Adaptation to a neustonic habit evolved twice in Epitoniidae. Twenty-two neotypes and six lectotypes are designated.
