Systematic Overview of the Pliocene Molluscs and Barnacles of the Barmur Group on Tjörnes, North Iceland

Systematic overview of the molluscan and barnacle assemblages of the Pliocene Tjornes sequence in North Iceland is primarily based on collections and fieldwork carried out during the last 50 years and collections of the Institute of Natural History in Reykjavik, the Geological Museum in Copenhagen, and the collection of the late farmer Johannes Bjornsson in Ytri-Tunga on Tjornes. We have identified 65 species of prosobranch gastropods, five opistobranch gastropod, 49 bivalve, one ammonite, and one barnacle species. Of the 119 molluscan species, 24 have not been recorded before from Tjornes. About 25% of the mollusc species are extinct, and 25 of the recent molluscan species now live in southerly localities with higher sea temperatures. At least 32 of the species have their first appearance (FAD) in Tjornes. The species are depicted on plates and variation in shape is demonstrated wherever possible. The distribution, recent or fossil, of species is shown, and ecological and biological features discussed. The larval development of the species is also summarized. The Tjornes fauna is major record of trans-Arctic oceanic interchange that has been imperative in shaping the modern North Atlantic faunas. This review enables us to improve our understanding of the interchange.