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Abstract
A new protoperidiniacean dinoflagellate cyst species recorded from the Lower Pliocene Serripes Zone of the Tjörnes beds in northern Iceland is formally described and its palaeoecological preferences are evaluated. Selenopemphix islandensis sp. nov. is a thin-walled cyst with strong polar compression and a reniform outline in apical view. The wide cingular margins are dorsally ornamented with processes of varying morphology and ventrally with large fan-shaped processes. A distinct size difference between the dorsal and ventral cingular processes is a major diagnostic characteristic of this species. A differential diagnosis for Selenopemphix islandensis sp. nov. is presented. Within the Tjörnes section, Selenopemphix islandensis sp. nov. is restricted to the uppermost Serripes Zone of the Tjörnes beds. The base of this zone corresponds to the invasion of cold-water molluscs of Pacific affinity through the Bering Strait into the northern Atlantic. The sudden appearance of Selenopemphix islandensis sp. nov. from this level can possibly be related to this northern migration through the Bering Strait, and suggest a Pacific origin. The new species is not recorded in the underlying Lower Pliocene Tapes Zone and Mactra Zone of the Tjörnes beds, and is also absent in the superjacent Pleistocene Breidavík Group. Selenopemphix islandensis sp. nov. has a first and last appearance in the Tjörnes region at c. 4.5 Ma and 4.2 Ma, respectively. Palaeoecological studies on molluscs, ostracods, plants and oxygen isotopes indicate an average summer temperature of 5–10°C for the Serripes Zone, which is comparable to the present-day situation in northern Iceland.
Acknowledgements
This study was carried out in the framework of the Ph.D. research of Koen Verhoeven at the Research Unit of Palaeontology, Ghent University. Margrét Hallsdóttir and the library staff of the Museum of Natural History in Reykjavik are thanked for their help with the preparation of the sampling trip. Jon Eíriksson is kindly thanked for his assistance in the field campaign and the fruitful discussions on the Tjörnes stratigraphy. The discussions on dinoflagellate cysts morphology with Jan De Coninck are much appreciated. Thomas Verleye's help with the figures and his constructive comments are kindly appreciated. Stefan Piasecki and an anonymous reviewer are kindly thanked for their constructive comments, which improved the manuscript considerably.