Endemic evolution of Tethyan-derived belemnites in North-East Greenland: the middle Barremian Duvalia Event

Marine sequences on Wollaston Forland, North-East Greenland have provided rich belemnite assemblages of Barremian (Early Cretaceous) age. Most common are belemnites of Boreal affinities, closely related to northwest European faunas. Remarkable are the findings of 47 rostra of Duvalia, a genus of Tethyan origin. In addition to Duvalia grasiana, Duvalia arctica sp. nov., Duvalia aff. silesiaca and Duvalia sp. have been recognized. Duvalia grasiana is well known from the Barremian–Aptian of the western Tethys. The other three taxa differ, however, morphologically from contemporaneous Duvalia species common in the Barremian of the Tethys. Our findings suggest a migration of D. grasiana to North-East Greenland in the early Barremian and a subsequent in situ evolution of D. arctica in the Greenland Norwegian Seaway. Duvalia aff. silesiaca, second in abundance, most probably also evolved from a Tethyan precursor species (Duvalia silesiaca). The taxonomic affinities of Duvalia sp. remain unclear. Duvalia arctica, D. aff. silesiaca and Duvalia sp. are all characterized by small size, indicating an endemic evolution and adaptation to a well-confined position in the food chain. The niche occupied by these small-sized Duvalia species must have differed substantially to that occupied by co-occurring Boreal belemnites, which have robust, stout rostra. The findings make North-East Greenland part of a migration route from the Tethys via the north Atlantic to the high Boreal. The Duvalia Event corresponds stratigraphically to the middle Barremian warming.