<i>Pentadinium alabamensis</i>: A new, unusual dinoflagellate from the early Oligocene of the Gulf Coast, Alabama, USA

The Eocene–Oligocene Transition (EOT, ~ 34 Ma) marks the onset of major Antarctic ice sheets. The environmental consequences of the transition included major changes in e.g., sea level, temperature, and ocean circulation, complicating biostratigraphic correlations in this interval. Organic walled dinoflagellate cysts (dinocysts) however do show potential for EOT biostratigraphy, especially for ancient shallow marine settings.At St. Stephens Quarry, Alabama, USA, we found a new, extremely suturocavate dinocyst, Pentadinium alabamensis sp. nov., described herein. The range of the new species spans the critical EOT magnetosubchron C13n, making this taxon a useful biostratigraphic marker for this interval in the Gulf Coast region. The species appears to be associated with shallow marine, euryhaline conditions