New Selachian Paleofaunas from "Fluvial" Deposits of the Ferris and Lower Hanna Formations (Maastrichtian- Selandian: 66-58 Ma), Southern Wyoming

Abstract

Abstract Historically, sandy paleochannel deposits of the 2,000 m- thick Ferris (Maastrichtian–Danian: 66–62 Ma) and overlying 3,000 m-thick Hanna Formation (Danian–Thanetian: 62–55 Ma) in southern Wyoming's Hanna and Carbon basins have been interpreted as fluvial channel fills. New selachian paleofaunas from both formations are concentrated in stratigraphic intervals that also exhibit an abundance of mechanical tidal indicators and low-diversity marine ichnofossil assemblages (indicating brackish-water). Their presence in these two continental formations supports the reinterpretation of some sandy paleochannel deposits and shaly intervals as brackish-water estuaries, tidally influenced distributary channels, and interdistributary bays. Cederstroemia and Cretorectolobus are reported for the first time from Maastrichtian deposits (they previously have been documented only from Campanian and older strata). A new species of dasyatid is preserved in the middle Ferris Formation (earliest Paleocene: 64 Ma) and ...