A New Fossil Marine Vertebrate Assemblage from the Upper Cretaceous Fairport Chalk Member of the Carlile Shale in Russell County, Kansas, U.S.A.

The Fairport Chalk (lower middle Turonian) of the Carlile Shale is an Upper Cretaceous rock unit that was deposited in the middle of the Western Interior Seaway. This study presents the results of the first examination of microscopic marine vertebrate fossils from a single basal horizon within the Fairport Chalk at a new locality in Russell County, Kansas. The paleofauna consists of at least 12 vertebrate taxa, including seven chondrichthyans and five osteichthyans. They include durophagous (Ptychodus) and macrophagous (Cardabiodon and Cretoxyrhina) species, opportunistic scavengers and feeders (Squalicorax), and pelagic predators (plethodids and Enchodus). There is a scarcity of Enchodus and an abundance of caturid teeth, which is similar to the upper half of the Greenhorn Limestone, but in striking contrast with the basal Greenhorn Limestone, upper Carlile Shale, and upper Niobrara Chalk. The abundance of caturid teeth in the Jetmore Chalk–Fairport Chalk interval indicates that the specific caturid taxon was more common in the offshore environment than E. shumardi.