A new species of Hypolophites (Chondrichthyes, Myliobatiformes) from the Lower Clayton Limestone Unit of the Midway Group (Paleocene), near Malvern, Arkansas, USA

摘要

A new species of Hypolophites (Chondrichthyes, Myliobatiformes) is described from an assemblage of isolated pavement teeth recovered from the Lower Clayton Limestone Unit of the Midway Group (Paleocene) near Malvern, Arkansas. These teeth were collected from several localized lag deposits containing an abundance of chondrichthyan and osteichthyan teeth, invertebrate remains, and trace fossils indicative of a marginal-shallow marine depositional environment. To date, only four additional species of Hypolophites have been reported from Paleocene deposits that occur along the west coast of central-northern Africa and in central New Jersey, USA. The identification of Hypolophites beckeri n. sp. in southwestern Arkansas extends the distribution of this biostratigraphically significant genus similar to 1,750 km westward into the Mississippi Embayment and Gulf Coastal Plain of the USA. The distribution of Hypolophites species during the Paleocene attests to the uniformity of shallow marine shelves between western Africa and the Atlantic and Gulf Coastal Plains of the USA, as well as myliobatiform diversification following the K/Pg mass extinction event. UUID: http://zoobank.org/3a1580d1-a2f4-49b6-8170-69a778c49181