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

Abstract

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 ~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

The evolutionary origin of the durophagous pelagic stingray ecomorph

“…Crushing–grinding dentition allowed these taxa to feed not only soft‐prey (bony fishes, worms, thin‐shelled crustaceans) but also to crush hard‐shelled molluscs (Underwood et al . 2017 ; Maisch 2019 ), as in living Pastinachus (Devadoss 1978 ; Jacobsen & Bennett 2013 ; Rastgoo et al . 2018 ).…”

First Cretaceous teleostean otolith assemblage (Arkadelphia Formation, upper Maastrichtian) from Arkansas, USA, early Gadiformes, and the Western Interior Seaway

“…Therefore, it is not clear whether all of the bony fishes actually occurred in the Arkadelphia Formation or could have originated in the Midway Group. Maisch (2020) described a new myliobatid from the area, but it was from Clayton Formation (Paleocene) rather than the underlying Cretaceous Arkadelphia Formation.…”