Osteichthyans from an Arkadelphia Formation–Midway Group lag deposit (Late Maastrichtian–Paleocene), Hot Spring County, Arkansas, U.S.A.

Abstract

ABSTRACT A lag deposit that separates the underlying late Maastrichtian Arkadelphia Formation marl from the overlying Paleocene Midway Group limestone in Hot Spring County, Arkansas, U.S.A., contains osteichthyan teeth, scales, and skeletal elements belonging to: Cylindracanthus ornatusLeidy, 1856, Atractosteus sp., Lepisosteus sp., cf. Hadrodus priscusLeidy, 1857, Pseudoegertonia cf. P. granulosus (Arambourg, 1952), Paralbula caseiEstes, 1969, Enchodus feroxLeidy, 1855, Enchodus gladiolus (Cope, 1872), Enchodus petrosus (Cope, 1874), Enchodus sp., and Teleostei incertae sedis. Outcrop exposures of this lag deposit occur within the Ouachita River and are expressed as a series of partially submerged, steeply inclined fold limbs that strike obliquely to water flow. The co-occurring osteichthyans recovered in this study span a broad range of salinity tolerances, foraging behaviors, and dietary preferences. Concentration of these osteichthyans indicates transport, exhumation, and reburial associated with storm activity or sea level cyclicity across a shallow Late Cretaceous marine shelf. Arkadelphia–Midway osteichthyan taxa belong to groups that survive the Cretaceous–Paleocene extinction event.