A NEW VERTEBRATE FAUNA FROM THE LATE CRETACEOUS (MAASTRICHTIAN) NEW EGYPT FORMATION OF NEW JERSEY

“Spheno Run”, nicknamed after the many septal fragments from the ammonite Sphenodiscus lobatus (Tuomey, 1856) that litter the site, is a new and unique fossil locality located in the Inner Coastal Plain of New Jersey. This site is producing an unusually diverse array of associated vertebrate and invertebrate remains from the basal New Egypt Formation of the Late Maastrichtian deposits of the Atlantic Coastal Plain. Spheno Run is of particular interest because the fauna is derived from a single, non-reworked horizon in the basal New Egypt Formation approximately 25 feet below the Cretaceous/Tertiary boundary. The basal New Egypt is a massive clayey, glauconitic marl that closely resembles the Navasink Formation into which it grades below. Spheno Run is unique in that this part of the lower New Egypt is neither well-exposed nor expressed elsewhere in New Jersey. Additionally, ammonites and other invertebrates found at this site correlate well with the middle Severn Formation of Maryland. Spheno Run has so far produced a remarkable number of vertebrate specimens, especially from marine reptiles, including: carapace elements from at least two species of turtles, Peritresius ornatus (Leidy, 1856) and Taphrosphys sulcatus (Leidy, 1856); various bone elements from at least two species of mosasaurs including a sizable fragment of dentary bone from Prognathodon rapax (Hay, 1902) and numerous shed teeth from Mosasaurus maximus (Cope, 1869). Vertebrate remains also include material from sharks, particularly teeth and unusually large vertebral centra from an individual lamniform shark Squalicorax pristodontus (Agassiz, 1843), bony fish, and, rarely, dinosaurs. In addition to the vertebrate collection, Spheno Run also yields an abundance of invertebrate species including: twenty-two bivalves, seven gastropods, six cephalopods, and one each of echinoidea, porifera, and scaphopoda. It is rare to find such an extensive array of both vertebrate and invertebrate species within one horizon in New Jersey. This site presents an exciting opportunity to study the full-spectrum of Late Cretaceous paleoecology as expressed in the basal New Egypt Formation.