Southeastern Section - 63rd Annual Meeting (10–11 April 2014)

Paper No. 5
Presentation Time: 11:35 AM


DENTON Jr., Robert K., Geology, GeoConcepts Engineering Inc, 19955 Highland Vista Drive, Suite 170, Ashburn, VA 20147,

Up to the final decades of the 20thcentury our knowledge of the Mesozoic Mammals of Appalachia, the Late Cretaceous “island continent” of eastern North America, was limited to only five relatively undiagnostic specimens. With the 1980 discovery and subsequent study of the Ellisdale site (Late Cretaceous, Campanian) of New Jersey, the number of mammalian specimens from the east jumped from five (5) to twenty nine (29), many of which could be diagnosed to family and genus level. Nevertheless, Ellisdale would remain for many years as the only eastern North American site to have a relatively diverse terrestrial microfauna, comparable to the well-known and intensely studied Judithian sites of Laramidia. This would change with the discovery and study of the terrestrial microvertebrate faunas of the Bladen County Landfill Annex (BCLA) site near Elizabethtown, NC, and the Stokes Pit (SP) site near Darlington, SC.

Two distinct taxa of multituberculates identified from the BCLA site are represented by the P4 and P2 of a Ptilodontoidean which appears transitional between the Laramidian genera Mesodma and Cimolodon, and the P4 of a cimexomyid comparable to Paracimexomys. The posterior half of a well-preserved multituberculate p4 has also been identified from the SP site, which appears to have cimolodontid affinities. It is of note that the preserved portion of the Stokes Pit p4 is nearly 4.5 mm in length, and if complete the tooth is inferred to have been at least 8 to 10 mm in length along the gingival margin based on the p4s of comparable taxa. This would make the SP taxon among the largest Cretaceous multituberculates known, similar in size to Meniscoessus major and Cimexomys magnus.

It has been suggested that land animals may have dispersed across eastern North America throughout the Late Cretaceous; however the presence of endemic taxa at both the Ellisdale site and the Carolina localities does not support this hypothesis. The eastern mammalian assemblages together with geological data suggest that Appalachia was an isolated continent from the Turonian onward, and thus may have been a refugium for relatively underived Early Cretaceous taxa that underwent vicariant speciation. If dispersal between Laramidia and Appalachia did take place, it could not have happened until the end of the Late Cretaceous, based on paleogeographic data.