Paper No. 162-53
Presentation Time: 9:00 AM-6:30 PM
PROLIFIC NEW COPROFAUNA FROM THE EOCENE OF VIRGINIA
The Fisher/Sullivan site is located at the base of bed B of the Potapaco Member of the Nanjemoy Formation (Early Eocene: middle Wasatchian), Stafford County, Virginia (NMMNH [New Mexico Museum of Natural History] locality L-10143). This locality has yielded over 100 species of fossil vertebrates, including abundant specimens of chondrichthyans and actinopterygians, as well as reptiles, birds and mammals. The locality also yields invertebrate fossils and a diverse fruit and seed flora. The environment of deposition was high energy, shallow marine. Initial reports mentioned the presence of coprolites, but they were generally ignored until one of us (MGN) collected over 12,000 specimens and donated them to NMMNH. This represents the largest known pre-Quaternary coprofauna. The coprolites display diverse morphotypes. The majority of specimens are small (less than 20 mm in length), elongate, narrow and rod- or spindle-shaped. Many coprolites are spiral-shaped, and a smaller number have a scroll morphology. Amphipolar morphotypes are more common than heteropolar. Scroll coprolites tend to be larger than spiral. Inclusions are more common in non-spiral coprolites. Most of the smallest specimens are non-spiral. The majority of specimens represent actinopterygians and chondrichthyans. Large, non-spiral coprolites (up to 60 mm in length) are less common and probably pertain to crocodiles. Amorphous bromalites rich in bone fragments (e.g., actinopterygian vertebrae and skull fragments) may represent regurgitalites. The coprofauna is distinctive from other shallow marine ichnofaunas in: (1) large sample size; (2) proportion of small coprolites; (3) diversity of morphotypes; and (4) relative abundance of non-spiral forms. The Fisher/Sullivan coprofauna differs from other large Eocene samples (middle Eocene Fürstenau Formation of northern Germany, late Eocene Yazoo Clay of Louisiana) in the lower percentage of spiral and scroll morphotypes and the smaller size of specimens.