NEW LARGE COPROFAUNAS FROM THE PENNSYLVANIAN OF NEW MEXICO AND THE EOCENE OF VIRGINIA DEMONSTRATE THE PERVASIVE NATURE OF THE SHARK SURPLUS PARADOX IN SHALLOW MARINE ENVIRONMENTS

The Tinajas Member of the Atrasado Formation (Upper Pennsylvanian: Missourian) yields vertebrate coprolites from the Kinney Brick Quarry and the Tinajas Lagerstätten in central New Mexico, but the largest coprofauna from these strata derives from a new locality in the Cerros de Amado of Socorro County. (NMMNH locality L-9096). The majority of coprolites are spiral in morphology (heteropolar, amphipolar, scroll). Five ichnotaxa are heteropolar spiral in morphology and include Crassocoprus mcallesteri, Kalocoprus oteroensis, two ichnospecies of Heteropolacopros and ?Speirocoprus isp. There are numerous specimens of Crassocoprus mcallesteri. Heteropolar microspiral coprolites are assigned to Heteropolacopros, but there is a need for an ichnotaxonomic review of this ichnogenus. Amphipolar coprolites are represented by Hyronocopros amphipola, and there are several specimens of the scroll coprolite Bibliocoprus beemanensis. Diverse vertebrate bones occur elsewhere in the Tinajas Member but not at this locality. The coprolites were preserved in a shallow, low energy marine environment.

The Fisher/Sullivan site is located at the base of bed B of the Potapaco Member of the Nanjemoy Formation (Eocene: middle Wasatchian), Stafford County, Virginia (NMMNH locality L-10143). This locality has yielded abundant specimens of chondrichthyans, actnopterygians, reptiles, birds and mammals as well as invertebrates and fruit and seeds. Marco Gulotta Sr. collected several thousand coprolites from this locality, which he has donated to New Mexico Museum of Natural History and Science. The majority of the coprolites are of spiral morphology. The environment of deposition was high energy, shallow marine.

The majority of large coprofaunas from shallow marine strata are dominated by spiral morphologies. Given that many spiral coprolites derive from chondrichthyans, but most ichthyofaunas are dominated by other taxa, this phenomenon has been termed the “shark surplus paradox.” The new large samples from the Pennsylvanian of New Mexico and the Eocene of Virginia provide strong evidence for the pervasive extent of this paradox. The most probable explanations of the paradox are taphonomic and relate to the preferential preservation and lithification of chondrichthyan feces.