DIPNOAN AND CHONDRICHTHYAN REMAINS FROM THE UPPER KERBER FORMATION (PENNSYLVANIAN), BASSAM PARK, SAN ISABEL NATIONAL FOREST, COLORADO

The paleontology of the Pennsylvanian fossil beds of Bassam Park, San Isabel National Forest, Colorado, has been the subject of a cooperative research project undertaken by the Forest Service and the University of Colorado at Denver, with assistance from members of the Western Interior Paleontological Society, an amateur paleontological organization. In the course of this study, remains of various marine vertebrates were found.

A chondrichthyan tooth has been assigned to the genus Petalodus. Petalodus is common and widespread in the Pennsylvanian of North America.

A fragmentary tooth plate and some bone fragments, including a dorsal skull roof bone, belong to dipnoans (lungfish), probably Sagenodus. These remains represent the first report of dipnoans from the Pennsylvanian of Colorado. While Sagenodus is the most common dipnoan in the Pennsylvanian of North America, these remains would be the oldest (early Atokan) to be reported from the United States, if the identification is confirmed. Sagenodus is known from the Mississippian and Pennsylvanian of Nova Scotia and Europe. It has not been reported in the United States earlier than the Desmoinesian of Illinois.

There has been some question as to whether Sagenodus lived exclusively in freshwater environments or whether it was also tolerant of marine conditions. The occurrence of these remains, together with marine invertebrates, including nautiloid and ammonoid cephalopods, bellerophontid gastropods, productid brachiopods, and nuculid bivalves, is evidence for the latter hypothesis.