BIOGEOGRAPHIC PATTERNS OF LATE DEVONIAN VERTEBRATES FROM NORTH AMERICA

The North American record of Late Devonian fossil vertebrates has improved significantly in the past decade, providing a larger and more detailed data set for biogeographic hypotheses. Knowledge of the vertebrate fauna from the Frasnian-age Okse Bay Group (specifically the Fram and Nordstrand Point Formations) on southern Ellesmere Island, Nunavut Territory, Canada, has grown dramatically as the result of three field seasons of paleontological exploration in the region. The psammosteid agnathans, bothriolepid placoderms, and porolepiform sarcopterygians from the Okse Bay Group are very similar to Frasnian faunas from East European Platform regions. These Frasnian-age Euramerican (Larussian) faunas are quite distinct from contemporaneous deposits on the Gondwanan continents. In contrast, the newly emerging fauna from the late Famennian Catskill Formation in Pennsylvania includes groenlandaspidid and phyllolepid placoderms, gyracanthid acanthodians, dipnoan and tristichopterid sarcopterygians, as well as early tetrapods, that are very similar to Gondwanan forms from the same time interval.

The global biogeographic pattern of Frasnian endemism and Famennian cosmopolitanism within Late Devonian vertebrates has been recognized previously but new records and improved systematic data provide a sharpened tool for paleogeographic reconstruction. Additionally, new paleoecological and stratigraphic data refine our ability to characterize the biogeographic and other biotic events during the Late Devonian.