PELYCOSAURIAN-GRADE (AMNIOTA: SYNAPSIDA) FOOTPRINTS FROM THE LOWER PERMIAN DUNKARD GROUP OF PENNSYLVANIA AND WEST VIRGINIA

摘要

The Lower Permian Dunkard Group has yielded a sparse record of tetrapod footprints that are assigned to the ichnogenera Dimetropus Romer and Price, 1940, Dromopus Marsh, 1894, and Limnopus Marsh, 1894. We report two new occurrences of Dimetropus that significantly extend its strati graphic range in the Dunkard Group to the Washington and Greene formations. The only previous Dunkard record of Dimetropus is of D. berea (Tilton, 1931), the type ichnospecies of the ichnogenus, from the Waynesburg Formation of West Virginia. Dimetropus (eupelycosaur), Dromopus (araeoscelid), and Limnopus (large temnospondyl) footprints are present in many Late Pennsylvanian-Early Permian footprint assemblages. The Dunkard footprints of Dimetropus reported here are very large for the ichnogenus, so it seems likely they were made by one of the relatively large eupelycosaurs, Dimetrodon Cope, 1877, Ophiacodon Marsh, 1878, or Ctenospondylus Romer, 1936, known from Dunkard Group body fossils.