LARGE TETRAPODS IN THE EARLY PENNSYLVANIAN - ICHNOLOGICAL EVIDENCE FROM ALABAMA

Two localities in the Pottsville Formation of Walker County, Alabama--the Number 11 Mine of the Galloway Coal Company near Carbon Hill and the Union Chapel Mine near Jasper--yield extensive assemblages of tetrapod footprints. Invertebrate ichnotaxa in these strata include abundant limulid trails (Kouphichnium) and insect feeding traces (Treptichnus), as well as less common arthropod walking and feeding traces. Fish swimming traces (Undichna) are also present, as are the tracks of small amphibians (Batrachichnus) and small captorinomorph reptiles (Notalacerta and Cincosaurus). Large tetrapod tracks (~ 200 mm long pes), previously assigned to Attenosaurus, encompass three distinct morphotypes: (1) typical Attenosaurus-pentadactyl manus and pes impressions, with narrow elongate digit impressions and short, rounded sole impressions; pedal digit impression V has a “thumb-like” origination several cm posterior to other digit impressions; (2) a second ichnotaxon differentiated by its pentadactyl manus and pedal impressions with elongate, narrow, L-shaped heel impressions, the impression of digit I oriented medially or posteriorly and pedal digit impressions that increase in length from digit impression II to IV with digit impression V slightly shorter than IV; and (3) a third morphotype with five, anteriorly-directed digit impressions and a long and broad pedal heel impression comparable to Late Pennsylvanian-Permian Dimetropus. Clearly, the large tracks from the Pottsville Formation demonstrate the presence of several large tetrapods (pelycosaurs?) in the Early Pennsylvanian for which there is no bone record, and they thus have a potential to further elucidate our understanding of late Paleozoic tetrapod evolution.