Limnopus trackways from the Conemaugh Group (Late Pennsylvanian), southern West Virginia

Abstract

Abundant and well-preserved tetrapod footprints have been discovered in the Glenshaw Formation (Lower Conemaugh Group) in Wayne County, West Virginia. The tracks occur along at least three horizons within a 30-cm-thick stratigraphic interval about 15 m (50 ft) above the Brush Creek Limestone; they are of Missourian age. The tracks are preserved mainly as casts on the underside of thin-bedded, ripple cross-laminated sandstones and less commonly as molds in intervening dark-gray shales. Associated body fossils include Spirorbis worm tubes and washed-in plant debris. Facies characteristics indicate the tracks were formed along the margins of an ephemeral lake in a flood basin setting adjacent to delta plain fluviodeltaic channel systems. Short-lived lacustrine conditions were likely to have resulted from a seasonal tropical to subtropical climate.Most of the tracks can be assigned to the ichnogenus Limnopus, making them one of the earliest known occurrences. At least five trackways are discernible with an external width ranging from 320 to 400 mm. Limnopus glenshawensis, a new ichnospecies, is herein proposed and various morphologic and locomotion parameters are quantified. Mean values include stride/manus, 407 mm; stride/pes, 411 mm; oblique pace/manus, 313 mm; oblique pace/pes, 317 mm; pace angle/manus, 82.4 degrees; pace angle/pes, 80.5 degrees; glenoacetabular distance, 329 mm; manus length, 87.2 mm; manus width, 104.2 mm; pes length, 121.4 mm; pes width, 112.7 mm. The tracemaker was most likely an eryopoid amphibian with a total length of slightly over 1 m.