THE TRACKWAY OF A LARGE SPRAWLING TETRAPOD IN THE LOWER PERMIAN QUEANTOWEAP SANDSTONE OF SOUTHERN NEVADA

We report the discovery of a Lower Permian tetrapod trackway in the Queantoweap Sandstone of Southern Nevada. The Queantoweap Sandstone is correlative with the Esplanade Sandstone, the uppermost unit of the Supai Group in the Grand Canyon.

The trackway consists of six strides, with an average stride length of about 15 cm and a trackway width of 17 to 18 cm. Three conspicuous digits are present in each track, but they are not tridactyl tracks; other digits were probably present but were not clearly pressed into the substrate. The trackway occurs on a rock-varnish-coated surface of ripple-marked, marine sandstone. It lies in a trough, running parallel to the ripple crests. We tentatively interpret the depositional environment to have been a tidal flat. The trackway is unusual because of its size and sprawling gait, with the trackway width being greater than the stride length. Much smaller trackways are well known in the younger Permian Coconino Sandstone, but this is the first report of vertebrate tracks that we are aware of in the Quantoweap or Esplanade sandstones. The trackway is similar to some pelycosaur tracks reported from the Lower Permian Hueco Group of southern New Mexico.

Ongoing research will involve further analysis of the trackway and sedimentology of the associated sandstone, as well as actualistic studies of the gaits of extant reptiles and amphibians.