ISOLATED VERTEBRATE TRACKS FROM THE UPPER CRETACEOUS CAPPING SANDSTONE MEMBER OF THE WAHWEAP FORMATION: GRAND STAIRCASE - ESCALANTE NATIONAL MONUMENT, UTAH

Although track sites are common throughout Late Cretaceous strata, few have been reported from the capping sandstone member of the Wahweap Formation in Grand Staircase - Escalante National Monument. Recent discovery of isolated tracks preserved in the capping sandstone indicates that several track makers including crocodylomorphs, previously known from teeth elements, and ornithischians were present during fluvial deposition.

An isolated crocodylomorph pes track was found in fluvial deposits at Wesses Canyon locality. The track is 14 by 10 cm and has five digits with divarication of approximately 60º. These measurements are consistent with other crocodylomorph tracks from the literature. At Tommy Smith Canyon near the contact of the capping sandstone member and the overlying Kaiparowits Formation, several isolated pes tracks occur that range from 16 to 32 cm in length and 9 to 27 cm wide. Tracks have three distinct digits with a divarication of 50º to 75º. These tracks are assignable to an ornithischian track maker. A possible therapod track is present based on size and morphology, but does not display definitive criteria.