SCIENTIFIC SIGNIFICANCE OF THE EARLY PERMIAN VERTEBRATE AND INVERTEBRATE ICHNOLOGY OF THE PREHISTORIC TRACKWAYS NATIONAL MONUMENT, ROBLEDO MOUNTAINS, DOÑA ANA COUNTY, NEW MEXICO

The Prehistoric Trackways National Monument (PTNM), Robledo Mountains, Doña Ana County, New Mexico, includes significant exposures of the Robledo Mountains Formation of the Hueco Group. This unit contains extensive trace fossil assemblages made by invertebrates and vertebrates that lived on tidal flats of the Early Permian Hueco seaway. The Robledo trace fossils are one of the most scientifically significant ichnofossil Lagerstätten known. This significance derives from documentation by the PTNM traces of the: (1) presence of many organisms, especially arthropods, not known from coeval strata in New Mexico; (2) new ichnotaxa, not previously known from the ichnofossil record; (3) complex apterygote insect behaviors, including some of the oldest records of jumping; (4) diversity, inferred trophic dynamics and paleoecology of the Early Permian tidal flat biota; (5) extramorphological variation in tetrapod footprint morphologies, allowing comprehensive ichnotaxonomic revisions; and (6) composition of ichnofossil assemblages, ichnocoenoses and ichnofacies that are a pivotal part of modeling spatial variation in Early Permian red-bed terrestrial communities. Despite intensive collecting and study, much new information about the PTNM ichnofossils continues to be discovered, including the identification of a new assemblage that preserves limulid and anemone traces together with chondrophorine body impressions. Continued study of the PTNM is helping to advance our understanding of the Early Permian tidal flat communities.