Mammal Track Assemblages from the Early Tertiary of China, Peru, Europe and North America

Abstract

Recent discovery of small, tridactyl vertebrate tracks in a remote region of northwestern China has expanded the data set for the interpretation of similar trackways elsewhere in the world. Previously, similar tracks reported found in Peru from the Formation des Couches Rouges, were attributed to ornithopod dinosaurs, and then used to reinterpret the age of the section as Late Cretaceous. Similarly, the Chinese trackways were, prior to this study, assigned to the very broad chronological interval Cretaceous through Oligocene. Comparison with the similar ichnofaunas in North America and Europe where the age of the tracks is well constrained to Paleogene, and where the tracks are attributed to odd-toed ungulates (perissodactyls), necessitates careful analysis of the affinity and age of the Chinese and Peruvian trackways. In all regions the track assemblages are mammalian (i.e., of ungulate affinity). The Northern hemisphere tracks maybe be attributed to perissodactyls, but the South American tracks probably represent native ungulate groups such as the Notungulata and Litopterna, that show convergent foot morphology. Even at the high taxonomic level of odd toed ungulate such broad biostratigraphic (palichno-stratigraphic) correlations are useful in providing insights into the geologic and tectonic history of terrestrial successions, where the age and faunas are poorly known.