Theropod Dinosaur Trackways from the Lower Cretaceous of the Chacarilla Formation, Chile

Abstract

We describe sixteen theropod dinosaur trackways from site III (Lower Cretaceous?) of the Quebrada Cha- carilla in the Chacarilla Formation (Jurassic-Lower Cretaceous), northern Chile. The trackbed belongs to a meandering river environment, with recurrent track assemblages. We fi nd that the main direction of the ichnites from site III parallels that of water fl ow. Two theropod footprint morphotypes are recognized: A) digit II and IV occupying about 0.5 times the total footprint length, and B) digit II and IV occupying less than 0.35 times the total footprint length. We estimate similar speed (~7 km/h) for the two parallel theropod trackways of morphotype A, suggesting synchro nized walking. We also describe some of the largest theropod footprints from South America (>60 cm), which are all of morphotype B.