Upper Jurassic dinosaur tracks from the Majala Formation in the Huatacondo area (Tarapacá Basin, Chile): reappraisal of known localities and new tracksite discoveries

The bone record of non-avian dinosaurs from Chile consists of sauropods, theropods, ornithopods, and rare thyreophorans. However, the ichnological record is potentially even more abundant and plays a significant role in supplementing and enlarging the Chilean dinosaur record. Rich track-bearing levels, dated from the Upper Jurassic to the Lower Cretaceous, are known mainly from northern Chile. This study describes for the first time a stratigraphic section of the Majala Formation (late Oxfordian) in the Quebrada Huatacondo. In this section, five track-bearing levels were recorded confirming the presence of ichnites of giant (lengths between 51 and 52.8 cm), large (lengths between 43.5 and 46.5 cm) and medium (lengths between 25 and 27 cm) theropods. One surface (Maj5) has more than 25 footprints of minute to small theropods (footprints lengths ranging from 8 to 13 cm). Morphological parameters from the small footprints are similar to Carmelopodus, Grallator, and Therangospodus. Meanwhile, some similarities were observed with Kayentapus and Megalosauripus for the range of medium to giant footprints. When comparing track sizes from Quebrada Huatacondo with other theropod tracks from the Tarapacá Basin (Quebrada Chacarilla and Río San Salvador localities), their dimensions and morphology are similar, but the small tracks are substantially smaller than those from the other localities and constitute to the smallest footprints found on the western margin of Gondwana for this time. These tracks and trackways represent the oldest dinosaur footprints reported for Chile and the western margin of Gondwana.