Titanosaur trackways from the late cretaceous el molino formation of Bolivia (Cal orck’o, sucre)

The Cal Orck’o tracksite is exposed in a quarry wall, approximately 4.4 km NW of Sucre (Department Chuquisaca, Bolivia) in the Altiplano/Cordillera Oriental, in the El Molino Formation (Middle Maastrichtian). Fossiliferous oolitic limestones, associated with large, freshwater stromatolites and nine levels of dinosaur tracks in the El Molino Formation document an open lacustrine environment. The main track-bearing level is almost vertical with a surface area of ~ 65,000 m 2 . The high-resolution mapping of the site from 1998 to 2015 revealed a total of 12,092 individual dinosaur tracks in 465 trackways. Nine different morphotypes of dinosaur tracks have been documented. Amongst them are several trackways of theropods, orni-thopods, ankylosaurs and sauropods, with the latter group accounting for 26% of the trackways. Two different types of sauropod trackways are present. One exhibits speech-bubble-shaped manus impressions that are rotated outwardly and located more outwards than pes prints, and oval to rounded pes imprints with few details, but with a characteristic oval track shape. The second morphotype has more rounded and axially compressed pes imprints and horseshoe-like manus impressions. The manus shows clear impressions of digits I and V. The first morphotype with the more rounded manus can be attributed to a derived titanosaur. The second is assigned to the new ichnogenus Calorckosauripus and was probably made by a basal titanosaur. Both sauropod morphotypes exhibit a narrow-gauge and a wide-gauge stance along the same trackway, and therefore the authors suggest that trackway width may not be correlated, or may not be correlated completely with the osteological characters of the trackmaker’s skeleton.