Dinosaur tracks from the Lower Cretaceous of Regumiel de la Sierra (province of Burgos, Spain): Inferences on a new quadrupedal ornithopod trackway

Abstract

A dinosaur tracksite has been discovered comprising three types of tridactyl footprints at Regumiel de la Sierra (province of Burgos, north‐central Spain). The rocks belong to Lower Cretaceous Wealden deposits of the Western Cameros Basin and two ichnological levels comprising 8 trackways and several isolated tracks were noted. All the footprints are tridactyl, although there are three types. Level 1 holds a trackway of which the footprints belong to a big iguanodontid dinosaur. Level 2 has yielded 6 trackways and several isolated tracks of Iguanodon‐like morphology, and also a theropod trackway. One iguanodontid trackway of level 2 has manus impressions suggesting that the dinosaur used a quadrupedal gait. The degree of inward rotation of footprints (similar to that of the other ones) suggests that this did not significantly modify the slight rotation of the pelvic girdle or the role of the tail during progression. The shape of manus prints suggests that the digit II was almost free and the III and TV ones were probably included within a single support structure. The trackway of level 1 suggests the presence of an unknown big iguanodontid dinosaur, probably more graviportal than Iguanodon bernissartensis. All the trackways suggest that the trackmakers were walking.