Stops and turns: Uncommonly preserved theropod locomotive behavior patterns in an Upper Cretaceous tracksite from Torotoro National Park, Bolivia

Abstract

The Carreras Pampa tracksite from the Upper Maastrichtian of Bolivia preserves one of the world's largest concentrations of dinosaur trackways. Thus far, we have assigned all but a small number of these trackways to theropod trackmakers. With such a high concentration of trackways, the Carreras Pampa tracksite is an excellent place to find evidence of a diversity of uncommonly preserved dinosaur locomotive behaviors. To date, we have found four trackways with turns ranging from 44° to 84° and describe a fifth trackway with a turn of 38° that contains unusual features. Four trackways have been found that indicate the trackmaker was walking, stopped or paused, and then began walking again. One of the trackways that records a stop also shows evidence that the trackmaker was limping. Another trackway shows that the trackmaker made a sudden, abrupt change in its direction of movement, probably in response to an unknown obstacle, and then gradually returned to its original orientation. One series of fossil traces is reported that we believe is best interpreted as a crouching trace involving multiple tracks and tail traces. These tracks were made by theropods of various sizes, with track lengths ranging from 7.3 to 32.4 cm. These trackways show that a diversity of locomotive behavior patterns occurred during the formation of the Carreras Pampa tracksite.