A new investigation of the sedimentology and ichnology of the Early Jurassic Moyeni tracksite in Lesotho, southern Africa has yielded new insights into the behavior and locomotor dynamics of early dinosaurs.
The tracksite is a pont bar in an old river that had a lot of variation in slope and the nature of the sediment on which one would walk. There are trackways of numerous different kinds of dinosaurs that walked across this surface over a very short period of time (of several days or a bit longer). The different dinosaurs responded to the different surfaces differently. That is not a surprise, but it is very cool. A new paper in PLoS ONE presents an analysis, and they conclude:
The locomotor adjustments coincide with changes in substrate consistency along the trackway and appear to reflect 'real time' responses to a complex terrain. It is proposed that these responses foreshadow important locomotor transformations characterizing the later evolution of the two main dinosaur lineages. Ornithischians, which shifted from bipedal to quadrupedal posture at least three times in their evolutionary history, are shown to have been capable of adopting both postures early in their evolutionary history. The substrate-gripping behavior demonstrated by the early theropod, in turn, is consistent with the hypothesized function of pedal claws in bird ancestors.
Wilson, J., Marsicano, C., & Smith, R. (2009). Dynamic Locomotor Capabilities Revealed by Early Dinosaur Trackmakers from Southern Africa PLoS ONE, 4 (10) DOI: 10.1371/journal.pone.0007331
Wow! That's a nice level of detail.