Reply to Cale:

Thanks for sharing your thoughts about metatarsal impressions. Your suggestion was one of the possible explanations that occurred to me soon after finding metatarsal dinosaur tracks (in 1980), as I discuss in my paper "Elongate Dinosaur Tracks...". However, a couple considerations seem to argue against it: 1. Deep bipedal dinosaur tracks are more often non-metatarsal tracks, and 2. Generally the pace lengths for metatarsal tracks are about the same as for normal digitigrade (toe-walking) tracks, whereas if they animals were trying to gain more stable footing in deep or slippery mud, I for one would expect them to take shorter steps. I think a more likely explanation is that the dinosaur were sometimes crounching down as they walked, which would force a smaller angle at their ankle, and thus foster metatarsal impressions. (Try walking on your toes, then crounch down by bending your knees, and you'll see what I mean). The reason dinosaurs would have crounched down is a separate questions. Some possibilities are foraging in the soft mud or very shallow water (even today many large carnivores will eat small animals when the opportunity arises), stalking, or interactive behaviors. Last, it is possible there is more than one cause fo the metatarsal tracks. Reportedly some large modern birds like emus make such tracks at times, and want to pursue that further. GK