When I see reconstructions of pseudosuchians in a bipedal stance I always reflect upon the question of whether or not it is functionally possible for an animal with a crocodile-normal ankle type to actually be bipedal, especially an obligate biped. I've perused the literature but have found very little to address this problem. I'm certain that Emma Schachner dealt with this in her recently completed PhD on the new equisitely preserved Poposaurus specimen from the Chinle Formation in Utah, but unfortunately I've not had a chance to borrow and read a copy. Her 2009 SVP abstract suggests that myological developments differ between bipedal pseudosuchians and bipedal dinosaurs, suggesting that these myological changes compensate for the alternate ankle structures.
According to Tarsitano (1981, 1983) it is very difficult, if not impossible, to be an obligate biped with a crurotarsan ankle structure. He has a large discussion of this. Furthermore, according to the same author and older work by Al Romer other characteristics that are not good indicators of bipedality are plantigrady and tibiae/fibulae that are shorter than the femora. Are these still valid points?
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