what are prehallax? and whatis its significance?

Answer 1

This isn't a very accurate answer, but its the best I can do: The prehallux is a free-floating bone (a sesmoid bone) that is present in the ankles and wrists of fossils (and some modern-day animals?). Joints that are formed with a prehallux are less-restrictive in movement than a human ankle - its presence is associated with certain animals that crawl or climb. Apparently, anthropologists and evolutionary biologists have had a hard time trying to figure how this thing fits into evloution, but it seems important since loss of the prehallux and shift to different ankle structure was essential for bipedalism in hominid evolution.