I think this is in the Hedgehog cactus family. Yes, those thrones are sharp! We have seen folks hiking in all sorts of foot wear but good hiking boots are the best thing. Not only do boots provide better support, they also protect against all those sharp and pointy things. If you happen to pick-up any cactus thorns, try this trick - smother the area with a thick layer of white glue, such as Elmer's, and let dry completely. When good and dry, peel off the glue and thorns.