I believe this item is a manufactured artifact- a 7,000 year old mountaineering boot made from the skin peeled from a bear's leg. The bones inside are probably human, with the bear's skin deformed over it. I have argued this position extensively at cryptozoology.com. Here is a link to one of my web pages with comparative pics and links to forum arguments:

wormspew-mysteries of the worm

the relevant pics are 1/2 way down the page.

Very intresting website, thanks for that!