it's a lizard's tail. The lizard must have been attacked by something in the tree. A lot of lizards have a defense mechanism that includes making their own tails fall off. The predator generally plays around with the severed tail while the lizard runs away. It's a pretty strange thing to do but the tail eventually grows back!
There was some chemical/bioagent that was recently created that can allow small areas of human skin/bone/muscle to grow back, including fingertips and toes as long as the joints stayed intact, but I don't remember where I read about it. It was some kind of bio-engineered stem cell I think..
EDIT:
http://news.bbc.co.uk/2/hi/health/7354458.stm