One of the permafrost features is to preserve the biologic material for a long time. This horse is more than 10000 years old (I believe it does more, but paleonthologists also could see it). Even skin and hair left. It was found in one of the outcrops on a river or sea bank in the Eastern Arctic. Vivianite - blue mineral on its leg forms when any organic starts thawing still covered with the thawed soil.