My opinion is that this skull could be:

• Part of the skeleton of big animal, as mastodon. It's strange that this is not a petrified bone, which means it's not a very old one. And mastodons lived on Earth not so long ago.
• Some sort of mystification, but I think that it's very difficult for someone to make this skull from other bones.

Hristo Pophristov

A Bulgarian physician and mathematician