I would take this to the local collage in your area I am sure they can help figure out what this was. Pretty cool though. How large of a rock is it? Maybe some alien from outer space. LOL
You're also not too far from the Denver Museum of Nature and Science. They have a massive collection of fossils and such, and they might be able to help you ID this guy, You could email a photo to Kim Evans. She is the director of earth sciences there, and might be able to help you.
Kim.Evans@dmns.org