Story highlights The mountain lion was killed last week in Idaho

It had fully-formed teeth growing out of the top of its head

The deformity could be a "monster tumor"

(CNN) A hunter tracking down a mountain lion has stumbled upon a biological mystery.

Fish and Game officials say a male mountain lion involved in an attack on a dog near Preston, Idaho, was killed last week near the Utah border.

What the hunter discovered after examining the corpse can only be described as bizarre, even monstrous.

A photo released Thursday by Idaho Fish and Game shows the big cat had another set of fully-formed teeth and whiskers growing out of the top of its head. Wildlife officials say they have never seen a deformity like that -- but have offered up several theories.

They say it's possible the teeth could be the remnants of a conjoined twin that died in the womb and was absorbed into the other fetus. They then grew on their own.

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