Fearsome-looking mountain lion is found with a second set of TEETH growing out of its forehead

A mountain lion has been discovered in southeast Idaho with a second set of teeth growing out of its head.

The big cat was killed by an unidentified hunter last week in Weston, who then reported the animal's bizarre deformity to the authorities, Idaho State Journal reports.

 Idaho conservation officers, who were sent a photograph of the kill, were shocked to find the year-old lion had a separate set of teeth growing out the left side of its forehead.

Experts have not been able to agree on the cause of the unusual mutation.

One theory is that the mountain lion's extra set of teeth may be remnants from a conjoined twin which died in the womb.

Another is that it is a type of tumor called a teratoma which can sometimes grow other body parts such as hair, teeth, bones - even eyes.

Regional wildlife biologist Zach Lockyer told Idaho State Journal the unusual deformity had left experts stumped.