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.

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.

It was initially seen attacking a dog on the hunter’s rural property in Weston. It was chased off, but its tracks were followed through other properties in the area and then through the hills.

Within three hours of the attack, the hunter tracked the animal with the use of hounds and killed it legally. The hunter’s dog survived the lion’s attack, officials told Fox News.

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.

‘It’s a bizarre situation and a bizarre photo,’ he added. ‘We may never know why those teeth are there.’

The hunter which killed the mountain lion had been planning to take the rare kill to a taxidermist.

But Idaho Fish and Game’s Southeast Regional Office, in Pocatello, are hoping to bring the carcass in for examination.

They are hoping x-rays and analysis may reveal the mystery to why the big cat developed such a fearsome second set of teeth.