A taxidermy “fox head” bought for £50 at an antiques market has sold for £50,000 after it was revealed to be a rare Tasmanian tiger.

The thylacine head, which has been described as “one of the most important specimens sold in recent years”, saw a bidding war break out at a Bristol auction house last week.

An anonymous seller had bought it at a West Country fair earlier this year because “the novelty googly eyes attached to it made them laugh”.

Andrew Stowe, the auctioneer at Auctioneum, said: “When we told the vendor how much it had sold for, I thought they were about to pass out.

“I actually had to offer them a chair, they couldn’t believe it!”

Successful bidder James Cranfield, who paid another £10,000 in fees, had gone to examine the head after seeing it in the catalogue and suspecting it did not belong to a fox, reported.

“It was sat on a table surrounded by all sorts of bric-a-brac and pottery. It confirmed exactly what I wanted to know,” he said.

Mr Cranfield had hoped to buy it for the guide price of around £30-£50, but had to battle it out with other bidders who had also discovered it was the rare thylacine.

“Unfortunately, someone else also had all the same suspicions as me and therefore I had a battle to win it,” he said.

“There is only one documented specimen on the database and its whereabouts are unknown. But the head I now own is the only one in existence. It is incredible.”

The extinct marsupial, which was unique to Australia and New Guinea, largely disappeared from the mainland around 2,000 years ago.

An isolated population survived in Tasmania by the time of British occupation, but European settlers wiped out the species in the 19th century through hunting, habitat fragmentation, and introduced diseases.

The last officially recorded thylacine died in 1936 at a zoo in Hobart, Tasmania.

“Pelts, mounted heads, bones and other taxidermy specimens of the creature are touted as ‘holy grails’ for zoologists, museums, scientists and collectors alike,” Auctioneum said.

“Complete mounted heads of the species are virtually non-existent outside of major national museums and scientific institutions. Only 756 specimens are known to exist and of those only 101 are taxidermy. Only one taxidermy head is believed to exist.”

Mr Stowe said the find was “unbelievably rare”, adding: “Even replicas of skulls or bones sell for thousands of pounds. To find a complete item like this, is almost unheard of, especially here in the UK.

“It was quite a shock to discover we were sitting on something so special.”