Accusations of questionable meat are once again on the table, this time over a group of animal experts' claims that their leg of lamb dinner at a Zhengzhou restaurant was sneakily substituted for much cheaper pork.

The controversy stewed after one of the diners posted about the mystery meal on social media.

"We all thought it was just funny and never thought this post would have attracted so much attention," said Li Fan, the animal archaeologist who posted the photo Thursday.

Li said the group, in town for an academic conference, had gotten together at the local restaurant on Thursday night for a mutton meal.

When the food came Li said he immediately observed something was not kosher.

"I noticed the shoulder blade right away, as those in pigs and sheep are completely different," Li, who is also a lecturer at Zhengzhou University's College of History, told the Beijing Youth Daily.

"Apart from the spine and ribs, pig and sheep bones are very easy to differentiate. Sheep shoulders are more triangular in shape, but those in pigs have a circular arc. The rotator cuffs are different also."

The on-duty manager covered the cost for the meal.

The owner has since denied the accusation, saying they have served leg of lamb for the last six years without complaints.

"It was a whole lamb leg - the bone was buried in the meat. There is no way that it was anything other than lamb," the owner said.

"I would treat them to a meal so they could tell us honesty [what the meat really is]," he added.

Beijing Youth Daily