A skeleton from the third or fourth century AD has been found with the tongue apparently severed and a flat stone pushed into his mouth, in what may have been a harsh form of punishment.

The grisly find is thought to be unique, according to Simon Mays, Historic England’s human skeletal biologist. “This isn’t something that’s been identified so far in the archaeological records. So it’s identifying a new practice,” he told The Guardian.

“The fact that he’s buried face down in the grave is consistent with somebody whose behaviour marked them out as odd or threatening within a community.”

A study of facedown burials has suggested that the practice was used across societies to humiliate or disrespect the deceased person.

Lead study author Caroline Arcini, of Sweden’s National Heritage Board, said that the custom “sanctioned this apparently negative treatment of the dead”.

Shaming the dead “is most probably a deep-rooted behaviour in humankind,” she told National Geographic News.

The skeleton was discovered at Stanwick near the River Nene in Northamptonshire 1991. Research on the human remains has only recently been published by archaeologists and specialists at Historic England.

The so-called prone burials have been discovered previously in late Roman cemeteries. Mays said: “It’s a way of stopping the corpse from rising from its grave and menacing the living.” There have also been other examples of skulls with stones in their mouths.

Why the man had his tongue cut out and replaced with a stone object has led to several theories, including that he had mental health issues and severed his own tongue. Mays argues that it could have been a form of punishment. “There are Germanic law codes which talk about cutting people’s tongues out because they spread malicious accusations against other people.”

The tongue is believed to have been amputated, because there are other burials in Roman Britain where “missing body parts are replaced by objects at the appropriate anatomical location,” Mays said.

“There are only about 10 of these that we’ve so far been able to identify. The great majority are decapitations, where you’ve got a stone or a pot placed where the head should be. We thought that, because of this, perhaps a stone could replace the tongue because it’s in the front part of the mouth where the tongue ought to be.”