Medieval dolphin burial

"The big puzzle from an archaeological point of view is that it really does look like a grave cut for a human — exactly like we would find in a medieval cemetery," De Jersey told Live Science. "So, it was a bit of a surprise to start excavating it and find a sea creature in there instead."

De Jersey added that he hasn't heard of any similar archaeological findings, saying, "It’s just a strange thing to do, and it would have taken a lot of effort."

Another possibility is that the animal was butchered for food, then packed with salt as a form of preservation and buried in the pit, he said.

"There is literary evidence from the 13th and 14th centuries which mentions that porpoise was definitely eaten at that time," De Jersey said. "And the implication is that it wasn't eaten fresh, so there must have been some way to preserve it, by drying it or salting it in some way," he added. "So, we've wondered whether this was a pit filled with salt, and they've put the animal in, and for whatever reason, it was never retrieved."

I prefer the interpretation that it was a medieval Flipper, helping monks rescue stranded sailors at sea and fighting off pirates and suchlike.

https://www.livescience.com/60522-dolphin-bones-unearthed-in-medieval-grave.html