Zoologists are seeking the public's help as they try to discover how two jawbones disappeared from a 56ft whale washed ashore on an island.
The whale was washed up on Coll in February
The skeleton of the fin whale was removed from the beach on Coll, in the Inner Hebrides, earlier this month.
It was taken to the National Museums of Scotland (NMS) research facilities at Granton in Edinburgh - but the 12ft long jawbones are nowhere to be found.
The disappearance was described as "a most unusual zoological phenomenon".
NMS would not speculate on the possible fate of the bones, which weigh about 250kg.
However, a spokesperson said experts were "intrigued" about where they had gone.
It is thought that the fin whale was already dead by the time it arrived on the beach at Coll at the beginning of February.
The operation to remove it from the beach saw the blubber and soft tissue removed from the skeleton, which was transported by truck and ferry to Edinburgh three weeks ago.
Staff at Granton will spend the next few weeks cleaning the bones before the whale joins the NMS research collections.
Andrew Kitchener, curator of birds and mammals, said that the NMS does not have a complete fin whale skeleton.
"Finding these jaw bones would help fill a massive gap in our collection," he said.
And he added: "The disappearance of these jawbones is a most unusual zoological phenomenon.
"We would be very grateful to anybody on Coll who might happen to stumble across them."
The fin whale is second only in size to the blue whale, the biggest mammal on earth.