I had a tuna sandwich a couple of weeks ago,
and it had a flat crunchy bit of bone in. I can only assume it was a bit of skull or spine.
It was John-fucking-West tuna too.
(
Spunkmeyer,
Wed 26 Jan 2005, 12:58,
archived)
Most likely dolphin spine.
(
gronkpan @vomitinglarry.bsky.social,
Wed 26 Jan 2005, 13:09,
archived)