Take him out! Cut off his head, boil some water, put his head in a bucket, pour the hot water, remove scales and flesh, let it sit by a ant hole, and you got yourself a pleco skull!
Knifegill I couldn't, possibly assemble an entire skeleton. By the time I finished I would be on my deathbed.
Studd muffin, I might consider the skull idea. I have a cat skull and turtle shells, a pleco skull might be nice.