I thank you.
I got it from dinosaur comics.

I then looked up the meaning, and decided it was a fair adjective.
( Rev. Cleo still alive, Wed 27 Dec 2006, 23:07, archived)

Callipygian was used in a dinosaur comic?
It's most commonly used to describe a womans bottom.
( stuj (^(^;;^)^) GO TEAM SPIDERS!(^(^;;^)^), Wed 27 Dec 2006, 23:10, archived)

Indeed.
dictionary.reference.com/browse/Callipygian
( NobbyNobody 21 years a b3tan, Wed 27 Dec 2006, 23:16, archived)

The dinosaur was describing himself.

( Rev. Cleo still alive, Wed 27 Dec 2006, 23:20, archived)