A type of dinosaur from the Jurassic period that often received anal sex from every other dinosaur in the immediate vicinity.
It was often taboo back in those days as there was a disease known as DAIDS, or dino-AIDS. It is rumored to be the cause of the dinosaur extinction, even more so than an ice age.
Oh my GOD! Littlefoot! Stop receiving anal sex from that sharptooth! You don't want to be known as a Butt-Sex-A-Saurus, do you?