Turtles are a group of reptiles whose bodies are enclosed in a shell, into which many species can retract their legs, tail and head for protection.
The Rigellians are a reptilian species that evolved from turtles. (Star Trek: The Motion Picture)
While growing up B'Elanna Torres was made fun of for being half Klingon. She was once called "Miss Turtle Head" by Daniel Byrd, an insult which referred to her cranial ridges. (VOY: "Juggernaut")