I wasn't sure what word to use! [ she's a little flustered. ] I'm used to the word mandible referring to the jawbone and that's clearly different than your... mandibles. Since you have a lower jaw too.

[ excuse her while she flushes a bit because that phrasing is a little awkward too. ]

Anyway--I was asking because I noticed it looked like the equivalent of human mouth movements in our facial expressions.