<Non-hadrosauriform ornithopods? In a sense we have no idea what
*Hypsilophodon* is...>
It's a hypsilophodontid ornithopod.
That's true -- by definition. And this doesn't tell us anything. We don't
have a good idea currently on whether anything else is a hypsilophodontid,
respectively where else all those hypsilophodontids in the classical sense
are on the ornithopod, wait, cerapod tree.