What is the Briontosaurus new name?

Here's the story: The great bone hunter O.C. Marsh needed a really impressive skeleton to wring some more grant money out of his rich uncle, Peabody (of the Peabody Coal Company). He uncovered almost a complete Apatosaurus, a creature that had already been described, but lacking a head. He found a head nearby that had belonged to a Camarasaurus ("lizard as big as a room") which fitted nicely for size and assembled the composite animal as a Brontosaurus or "thunder lizard." The skeleton was displayed at the Peabody Museum with the questionable head and then without it until enough evidence rolled up to end any doubt, but by then "bronty" was firmly established in the popular mind. Since brontosaurus was mostly (and, headless, completely) Apatosaurus, modern listings usually give a nod to both names, as in "Apatosaurus (Brontosaurus)".

As a creature with another creature's head, Brontosaurus was technically a chimera.