ON THE HETEROCELOUS VERTEBRAE IN HORNED DINOSAURS (PROTOCERATOPIDAE, NEOCERATOPSIA)

Abstract

Four or five anterior caudal vertebrae of archaic horned dinosaurs (Protoceratopidae) have the heterocelous centrum. The cranial and caudal articular surfaces of these centra are posteriorly concave in the ventral view and anteriorly concave in the lateral view. The heterocelous shape of such centra allows neighboring vertebrae to move relative to one another in both the vertical and horizontal planes and prevents torsion. The torsional force in the proximal caudal vertebrae is exerted by the caudofemoral muscles.