ON THE MORPHOLOGY OF THE MANDIBULAR JOINT IN PALEONISCOIDS

Abstract

Comparisons with extant acipenserids suggest the presence of a cartilaginous plate evolving in ontogeny externally from the dermal ossifications. The plate in the paleoniscoid lower jaw is a projection of Meckel's cartilage close to the caudal flange of the maxillary overlap. Besides that, there is an incompletely ossified orbital process of the palatoquadrate that in paleoniscoids served to attach the caudal part of the maxilla, which participated, together with the cartilaginous plate of the mandible, in the formation of an additional articulation component of the mandibular joint. The functional importance of this additional articulation was to prevent a lateral shift of the lower jaw with respect to the palatoquadrate.