P1.121 Wednesday, Jan. 4 Connective Tissues of the Craniovertebral Joint in Rajidae CLAESON, Kerin M.; Ohio University Heritage College of Osteopathic Medicine email@example.com
The craniovertebral joint (CVJ) exhibits arrangements and morphologies of skeletal and connective tissues that vary according to ontogeny and systematics. For instance, within chondrichthyans a broad articulation between the skull and basiventral skeletal cartilages of the adjacent vertebrae is known to occur in Squatiniformes, Orectolobiformes, Carcharhiniformes, Pristiophoriformes, and Batoidea. Among these taxa, there is a difference in the number of expanded basiventrals, the ultimate length of each expanded basiventral, and the degree and/or direction of curvature of each basiventral. To begin to quantify the connective tissues at the CVJ in chondrichthyans, I examined histological sections of embryonic specimens of three species of skate (Batoidea:Rajidae), Raja asterias, Raja sp., and Leucoraja erinacea. These embryonic data are part of a broader project examining the ontogenetic changes in chondrichthyans. Preliminary data indicate tight junctions between the occipital cotyle and occipital condyle with little articular cartilage present early in development. In addition, there is a distinct septum of dense connective tissue that extends between the anterior tip of the median crest of the synarcual and a perpendicular sheet of dense connective tissue above the foramen magnum. This septum is broadest ventrally and tapers dorsally. Epaxial musculature appears to connect directly to the median crest of the synarcual proximally but does not adhere to the dense connective tissue septum or sheet distally. Understanding the evolutionary and developmental history of variability of both skeletal and connective tissues in the CVJ will facilitate biomechanical study of the stresses imposed on this joint during a variety of functions such as locomotion and feeding.