the connection between a tooth and its socket in the jaw bone is an example of dentoalveolar syndesmosis.
the connection between a tooth and its socket in the jaw bone is an example of dentoalveolar syndesmosis.
the connection between a tooth and its socket in the jaw bone is an example of what kind of connection?
dentoalveolar syndesmosis
"stereosternum" had small teeth compared to "mesosaurus tenuidens", but it had larger teeth compared to "brazilosaurus sanpauloensis". the teeth of "stereosternum" are 6 times the length of "brazilosaurus sanpauloensis", but has smaller teeth compared to "mesosaurus tenuidens", which has teeth that are 12 times longer than "brazilosaurus". these differentiations with tooth length possibly correspond to different ecological niches being filled. the way the teeth are positioned inside the jaw is a unique feature of this species; with the teeth more apically being inserted within the alveolar bone and the fully developed teeth show dental ankylosis. from looking at the teeth and how they are positioned, it seems that the replacement pulse occurred anteroposteriorly in "stereosternum", in a quasi-alternate polyphyodont pattern. going more distally, the teeth seem to have periodontal ligaments connecting the teeth to the alveolar bone and then even more distally the tooth is connected by the anchorage trabeculae, which is composed of cementum and probably the alveolar bone. the anchorage trabeculae structure acts as an additional structure to hold the teeth in place. within the adult teeth, the pulp cavity is enclosed within on itself, and inside those pulp cavities are canals that connect the tooth to the alveolar bone. those canals were the spaces that were filled by blood vessels and nerves, which supplemented the growth of the tooth and gave the tooth some sensory abilities. during the early part of the development of the teeth, the roots would have been open, and the only connection that would have been facilitated would have been the cementum between the tooth and the alveolar bone, the periodontal ligament and the cementum made anchorage trabeculae would have mediated this connection. this complex, called the tripartite periodontium, during the life of "stereosternum", would have acted as a mechanism for keeping the teeth within the jaw, working against the lateral forces that could easily pull teeth out of the socket, given the size of these teeth. the teeth also have multiple different types of dentine and there are different orientations of the dentine tubules along the tooth, including mixed composition in the dentary wall. these adaptations helped to increase the tooth's resistance to tension forces, especially the lateral forces.
stereosternum
the skull of "acrocanthosaurus", like most other allosauroids, was long, low and narrow. the weight-reducing opening in front of the eye socket (antorbital fenestra) was quite large, more than a quarter of the length of the skull and two-thirds of its height. the outside surface of the maxilla (upper jaw bone) and the upper surface of the nasal bone on the roof of the snout were not nearly as rough-textured as those of "giganotosaurus" or "carcharodontosaurus". long, low ridges arose from the nasal bones, running along each side of the snout from the nostril back to the eye, where they continued onto the lacrimal bones. this is a characteristic feature of all allosauroids. unlike "allosaurus", there was no prominent crest on the lacrimal bone in front of the eye. the lacrimal and postorbital bones met to form a thick brow over the eye, as seen in carcharodontosaurids and the unrelated abelisaurids. nineteen curved, serrated teeth lined each side of the upper jaw, but a tooth count for the lower jaw has not been published. "acrocanthosaurus" teeth were wider than those of "carcharodontosaurus" and did not have the wrinkled texture that characterized the carcharodontosaurids. the dentary (tooth-bearing lower jaw bone) was squared off at the front edge, as in "giganotosaurus", and shallow, while the rest of the jaw behind it became very deep. "acrocanthosaurus" and "giganotosaurus" shared a thick horizontal ridge on the outside surface of the surangular bone of the lower jaw, underneath the articulation with the skull.
acrocanthosaurus