TOOTH SOCKET HISTOLOGY IN THE CRETACEOUS SNAKE DINILYSIA, WITH A REVIEW OF AMNIOTE DENTAL ATTACHMENT TISSUES

The dental attachment site histology and gross morphology of Dinilysia patagonica, a Cretaceous terrestrial, trial snake, is examined in a thin section through the tissue-filled mesial-distal region between tooth positions of a left maxilla, and other partial tooth-bearing bones with teeth. We observed compact zonal bone and cancellous bone forming the maxilla, and alveolar bone (a woven-fibered bone) lining the tooth socket and filling the region between tooth positions. The discovery of alveolar bone in D. patagonica is significant because alveolar bone was found previously in only one other group of squamates, mosasaurs (extinct large marine lizards), and other amniotes with a thecodont tooth-attachment anatomy (archosaurs, mammals). The presence of alveolar bone in D. patagonica, associated with the recent finding of alveolar bone and other tissues associated with thecodonty (alveolar bone, cement, periodontal ligament) in mosasaurs. suggest that these tissues might be broadly distributed among squamates. Dinilysia patagonica is inferred to have a hinged tooth-attachment type, based on the tooth socket morphology and relationship between preserved teeth and the tooth-bearing bone.