Tooth Characters And Biological Significance Of Adamisaurus Magnidentatus(Squamata:Polyglyphanodontia) From The Late Cretaceous Of Inner Mongolia,China

The teeth of vertebrates,as a medium for realizing the important process of exchange between organisms and the environment,are influenced by both heredity and environment and reflect the information of phylogeny and ecology.The tooth characters are not limited to the crown morphology,but also involve various aspects such as tooth implantation,the frequency,and mode of tooth replacement,the composition and the proportion of periodontal tissue,and the attachment mechanism.However,studies other than tooth shape(morphology)in squamates are extremely limited,and the distribution and evolution of these characters in squamates are not clear,especially how these characters relate to function.To understand the biological significance of tooth characters within the squamates such as tooth implantation,tooth replacement,and tooth attachment and the related function,the thesis describes the Late Cretaceous lizard Adamisaurus magnidentatus(Squamata: Polyglyphanodontia)from Bayan Mandahu,Inner Mongolia,China,which is rich in material and has typical special tooth morphology and function.Fusing high-resolution data obtained by computed tomography(CT),the thesis revised the tooth number and the type of tooth implantation of Adamisaurus,and confirmed that the dentitions Adamisaurus are heterodont;In addition,the tooth abrasion and replacement are described in detail.Histological sectioning techniques were further used to examine the periodontal tissues of Adamisaurus.Compared with other members of the Polyglyphanodontians and other squamates,Adamisaurus reveals the complexity and diversity of the tooth characters.Adamisaurus has the following tooth characters: the teeth number is small,the posterior teeth are enlarged,the tooth bases are expanded and associated with the jawbone in a large area,and the teeth are firmly anchored to the jawbone(Ankylosis).The dentine and enamel are thick.The posterior teeth are generally severely abraded,and the tooth replacement is active and does not cease at any developmental stages.The crown is high and has one or two inconspicuous cusps on the occlusal surface and upper and lower teeth are interlocking.It is likely that Adamisaurus have the ability to crush relatively hard food.The complex tooth characters of Adamisaurus magnidentatus,and the diversity of tooth characters in the squamates,prompt further studies on tooth characters in the future to reveal more biological and functional information.And with the increasing data,it is possible to discuss the distribution and evolution of tooth characters within the squamates or other subclades,as well as to discuss the magnitude of genetic or ecological influences on tooth characters.