title: The mosasaur tooth attachment apparatus as paradigm for the evolution of the gnathostome periodontium.
abstract: Vertebrate teeth are attached to jaws by a variety of mechanisms, including acrodont, pleurodont, and thecodont modes of attachment. Recent studies have suggested that various modes of attachment exist within each subcategory. Especially squamates feature a broad diversity of modes of attachment. Here we have investigated tooth attachment tissues in the late cretaceous mosasaur Clidastes and compared mosasaur tooth attachment with modes of attachment found in other extant reptiles. Using histologic analysis of ultrathin ground sections, four distinct mineralized tissues that anchor mosasaur teeth to the jaw were identified: (i) an acellular cementum layer at the interface between root and cellular cementum, (ii) a massive cone consisting of trabecular cellular cementum, (iii) the mineralized periodontal ligament containing mineralized Sharpey's fibers, and (iv) the interdental ridges connecting adjacent teeth. The complex, multilayered attachment apparatus in mosasaurs was compared with attachment tissues in extant reptiles, including Iguana and Caiman. Based on our comparative analysis we postulate the presence of a quadruple-layer tissue architecture underlying reptilian tooth attachment, comprised of acellular cementum, cellular cementum, mineralized periodontal ligament, and interdental ridge (alveolar bone). We propose that the mineralization status of the periodontal ligament is a dynamic feature in vertebrate evolution subject to functional adaptation.
authors.affiliation: Departments of Oral Biology, University of Illinois at Chicago, Chicago, IL 60612, USA. xhluan@gmail.com
authors.forename: Xianghong
authors.initials: X
authors.lastname: Luan
authors.forename: Cameron
authors.initials: C
authors.lastname: Walker
authors.forename: Smit
authors.initials: S
authors.lastname: Dangaria
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Ito
authors.forename: Robert
authors.initials: R
authors.lastname: Druzinsky
authors.forename: Kristina
authors.initials: K
authors.lastname: Jarosius
authors.forename: Herve
authors.initials: H
authors.lastname: Lesot
authors.forename: Olivier
authors.initials: O
authors.lastname: Rieppel
mesh_terms: D000818:Animals; D005075:Biological Evolution; D025061:Dinosaurs; D010519:Periodontium; D014070:Tooth