title: Evolution and Function of Dinosaur Teeth at Ultramicrostructural Level Revealed Using Synchrotron Transmission X-ray Microscopy.
abstract: The relationship between tooth form and dietary preference is a crucial issue in vertebrate evolution. However, the mechanical properties of a tooth are influenced not only by its shape but also by its internal structure. Here, we use synchrotron transmission X-ray microscopy to examine the internal microstructures of multiple dinosaur teeth within a phylogenetic framework. We found that the internal microstructures of saurischian teeth are very different from advanced ornithischian teeth, reflecting differences in dental developmental strategies. The three-tissue composition (enamel-mantle dentin-bulk dentin) near the dentinoenamel junction (DEJ) in saurischian teeth represents the primitive condition of dinosaur teeth. Mantle dentin, greatly reduced or absent from DEJ in derived ornithischian teeth, is a key difference between Saurischia and Ornithischia. This may be related to the derived herbivorous feeding behavior of ornithischians, but interestingly, it is still retained in the herbivorous saurischian sauropods. The protective functions of mantle dentin with porous microstructures between enamel and bulk dentin inside typical saurischian teeth are also discussed using finite-element analysis method. Evolution of the dental modifications in ornithischian dinosaurs, with the absence of mantle dentin, may be related to changes in enamel characteristics with enamel spindles extending through the DEJ.
authors.affiliation: National Synchrotron Radiation Research Center, 30076 Hsinchu, Taiwan.
authors.forename: Chun-Chieh
authors.initials: CC
authors.lastname: Wang
authors.affiliation: National Synchrotron Radiation Research Center, 30076 Hsinchu, Taiwan.
authors.forename: Yen-Fang
authors.initials: YF
authors.lastname: Song
authors.affiliation: Department of Geosciences, National Taiwan University, 10617 Taipei, Taiwan.
authors.forename: Sheng-Rong
authors.initials: SR
authors.lastname: Song
authors.affiliation: Institute of Geology, Chinese Academy of Geological Sciences, 100037 Beijing, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ji
authors.affiliation: National Synchrotron Radiation Research Center, 30076 Hsinchu, Taiwan.
authors.forename: Cheng-Cheng
authors.initials: CC
authors.lastname: Chiang
authors.affiliation: Beijing Museum of Natural History, 100050 Beijing, China.
authors.forename: Qingjin
authors.initials: Q
authors.lastname: Meng
authors.affiliation: Institute of Geology, Chinese Academy of Geological Sciences, 100037 Beijing, China.
authors.forename: Haibing
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Geology, Chinese Culture University, 11114 Taipei, Taiwan.
authors.forename: Kiko
authors.initials: K
authors.lastname: Hsiao
authors.affiliation: Department of Geosciences, National Taiwan University, 10617 Taipei, Taiwan.
authors.forename: Yi-Chia
authors.initials: YC
authors.lastname: Lu
authors.affiliation: National Synchrotron Radiation Research Center, 30076 Hsinchu, Taiwan.
authors.forename: Bor-Yuan
authors.initials: BY
authors.lastname: Shew
authors.affiliation: Institute of Genomics and Bioinformatics, National Chung Hsing University, 402 Taichung, Taiwan.|Department of Optics and Photonics, National Central University, 32001 Tauyuan, Taiwan.
authors.forename: Timothy
authors.initials: T
authors.lastname: Huang
authors.affiliation: Department of Biology, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada.|Department of Optics and Photonics, National Central University, 32001 Tauyuan, Taiwan.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Reisz
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003804:Dentin / Q000000981:diagnostic imaging* / Q000648:ultrastructure; D025061:Dinosaurs / Q000145:classification; D005580:Fossils; D021621:Imaging, Three-Dimensional; D008855:Microscopy, Electron, Scanning; D010802:Phylogeny; D016062:Porosity; D011859:Radiography; D017356:Synchrotrons; D014965:X-Rays