title: Incremental markings of enamel in ectothermal vertebrates.
abstract: The deposition of enamel is marked by the formation of growth lines, which reflect incremental growth. Although periodic markings have been observed in enamel of non-mammalian vertebrates, the cross-striation interval and the pattern of enamel deposition have not been formally investigated. Here a structural study was made of the enamel in four non-mammalian vertebrates, with emphasis on periodic markings. Teeth from Rana catesbeiana, Tropidurus torquatus, Caiman crocodilus and a Canadian carnosaur were analysed. Enamel of T. torquatus and R. castebeiana was aprismatic; that of C. crocodilus and the carnosaur was formed by large, prism-like structures. Conspicuous incremental lines were observed in the enamel of the three living species, which presented a cross-striation repeat smaller than the prism cross-striations of mammalian enamel. Incremental lines of carnosaur enamel had a mean repeat interval similar to that of mammalian prism cross-striations. As metabolic activity in ectotherms is influenced by environmental conditions, the analysis of incremental markings of enamel is a potentially valuable source of information in the study of living and fossil reptiles and amphibians.
authors.affiliation: Faculdade de Odontologia de Piracicaba-UNICAMP, Av.Limeira 901, 13414-018, Piracicaba-SP, Brazil. serglin@fop.unicamp
authors.forename: S R
authors.initials: SR
authors.lastname: Line
mesh_terms: D000489:Alligators and Crocodiles / Q000033:anatomy & histology; D000566:Amelogenesis / Q000502:physiology; D000663:Amphibians / Q000033:anatomy & histology*; D000818:Animals; D003743:Dental Enamel / Q000648:ultrastructure*; D005580:Fossils; D049690:History, Ancient; D008116:Lizards / Q000033:anatomy & histology; D008855:Microscopy, Electron, Scanning; D010161:Paleodontology; D011892:Rana catesbeiana / Q000033:anatomy & histology; D012104:Reptiles / Q000033:anatomy & histology*