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        Authors:        GM Erickson
        Title:  Incremental lines of von Ebner in dinosaurs and the assessment 
of
tooth replacement rates using growth line counts
        Full source:    Proceedings of the National Academy of Sciences of the 
United
States of America, 1996, Vol 93, Iss 25, pp 14623-14627
        Author keywords:        dentine; histology; evolution; Crocodylia; 
Richard Owen
        KeyWords Plus:  DENTINOGENESIS; INCISOR
        TGA/Book No.:   VY448
        Discipline:     Multidisciplinary
        Document type:  Article
        Language:       English
        Address:        Erickson GM,Univ Calif Berkeley,Dept Integrat 
Biol,Berkeley,CA
94720 USA
        ISBN/ISSN:      0027-8424
        Publisher:      Natl Acad Sciences,2101 Constitution Ave 
NW,Washington,DC 20418
        Abstract:       Dinosaur dentine exhibits growth lines that are tens of
micrometers in width, These laminations are homologous to incremental lines
of von Ebner found in extant mammal and crocodilian teeth (i.e., those of
amniotes). The lines likely reflect daily dentine formation, and they were
used to infer tooth development and replacement rates. In general, dinosaur
tooth formation rates negatively correlated with tooth size. Theropod tooth
replacement rates negatively correlated with tooth size, which was due to
limitations in the dentine formation rates of their odontoblasts. Derived
ceratopsian and hadrosaurian dinosaurs retained relatively rapid tooth
replacement rates through ontogeny. The evolution of dental batteries in
hadrosaurs and ceratopsians can be explained by dentine formation
constraints and rapid tooth wear. In combination with counts of shed
dinosaur teeth, tooth replacement rate data can be used to assess population
demographics of Mesozoic ecosystems. Finally, it is of historic importance
to note that Richard Owen appears to have been the first to observe
incremental lines of von Ebner in dinosaurs more than 150 years ago.

Graeme Worth
The Dinosaur Encyclopaedia