Testing models of dental development in the earliest bony vertebrates, Andreolepis and Lophosteus.

Publication Type:Journal Article
Year of Publication:2012
Authors:Cunningham, JA, Rücklin, M, Blom, H, Botella, H, Donoghue, PCJ
Journal:Biol Lett
Volume:8
Issue:5
Pagination:833-7
Date Published:2012 Oct 23
ISSN:1744-957X
Keywords:Animals, Biological Evolution, Dentin, Dentition, Fossils, Jaw, Odontogenesis, Phylogeny, Surface Properties, Synchrotrons, Tooth, Vertebrates, X-Ray Microtomography
Abstract:

Theories on the development and evolution of teeth have long been biased by the fallacy that chondrichthyans reflect the ancestral condition for jawed vertebrates. However, correctly resolving the nature of the primitive vertebrate dentition is challenged by a dearth of evidence on dental development in primitive osteichthyans. Jaw elements from the Silurian-Devonian stem-osteichthyans Lophosteus and Andreolepis have been described to bear a dentition arranged in longitudinal rows and vertical files, reminiscent of a pattern of successional development. We tested this inference, using synchrotron radiation X-ray tomographic microscopy (SRXTM) to reveal the pattern of skeletal development preserved in the sclerochronology of the mineralized tissues. The tooth-like tubercles represent focal elaborations of dentine within otherwise continuous sheets of the dermal skeleton, present in at least three stacked generations. Thus, the tubercles are not discrete modular teeth and their arrangement into rows and files is a feature of the dermal ornamentation that does not reflect a polarity of development or linear succession. These fossil remains have no bearing on the nature of the dentition in osteichthyans and, indeed, our results raise questions concerning the homologies of these bones and the phylogenetic classification of Andreolepis and Lophosteus.

DOI:10.1098/rsbl.2012.0357
Alternate Journal:Biol. Lett.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith