Tooth attachment and pleurodont implantation in lizards: Histology, development, and evolution

December 29, 2020

Aaron R. H. LeBlanc (1), Ilaria Paparella (1), Denis O. Lamoureux (2), Michael R. Doschak (3), Michael W. Caldwell (1,4)
Journal of Anatomy, December 2020. DOI: 10.1111/joa.13371


alveolar bone, bone of attachment, cementum, dental histology, Iguana, periodontal ligament, squamata, Varanus


Squamates present a unique challenge to the homology and evolution of tooth attachment tissues. Their stereotypically pleurodont teeth are fused in place by a single “bone of attachment”, with seemingly dubious homology to the three‐part tooth attachment system of mammals and crocodilians. Despite extensive debate over the interpretations of squamate pleurodonty, its phylogenetic significance, and the growing evidence from fossil amniotes for the homology of tooth attachment tissues, few studies have defined pleurodonty on histological grounds. Using a sample of extant squamate teeth that we organize into three broad categories of implantation, we investigate the histological and developmental properties of their dental tissues in multiple planes of section. We use these data to demonstrate the specific soft‐ and hard‐tissue features of squamate teeth that produce their disparate tooth implantation modes. In addition, we describe cementum, periodontal ligaments, and alveolar bone in pleurodont squamates, dental tissues that were historically thought to be restricted to extant mammals and crocodilians. Moreover, we show how the differences between pleurodonty and thecodonty do not relate to the identity of the tooth attachment tissues, but rather the arrangements of homologous tissues around the teeth.

Author Affiliation

(1) Department of Biological Sciences, University of Alberta.
(2) St. Josephs College, University of Alberta.
(3) Faculty of Pharmacy & Pharmaceutical Sciences and Department of Biomedical Engineering, University of Alberta.
(4) Department of Earth and Atmospheric Sciences, University of Alberta.