Tooth attachment and pleurodont implantation in lizards: Histology, development, and evolution. Issue 5 (29th December 2020)

• Record Type: Journal Article
• Authors: LeBlanc, Aaron R. H.; Paparella, Ilaria; Lamoureux, Denis O.; Doschak, Michael R.; Caldwell, Michael W.
• Is Part Of: Journal of anatomy. Volume 238:Issue 5(2021)
• Page Start: 1156
• Page End: 1178
• Publication Date: 2020-12-29
• Subjects: alveolar bone -- bone of attachment -- cementum -- dental histology -- Iguana -- periodontal ligament -- squamata -- Varanus; Anatomy -- Periodicals; 571.3
• DOI: 10.1111/joa.13371
• Languages: English
• ISSNs: 0021-8782

Abstract

Abstract: 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. Abstract : A look into the teeth and jaws of modern lizards reveal similar tooth attachment tissues to those in mammals. This challenges over a century of assumptions about dental evolution.