Studies of tooth implantation in fossil tetrapods using high-resolution X-radiography

Abstract

The concept that reptilian tooth implantations fall neatly into a number of separate categories which can be used in phylogenetic studies is called into question. The use of microfocal Xradiography in preliminary studies of reptilian dentitions reveals that, at least in sphenodontids, there is no clear distinction between acrodonty and pleurodonty. Although the technique is used here specifically in connection with microvertebrates, it may have considerable potential in evaluating internal structures in a wide range of fossils.

Microstructure of Dental Hard Tissues and Bone in the Tuatara Dentary, <i>Sphenodon punctatus</i> (Diapsida: Lepidosauria: Rhynchocephalia)

“…This study is the first evidence for hard tissue turnover in tuatara and provides a platform for assessing tooth implantation in the tuatara's fossil relatives, particularly those taxa that are not fully acrodont [2,17,19,20].…”

“…One exception to this is the large anterior caniniform teeth that replace some of the hatchling dentition during the juvenile period [10]. This system of tooth growth and implantation seems to have been acquired early on in the group's history and may have been required for their initial radiation [16][17][18][19][20]. However, the exact nature of the tooth tissues that exist as well as the tissues involved in tooth growth and replacement has remained unclear.…”

A redescription of Orovenator mayorum (Sauropsida, Diapsida) using high‐resolution μCT, and the consequences for early amniote phylogeny

“…The scan reveals the apices of replacement teeth erupting from the labial surface of several alveoli. Dental implantation is broadly ‘subthecodont’ ( sensu Fraser & Shelton ) with thin interdental plates. The labial wall of the alveolar row is slightly taller that the lingual wall, which is comprised of low, triangular paradental plates.…”

A bird-like skull in a Triassic diapsid reptile increases heterogeneity of the morphological and phylogenetic radiation of Diapsida

“… — This character has been modified from Character 94 in Pritchard et al [ 68 ] and Nesbitt et al [ 10 ], incorporating two states for what was regarded as acrodonty (superficial attachment of teeth to dentigerous bones) in the original datasets. The new states describe intermediate stages of acrodonty, as revealed by CT scanning of early rhynchocephalians (described in [ 157 ]). In Planocephalosaurus robinsonae and Diphydontosaurus avonis , teeth appear to be superficially attached to their respective dentigerous bones, but with pulp cavities that extend into said bones.…”