Wednesday, 8 January 2014

Odontography - all about teeth

Once again I have neglected 'MM', but it is not dead just yet. I felt that a little update was necessary. Currently I am working on some taxonomic issues within Pterosauria that it seemed impossible to ignore during a project attempting to resolve the evolutionary relationships of these creatures. I have also taken part in a project on a new genus and species of crocodile, but this is in review, so it's all hush hush for now.

So, let's talk teeth again shall we.

Teeth are used for aggression, defence, prey capture, digestion, grooming, communication, fighting, digging, sensing the surroundings, child rearing, sexual selection, sex and many more things, and they have a high preservation potential, so they are important to palaeontologists.
A slide from a presentation on understanding pterosaur teeth that I gave

A slide from a presentation on understanding pterosaur teeth that I gave
Some time ago I bought the domain The website and its concept are still in the development stages. It is an ambitious project for one man without funding and too little time on his hands, but one that is close to my heart.

The concept of is to be an all encompassing dental resource for Biologists, Palaeontologists and other interested parties. I hope to provide general educational material as well as a search based resource for as many extinct and extant animals as possible. The concept is to build upon what Sir Richard Owen started in the 1840s with his Odontography. This treatise was a seminal piece of work, giving us terminology in common use today, e.g. dentine. The work was ~750 pages long with 150 plates of figures, contained in two separate volumes. The study looked at the teeth of fishes, reptiles (including amphibians, pterosaurs, dinosaurs and mesozoic marine reptiles) and mammals. There are histological (the study of microscopic mineralised tissue structures) images as well as depictions of the entire dental arrangement, it was a truly inspired piece of anatomical work.

Take for example the tooth of Megalosaurus which is beautifully illustrated, demonstrating the pulp cavity with the dentine tubules radiating out, through 9 bells of dentine, toward the enamel, terminating at a granular layer of tomes at the enamel dentine junction.
Megalosaurus section through the crown, originally figured by Owen 1845

Modern photograph of a Carcharodontosaurus tooth, taken by Steven Vidovic, material supplied by David Martill University of Portsmouth UK - For comparison with Megalosaurus

As you can see there is more to a tooth than what is just on the surface. In overall anatomy you have the root, cervical region and crown. The crowns can also have varying morphologies within a dentition, this is called heterodonty, as opposed to homodonty (all the same, just varying in size). The crown morphology can be divided into it's four overlapping halves, labial (cheek/lip side) and lingual (tongue side) sides, and mesial (front/central) and distal (back). Within the the tooth you have further divisions of structure; various types of dentine and cements and externally, usually (one exception being my favourite, the sloth), enamel. The varying compositions of these hard parts with soft tissues change the nature of the material all together, but I may be in danger of boring you if I go into the differences between cementums and dentines. The most impotant thing to know is your tooth is alive, with a complex network of cells working to keep it healthy. These cells are located with the pulp cavity which is accessed by the apical foramen, in many cases a tiny hole which prevents infection from entering the bone or blood.

Sloth tooth sectioned along the coronal plane, originally figured by Owen 1845
A demonstration of tooth implantation, arrangement and replacement in crocodiles, originally figured by Owen 1845

The volume should continue to serve as a valuable resource to palaeontologists. The resources should be used to test modern theories, through comparative anatomy.

So... there is life in Odontography yet. I would like to try and bring it to the 21st Century.

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