The most imposing and impressive part of a shark is its teeth. This is also the only part left behind when a shark dies, because the animal has no bones. Other than the teeth, a shark's skeleton is completely cartilage. Cartilage deteriorates quickly after the shark dies, leaving the teeth behind – along with a lot of questions about the age of the shark and the teeth. The last study of sharks' dentition was in 1968. With technology developed since then, scientists are able to learn more about the creatures than ever before.
In 1968, Bernhard Peyer, a German professor of paleontology and Dean of the Faculty of Science at the University of Zurich, published a paper titled "Comparative Odontology". This was the last published study on the structure of shark's teeth, using fossilized teeth. He could only study the external structure of the teeth, not the vasculature or mineralization.
This new study, using CT scans, allows scientists to view the internal anatomy of the teeth for the first time. The scans are being conducted at the Cornell Micro CT Facility for Imaging and Preclinical Research in Weill Hall. Director Mark Riccio, evolutionary biology professor Willy Bemis, and graduate student Josh Moyer are using the CT scans to analyze the anatomy of the teeth as well as how they develop and evolve. They can now create detailed 3D models based on the scans for detailed study.
When CT scan technology was first available, the scanners were large with complex computer software interfaces and obtaining each image was expensive and time consuming. Within the last ten years or so, advances in computerized tomography have allowed research like this to become accessible to scientists.
Sharks' teeth have a unique pattern of growth. They continually grow and regenerate. The teeth rotate every few weeks. This presents difficulty in understanding the age of a shark from one fossilized tooth, as it could have been grown at any time during the shark's life.
Using CT scans, scientists can now view where blood vessels grew, at what rate during the growth cycle, and determine when the tooth began to mineralize. This is the first step in establishing an evolutionary timeline for sharks, the way their teeth develop, and growth patterns.
This study not only includes fossilized shark teeth, but those of existing great white sharks at the Shoals Marine Laboratory where Bemis is John M. Kingsbury Director. He has accumulated hundreds of shark jaws and teeth for examination with the CT scanner. Fossilized and living sharks' teeth can be compared at the laboratory without taking the tooth apart, which will also assist in the study.
During the last 45 years, very little has been done to study the odontology of sharks. With advances in technology, resources, and the interest of scientists, things are changing. Hopefully we will learn much more about the mysterious creatures... and it won't take 45 years to learn it.
