Thursday, September 1, 2011

New microCT method for dental dietary reconstructions

van Dam and colleagues report in P3 on new methods to determine the diet of fossil mammals, using microCT scans of fossil micromammal teeth.  The new method involves using 3D X-ray scans to calculate enamel volumes rather than traditional methods which simply measure maximum crown height.

Measurements of the overall maximum height of a tooth, called hypsodonty (literally "high tooth") indices, are probably the most common measurement used to determine the diet of extinct critters of all shapes and sizes. Mammals with abrasive diets consisting mainly of grasses tend to have higher teeth than animals which subsist on less abrasive diets, such as tree leaves. The general idea is that higher crowned teeth have a longer functional lifespan than lower-crowned teeth. Even as the chewing surface of the hypsodont tooth wears away, there is always more enamel being uncovered.  Low-crowned (bunodont) teeth become functionally obsolescent more quickly when worn heavily, because they don't have lots of extra enamel in reserve under the surface. 

Pros of new hypsodonty method: appears to work well across a broad range of tooth types, while height measurements are less homologous across dramatically different tooth shapes.

Cons of new hypsodonty method: it takes forever to get a single hypsodonty value for a single tooth, compared to the blindingly fast old fashioned way involving a couple of caliper measurements.

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