Transport Abrasion of Fossil Reptilian Teeth

Do fossil teeth that lack abrasion indicate that dinosaurs survived the Cretaceous extinction?

The Hell Creek formation of Montana represent sediments deposited by rivers in the time period following the supposed extinction of dinosaurs 65 million years ago. These rocks include pollen grains that have been dated to be younger than 65 million years old as well as dinosaur teeth.

Sediments transported long distances in rivers typically show surface abrasion from collisions during the transport process. Since the dinosaur teeth found in the Hell Creek formation lack abrasion, one group of geologists have suggested that the teeth represent dinosaurs that survived the Cretaceous extinction.

An experiment was devised to determine if dinosaur teeth would be abraded in river transport. Five teeth of various sizes were mixed with sand similar to that in the Hell Creek formation in a rotating rock tumbler. The teeth were examined at various intervals for changes in weight and visual signs of abrasion. From the measurements of the tumbler diameter, rate of rotation, and duration of the experiment (as long as 577 hours) the researchers estimated the samples had been tumbled the equivalent of 360 to 480 kilometers.

The results are that the teeth showed no significant changes for the equivalent of transport over 360 kilometers. This experiment showed that dinosaur teeth are abraded extremely slow by transport, and thus cannot be inferred to have been of the same time period as the rocks they were discovered. Therefore, they could not rule out the possiblity that the teeth had been eroded from older rocks.

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Argast S., Farlow J.O., et al., 1987. Transport abrasion of fossil reptilian teeth: Implications for the existence of Tertiary dinosaurs in the Hell Creek Formation, Montana. Geology, 15:927-930.