Quantifying a possible miocene phyletic change in Hemipristis (Chondrichthyes) teeth
Using a new MATLAB-based measuring tool, teeth of the fossil shark Hemipristis serra from active mining sites were analyzed for changes in size and extent of serrations. Teeth were taken from disturbed sediments of the Late Oligocene - Pliocene Belgrade, Pungo River, and Yorktown Formations at two mining sites in eastern North Carolina. Four populations (approximate ages: 4.5 Ma, 15.2 Ma, 17.35 Ma, and 23.8 Ma) were analyzed and seem to differ in average size and proportion of serrated edge. Linear regression yields two plausible models for the relationship between the population age, the length of tooth edge, and the ratio of the unserrated portion to total edge length. While individual teeth vary, the average tooth length decreases with geologic age of the population. The ratio (unserrated tip length)/(total edge length) is length dependent (larger teeth have a smaller ratio on average), but is also age dependent (older populations generally have a larger ratio). To argue the soundness of these models, teeth from a chronostratigraphically better constrained Miocene deposit were also analyzed and compared to the quarry derived sample populations. Copyright: Society of Vertebrate Paleontology. February 2006.
Chandler, RE; Chiswell, KE; Faulkner, GD
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