QUANTITATIVE DESCRIPTION OF UPPER CRETACEOUS ELASMOBRANCHS USING DIGITAL THREE-DIMENSIONAL MICROSCOPY

Upper Cretaceous freshwater and marine strata in western North America preserve an abundance of elasmobranch teeth. Research conducted in the Upper Cretaceous Menefee Formation of New Mexico has yielded numerous microvertebrates, most of which are representatives of previously named taxa. This microvertebrate locality, however, has yielded two potentially new species of rays and one ray that represents a new genus and species, but the identification of specimens is hampered in part by a lack of quantitative work in previous analyses. Our goal was to improve the description and identification of the rays in particular by providing a quantitative method of analysis, and to provide an overview of the benefits of three-dimensional microscopy, especially in comparison to scanning electron microscopy (SEM). Therefore, measurements of one new ray species, Myledaphus n. sp., from the Menefee microvertebrate locality, were obtained using a Keyence digital three-dimensional microscope. The sample of Myledaphus n. sp. specimens included twenty-five teeth, which were measured for crown height, root height, maximum root width, and overall height (mean values of 1743 μm, 1367 μm, 3619 μm, and 3103 μm, respectively). Applying measuring tools, included in the microscope software, precise measurements (to 0.01 µm) of both two-dimensional and three-dimensional images were obtained, providing a higher resolution data set with which to describe and evaluate taxa. Three-dimensional images may be rotated in virtual space and given scale grids along with lighting adjustments allowing for optimal illustration. In addition, all measurements taken can be readily saved as a comma-separated values file and opened with spreadsheet or statistical programs in order to present data in charted or graphical form. With an interchangeable objective lens, the digital microscope we used is capable of taking high-resolution images (up to 54 megapixels) with up to two hundred times magnification, and, unlike SEM, provides an open platform design that allows for easy manipulation of specimens under the objective. The digital three-dimensional microscope is a valuable tool for analyzing and illustrating specimens and holds great potential in the field of paleontology regarding the description and identification of taxa.