MORPHOLOGICAL PATTERN OF MIDDLE CAMBRIAN TRILOBITE ELRATHIA KINGII OVER TIME: STATIC OR DYNAMIC

High-resolution examination of ptychoparioid trilobite Elrathia kingii populations is done using digital images captured at fine scale. Images are collected using optical magnification techniques coupled with recent advances in digital technology. This mode of photography allows finer detail to be examined than was previously possible to do due to the exorbitant costs of such photography with traditional films. Images are collected in a digital format known as RAW at an optimal level of magnification for critical examination and measurement of desired attributes. RAW files are saved and processed as TIFF files to preserve integrity of images in a lossless method. TIFF files used in this project are maintained in a grayscale mode to enhance contrast and visible detail. TIFF files are annotated digitally using a program known as SCION to specify individual points of preselected landmarks common to specimens. Landmarks are unique identifiable attributes of morphology that can be visually identified at a precise position in relation to other attributes of the specimen. Annotation to TIFF files using SCION leaves an icon identifying the landmark optically visible on the file along with generating a set of Cartesian coordinates for the landmark in reference to a preselected orientation axis of the specimen. Spatial relationships of coordinates are mathematically normalized for size using distance between selected landmarks as an arbitrary unit of distance 1. Normalized coordinates are used in analytic programs IMP and PALEOSTAT to generate standard geometric shapes for specimens that are compared to other specimens in relevant data sets to determine differences and similarities of shape between specimens. Sets of fossils from same beddings planes are used to generate image sets representing shape of E. kingii at that geologic time at the geographic location the specimen was collected. An overall mean shape is calculated for that time and location. A range of diversity in shape at that point in time and space is also represented by collected data. Comparison of means between times and locations allow determination of change or stasis in morphology of E. kingii. Comparison of diversity range allows determination of change in overall diversity of E. kingii.