STABILIZING INSTABLE SKELETONS: MAPPING PLATE CONNECTIONS AND INTERNAL SUPPORTS OF CLYPEASTEROID ECHINOIDS AND THEIR IMPLICATION FOR PRESERVATION POTENTIALS IN THE ROCK RECORD

As multi-element skeletons, echinoderm show a whole range of preservation potentials from complete tests to disarticulated single plates. In a study conducted within the auspices of a biomimetic approach to clypeasteroid skeletons as a basis for architectural design, the morphology of clypeasteroids is investigated with special emphasis on shell strengthening features making this group arguable the echinoderm group with the highest preservation potential. Clypeasteroids represented by sand dollar, sea biscuits and the like are a relatively young group of echinoids originating in the Paleogene and are immediately recognizable as most show, among others characters, a dorsal-ventrally flattened test, internal supports joining the oral and aboral side, and interdigitating plate connections. Studies in the both recent and fossil environments demonstrate that clypeasteroids have a high preservation potential also in high energy environments. The continuing presence of complete skeletons on the sea floor means the tests can serve as a platform for encrustation as well as a unique substrate for bioerosion as seen in both recent and fossil specimens. Plate connections of various Clypeasteroids including Clypeaster, Echinocyamus, Jacksonaster and Dendraster are mapped with respect to the diversity of plate connections and their distribution in different areas of the test. The morphology and distribution of internal supports is mapped with respect to the ambulacral and interambulacral plate rows. In addition, the morphology and density of stereom types within the internal supports are compared.