MORPHOLOGIC ANALYSES OF PALEOZOIC RHOMBIFERAN ECHINODERM STEMS

During the Paleozoic, echinoderms exhibited a diverse array of morphologies. This work specifically deals with an extinct stemmed group called glyptocystitoid rhombiferans. The goal of this work is to investigate functional morphology of the stem in this enigmatic group. Abnormalities in form are addressed herein by a brief literature review of teratologic features and in the description of a new species of pleurocystitid Pleurocystites? scylla. Morphologic specialization is discussed in the investigation of the internal structure and morphometrics of the mesotem of Brockocystis. Linear morphometrics, multiple imputation, and multivariate statistics were used to describe the variability exhibited in a single element with ontogenetic implications. The mesostem structure is highly biologically controlled in its calcification and appears to originate in the midstem region. Finally, computational fluid dynamics was used to test various hypothesized posture models of the generalized motile bauplan. Simulated posture models found a buried life mode was most unstable and unrealistic. The coiled or Snake posture model was the most stable at a velocity of 0.05 m/s. From these findings, new information regarding the development, growth, and life mode of glyptocystitoid rhombiferan echinoderms is elucidated.