SPECIES DISCRIMINATION, SYSTEMATICS, AND ONTOGENY OF BLASTOIDEA

Blastoids are ideal model organisms with which to study evolutionary processes because nearly all of the skeletal elements are shared among all taxa, there have been recent advances in the understanding of blastoid homology, and they are more commonly preserved fully inflated than any other blastozoan. Because of this homology and preservation, blastoids are the perfect candidate for studies involving geometric morphometrics and systematics. But the potential of blastoids to be a model clade has been extremely hampered by the lack of a modern phylogenetics and classification.

The focus of this dissertation is to increase our understanding of blastoid species delineation, ontogeny, and systematics. The first chapter examines the blastoid population at one locality. Geometric morphometrics was used to show that four closely related blastoid species could be delineated statistically with very little error. Chapter two uses geometric morphometrics to examine the ontogenies of six different Pentremites species that were collected at four different localities in Indiana, Illinois, Kentucky, and Tennessee. It was possible using these techniques to describe similarities in their ontogenies and well as how individual plates develop. The final chapter of this dissertation focuses on systematics of blastoids. For this study, blastoids were examined from all over the world and were used to conduct a maximum parsimony analysis. These robust results were then compared to earlier work.