Poster Number 66
See more from this Division: General Discipline Sessions
See more from this Session: Paleontology (Posters) I - Diversity, Evolution, and Biogeography
Abstract:
According to the Extraxial/Axial Theory of body wall organization, the ambulacra of H. gilberti are a feature of the axial skeleton. Interambulacra are interpreted here to be part of the imperforate extraxial skeleton. At some point in development, the genes coding for the axial skeleton were expressed in lieu of those coding for the imperforate extraxial skeleton, resulting in an individual with one morphologically and developmentally distinct skeletal system substituting for another. The resulting mutant nonetheless survived to be at least a late juvenile, as it is nearly as large as the largest known helicoplacoids. The apparent success of this individual suggests plasticity of the echinoderm body plan, such that the skeletal systems were transposable without any apparent deleterious effects in regards to the viability of the animal. This skeletal substitution may therefore serve as a mechanism responsible for the tremendous disparity seen in the Early Cambrian echinoderms (helicoplacoids, edrioasteroids, eocrinoids), and have some role in explaining how novel morphological characteristics arose and persisted during the Cambrian Explosion.
See more from this Division: General Discipline Sessions
See more from this Session: Paleontology (Posters) I - Diversity, Evolution, and Biogeography