Graduation Year

2022

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Geology

Major Professor

Sarah Sheffield, Ph.D.

Committee Member

Jen Bright, Ph.D.

Committee Member

Imran Rahman, Ph.D.

Committee Member

Ping Wang, Ph.D.

Keywords

Computational Fluid Dynamics, Diploporita, Echinodermata, Paleozoic

Abstract

Diploporan echinoderms were one of the most speciose groups of stemmed echinoderms during the Ordovician. Despite this widespread abundance, the fossil record of diploporan fauna consists primarily of incomplete specimens, with complete specimens being rare. While the theca, or body, is more commonly preserved, the feeding appendages and the attachment structures (i.e. stems or holdfasts) are seldomly preserved. Insight into these features is highly valuable to the understanding the paleoecology, like the feeding and respiratory strategies, of these enigmatic creatures.

One group of diploporan echinoderms which does have an extensive fossil record, is the Holocystites Fauna, primarily known from the Silurian of North America. The first chapter of this thesis will describe three specimens of this group which display preservation not previously observed in the extensive record of the Holocystites Fauna. These preserved features include descriptions of the feeding appendages, oral cover plates, and anal cover plates. Also described is a new species of diploporan echinoderm, Eucystis xxxxxx, from the Silurian of Missouri, USA (species name redacted pending formal publication). The description of the new species from the genus Eucystis Angelin, 1878 expands our knowledge from a time period where few articulated fossils exist. This example represents the first known occurrence of Eucystis in Laurentia. This find also expands this taxon’s already extensive biogeographic range and follows trends laid out in recent biogeographic studies which suggest an important speciation pathway from Baltica to Laurentia in the Ordovician–Silurian.

The second chapter builds upon the first by using these new descriptions of arm structures to create 3D digital models of feeding morphology in two disparate diploporan taxa, Holocystites Hall, 1861 and Eumorphocystis Branson & Peck, 1940.These models are then used in a computational fluid dynamic (CFD) study which, is the first of its kind performed on diploporan echinoderms. Though these specimens lack closely related, extant modern analogs, the results of this study indicate that these animals utilized feeding strategies observed in other echinoderms and modern marine suspension feeders.

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