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Full-Text Articles in Physical Sciences and Mathematics
A Morphometric Analysis Of The Highly Variable Clypeasteroid, Periarchus Lyelli, Lauren Elizabeth Williamson
A Morphometric Analysis Of The Highly Variable Clypeasteroid, Periarchus Lyelli, Lauren Elizabeth Williamson
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The Late Eocene echinoid, Periarchus lyelli (Conrad, 1834), known for its wide geographic range, high abundance, and specific stratigraphic range, is an ideal example of a guide fossil. However, due to its highly variable test morphology, many have questioned if, in fact, this sand dollar is actually two or three distinct species that have been misclassified. A preliminary study on this subject has been performed on specimens from Mississippi, North Carolina and South Carolina (Williamson, 2006), showing significant separation in test shapes. Continuing previous research, this study analyzes the test shapes of P. lyelli over its entire North American geographic …
Using Morphometrics, Phylogenetic Systematics And Parsimony Analysis To Gain Insight Into The Evolutionary Affinities Of The Calymenidae Trilobita, Alex J. Chestnut
Using Morphometrics, Phylogenetic Systematics And Parsimony Analysis To Gain Insight Into The Evolutionary Affinities Of The Calymenidae Trilobita, Alex J. Chestnut
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The most common trilobite in the Silurian carbonates of Ohio - especially the Springfield Dolomite - is a species that has been assigned to at least five genera over the past 100 years. This trilobite has been variously referred to as Calymene celebra, Apocalymene celebra, Flexicalymene celebra, Gravicalymene celebra, and Sthenarocalymene celebra. Reexamination of the species "Calymene" celebra through parsimony and morphometric analysis was conducted to properly place this calymenid species within the correct genus. What compounds the confusion is that the characters used to seperate the genera within the family Calymenidae, and therefore create the basis for the argument …