Illustrations of the Comparative Method: Trilobite Fossils, Fossil Fishes, and Fish Evolution

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Doctor of Philosophy (PhD)
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Earth and Environmental Science
Earth Sciences
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Sime, John

The comparative method is a core tool of the natural sciences. The following three vignettes in natural history illustrate the comparative method, though they are about disparate topics. First, I reconstruct the how the first monograph on American trilobite fossils (1832) was envisioned, created, and used by naturalists from the nineteenth century to present. The monograph was an experiment in scientific illustration and taxonomic description--new species were illustrated with painted plaster-of-Paris casts not engravings. I discuss the impact of this experiment on the nascent science of paleontology and its legacy. Second, I describe a new genus and species of fossil fish from Late Devonian rocks of Pennsylvania, developing a current example of a comparative work. This study adds to the diversity of early ray-finned fishes and expands our understanding of their paleoecology in fluvial environments. Third, and finally, I apply the fruits of previous descriptive work to a macroevolutionary problem, specifically a pattern that the number of vertebrae in fishes tends to increase as water temperature decreases. I show that this pattern is valid and indeed related to temperature in several clades of ray-finned fishes. These topics vary significantly in the dimensionality of the data, the scope of comparison, and the role of history, but what they share is an emphasis of these features in pursuit of knowledge.

Goldsby, David, L
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