Scherer, Reed P.
M.S. (Master of Science)
Department of Geology and Environmental Geosciences
Paleontology; Geobiology; Biometry
Since its discovery in 1939, the Late Jurassic, Cleveland-Lloyd Dinosaur Quarry (CLDQ) has been assumed to be a Jurassic predator trap by most visitors to the site. This idea's longevity is due in part to the disproportionately high ratio of carnivores to herbivores (3:1) uncovered from the quarry. However, despite decades of active research on the taphonomy and geochemistry of the deposit, the predator trap hypothesis remains unproven. In order to test whether the quarry has or does not have the characteristics of a predator trap, this study specifically analyzed the population of the quarry's most abundant animal, Allosaurus fragilis. The widely accepted predator trap that is the La Brea Tar Pits (LBTP) of Los Angeles, California was used for comparison. For the most accurate analysis, femora belonging to Allosaurus fragilis from the CLDQ were compared to femora of Canis dirus from the LBTP by their femoral lengths and ratios. Every available bone from each animal was measured to produce as precise an analysis as possible. After all of these values were compiled, they were statistically compared using the Kolmogorov-Smirnov test. Results suggest that the two quarries do not exhibit the same population distribution. However, the same population at LBTP when divided into individual pits, exhibited the same population distribution as the CLDQ. Hence, a Simpson's paradox has been achieved, which is when one trend is observed in separate groups of data but the trend reverses when the data is combined, which means that there is some additional variable that has not yet been considered that is swaying the data. This leads to the conclusion that the quarry is not a predator trap, though in order to resolve the paradox future studies and additional measurements are needed to complete a more thorough analysis.
Reddick, Angela D., "Assessing the Jurassic Cleveland-Lloyd bone bed predator trap hypothesis by statistical comparison of Allosaurus fragilis and Pleistocene La Brea Canis dirus femora" (2018). Graduate Research Theses & Dissertations. 1543.
Northern Illinois University
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