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" Sampling Impacts the Assessment of Tooth Growth and Replacement Rates in Archosaurs: "
Dieter Kosch, Jens Carl
D'Emic, Michael;Hartstone-Rose, Adam;Langerhans, Randall;Schweitzer, Mary;Zanno, Lindsay
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1114062
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| Doc. No
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TLpq2401068095
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| Main Entry
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D'Emic, Michael
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Dieter Kosch, Jens Carl
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| Title & Author
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Sampling Impacts the Assessment of Tooth Growth and Replacement Rates in Archosaurs:\ Dieter Kosch, Jens CarlD'Emic, Michael;Hartstone-Rose, Adam;Langerhans, Randall;Schweitzer, Mary;Zanno, Lindsay
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| College
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North Carolina State University
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| Date
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2020
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| student score
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2020
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| Degree
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M.Sc.
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| Page No
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66
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| Abstract
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Dietary habits in extinct species cannot be directly observed; thus, in the absence of extraordinary evidence, the dietary ecology of extinct species must be reconstructed with a combination of morphological proxies. Such proxies often include information on dental organization and function such as tooth formation time (TFT) and replacement rate (TRR). In extinct organisms, TFT and TRR are calculated, in part via extrapolation of the space between incremental lines in dental tissues representing daily growth (von Ebner Line Increment Width; VEIW). Tooth formation times and replacement rates in extinct species are becoming regularly calculated; however, to date, little work has been conducted testing assumptions about the primary data underpinning these calculations, specifically, the potential impact of differential sampling and data extrapolation protocols. To address this, we tested a variety of intradental, intramandibular, and ontogentic sampling effects on calculations of mean VEIW, TFT, and TRR using histological sections and CT reconstructions of a growth series of three specimens of the extant archosaurian Alligator mississippiensis. We find transect position within the tooth and orientation with respect to VELs to have the greatest impact on calculations of mean VEIW—a maximum number of VEIW measurements should be made as near to the central axis as possible. Measuring in more crowded regions of the tooth off the central axis can reduce mean VEIW by 36%, causing inflated TFT calculations. We find little demonstrable impact to calculations of mean VEIW from the practice of subsampling along a transect, or from using mean VEIW derived from one portion of the dentition to extrapolate TFT and TRR for other regions of the dentition. Subsampling along transects contributes only minor variation in mean VEIW calculations (<12%) that are dwarfed by the standard deviation of mean VEIW. Moreover, variation in VEIW with distance from the pulp cavity likely reflects idiosyncratic patterns related to life history, which are difficult to control for; however, we recommend increasing raw VEIW data to minimize this effect. Our data reveal only a weak correlation between mean VEIW and body length, suggesting minimal ontogenetic impacts for the calculations of TFT and TRR. Finally, we provide a relative standard deviation of mean VEIW for Alligator of 29.94%, which can be used by researchers to create data-driven error bars for TFTs and TRRs in fossil taxa with small sample sizes. We caution that small differences in mean VEIW calculations resulting from nonstandardized sampling protocols, especially in a comparative context, will produce inflated error in TFT estimations that intensify with crown height. The same holds true for applications of our relative SD to TFT calculations in extinct taxa, which produce highly variable maximum and minimum TFT estimates in large-toothed taxa (e.g.,718‒1331 days in Tyrannosaurus).
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| Subject
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Zoology
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| Added Entry
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Hartstone-Rose, Adam
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Langerhans, Randall
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