University of Illinois at Chicago
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data files for Variation and Taphonomic Implications of Composition in Modern and Fossil Malacostracan Cuticles

posted on 2023-08-23, 17:57 authored by Roy PlotnickRoy Plotnick, Steve McCaroll

Data Files for Variation and Taphonomic Implications of Composition in Modern and Fossil Malacostracan Cuticles by Roy E. Plotnick and Steve McCarroll. Journal of Crustacean Biology.  

This data set contains major element chemical analyses (Ca, Mg, Na, P) using SEM-EDS of modern crustacean exoskeletons from Bermuda, Georgia (U.S.A.), and Lake Tanganyika, Burundi and fossils from Texas. Elemental compositions of these cuticles were determined utilizing a JEOL JSM-35CE Scanning Electron Microscope (JEOL, Tokyo, Japan) equipped with a Tracor Northern 5500 (Microscan Energy Dispersive Spectrometer (EDS) (Tracor Northern, Middleton, Wisconsin, USA), using Bence-Albee or ZAF quantitative methods. 

Each data file has a name and/or an original file number. These are listed, along with the taxonomic data, in Supplemental File S4 of the paper, included here. 

The ZAF analyses reported by the probe software were elemental weight percents, whereas Bence-Albee (BA) analyses were reported as normalized oxide weight percents. For consistency, the oxide values were converted to elemental values. This was a two-step process:

1) The normalization of the oxide values needed to be reversed. This required locating the original data for the total percents for each data point. The normalized data could then be converted back to the “calculated weight” for the oxide. For example:

a. Normalized weight percent CaO = 50.43%

b. Total non-normalized weight percent all data = 85.06%

c. Original calculated (non-normalized) percent CaO = 42.90%

2) The oxide percents could then be converted to element percent using the following conversion factors:

a. Ca = CaO *0.71469

b. Mg = MgO * 0.60311

c. Na = Na2O * 0.74186

d. P = P2O5 * 0.43642

ZAF: remainder of weight assumed to be oxygen

BA – remainder CO2 by stochiometry

Data was originally on dot matrix computer printouts. These were typed into Excel spreadsheets by Erin Conley. Original hard copies of the summary data and the point-by-point analyses are stored in Roy Plotnick’s office in 2454 SES. 


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