Data from: Occlusal enamel complexity in beaver (Rodentia: Castoridae) genera from John Day Fossil Beds National Monument, Oregon, U.S.A
Data files
Aug 03, 2026 version files 23.64 KB
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Beaver_Phylo_FAD_LAD.csv
337 B
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Beaver_Phylo_OEI.csv
330 B
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Beaver_Phylo_Tree
6.33 KB
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OEI_R_data_2026.csv
12.85 KB
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README.md
3.79 KB
Abstract
Dental adaptations to abrasive wear include increased tooth crown height and complexity of occlusal enamel folds. These trends have been studied extensively in ungulates and some other mammal groups with hypsodont dentition. Beavers (family Castoridae) represent diverse lineages which occupied different ecological niches through time, including the fossorial beavers of the Oligocene and the semi-aquatic beavers which diversified in the Miocene. As an adaptation to the high volume of abrasive grit entering their mouths from digging with their incisors, we hypothesized that the cheek teeth of fossorial beavers had increased occlusal enamel complexity compared to semi-aquatic beavers. We chose John Day Fossil Beds National Monument (JDFB) in eastern and central Oregon for this study because of its extensive time range and exceptional preservation of castorid fossils. We took scaled photographs of the occlusal surface of 43 beaver specimens (n = 84 teeth) from six genera (Capacikala, Castor, Dipoides, Microtheriomys, Monosaulax, and Palaeocastor) from previously collected JDFB specimens. Each tooth was measured using ImageJ to calculate occlusal enamel index (OEI). We performed an analysis of variance on linear models using a residual randomization permutation procedure to test the dependence of enamel complexity on taxonomy, dentition, time, geology, and ecology. Results indicate that genus, epoch, ecology, geologic formation, and geologic formations with combined units of the John Day Formation were significant; however, post-hoc pairwise comparisons resulted in no differences between groups. This suggests that enamel complexity in JDFB beavers does not significantly differ between fossorial and semi-aquatic lifestyles.
Dataset DOI: 10.5061/dryad.2z34tmq2g
Description of the data and file structure
These supplemental files include the R script and data to replicate the analysis, as well as post-hoc results produced from the analyses in Occlusal enamel complexity in beaver (Rodentia: Castoridae) genera from John Day Fossil Beds National Monument, Oregon, U.S.A.
Supplemental data are reposited both through Dryad and Zenodo. Data hosted on Zenodo includes the R script (JDFB_BEAVER_OEC_Analysis.R) for the code to run the analysis and the supplemental tables for the results of the post-hoc pairwise comparisons from the analysis (Pairwise_Comparison_Results.docx). Data files hosted on Dryad include the full dataset (OEI_R_data_2026.csv) of which specimens and teeth were used in the analysis, calculated occlusal enamel index (OEI) measurements from each tooth studied, the catalog number for each specimen, taxonomic names, geologic context, and ecological classifications assigned to all studied specimens. Other data hosted on Dryad include first and last occurrence data for each taxa (Beaver_Phylo_FAD_LAD.csv), averaged OEI calculations for each taxa (Beaver_Phylo_OEI.csv), and an informal supertree (Beaver_Phylo_Tree), which are all used for the phylogenetic component of the analysis.
Files and variables
File: OEI_R_data_2026.csv
Description: Overall dataset for each individual tooth included in the analysis. Data required for the bulk of the analysis.
Variables
- cat_num: Catalog Number
- genus: Genus
- taxon: Species
- locality: Locality name of where fossil was collected
- tooth: Tooth position (Upper case or "U" indicates upper tooth, lower case or "L" for lower tooth, mx for undetermined molar)
- OEI: Occlusal Enamel Index
- epoch: Epoch
- geo_form: Geologic formation
- geo_memb: Geologic member (splits John Day Formation into "upper" and "lower" members based on PGI boudary)
- geo_unit: Geologic unit (seperates John Day Formation into individual units: Turtle Cove Member Units A-F, Kimberly Member Units L-M)
- eco: Ecology (Fossorial or Semiaquatic)
- eco_2: Ecology with semiaquatic split (Fossorial, Non-woodcutting, Woodcutting)
- fad: First appearance datum (mya)
- lad: Last appearance datum (mya)
File: Beaver_Phylo_FAD_LAD.csv
Description: First and last occurance dates for taxa included in analysis; used in phylogenetic component of analysis
Variables
- taxon: Species
- FAD: First appearance datum (mya)
- LAD: Last appearance datum (mya)
File: Beaver_Phylo_OEI.csv
Description: Averaged OEI values for all taxa included in analysis; used in phylogenetic component of analysis
Variables
- taxon: Species
- OEI: Occlusal enamel index (averaged for each taxon)
File: Beaver_Phylo_Tree
Description: Informal supertree of taxa included in the phylogenetic component of the analysis (.NEX file)
Code/software
The analysis was completed using R statistics program (version 4.5.2).
JDFB_BEAVER_OEC_Analysis.R: R script containing the code used to run all components of the analysis (i.e., normality, phylogenetic signal, linear model comparisons, analysis of variance, post-hoc pairwise comparisons). For additional information and explanations of the tests used in the analyses, please refer to methods section in Occlusal enamel complexity in beaver (Rodentia: Castoridae) genera from John Day Fossil Beds National Monument, Oregon, U.S.A.
R Packages required for analysis: ape, dplyr, geomorph, ggplot2, openxlsx, paleotree, RRPP (code for package downloads incorporated R script).