DOI: 10.5061/dryad.fxpnvx0zd
title: Morphometric data for Mesodma species discrimination

description: Multituberculates remain one of the more poorly understood mammalian
 clades. The North American multituberculate record is comprised mostly of
 isolated teeth and incomplete jaws leading to interpretations of
 relationships based on limited anatomy. Despite the fragmentary record,
 the p4 of cimolodontan multituberculates is both common and a source of
 diagnostic characters in systematic studies. The results of a recent
 morphometric study on the neoplagiaulacid Mesodma suggest that p4 size may
 be more useful than shape in diagnosing the various species referred to
 this genus. We tested this hypothesis by applying two different
 morphometric methods (2D geometric morphometrics and linear measurements)
 to two samples – (1) one including the p4s of four known species (M.
 ambigua, M. thompsoni, M. formosa, and M. pygmaea), and (2) a sample of
 unidentified p4s of Mesodma from the Bug Creek Anthills locality of
 Northeastern Montana. Our results indicate that while form explains most
 of the morphological variation in p4s of the various species of Mesodma,
 linear measurement data support differences in p4 morphology that are not
 recovered by form data alone. Depending on the methods used, we found
 evidence for the presence of one or more species of Mesodmain the Bug
 Creek Anthills fauna. Although shape and size both contribute to
 morphological variation in the p4 of Mesodma, our results suggest that the
 diagnostic power of each in isolation, or in combination, varies
 significantly with the type of methodology employed.
description: 2D
 GMM: To capture the relevant morphology of the p4, digital landmarks were
 placed at the anterior-most and posterior-most projections of the serrate
 crest (TL1 and TL2 respectively). TL1 was positioned at the point of
 maximum curvature at the anterior margin of the crown. TL2 was placed at
 the posteriormost part of the crown-root junction at the posterior root.
 After TL1 and TL2 were located, a curve was traced in TPSDig (version
 2.31; Rohlf 2013a)
 along the apical portion
 of the crown to join the two landmarks. Eighteen semilandmarks were then
 resampled from the curve with 19 helper points (HP) placed between
 semilandmarks to assist in later standardization. We resampled all
 landmarks to be equally spaced using TPSUtil (version 1.78;
 Rohlf
 2013b). Landmark
 configurations were then prepared for 2D GMM analyses.
 Linear Measurements: Standard linear
 measurements taken in millimeters were collected for specimens in both the
 known species data set (KDS) and the Bug Creek Anthill data set (BCADS).
 Three standard linear measurements have traditionally been employed in
 describing the shape of multituberculate p4s: crown length (L), crown
 height (H), and the length from the anterior margin of the crown to the
 intersection with the crown apogee (L1; Clemens 1964; Krause 1977; Novacek and Clemens
 1977; Sloan 1981; Archibald 1982a; Sloan et al. 1987). L refers to the length of the crown, as
 measured along a baseline from the anteriormost point on the crown to the
 point where the posterolabial shelf intersects the posterior margin. H
 refers to height, the distance from the baseline to crown apogee. Lastly,
 L1 is the distance between the anteriormost point on the crown and the
 point where the lines used to measure L and H intersect. Measurements were
 taken in Fiji version 1.53c and recorded for further analysis
 (Schindelin et al.
 2012). Linear measurements
 for all specimens are compiled in Appendix 1.
description: # Morphometric data for *Mesodma* species discrimination
 We use the following data
 sets, code, and supplemental information to run all of our morphometric
 analyses in our study including the following: * Procrustes analysis *
 Principal component analysis * Linear discriminant analysis * Canonical
 Variate analysis * MANOVA + Pairwise comparisons * Figure generation using
 GGplot2 * Both Appendix 1 and 2 ## Methods for the files used 2D GMM: To
 capture the relevant morphology of the p4, digital landmarks were placed
 at the anterior-most and posterior-most projections of the serrate crest
 (TL1 and TL2 respectively). TL1 was positioned at the point of maximum
 curvature at the anterior margin of the crown. TL2 was placed at the
 posteriormost part of the crown-root junction at the posterior root. After
 TL1 and TL2 were located, a curve was traced in TPSDig (version 2.31;
 Rohlf 2013a) along the apical portion of the crown to join the two
 landmarks. Eighteen semilandmarks were then resampled from the curve with
 19 helper points (HP) placed between semilandmarks to assist in later
 standardization. We resampled all landmarks to be equally spaced using
 TPSUtil (version 1.78; Rohlf 2013b). Landmark configurations were then
 prepared for 2D GMM analyses. Linear Measurements: Standard linear
 measurements taken in millimeters were collected for specimens in both the
 known species data set (KDS) and the Bug Creek Anthill data set (BCADS).
 Three standard linear measurements have traditionally been employed in
 describing the shape of multituberculate p4s: crown length (L), crown
 height (H), and the length from the anterior margin of the crown to the
 intersection with the crown apogee (L1; Clemens 1964; Krause 1977; Novacek
 and Clemens 1977; Sloan 1981; Archibald 1982a; Sloan et al. 1987). L
 refers to the length of the crown, as measured along a baseline from the
 anteriormost point on the crown to the point where the posterolabial shelf
 intersects the posterior margin. H refers to height, the distance from the
 baseline to crown apogee. Lastly, L1 is the distance between the
 anteriormost point on the crown and the point where the lines used to
 measure L and H intersect. Measurements were taken in Fiji version 1.53c
 and recorded for further analysis (Schindelin et al. 2012). Linear
 measurements for all specimens are compiled in Appendix 1. ## Description
 of the data and file structure We include four files here associated with
 our analyses and : **1. Mesodma_2023_AJA_DataDryad.Rmd** = Annotated R
 markdown file with all the code necessary to conduct our analyses. [in
 Zenodo] **2. curve slide.csv** = CSV file indicating which landmarks are
 fixed and which are sliding. Should also be automatically generated after
 running the define.sliders line of code. **3. M_Wilson_data.TPS** = TPS
 file exported from TPSDig suite of all KDS and BCADS specimens. **4.
 Linear_measurements.txt** = All linear measurements taken in mm (L, H, and
 L1) for all KDS and BCADS specimens. **5. Ashbaugh_2023_Appendix1_FINAL**
 – Additional tables; Specimen metadata, PC loadings, CVA classifications
 [in Zenodo] **6. Ashbaugh_2023_Appendix2_FINAL** – Additional figures; PC2
 – PC3 plots for KDS and BCADS [in Zenodo] ## Sharing/Access information If
 using the code or modifying the code and using it please contact
 to collaborate! ## Code/Software We
 have included the R markdown with detailed comments on how each of the
 morphometric steps were performed. Please feel free to contact the lead
 author of the manuscript to discuss the code as it is listed. Note that we
 list the required library needed to run the code within the markdown file
 itself - You will need to modify directory information seeing as these
 will be filled with a template as it stands.