DOI: 10.5061/dryad.d7wm37qd7
title: Qualitative approaches reveal parallelism of mandibular function in therian carnivores

description: The evolution of the mandible in mammalian carnivores is influenced by
 ecological demands that have changed over their phylogenetic
 history.  We combined geometric morphometrics and biomechanical
 analysis (including beam analysis and finite element analysis or FEA) to
 assess the interaction between form and function as the mandible has
 adapted independently to carnivorous diets in therian clades, including
 Metatheria, Mesonychia, “Creodonta,” and Carnivoramorpha. Our goal was to
 determine the relative contributions of mechanical advantage, mandibular
 force or resistance to bending and torsion, to the evolution of mandibular
 shape in these groups, and to determine whether they produce differential
 rates of shape evolution in the horizontal and ascending rami, which
 respectively are the tooth-bearing and muscle-loading parts of the
 structure. We found that the ascending ramus has higher rates of evolution
 than the horizontal ramus, making it the more rapidly evolving portion of
 the mandible. Statistical evaluation supports this interpretation as
 mechanical advantage and resistance to force explain more of the variance
 in shape than do the beam mechanics estimates that are heavily influenced
 by the mandibular body.  Regression analysis shows that the
 evolution of specialized carnivory was associated with stronger mandibles
 in which mandibular shape changed by shortening and thickening of the
 mandible, increasing the areas of muscle attachment, and increasing the
 carnassial blade length. Principal component analysis of mandible shape
 shows that different clades in Theria have been able to fill out similar
 specialized carnivorous niches with similar functional metrics despite
 having different mandibular morphologies.
description: # Qualitative approaches reveal parallelism of mandibular function in
 therian carnivores Dataset DOI:
 [10.5061/dryad.d7wm37qd7](10.5061/dryad.d7wm37qd7) ## Description of the
 data and file structure * Supplementary_Table_1(1).csv contains all the
 specimens used in this study, their categorical information (i.e.,
 taxonomic group and dietary ecology), and functional
 morphological/biomechanical measurements that were used in data analyses.
 Measurements include mandible length (measured in centimeters), surface
 area (measured in cm^2^), volume (measured in cm^3^), dorosventral bending
 force (DBF) which is a ratio, labiolingual bending force (LBF) which is a
 ratio, relative mandibular force (RMF) which is a ratio, mechanical
 advantage (MA) which is ratio between lever arms between either the
 masseter or temporalis muscle in-levers and either the canine or
 carnassial out-levers, stress (measured in pascals) for loads of scaled
 100 N (newtons) on the canine or the canrassial, and the strain (a
 dimensionless unit) for a load of scaled 100 N on the canine. -
 Supplementary_Table_2.csv is the result of the convergence testing of
 volumetric average stress data of derived dietary ecologies with raw Ct1,
 Ct2, Ct3, and Ct4 values for the overall groups and taxonomic pairs. *
 Theria_LM_tps_format.txt is the landmark coordinates for all specimens
 used for geometric morphometric analyses in TPS format. This can be loaded
 in geometric morphometric analysis software/code packages such as
 *geomorph* in R using the function readland.tps. -
 Therian_mandible_manuscript_code.R is the R code script used to run the
 analyses, including geometric morphometrics (including Procrustes
 alignment, multivariate regression, ANOVA, determining mean shapes, and
 comparing rates of shape evolution), phylogenetic analysis, and convergent
 analysis. Code compatible with R Studio to read and work with. ## Access
 information Other publicly accessible locations of the data: * Zenodo Data
 was derived from the following sources: * Museums: the American Museum of
 Natural History; USA (AMNH), Natural History Museum, London (formerly the
 British Museum of Natural History); UK (BMNH), the Egyptian Geological
 Museum; Egypt (CGM), Museo de Paleontologia, Facultad de Ciencias Exactas,
 Fisicas y Naturales de la Universidad Nacional deo Cordoba; Argentina
 (CORD-PZ), Indiana University Paleontology Collections; USA (IUPC), Museo
 de Historia Natural “Alcide d’Orbigny;” Bolivia (MHNC), Muséum d’Histoire
 Naturelle de Toulouse; France (MHNT.PAL), Museum National d’Historie
 Naturelle; France (MNHN), Museo Regional Provincial “Padre M. J. Molina;”
 Argemtoma (MPM-PV), University of Michigan Museum of Zoology; USA (UMMZ),
 University of Florida; USA (UF), Smithsonian Institution National Museum
 of Natural History; USA (USNM), Yale Peabody Museum; USA (YPM) * Data
 acquisition was either taken in person, from photographs posted on museum
 databases, or from published research papers.