DOI: 10.5061/dryad.s9b6070
title: Data from: Unravelling the distinctive craniomandibular morphology of the Plio‐Pleistocene Eumysops in the evolutionary setting of South American octodontoid rodents (Hystricomorpha)

description: Abstract: Echimyidae is a species-rich clade of Neotropical rodents, which
 diversified in association with forested biomes. A few lineages were
 adapted to open environments from southern South America since the late
 Miocene. Eumysops is one of these southern echimyids, and its peculiar
 craniomandibular morphology has been assumed to be a result of adaptation
 to open environments. We performed a geometric morphometric analysis of
 craniomandibular shape variation in order to explore if Eumysops is, as
 suspected, divergent from other echimyids and octodontoids. In addition,
 we explored whether deterministic factors driven by different ecological
 dimensions can explain the diversification of shape among octodontoids. We
 found that craniomandibular shape variation in octodontoids was related to
 ecological variables. Comparing competing evolutionary models suggested
 that the input of selective factors play a key role in octodontoid
 craniomandibular shape diversification; habitat and habits were found to
 be the most influential factors. In the analysed morphospaces, Eumysops
 was located distant from other echimyids due to its distinctive traits,
 especially wide and posteriorly displaced orbits, and related low
 craniomandibular joint. Divergent orbits and resulting wider panoramic
 vision support the interpretation of Eumysops as an open-habitat
 specialist echimyid. But what is more relevant, Eumysops occupied a sector
 of the octodontoid cranial morphospace not filled by living
 representatives; this highlights the contribution of fossils in providing
 key information on the specialization boundaries explored by a clade
 throughout its history.
description: SUPPLEMENTAL DATA
 S1SUPPLEMENTAL DATA S1. A.
 List of taxa and specimens examined. B. Accession numbers of GenBank for
 the mitochondrial (12S, cytb) and nuclear (GHR, vWF) genes used in the
 phylogenetic analysis. C. Fossil constraints. D. Landmarks and
 semi-landmarks definitions. E. Ecological variables.SUPPLEMENTAL DATA
 S2SUPPLEMENTAL DATA S2.
 Figure S2.1. Allometric changes in the cranial (A) and mandibular (B)
 shape of octodontoids, excluding Myocastor. Figure S2.2. Residual Shape
 Component (RSC) analysis of cranium (A) and mandible (B) of living
 octodontoids, excluding Eumysops.SUPPLEMENTAL DATA
 S3SUPPLEMENTAL DATA S3.
 Table S3. Support for BM, OU, and EB models for the evolution of the APC
 of cranium and mandible of octodontoids.SUPPLEMENTAL DATA
 S4SUPPLEMENTAL DATA S4.
 Figure S4. (A) Lateral view of the cranium and mandibles of Eumysops
 chapalmalensis MMP-M 4201 showing anatomical traits mentioned in the text.
 (B) Adductor muscles of Myocastor coypus in dorsolateral
 view.Octodontoidea_Eumysops_ingroup_phyPhylogenetic relationships and divergence time among octodontoid species including Eumysops, together with several outgroups (representatives of the families Erethizontidae, Chinchillidae, Caviidae, and Dasyproctidae), were estimated through Bayesian inference method implemented in BEAST v2.4.7. The analysis was based on a combined matrix of molecular and morphological evidence (54 cranial, mandibular and dental characters). Sequences from the mitochondrial subunit 12S (12S rRNA; 968 bp) and cytochrome b (cytb; 1140 bp), as well as Growth Hormone Receptor (GHR; 886 bp) and von Willebrand factor (vWF; 1263 bp) nuclear genes were obtained from Genbank (accession numbers in Olivares et al. 2019, data S1). As the matrix contained the extinct genus Eumysops as a tree tip, the fossilized birth-death speciation model was selected, with its priors set as uniform (diversification rate, origin, rho, sampling proportion, and turnover) (Stadler 2010; Heath et al. 2014; Gavryushkina et al. 2017).PC_scores_Cranium_Olivares_etal.PC scores of octodontoids, including the extinct Eumysops. PCA was performed on the Aligned Procrustes Coordinates (APC) of 24 landmarks, 32 semi-landmarks representing cranial shape. This analysis was carried out using MorphoJ (Klingenberg, 2011).PC_scores_Mandible_Olivares_etal.PC scores of octodontoids, including the extinct Eumysops. PCA was performed on the Aligned Procrustes Coordinates (APC) of 11 landmarks, 7 semi-landmarks representing mandibular shape. This analysis was carried out using MorphoJ (Klingenberg, 2011).RSC_Cranium_Olivares_etal.Residual shape components (RSC) of the cranium of octodontoids, including the extinct Eumysops.RSC_Mandible_Olivares_etal.Residual shape components (RSC) of the mandible of octodontoids, including the extinct Eumysops.