DOI: 10.5061/dryad.ht76hdrkx
title: Data from: Ankylosaurian body armor function and evolution with insights from osteohistology and morphometrics of new specimens from the Late Cretaceous of Antarctica

description: The body armor of ankylosaurians is a unique morphological feature among
 dinosaurs. Despite being studied for decades, paleohistological analyses
 have only started to uncover the details of its function. Yet, there has
 been an overall bias toward sampling ankylosaurian remains from the
 Northern Hemisphere and limited quantitative studies on the morphological
 and functional evolution. Here, we describe new ankylosaurian materials
 recovered from the Late Cretaceous of Antarctica that, in combination with
 data compiled from the literature, reveal new insights into the evolution
 of the ankylosaurian body armor. Based on histological microstructure and
 phylogenetic results, the new Antarctic material can be assigned to
 Nodosauridae. This group shares the absence/poor development of the basal
 cortex and highly ordered sets of orthogonal structural fibers in the
 superficial cortex. Our morphospace analyses indicate that large
 morphological diversity is observed among both nodosaurids and
 ankylosaurids, but they became more functionally specialized in
 late-diverging nodosaurids. Besides acting as effective protection against
 predation, osteoderms also exhibit highly ordered structural fibers in
 nodosaurids, enabling a decrease in cortical bone thickness (as in
 titanosaurs), which could have been co-opted for secondary functions, such
 as calcium remobilization for physiological balance. The latter may have
 played a key role in nodosaurid colonization of high-latitude
 environments, such as Antarctica and the Arctic Circle.
description: <strong>Material </strong> The
 figures of specimens CAV-4 and 5 before the paleohistological sections are
 available in Supplementary Fig. 1. There is no figure for the specimen
 CAV-10. <strong>Statistical
 Analyses</strong> The dataset
 compiled from the literature for our linear morphometric analyses is
 available in the file “Dataset_osteoderms.xlsx”. The compiled specimens
 are listed in Table 1. The entire dataset of PAST files to osteoderms is
 available in “Dataset_osteoderms.dat”.  The
 abbreviations and description of variables used in both datasets are: B,
 thickness of the osteoderm basal cortex; BI, basal index (BI = 100B/T);
 CI, cortical index (CI = 100*(S + B)/T); Co, thickness of the osteoderm
 core; CoI, core index (CoI = 100Co/T); Group, main group that the
 specimens are assigned (Ankylosauridae, Nodosauridae or Titanosauria);
 Osteoderm, shape of the osteoderm; Group+osteodem, classification joining
 main group and shape of osteoderm; S, thickness of the osteoderm
 superficial cortex; S+B, sum of osteoderm superficial and basal cortex
 (=cortical thickness); Specimen, collection number of the analysed
 specimens; SI, superficial index (SI = 100S/T; T, total thickness of the
 osteoderm; Taxon, specific classification of the analysed specimens; all
 Log. variables are at the base Log10. These variables comprise linear
 measurements and relative thickness of osteoderm paleohistological slides
 (all in mm), comprising the compact bone walls (basal and superficial) and
 the core. They followed the proposal of Burns and Currie (2014).
 We performed the Shapiro-Wilk (W) test for normality to evaluate
 if our data follows a normal distribution. We also performed the linear
 discriminant analysis (LDA) to discriminate the morphospace by reducing
 the dimension of the parameters. <strong>Phylogenetic
 Analysis</strong> The codification of the specimens based on the
 compilation of the matrix of Soto-Acuña et al. (2021)—the modification of
 the authors on the dataset of Arbour and Curie (2016). The matrix is
 available in the files “PhyloAnk.nex” and “PhyloAnk.tnt”. The description
 of the characters is available in “PhyloAnk.nex”.