Comparative Anatomy and Phylogenetic Contribution of Intracranial Osseous Canals And

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1 TITLE:

2 Comparative anatomy and phylogenetic contribution of intracranial osseous canals and

3 cavities in armadillos and glyptodonts (Xenarthra, Cingulata).

5 SHORT RUNNING TITLE:

6 Internal cranial structures in armadillos

8 AUTHORS:

9 KÉVIN LE VERGER1*; LAUREANO R. GONZÁLEZ RUIZ2; and GUILLAUME BILLET1

11 1 Museum national d’Histoire naturelle, Centre de Recherche en Paléontologie – Paris, UMR

12 7207 CR2P MNHN/CNRS/UPMC, Sorbonne Universités, 8 rue Buffon, CP 38, 75005 Paris,

13 France.

15 2 Laboratorio de Investigaciones en Evolución y Biodiversidad (LIEB-FCNyCS sede Esquel,

16 UNPSJB) y Centro de Investigaciones Esquel de Montaña y Estepa Patagónica (CIEMEP),

17 CONICET, Universidad Nacional de La Patagonia San Juan Bosco (UNPSJB), Roca 780, 9200,

18 Esquel, Chubut, Argentina.

20 * Corresponding author: Kévin Le Verger; address: 8 rue Buffon, CP 38, 75005 Paris, France;

21 telephone number: 01.40.79.53.79; fax number: 01.40.79.35.80. E-mail: kevin.le-

22 [email protected].

24 ABSTRACT

25 The evolutionary history of the Cingulata, as for many groups, remains a highly debated

26 topic to this day, particularly for one of their most emblematic representatives: the glyptodonts.

27 There is no consensus among morphological and molecular phylogenies relative to their position

28 within Cingulata. As demonstrated by recent works, the study of the internal anatomy constitutes

29 a promising path for enriching morphological matrices for the phylogenetic study of armadillos.

30 However, internal cranial anatomy remains under-studied in the Cingulata. Here we explored and

31 compared the anatomy of intracranial osseous canals and cavities in a diverse sample of extant and

32 extinct cingulates, including the earliest well-preserved glyptodont crania. The virtual 3D

33 reconstruction (using X-ray microtomography) of selected canals, i.e., the nasolacrimal canal, the

34 palatine canal, the sphenopalatine canal, the canal for the frontal diploic vein, the transverse canal,

35 the orbitotemporal canal, the canal for the capsuloparietal emissary vein and the posttemporal

36 canal, and alveolar cavities related to cranial vascularization, innervation or tooth insertion allowed

37 us to compare the locations, trajectories and shape of these structures and to discuss their potential

38 interest for cingulate systematics. We tentatively reconstructed evolutionary scenarios for eight

39 selected traits on these structures, in which glyptodonts often showed a greater resemblance to

40 pampatheres, to the genus Proeutatus and/or to chlamyphorines. This latter pattern was partly

41 congruent with recent molecular hypotheses, but more research is needed on these resemblances

42 and on the potential effects of development and allometry on the observed variations. Overall,

43 these comparisons have enabled us to highlight new anatomical variation that may be of great

44 interest to further explore the evolutionary history of cingulates and the origins of glyptodonts on

45 a morphological basis.

47 Keywords: Glyptodont – Cingulata – Cranial canals – Alveolar cavities – Comparative anatomy –

48 Evolutionary scenarios – Phylogeny.

50 1. INTRODUCTION

52 The peculiar morphology of xenarthrans, which include armadillos (Cingulata), sloths

53 (Folivora) and anteaters (Vermilingua), has aroused the curiosity of anatomists since the end of

54 the 18th century (Cuvier, 1798). Compared to other mammals, the sum of their unique

55 characteristics has led them to be considered by some earlier workers the most unusual mammals

56 (Vizcaíno & Loughbry, 2008; for a summary see Superina & Loughry, 2015). They represent the

57 only known mammals with a carapace formed by a mosaic of osteoderms (fixed and mobile)

58 covering the head, body and tail (Vizcaíno & Loughry, 2008). Cingulates include extant and

59 extinct armadillos, among them the four extant subfamilies Dasypodinae, Euphractinae,

60 Tolypeutinae, and Chlamyphorinae, as well as the extinct glyptodonts, a group of herbivorous and

61 large bodied mammals appearing in the late Eocene and disappearing at the beginning of the

62 Holocene (Delsuc et al., 2016; see also Gaudin & Lyon, 2017 for an alternative classification). The

63 phylogenetic position of glyptodonts within Cingulata is particularly difficult to resolve based on

64 morphological data because of their highly specialized anatomy and the large morphological gap

65 separating them from extant armadillos (Burmeister, 1874; Carlini & Zurita, 2010; Fariña et al.,

66 2013). This difficulty was recently emphasized by ancient DNA studies showing that phylogenetic

67 analyses of their mitogenomes support a position for glyptodonts at odds with that proposed in

68 prior morphological studies (Engelmann, 1985; Gaudin & Wible, 2006; Billet et al., 2011; Delsuc

69 et al., 2016; Mitchell et al., 2016; Herrera et al., 2017).

70 While it has long been accepted that glyptodonts were closely related to extant armadillos

71 (Huxley, 1864), their exact relationships with the latter were never clearly resolved on the basis

72 morphological data. Flower (1882) initially proposed that glyptodonts were the ancestors of extant

73 armadillos but Ameghino (1884, 1889) disputed this hypothesis, arguing that their great dental and

74 postcranial complexity, as described by Owen (1839) was evidence of their derived nature. The

75 nested position of glyptodonts among extant armadillos has been supported by many authors since

76 then, including by recent phylogenetic analyses using morphological data (Castellanos, 1932,

77 1959; Hoffstetter, 1958; Patterson & Pascual, 1972; Fernicola, 2008; Gaudin & Wible, 2006; Billet

78 et al., 2011; Herrera et al., 2017). However, the consensus stops here. Engelmann (1985) proposed

79 a close relationship of glyptodonts with the extinct Eutatini (Proeutatus and Eutatus) and

80 pampatheres, whereas the analysis of Gaudin & Wible (2006) retrieved glyptodonts in an apical

81 position nested within a large clade gathering euphractines, chlamyphorines, the extinct

82 pampatheres and some extinct eutatines. A similar hypothesis was also supported by other studies,

83 but with much variation in the composition of this large apical clade (Fernicola, 2008; Porpino et

84 al., 2010; Billet et al., 2011; Fernicola et al., 2017; Herrera et al., 2017). Most of these studies,

85 however, unvaryingly proposed a close relationship between the extinct giant pampatheres and

86 glyptodonts, in agreement with Patterson & Pascual (1972). Thanks to the progress made in ancient

87 DNA studies and the recent extinction of glyptodonts – at the beginning of the Holocene (Messineo

88 & Politis, 2009) – the complete mitochondrial genome of the Pleistocene glyptodont Doedicurus

89 Burmeister, 1874 could be successfully assembled, which gave rise to a completely new

90 phylogenetic hypothesis (Delsuc et al., 2016; Mitchell et al., 2016). Based on analyses of their

91 mitogenomes, glyptodonts are nested within extant armadillos and represent the sister group of a

92 clade formed by chlamyphorines and tolypeutines (Delsuc et al., 2016; Mitchell et al., 2016).

93 Although analyses of morphological matrices using a molecular backbone constraint can detect

94 morphological characters congruent with the molecular pattern (Mitchell et al., 2016), the high

95 level of disagreement between the two data partitions may call into question the phylogenetic

96 signal provided by morphological matrices on cingulates.

97 External cranial and postcranial skeletal anatomy are already well known for many groups

98 within Cingulata, but the internal cranial anatomy remains understudied. However, its study has

99 already provided data of systematic interest for both the extant and extinct xenarthran diversity

100 (Zurita et al., 2011; Fernicola et al., 2012; Billet et al., 2015; Tambusso & Fariña, 2015a; Tambusso

101 & Fariña, 2015b; Billet et al., 2017; Boscaini et al., 2018; Boscaini et al., 2020; Tambusso et al.,

102 2021). Intracranial osseous canals provide important pathways for innervation and vascularization

103 of the head (Evans & de Lahunta, 2012). The diversity and phylogenetic signal of their intracranial

104 trajectories are poorly known, as these hidden structures are rarely described in mammals in

105 general, including xenarthrans (e.g., Wible & Gaudin, 2004). In contrast, their external openings

106 on the cranium are often described and scored in phylogenetic matrices (e.g., 37/131 of cranial

107 characters – Gaudin & Wible, 2006).

108 Here we present a comparative investigation of intracranial osseous canals and cavities in

109 a diverse sample of extant and extinct cingulates, including the earliest well-preserved glyptodont

110 crania, using X-ray microtomography. The 3D virtual reconstruction of selected canals and

111 cavities related to cranial vascularization, innervation or upper tooth insertion enabled us to

112 compare the locations, trajectories and shape of each homologous structure and discuss their

113 potential interest for cingulate systematics. We tentatively reconstructed the evolutionary history

114 of these traits using a molecularly constrained phylogeny, and we discuss the potential effects of

115 development and allometry on their variation. These comparisons allowed us to propose new

116 potential characters that may be used to further explore the origins of glyptodonts within cingulates

117 on a morphological basis.

118

119 2. MATERIALS AND METHODS

120

121 2.1 Sampling

122 We examined the crania of 33 extant and extinct xenarthran specimens. Two specimens

123 belonging to the Pilosa (sloths and anteaters) were chosen as outgroups. The remaining 31 crania

124 belonged to Cingulata (Table 1). This sample included specimens representing the 9 extant genera,

125 as well as three small developmental series in phylogenetically distant species (Dasypus

126 novemcinctus, Zaedyus pichiy, Cabassous unicinctus), with the aim of better understanding the

127 ontogenetic variation of the selected anatomical structures. The cingulate specimens also included

128 14 specimens belonging to fossil species, among them six glyptodonts (Table 1). This sample

129 covered more than 40 million years of cingulate evolutionary history and includes all the major

130 cingulate subfamilies. Our sample does not allow us to evaluate intraspecific variation in all taxa.

131 However, we were able to estimate this variation in three species for which we dispose

132 developmental series. For each of them, we analyzed scans of 4 additional adult specimens. The

133 adult intraspecific sampling is available in Table S1. Species identification was based on collection

134 data, geographical origin, cranial anatomy, and the literature on cingulate taxonomy (e.g., Scott,

135 1903; McBee & Baker, 1982; Wetzel, 1985; Gaudin & Wible, 2006; Wetzel et al., 2007; Hayssen,

136 2014; Abba et al., 2015; Carlini et al., 2016; Gaudin & Lyon, 2017; Smith & Owen, 2017). Digital

137 data of all specimens were acquired using X-ray micro-computed tomography (μCT). Specimens

138 were scanned on X-ray tomography imagery platforms at the American Museum of Natural

139 History (New York, USA); the Museum national d’Histoire naturelle (France) in Paris (AST-RX

140 platform), the University of Montpellier (France – MRI platform) and the Museum für Naturkunde

141 (ZMB) in Berlin (Phoenix nanotom (General Electric GmbH Wunstorf, Germany)). Three-

142 dimensional reconstructions of the selected structures were performed using stacks of digital μCT

143 images with MIMICS v. 21.0 software (3D Medical Image Processing Software, Materialize,

144 Leuven, Belgium). The visualization of 3D models was also conducted with AVIZO v. 9.7.0

145 software (Visualization Sciences Group, Burlington, MA, USA). A large part of specimens

146 scanned will be available on MorphoMuseum for 3D models and on MorphoSource for scans.

147 Specimens scanned by LRG will be available upon request to LRG. The list of specimens is given

148 in Table S2.

149

150 2.2 Selected regions of interest and anatomical nomenclature

151 We selected several osseous anatomical complexes in the internal cranial anatomy of

152 cingulates that are poorly known and of interest for this study such as dental alveoli and several

153 specific intraosseous canals. The latter mostly correspond to vascular pathways and/or the courses

154 of cranial nerves involved in the innervation of various cranial areas: the nasolacrimal canal, the

155 palatine canal, the sphenopalatine canal, the canal for the frontal diploic vein, the transverse canal,

156 the orbitotemporal canal, the canal for the capsuloparietal emissary vein and the posttemporal

157 canal.

158 Our study is focused only on the cranium and does not include the mandible. Therefore,

159 we are only interested in the upper dentition. Except for Dasypus, which represents a special case

160 (see Ciancio et al., 2012), the homologies in the dental row between the different species of

161 Cingulata are not known mainly because of the drastic reduction in dental complexity (Vizcaíno,

162 2009). For glyptodonts, previous studies conventionally designated the whole set of teeth as

163 molariform but without further precision (e.g., González Ruiz et al., 2015). We therefore chose to

164 treat all teeth as molariform (= Mf; see Herrera et al., 2017 for a different nomenclature and Table

165 S3 for the dental formula of each specimen of our study with greater precision).

166 Only those intracranial canals whose sampled variation appeared to bear clear systematic

167 information were selected in this work (Figure 1). Non-selected canals generally showed

168 asymmetric and intraspecific variation according to our intraspecific sample (Table S1 – e.g.,

169 hypoglossal canal; trajectory of the internal carotid artery – see also Patterson et al., 1989; Gaudin,

170 1995) or provided no new data (e.g., infraorbital canal) with respect to what was already described

171 or scored for the systematics of the group (Wible & Gaudin, 2004; Gaudin & Wible, 2006; Gaudin

172 & Lyon, 2017). Other non-selected canals were rarely visible in all specimens (often due to

173 taphonomy – not in place and/or obscured by a hard and dense matrix) and were therefore difficult

174 to compare. Specimens that presented a canal that was too incomplete are not described in the

175 relevant section. For the identification and nomenclature of the selected intracranial canals, our

176 study used previous work describing intracranial anatomy in cingulates and eutherians in general

177 (Thewissen 1989; Wible, 1993; Gaudin, 2004; Wible & Gaudin 2004; Evans & de Lahunta, 2012;

178 Muizon et al., 2015; Gaudin & Lyon, 2017). We have indicated for each selected region of interest:

179 the variation of these regions during ontogeny, a synthetic comparison among specimens, and the

180 formalization of potential discrete or continuous characters to highlight potential evolutionary

181 scenarios to be mapped onto the tree of cingulates. The formalization of new characters was

182 performed based on observations that were stable among glyptodonts and were shared with some

183 non-glyptodonts cingulates, so that they could provide pertinent information when investigating

184 glyptodont origins.

185

186 2.3 Virtual reconstruction of the selected regions

187 When present, the most dorsal part of the teeth did not always fill the whole alveolar cavity,

188 leaving a void between the roof of the alveolar cavity and the dorsal edge of the tooth. Because we

189 selected the internal orientation and curvature of the whole dental row for study, the reconstruction

190 of alveoli was preferred over the modelling of teeth, which were sometimes absent for our

191 specimens. In some cases, the distinction between the limit of the alveolar wall, the tooth and the

192 sediment were not identifiable. In this case we modelled only the distinguishable structures to

193 allow comparison (e.g., Doellotatus in Figure 2).

194 Within the cranium, a canal corresponds to a duct completely enclosed in one or more

195 bones, and which usually provides passageway to vessels and/or nerves. In some cases, a canal

196 may not be continuously enclosed by bone, and thus turns into a groove for part of its course (e.g.,

197 orbitotemporal canal). In such a case, we have reconstructed the course of the groove in a manner

198 similarly to that of a canal, but we illustrated the areas corresponding to the groove with increased

199 transparency. In some cases, two canals were confluent in such a way that it was no longer possible

200 to distinguish which part of the duct corresponds to the passage of which vessel or nerve. These

201 regions of confluence were specified in each of our reconstructions by a shaded area (e.g.,

202 posttemporal canal and canal for the capsuloparietal emissary vein). Most selected canals were

203 continuous with external or internal foramina. Figure S1 shows the location of each of these

204 foramina in Euphractus.

205

206 2.4 Measurements

207 A few specific measurements were taken for comparison where quantification seemed to

208 offer a better account of the observed variation than a qualitative description. Cranium length,

209 height and width were measured to calculate the geometric mean of each specimen (= geometric

210 mean, an estimator of the size of a specimen defined by the cubic root of the product of the three

211 variables (Claude, 2008)). The geometric mean was log transformed to facilitate graphing of the

212 data (Claude, 2008). Several other cranial measurements were selected, and their variation was

213 compared to that of the geometric mean in our sample (Table S4 and Figure S2). These

214 measurements were selected in order to quantify the following aspects that appeared interesting to

215 us after our anatomical observations: i) the relative height of the dental row (i.e., GDRH/GCH =

216 the ratio between the greatest dental row height and the greatest cranium height); ii) the angle

217 between the straight line marked by the ventral most point of the tentorial process and the dorsal

218 most point of the annular ridge (see Wible & Spaulding, 2013) and the horizontal anteroposterior

219 axis defined here by the straight line between the mesial edge of the first tooth and the distal edge

220 of the last tooth in sagittal view. This served to compare the internal vault inclination (IVI angle)

221 among taxa. These measurements are further explained and summarized in Figure S2; they were

222 taken using the linear distance and angle tools of MIMICS v. 21.0 software.

223

224 2.5 Reconstructing evolutionary scenarios for intracranial traits

225 In order to visualize possible evolutionary scenarios for the discrete and continuous

226 intracranial traits defined based on our observations, we reconstructed a cladogram focused on the

227 taxa in our sample by performing a parsimony analysis using PAUP v. 4.0a167 (Swofford, 2002).

228 We used the morphological matrix of Billet et al. (2011) (largely based on that of Gaudin & Wible,

229 2006), which we limited to the genera in our sample. The initial matrix included all the genera of

230 our sample except for one extant genus (Calyptophractus), along with four fossil genera of

231 glyptodonts: “Cochlops”, Eucinepeltus, “Metopotoxus”, and Glyptodon. We have retained the

232 quotation marks for the genera "Cochlops" and "Metopotoxus" in agreement with the notes of Scott

233 (1903). They have otherwise not been revised since Scott's (1903) report. We scored these taxa

234 (i.e., Calyptophractus and several glyptodonts) based on our CT-scanned specimens and added

235 them to the analysis. After this stage, the matrix included 22 taxa scored for 125 characters

236 (Supporting information 1). We performed the same analysis as Billet et al. (2011), with a heuristic

237 search involving 1000 random addition replicates, with 27 morphological characters treated as

238 ordered and treating taxa with multiple states as polymorphic (Supporting information 1).

239 Following the recent molecular works of Delsuc et al. (2016) and Mitchell et al. (2016), we

240 enforced a backbone constraint similar to that of Mitchell et al. (2016). Because this resulted in an

241 unusual position for Proeutatus (i.e., as the sister group of euphractines), contrary to its usual

242 placement close to the glyptodonts in morphological analyses (Engelmann, 1985; Gaudin & Wible,

243 2006; Billet et al., 2011; Herrera et al., 2017), we added a constraint on this taxon to assign it a

244 priori to a position close to glyptodonts (Figure S3A).

245 By using this approach, our aim was only to obtain a more consensual topology, based on

246 recent morphological and molecular analyses, in order to discuss the relevance of our characters.

247 This study is thus not intended to produce a new phylogenetic analysis. The strict consensus of the

248 most parsimonious trees (with two polytomies – extant euphractines and glyptodonts except for

249 “Metopotoxus”) obtained was then used to calculate branch lengths in order to explore

250 evolutionary scenarios for our qualitative and quantitative observations over the entire topology of

251 the tree. The strict consensus was used as a baseline cladogram (Figure S3B – the strict consensus

252 of the same analysis without constraint is illustrated in Figure S3C for indication). As the

253 optimization options of the analysis can affect the length of the branches, we have chosen to favor

254 the hypothesis of convergence (= DELTRAN) rather than reversion because they have been

255 regarded as more likely (Wake et al., 2011). For the reconstruction of evolutionary scenarios for

256 intracranial discrete or continuous traits, one needs to complete missing data (n = 5 on 8 characters)

257 and resolve polytomies. For the latter, we used the multi2di function of the ape package of R

258 (Paradis & Schliep, 2019). The function resolves polytomies by adding one or several additional

259 node(s) and corresponding branch(es) of length 0. The duplicate nodes thus have the same values,

260 allowing the removal of duplicates a posteriori. In order to facilitate the visualization of the

261 evolutionary scenarios on the tree, we have rendered the tree ultrametric using

262 the force.ultrametric function of the phytools package of R (Revell, 2012). For the discrete traits,

263 the missing data (i.e., 1 taxon for characters 1 and 2 (not applicable), 7 taxa for character 4; 1 taxon

264 for character 5 – see results) were completed according to their ancestral node optimization. In

265 case of optimization uncertainties, we also favored convergences for the same reason mentioned

266 previously. The reconstruction and mapping of ancestral states was performed using stochastic

267 mapping with a symmetric condition matrix (i.e., one for which all transformation rates are

268 considered equivalent; see Bollback, 2006; Revell, 2012). This analysis was performed using

269 the make.simmap function of the phytools package of R, with which we produced 100 simulations

270 for each character. For continuous traits, missing data (i.e., 2 taxa for the character 8) were

271 estimated using an approach combining the use of multiple imputations with procrustean

272 superimposition of principal component analysis results performed on all measurement (Table S4;

273 Clavel et al., 2014) with the estim function of the mvMORPH package of R (Clavel et al., 2015).

274 Then, the reconstruction of the ancestral states was performed using maximum likelihood using

275 the contMap function of the phytools package of R (Revell, 2012).

276

277 2.6 Institutional Abbreviations

278 AMNH, American Museum of Natural History, New York, USA; FMNH, Field Museum

279 of Natural History, Chicago, USA; MHNG, Muséum d’Histoire Naturelle de Genève, Genève,

280 Switzerland; MNHN, Muséum National d’Histoire Naturelle, Zoologie et Anatomie comparée

281 collections (ZM), Mammifères et Oiseaux collections (MO), fossil mammal collections, Pampean

282 (F.PAM), Paris, France; NBC, Naturalis Biodiversity Center, Leiden, Holland; NHM, Natural

283 History Museum, London, ; NMNH, National Museum of Natural History, Smithsonian

284 Institution, Washington, DC, USA; UF, University of Florida, Gainesville, USA; YPM-VPPU,

285 Princeton University collection housed at Peabody Museum, Yale University, USA; ZMB,

286 Museum für Naturkunde, Berlin, Germany.

287

288 3. RESULTS – ANATOMICAL DESCRIPTION AND COMPARISON

289

290 3.1 Teeth and Alveolar Cavities – Orientation, Curvature and Height

291 The three species sampled intraspecifically (Dasypus novemcinctus, Zaedyus pichiy, and

292 Cabassous unicinctus – Table 1) do not show any ontogenetic variation in the orientation and

293 curvature of the teeth compared to the pattern observed in adults (see below). In Dasypus and

294 Zaedyus the relative height of teeth shows an increase from the youngest to the oldest specimens,

295 suggesting an increase in height during ontogeny (Figure 3). In Cabassous, which possess a

296 reduced dentition as Dasypus, no clear ontogenetic trend has been observed but we lack a stage as

297 young as Dasypus and Zaedyus (Figure 3).

298 Height--The relative height of the alveolar cavities distinguishes specimens with reduced

299 teeth such as Stegotherium, Dasypus, Cabassous and Priodontes, from other cingulate species,

300 some of which may even show extremely enlarged teeth, as is the case in glyptodonts (Figure 2,

301 Table S4).

302 In taxa with reduced teeth (unfunctional supernumerary teeth are not considered; see

303 González Ruiz & MacPhee, 2014; González Ruiz et al., 2014, 2015 2017), the height of the

304 alveolar cavity in lateral view is practically the same for all teeth (Figure 2). In the other taxa, the

305 dorsal profile of the dental row in lateral view is curved (dorsal convexity): teeth gradually increase

306 in height backward until the middle of the dental series and then gradually decrease in height

307 posteriorly. The most dorsal point is reached in the middle of the dental row (at the level of Mf5

308 in dental rows containing 7-10 Mf) in Euphractus (at Mf5/Mf9), Chaetophractus (at Mf5/Mf9),

309 Doellotatus (at Mf5/Mf9-10) and Tolypeutes (at 5Mf/Mf9) and more anteriorly in Peltephilus (at

310 Mf2/Mf7), and Proeutatus (at 4Mf/Mf9). In Bradypus, this dorsal point is attained more anteriorly

311 (at Mf2/Mf5). It is reached more posteriorly in Zaedyus (at Mf5/Mf8), Prozaedyus (at Mf5/Mf8),

312 (at Mf6/Mf9), chlamyphorines (at Mf6/Mf8) and most glyptodonts (at Mf5-6/Mf8). In addition,

313 the GDRH/GCH ratio, which express the relative dental height according to the cranium height,

314 seems to be correlated to the body size (R² = 0.5363; P-value = 9.42E-06), showing that large-

315 sized taxa have relatively taller dentitions. This is reminiscent of the increase in height of the dental

316 row during ontogeny in Dasypus and Zaedyus. Most large-bodied taxa in the sample, i.e., Vassallia

317 and glyptodonts, but not Priodontes, do indeed show a strongly elevated dentition in relation to

318 the cranium depth (Figure 4). This is also the case in Peltephilus, for which the height of the

319 cranium is particularly low in relation to its length. Although they are small (i.e., GCL< 43mm),

320 chlamyphorines show a tooth height comparable in proportion to the larger-sized Euphractus,

321 Chaetophractus and Proeutatus (Figure 4), meaning that they slightly depart from the detected

322 allometric trend in having higher teeth than expected for their size. Relative tooth height is lower

323 in Prozaedyus, Zaedyus, Tolypeutes and Cabassous, and extremely low in specimens with dental

324 reduction – Stegotherium, Dasypus and Priodontes (Figure 4).

325

326 Curvature & Orientation--As visible in anterior and ventral views (Figure 2), taxa with

327 reduced teeth and Peltephilus exhibit a rather homogenous curvature and orientation of teeth along

328 the dental row while most cingulates show gradual changes in these aspects anteroposteriorly. In

329 most cingulates, anterior teeth are tilted lingually, i.e., tilted with a medially offset apex, while

330 most posterior teeth often tilt labially. The tilt of posterior teeth is often much less pronounced

331 than for anterior teeth. Similarly, taxa that show curved crowns generally show anterior teeth with

332 an inward curvature (lingual convexity) which can be strongest in the middle of the dental row,

333 while the two posteriormost teeth often show a lesser degree of inward curvature or even an

334 outward curvature (labial convexity). A strong inward curvature of anterior teeth is observed in

335 Peltephilus, Doellotatus, Tolypeutes, Vassallia, chlamyphorines, and glyptodonts in our sample,

336 whereas other taxa show straighter crowns, and an outward curvature is observed in Dasypus. In

337 lateral view, the first tooth (Mf1; P1 for Dasypus) or teeth show a mesial curvature (mesial

338 convexity) and a mesially offset apex in Bradypus, Peltephilus, Proeutatus, Vassallia,

339 Propalaehoplophorus and Eucinepeltus. Mf1 is also tilted with a mesially offset apex in

340 Prozaedyus. Finally, the two to three posteriormost teeth are distinctly tilted with a distally offset

341 apex in Bradypus and glyptodonts. Most other loci and taxa exhibit a nearly vertical orientation of

342 teeth in lateral view.

343

344 Based on these observations, we propose scrutinizing evolutionary scenarios for the following two

345 characters of the dentition (see Table 2).

346

347 Character 1 (discrete - unordered): Position of the most dorsal point of the dorsal convexity of

348 the tooth row.

349 State (0): Toothrow not dorsally convex.

350 State (1): Anterior to middle of the tooth row.

351 State (2): At the middle of the tooth row.

352 State (3): Posterior to middle of the tooth row.

353

354 Character 2 (discrete - unordered): Curvature of anterior teeth in anterior view.

355 State (0): Inward curvature.

356 State (1): Straight.

357 State (2): Outward curvature.

358

359 3.2 Cranial Canals

360 3.2.1 Frontal Diploic Vein canal

361 The course of this canal is entirely within the frontal bone. It opens externally at one or

362 exceptionally two foramina located in the orbitotemporal fossa, slightly ventral to the most dorsal

363 part of the orbital margin (Figure S1). Internally, the canal opens through one or more foramina

364 located posteriorly to the annular ridge and near the midline without ever crossing it (Figure S4).

365 This canal conveys the frontal diploic vein, an emissary of the dorsal cerebral vein/dorsal sagittal

366 sinus or a vein issuing from the frontal diploë (Thewissen 1989; Wible & Gaudin, 2004; Evans &

367 de Lahunta, 2012; Muizon et al., 2015).

368 In early ontogeny, the canal of the frontal diploic vein is initially extremely thick in

369 youngest specimens of Dasypus (see also Billet et al., 2017) and Zaedyus and occupies a large part

370 of the frontal bone (Figure 3). Its relative diameter is considerably reduced in older specimens of

371 Dasypus and Zaedyus with no change in its curved trajectory in Zaedyus but becoming more

372 strictly transverse in the adult stage in Dasypus (Figure 3). In Cabassous, it remains fairly similar

373 from juvenile to adult stages in our sample (Figure 3).

374 In our adult sample, the canal is relatively straight, very thin, oriented posteromedially in

375 dorsal view and without ramifications in Bradypus (Figure 5). In Tamandua, Peltephilus,

376 Stegotherium, Dasypus, Euphractus, Priodontes and Cabassous, its overall course is transverse

377 but with a posterior bend or convexity of varying degree (Figure 5). Ramifications and a posterior

378 convexity are also found in Prozaedyus, Chaetophractus, Zaedyus and Proeutatus, but the overall

379 course of their canal is more anteromedially oriented, as is also observed in Stegotherium,

380 Priodontes and Cabassous (Figure 5). The same orientation is found in Doellotatus (incomplete),

381 except that the course of the canal is completely straight and has no ramifications (Figure 5).

382 Tolypeutes, on the other hand, shows a very peculiar course with a forked structure in dorsal view

383 (Figure 5). The canal is merged with diploe in chlamyphorines but its presence is observable in

384 Calyptophractus in which it has a straight and anteromedially oriented trajectory (Figure 5). This

385 canal was not observed in Vassallia or in all the glyptodonts sampled. However, Gaudin (2004)

386 notes the presence of this canal in glyptodonts and Gaudin & Lyon (2017) mention it in the

387 pampathere Holmesina Simpson, 1930 (but see below). We suspect a taphonomic bias for some

388 specimens (e.g., some glyptodonts) and call for a deeper study of this canal in cingulates before its

389 variation can be scored.

390

391 3.2.2 Nasolacrimal Canal

392 The nasolacrimal canal originates posteriorly at the anterior orbital edge with the lacrimal

393 foramen (Figures 1 & S1). It runs anteriorly within the lacrimal and the maxillary bones in its

394 posteriormost portion. More anteriorly, the canal is located between the inner wall of the maxillary

395 and turbinates. It opens anteriorly (in front of the tooth row, except in Peltephilus) and

396 ventromedially into the nasal cavity (Figures S1E & S5). This canal allows the transmission of

397 fluids from the lacrimal sac to the nasal cavity and is potentially accompanied by a vein in

398 Euphractus (see Wible & Gaudin, 2004).

399 The course of the nasolacrimal canal barely changes during ontogeny in our sample (Figure

400 3). Its length changes and follows the lengthening of the snout that accompanies the growth of the

401 cranium (Le Verger et al., 2020). In addition, Cabassous and, to a lesser degree, the adult stage of

402 Zaedyus show a more medial orientation of the course of the nasolacrimal canal in its most

403 posterior part which differs slightly from Dasypus and other stages of Zaedyus, where it runs more

404 parallel to the external surface of the cranium (Figure 3).

405 The position of the nasolacrimal canal and lacrimal foramen varies among taxa, although

406 this feature was not scored in previous matrices (e.g., Gaudin & Wible, 2006). The lacrimal

407 foramen is particularly high relative to the orbital edge (closer to the most dorsal point of the orbit

408 than to the jugal bone in lateral view) in chlamyphorines, Proeutatus and glyptodonts (Figure 6).

409 The trajectory of the nasolacrimal canal is strongly sigmoid in Tamandua (Figure 6). In Bradypus,

410 Peltephilus, Proeutatus, Euphractus and Chaetophractus, the course of the nasolacrimal canal is

411 slightly convex dorsally (Figure 6). The curvature is much pronounced in Vassallia in the posterior

412 half of its course as it passes above the tooth row (Figure 6). In dasypodines, Prozaedyus, Zaedyus,

413 tolypeutines, and chlamyphorines, the nasolacrimal canal is relatively straight or it bears a slight

414 ventral convexity in its posterior part (Figure 6). In glyptodonts, the canal runs ventromedially and

415 not anteriorly from the lacrimal foramen (Figures 6 & 7), and curves strongly inward anteriorly

416 when approaching the sagittal plane of the cranium (Figures 6 & 7).

417 Whereas glyptodonts appear to show a unique condition in the course of their nasolacrimal

418 canal, the anterior opening of this canal is located halfway up in their nasal cavity as in Bradypus,

419 Tamandua, Peltephilus, Doellotatus, Proeutatus and Vassallia. In comparison, this opening is

420 closer to the palate in other specimens (Figure 6). This variation can be scored in the following

421 character (see Table 2).

422

423 Character 3 (discrete - unordered): Anterior opening of the nasolacrimal canal in nasal cavity.

424 State (0): Halfway up in the nasal cavity.

425 State (1): Ventral in the nasal cavity, close to the palate.

426

427 3.2.3 Palatine and Sphenopalatine Canals

428 Two large canals are enclosed within the maxillary and palatine bones forming the hard

429 palate in cingulates: the palatine canal and the sphenopalatine canal (Wible & Gaudin, 2004). The

430 palatine canal is generally thinner, longer than and positioned medial to the sphenopalatine canal.

431 The palatine canal transmits the major and minor palatine nerve, artery, and vein in Euphractus

432 (Wible & Gaudin, 2004). This canal opens externally at the caudal palatine foramen posteriorly

433 and at the multiple foramina scattered throughout the hard palate (both in the palatine and

434 maxillary) anteriorly (Figure S1). The sphenopalatine canal, which is often very wide in cingulates,

435 transmits the caudal nasal nerve and the sphenopalatine artery and vein (Wible & Gaudin, 2004).

436 The sphenopalatine canal opens anteriorly in the nasal cavity and posteriorly in the pterygopalatine

437 fossa just posterior to the dental row and close to or confluent with the caudal palatine foramen

438 (Wible & Gaudin, 2004; Figure S1). The palatine canal and sphenopalatine canal are confluent in

439 part of their posterior course in many of the species in our sample.

440 The palatine canal and sphenopalatine canal vary little during ontogeny within the three

441 species of our ontogenetic series (Figure 3). The branch of the palatine canal posterior to its region

442 of confluence with the sphenopalatine canal in Dasypus and Cabassous appears in the subadult (or

443 intermediate) stage and elongates further in the adult stage (Figure 3). In the youngest specimen

444 of Zaedyus, the sphenopalatine canal is much wider relative to cranium size than in later stages,

445 and there is no region of confluence with the palatine canal (Figure 3). In the youngest Dasypus

446 specimen, the sphenopalatine canal is absent. It is present only as a wide groove in the youngest

447 to subadult stages, but is completely enclosed in the adult stage of Dasypus in our sample (Figure

448 3).

449 In our adult sample, the shape and trajectory of the palatine canal does not vary much

450 among species (Figures 6 & 7). In glyptodonts, the palatine canal strongly ascends posteriorly

451 (starting from Mf6) (Figure 6) and forms a groove running along the inner wall of the

452 nasopharyngeal canal (Figure S6). In other cingulates, the palatine canal does not show such an

453 ascending trajectory posteriorly. The sphenopalatine canal, which is thicker than the palatine canal,

454 features a relatively straight trajectory in lateral view in Peltephilus, dasypodines, Prozaedyus,

455 Doellotatus, Euphractus, Zaedyus, and “Cochlops”, whereas it shows a strong ventral curvature in

456 Chaetophractus, tolypeutines, chlamyphorines and Glyptodon (Figure 6). It should be further

457 noted that the dorsal position of the sphenopalatine canal relative to the nasopharyngeal canal is a

458 feature shared by Vassallia and Glyptodon (Figure S7). In Bradypus and Tamandua, the palatine

459 canal does not contact the sphenopalatine canal (Figures 6 & 7). The two canals are in contact in

460 a small region of confluence in the dasypodines whereas the palatine canal becomes completely

461 confluent with the sphenopalatine canal, and sometimes accompanied by ventrally oriented

462 auxiliary branches of the palatine canal, in Peltephilus, tolypeutines, chlamyphorines and

463 Glyptodon (Figures 6 & 7). In euphractines, the confluence between the sphenopalatine canal and

464 the palatine canal is not as clear-cut as in the above-cited cingulates (Figures 6 & 7). The palatine

465 canal of euphractines runs ventrally along the sphenopalatine canal in the same figure 8-shaped

466 canal while being completely conjoined only in their most posterior part and at their posterior

467 opening (Figures 6 & 7). The extent of this confluence is highly variable in Euphractus according

468 to Wible & Gaudin (2004), and in other cingulates as well (Gaudin & Wible, 2006 – character 71).

469 We observed the same variation as Gaudin & Wible (2006) concerning the extent of this

470 confluence in the vicinity of the posterior opening of the sphenopalatine canal for all the taxa in

471 our sample. Several branches may emerge from this region of confluence (Figures 6 & 7), some

472 of which present an interesting pattern. One branch opens externally from the caudal foramen of

473 the palatine canal in dasypodines, Priodontes and Cabassous (Figures 6 & 7). A second branch

474 extends posteriorly into the hard palate, before disappearing in the bone diploe in dasypodines. In

475 Euphractus, Zaedyus, Priodontes, and Cabassous, two or more branches extend posteriorly into

476 the hard palate, but they open in the nasopharyngeal canal (Figures 6 & 7). Several other

477 ramifications of the palatine canal are present in our sample, but it remains to be determined how

478 variable these are at the intraspecific level with a dataset larger than that of Table S1.

479

480 Based on the observation of these two canals, we proposed to scrutinize evolutionary scenarios for

481 the following character (see Table 2).

482

483 Character 4 (discrete - unordered): Sphenopalatine and palatine canal connection.

484 State (0): No contact.

485 State (1): Partial contact, with palatine canal running ventrally along the sphenopalatine canal

486 and producing posterior branches.

487 State (2): Complete fusion.

488

489 3.2.4 Transverse Canal

490 When present, the transverse canal is marked externally by a foramen positioned

491 anteroventrally to or within the foramen ovale in the alisphenoid (Figure S1). This canal crosses

492 the cranium transversally at the level of the basisphenoid and transmits a large vein issued from

493 the cavernous sinus (Sánchez-Villagra & Wible, 2002; Wible & Gaudin, 2004). Often, one or more

494 branches originate from this canal and extend posteriorly towards the lateral edge of the

495 basisphenoid to join the inferior petrosal sinus (Wible & Gaudin, 2004).

496 The transverse canal appears early in Dasypus and varies little during ontogeny. Although,

497 in Zaedyus and Cabassous, the connection between the transverse canal and the posterior branch

498 extending towards the inferior petrosal sinus varies in both series, we have not observed a clear

499 ontogenetic pattern of variation in our three species (Figure 3).

500 In Bradypus, Peltephilus, Stegotherium, Doellotatus, Tolypeutes and Glyptodon, there is

501 no transverse canal, or it is not detectable (scored as present in Doellotatus and Stegotherium,

502 variable in Tolypeutes by Gaudin & Wible, 2006 – character 111). Chlamyphorines have a

503 transverse canal foramen opening directly within the braincase, and thus there is a very short canal

504 that does not cross the midline of the cranium. Tamandua stands out in having a thin lateral part

505 of the transverse canal which is not comparable to the condition in Cingulata (Figure 8). In

506 Dasypus, Prozaedyus, euphractines, Priodontes and Cabassous, the branch starting from the

507 transverse canal foramen is oriented posteromedially in ventral view (Figure 8). In the Miocene

508 glyptodonts, it is medially oriented (Figure 8). In Vassallia it is anteromedially oriented (Figure

509 8). This lateral branch of the transverse canal splits into a branch that crosses the midline in the

510 basisphenoid bone and a branch that joins the inferior petrosal sinus (Figure 8). In Proeutatus, this

511 bifurcation occurs much closer to the transverse canal foramen than in other taxa (Figure 8). It is

512 relatively more medial in Prozaedyus, euphractines, Priodontes and Cabassous (Figure 8). In

513 Tamandua, Dasypus, Vassallia and Miocene glyptodonts, this bifurcation is closer to the sagittal

514 plane than to the foramen (Figure 8). The transverse medial branch is anteromedially oriented in

515 ventral view in Prozaedyus, Cabassous and Proeutatus, whereas it is medially oriented in the other

516 taxa (Figure 8). Our specimens of Tamandua, euphractines (not complete in Chaetophractus) and

517 Priodontes show an additional branch connecting the transverse medial branch to the posterior

518 branch reaching the inferior petrosal sinus (Figure 8). In Vassallia and the Miocene glyptodonts,

519 the posterior branch reaching the inferior petrosal sinus is much thinner than the rest of the canal,

520 in contrast to the other taxa, in which the whole canal exhibits a relatively homogeneous width

521 (Figure 8).

522

523 Based on these observations of the transverse canal, we propose to scrutinize evolutionary

524 scenarios for the following character (see Table 2).

525

526 Character 5 (discrete - unordered): Orientation of the branch starting from the transverse canal

527 foramen.

528 State (0): Posteromedial.

529 State (1): Medial or anteromedial.

530 State (2): No canal.

531

532 3.2.5 Orbitotemporal and Posttemporal Canals

533 Within the braincase, the orbitotemporal canal provides passageway to the rostral extension

534 of the ramus superior of the stapedial artery, or orbitotemporal artery (giving rise to the ramus

535 supraorbitalis in the orbital region), and a few small veins (Wible & Gaudin, 2004) whereas the

536 more posterior posttemporal canal transmits the arteria diploëtica magna and the large vena

537 diploëtica magna (Wible & Gaudin, 2004). These two canals can give rise to the arterial and

538 venous rami temporales along the lateral wall of the braincase which exit via numerous foramina

539 on the cranial roof to irrigate the temporalis muscle (Wible & Gaudin, 2004; Figure S1). The

540 posttemporal canal is connected posteriorly to an external groove in the petro-occipital region

541 marking the passage of the occipital artery (Wible & Gaudin, 2004; Figure S1). From there, the

542 posttemporal canal extends forward as a canal enclosed between the petrosal and squamosal (or

543 only in the squamosal) and oriented mostly horizontally. More anteriorly, past the petrosal, the

544 posttemporal canal is connected to the orbitotemporal canal, which runs further anteriorly within

545 or on the inner surface of the lateral braincase wall (formed by the squamosal, frontal and

546 sometimes the parietal). The delimitation between the two canals generally occurs where the canal

547 for the ramus superior joins them (Muizon et al., 2015). However, we were only able to observe a

548 canal possibly transmitting the ramus superior in Tolypeutes (Figure S8), but not in the other

549 specimens. Consequently, we followed the suggestion of Wible & Gaudin (2004), who separate

550 the two canals at the level of the postglenoid foramen. In some taxa, the orbitotemporal canal is

551 not completely enclosed for parts of its length, and appears instead as a groove on the internal wall

552 of the braincase. The anterior opening of the orbitotemporal canal is located in the orbitotemporal

553 region, just posteroventral to the postorbital constriction (Figure S1; Wible & Gaudin, 2004; =

554 cranioorbital foramen in Gaudin & Wible, 2006; see also Muizon et al. (2015) for multiple

555 illustrations of these canals in another placental taxon).

556 The orbitotemporal canal only appears as a short canal near the orbitotemporal region in

557 the youngest specimens of all three species, whereas the canal (or groove) is clearly visible for its

558 entire length in later stages (Figure 3). The connections of the orbitotemporal canal with canals for

559 the numerous rami temporales occur in the two last stages in both Zaedyus and Cabassous (Figure

560 3). The posttemporal canal is already well formed in the youngest specimen of Dasypus and hardly

561 changes during ontogeny (Figure 3). In Zaedyus, the posttemporal canal is not enclosed in the

562 youngest stage. In Cabassous, the posttemporal canal is present in the youngest stage sampled, but

563 it expands anteriorly during the two subsequent stages (Figure 3).

564 In our adult sample, Bradypus, Tamandua, euphractines, Vassallia and glyptodonts possess

565 a posttemporal canal emerging at the center of the occiput in lateral view and at the level of the

566 jugular foramen (Figure 9). In Peltephilus, it originates more ventrally, even with the most dorsal

567 margin of the occipital condyles in lateral view (Figure 9). In dasypodines, tolypeutines and

568 chlamyphorines, the posterior extremity of the canal is at an intermediate height (Figure 9). Apart

569 from the position of the posterior opening of this canal (= posttemporal foramen of Wible &

570 Gaudin, 2004), we were unable to determine any systematically significant variation regarding its

571 direction, length, or width.

572 In Bradypus and Tamandua, the orbitotemporal canal does not reach the orbitotemporal

573 region (Figures 9 & 10). It reaches the orbitotemporal region in all the cingulates in our sample

574 except for Priodontes (Figures 9 & 10). Gaudin & Wible (2006) mention the absence of the

575 anterior opening of the orbitotemporal canal in Priodontes (character 78), but also in

576 Chlamyphorus and Vassallia for which we observe a clear opening in the orbitotemporal region

577 (Figure 9). In Bradypus, Tamandua and Peltephilus, this canal bears a ventral curvature (strong in

578 Peltephilus), whereas its trajectory exhibits a more or less strong dorsal curvature in all the other

579 taxa (Figure 9). In Peltephilus, Dasypus, Prozaedyus, euphractines, Tolypeutes, Cabassous,

580 chlamyphorines, Proeutatus and Miocene glyptodonts, the orbitotemporal canal becomes a groove

581 on the internal lateral wall of the braincase before being enclosed again as a canal close to its

582 external anterior opening (Figure 9). In Calyptophractus, Proeutatus and glyptodonts, the anterior

583 half of the orbitotemporal canal displays a pronounced downward trajectory, and its anterior

584 opening is located lower than its posterior connection with the posttemporal canal (Figure 9).

585 Calyptophractus stands out, however, in having two branches that connect the orbitotemporal and

586 posttemporal canals (Figure 9). A large region of confluence between the orbitotemporal and

587 posttemporal canals and the canal for the capsuloparietal emissary vein is identified in Tamandua,

588 Peltephilus, Stegotherium, Dasypus, Chaetophractus, Priodontes, Vassallia and the glyptodonts

589 (and potentially also in Proeutatus but the orbitotemporal canal is not distinct in this region;

590 Figures 9 & 10). This confluent region is reminiscent of the petrosquamosal fossa in

591 Alcidedorbignya Muizon & Marshall, 1987 (Muizon et al., 2015). The orbitotemporal and

592 posttemporal canals connect with the rami temporales through multiple small canals whose

593 number remains quite variable at the intraspecific level. However, a high density of rami

594 temporales for the orbitotemporal canal is particularly noticeable in euphractines, Cabassous,

595 Calyptophractus and glyptodonts (Figure 9). This density is coded by Gaudin & Wible (2006),

596 who counted the number of foramina for rami temporales in the temporal fossa of parietal (0, equal

597 to or less than five; 1, greater than five – character 97).

598 In their matrix, almost all cingulates are coded as having more than 5 foramina. The

599 variations in the density of the canals for the rami temporales observed in our study call for further

600 investigation of these structures, which could potentially carry an interesting phylogenetic signal

601 among cingulates.

602

603 Based on these observations of the orbitotemporal canal, we propose to scrutinize evolutionary

604 scenarios for the following character (see Table 2).

605

606 Character 6 (discrete - unordered): Downward trajectory of the orbitotemporal canal.

607 State (0): Canal does not reach the orbitotemporal region.

608 State (1): The anterior part of the canal has a slight downward trajectory ending at the same or

609 almost the same height as its origin from the posttemporal canal.

610 State (2): The canal has a strong downward anterior trajectory, and its anterior opening is much

611 lower than its posterior connection to the posttemporal canal.

612

613 3.2.6 Canal of the Capsuloparietal Emissary Vein

614 The canal for the capsuloparietal emissary vein opens anteroventrally at the postglenoid

615 and suprameatal foramina, and connects to the groove for the transverse sinus posterodorsally

616 (Wible, 1993; Muizon et al., 2015). From the cranial roof, the transverse sinus runs lateroventrally

617 in a wide groove excavated in the inner surface of the parietal and extends anteroventrally within

618 a canal formed by the petrosal medially and the squamosal laterally. This canal opens externally

619 through the suprameatal foramen, the postglenoid foramen and accessory foramina at the posterior

620 base of the zygomatic arch (e.g., Wible & Gaudin, 2004; Figure S1). It transmits the

621 capsuloparietal emissary vein (= retroarticular vein in Canis Linnaeus 1758 (Evans & de Lahunta,

622 2012); postglenoid vein in Cynocephalus Boddaert 1768 (Wible, 1993) and Dasypus Linnaeus

623 1758 (Wible, 2010)). In our sample, this canal is often partly confluent with the posttemporal and

624 orbitotemporal canal in its posterodorsal portion (Figure S9).

625 The canal for the capsuloparietal emissary vein is already well formed in the youngest

626 specimen of Dasypus and hardly changes during ontogeny, except that it becomes relatively

627 thinner (Figure 3). In Zaedyus, it is only partly formed in the youngest specimen, and its trajectory

628 is better marked in older stages (Figure 3). In the youngest Cabassous, this canal is noticeably

629 short and only marked in its most ventral part (glenoid region). It is only in older stages that the

630 canal elongates posterodorsally (Figure 3).

631 The canal is absent and the passage of the vein is only indicated by a groove in Bradypus

632 and Chlamyphorus. The groove is very wide in the latter two (Figure 9). The canal of the

633 capsuloparietal emissary vein opens through the postglenoid foramen and potentially in the

634 suprameatal foramen as well (see rami temporales opening in the squamosal whose number varies

635 in our intraspecific sampling (Table S1)) in Peltephilus, Prozaedyus, Doellotatus, euphractines,

636 chlamyphorines, Proeutatus, Vassallia and the glyptodonts (as notably scored for the glenoid

637 region by Gaudin & Wible, 2006 – character 119; Figures 9 & 10). In tolypeutines, the canal

638 always opens by a suprameatal foramen with a well-marked branch, whereas its opening via the

639 postglenoid foramen may sometimes be absent, as we have occasionally observed the absence of

640 a postglenoid foramen in our intraspecific sample of Cabassous (Table S1). For all our taxa except

641 Bradypus, the canal extends anteroventrally the cranial roof (Figure 9). However, its inclination

642 varies considerably from one species to another. It is steeply inclined in dasypodines, slightly less

643 so in Prozaedyus, Doellotatus, euphractines and Proeutatus, and much less so in tolypeutines,

644 Calyptophractus, Vassallia and glyptodonts (Figure 9). The canal is sinuous in Euphractus and

645 Chaetophractus. In glyptodonts, the canal even has an almost anteroposterior orientation near its

646 anterior opening (Figures 9 & 10). The canal (or groove) for the capsuloparietal emissary vein

647 reaches a region of confluence (= petrosquamosal fossa, Muizon et al., 2015) with the other canals

648 of the braincase in Tamandua, Peltephilus, dasypodines (particularly thin in Dasypus),

649 Chaetophractus, Priodontes, Vassallia and glyptodonts (Figures 9 & 10). For the other taxa, the

650 canal for the capsuloparietal emissary vein is only adjacent to the other canals (Figures 9 & 10 –

651 see Figure S9 for an illustration of the different cases in our sample). The variation in length and

652 thickness of this canal does not provide clear systematic information. A relatively short canal is

653 present in Tamandua, Doellotatus, Zaedyus, and Proeutatus compared with dasypodines (Figure

654 9). Chlamyphorines and Zaedyus show a relatively thicker canal, as compared with the very thin

655 canal in Vassallia. The fact that small taxa have a relatively thicker canal is reminiscent of young

656 specimens of Dasypus as compared to older and larger specimens of the same species (Figure 3)

657 and suggest a potential allometric pattern.

658

659 Based on these observations, we propose to scrutinize evolutionary scenarios for the following

660 character related to the anterolateral extremity of the canal (see Table 2).

661

662 Character 7 (discrete - unordered): Canal of the capsuloparietal emissary vein inclination in

663 lateral view.

664 State (0): Anterodorsal orientation or canal very short.

665 State (1): Inclination anteroventral from the posterior opening to the anterior opening.

666 State (2): Less anteroventrally inclined, with an almost anteroposterior orientation close to the

667 anterior opening.

668

669 3.3 Inclination of the cranial roof

670 Digital study of the braincase of our sample enabled observation of notable variations in

671 the internal vault inclination (= IVI) relative to the anteroposterior axis of the cranium. The values

672 of the IVI angle (see Material & Methods) show an interesting pattern in our sample that does not

673 correlate (R² = 0.1768; P-value = 0.3246) with size (Figure 11). Whereas Glyptodon is

674 distinguished from the other cingulates by an exceedingly high inclination combined with a large

675 size, the large-sized Vassallia has a very low cranial roof inclination (Figure 11). Dasypus (adult

676 specimen), Stegotherium, Chlamyphorus, Proeutatus and Miocene glyptodonts are also

677 characterized by high inclinations (Figure 11). The juvenile Cabassous also displays a strong

678 inclination, which decreases with age whereas the inclination increases with age in Dasypus

679 (Figure 11). Calyptophractus shows an intermediate cranial roof inclination (Figure 11). The

680 outgroups, euphractines and Cabassous (adult) exhibit low values, and the remaining Peltephilus

681 and tolypeutines are even characterized by a negative tilting of IVI (Figure 11).

682

683 We propose to treat the IVI angle as a continuous character to scrutinize evolutionary scenarios

684 (see Table 2).

685

686 Character 8 (continuous): Internal Vault Inclination.

687

688 4. DISCUSSION

689

690 Due to their very unusual anatomy, even within the Cingulata, the phylogenetic placement

691 of glyptodonts has been long debated (Burmeister, 1874; Scott, 1903; Carlini & Zurita, 2010;

692 Fariña et al., 2013). Recent molecular analyses have proposed a new hypothesis (i.e., as sister

693 group of the clade tolypeutines + chlamyphorines – Delsuc et al., 2016; Mitchell et al., 2016) at

694 odds with the multiple hypotheses based on morphological analyses (Engelmann, 1985; Gaudin &

695 Wible, 2006; Billet et al., 2011; Herrera et al., 2017). The recent investigation of the internal

696 anatomy in the Dasypus novemcinctus species complex (Billet et al., 2017) underlined the potential

697 phylogenetic signal hidden in the internal cranial structures of cingulates. Comparative studies on

698 the paranasal sinuses and on brain endocasts of cingulates have been performed, but could not

699 provide consistent information on the placement of glyptodonts within the Cingulata (Zurita et al.,

700 2011; Fernicola et al., 2012; Tambusso & Fariña, 2015a). Our comparative study complements

701 these previous efforts by adding the analysis of the dental alveolar cavities (previously only

702 explored in the glyptodont genus Eucinepeltus by González Ruiz et al., 2020) and of various canals

703 involved in the vascularization and innervation of the cranium (see Wible & Gaudin, 2004). Based

704 on an extensive sample of extant and extinct cingulates, our survey enabled us to describe many

705 new aspects of the internal cranial anatomy in the group, and to propose 8 potential characters with

706 helpful phylogenetic information to aid in determining the placement of glyptodonts within

707 Cingulata.

708

709 The anatomical variation of the dental alveolar cavities in cingulates comprises many

710 aspects including the height, curvature, and orientation of teeth, along with their number and

711 distribution on the rostrum (Vizcaíno, 2009). Among our observations, we have proposed two

712 characters with potential bearing on the affinities of glyptodonts. The first corresponds to the

713 position of the most dorsal point of these cavities in lateral view (character 1). The dorsal margins

714 of the alveoli form a dorsally convex line for the whole dental row in most cingulates, except in

715 taxa with reduced teeth. This most dorsal point is situated posteriorly (i.e., at Mf5-6) in

716 Prozaedyus, Zaedyus, chlamyphorines, pampatheres and glyptodonts in our sample. The

717 distribution of this character would be congruent with the hypothesis of a close relationship

718 between pampatheres and glyptodonts, as suggested by many previous authors (Patterson &

719 Pascual, 1972; Gaudin & Wible, 2006; Billet et al., 2011; Herrera et al., 2017), but also supports

720 the clade formed by the latter two with chlamyphorines, as proposed by the morphological analysis

721 of Mitchell et al. (2016) constrained by the molecular backbone (Figure 12). On the other hand,

722 Proeutatus, generally considered to be a close relative of the clade pampatheres + glyptodonts

723 (Engelmann, 1985; Gaudin & Wible, 2006; Billet et al., 2011; Gaudin & Lyon, 2017), has its most

724 dorsal point situated much further anteriorly (i.e., ca. Mf1-3).

725

726 The second character derived from dental alveolar cavities corresponds to the curvature of

727 the anterior teeth in anterior view (character 2). As for character 1, chlamyphorines and

728 pampatheres resemble glyptodonts in this aspect, exhibiting an inward curvature. Peltephilus,

729 Doellotatus and also Tolypeutes show a similar condition (Figure 12). As shown by the

730 reconstructed evolutionary scenario (Figure 12), this character could still support the

731 morphological hypothesis of Mitchell et al. (2016) of a close relationship between chlamyphorines

732 and glyptodonts. The distribution of this character on the baseline cladogram shows some

733 homoplasy, however, with the condition in Proeutatus contrasting with that of glyptodonts, while

734 Peltephilus resemble the latter (Figure 12). Another point of interest concerning the variation of

735 dental alveolar cavities is the potential allometric pattern identified by the correlation between the

736 relative height of the dental row and cranium size (Figure 4). This needs to be analyzed further

737 and compared to other allometric patterns seen on the cranium. Mammals generally show an

738 allometric elongation of the rostrum as size increases, known as craniofacial allometry (Cardini &

739 Polly, 2013; Cardini, 2019). In Dasypus, this allometric pattern mostly affects the proportions of

740 the rostrum horizontally, much less vertically (Le Verger et al., 2020). The possible allometric

741 increase in the height of the dentition in cingulates thus seems unrelated to craniofacial allometry

742 but this certainly requires further testing. In addition, we do not know whether allometry could

743 affect the variation of the two aforementioned alveolar cavity characters, but the resemblance of

744 small taxa (i.e., chlamyphorines) and large taxa (i.e., pampatheres and glyptodonts) seems to argue

745 against this. In any case, our study brings to light interesting new variation regarding the upper

746 tooth roots/alveolar cavities of cingulates, which have in the past been compared to one another

747 on the basis of their number, the presence/absence of teeth in the premaxillary, tooth wear,

748 histology, and the orientation of the long axis of the teeth relative to the long axis of the dental row

749 (characters 1, 3 to 8 – Gaudin & Wible, 2006 ; see discussion for glyptodonts regarding these

750 characters – Scott, 1903; Ferigolo, 1985; González Ruiz et al. , 2015).

751

752 Our initial observations on the overall spatial organization of the alveolar cavities point

753 towards a resemblance between chlamyphorines, pampatheres and glyptodonts, which would be

754 partly compatible with molecular results (Delsuc et al., 2016; Mitchell et al., 2016). However, we

755 believe further information could be gained by more detailed quantified analyses of shape to more

756 fully reflect the complex spatial variation of the dental alveolar cavities.

757

758 Our analysis of selected intracranial canals described various aspects of their variation,

759 which were unknown in cingulates until now. Furthermore, it enabled us to propose five characters,

760 that provide potentially significant phylogenetic information. This analysis also demonstrated the

761 need to further examine the variation of several structures (e.g., canal of the frontal diploic vein).

762

763 Both the trajectory and position of the nasolacrimal canal vary within the sample. A

764 trajectory that is first directed medially at its posterior opening (i.e., the lacrimal foramen)

765 represents a unique characteristic of glyptodonts within the Cingulata (Figures 6 & 7). The most

766 informative feature on this canal regarding the relationships of glyptodonts with other cingulates

767 is the relative height of its anterior opening within the nasal cavity (character 3 – Figure 12). In

768 most cingulates, this opening is positioned ventrally in the nasal cavity, close to the hard palate,

769 whereas in glyptodonts it is near the vertical midpoint of the cavity. The distribution of this

770 character on the baseline cladogram supports the node linking Proeutatus, pampatheres and

771 glyptodonts (Figure 12), as in several previous morphological analyses (Engelmann, 1985; Gaudin

772 & Wible, 2006; Billet et al., 2011; Gaudin & Lyon, 2017).

773

774 The course and connection between the sphenopalatine canal and the palatine canal is

775 characterized by a complex pattern which is very peculiar in glyptodonts (Figures S6 & S7). The

776 degree of fusion between the two canals was variable within our sample. Because of taphonomic

777 issues, only “Cochlops” and Glyptodon allowed us to observe a fusion of the two canals in

778 glyptodonts. This fusion was also present as in the chlamyphorines. The uncertain condition in

779 Proeutatus and pampatheres does not allow us to draw clear conclusions (character 4 – Figure 12),

780 but the distribution of this character on the baseline cladogram could be congruent with the

781 morphological hypothesis of Mitchell et al. (2016) (Figure 12). However, caution is warranted,

782 because the confluence between the sphenopalatine foramen and the caudal palatine foramen is

783 known to exhibit substantial intraspecific variation in several taxa (see character 71, Gaudin &

784 Wible, 2006) including Euphractus (see Wible & Gaudin, 2004). In addition, the condition in

785 pampatheres needs further investigation because a caudal palatine foramen has been identified in

786 the floor of the sphenopalatine canal in Holmesina (see Gaudin & Lyon, 2017). Our study also

787 reveals a strong resemblance between pampatheres and glyptodonts, which share a dorsal position

788 of the sphenopalatine canal in relation to the nasopharyngeal canal (Figure S7). This feature could

789 have been coded as a character, but an investigation of potential allometry for this trait is required

790 before coding.

791

792 The course, orientation and connections of the transverse canal also vary in our sample.

793 We were unable to identify this canal in Tolypeutes, chlamyphorines and Glyptodon as well as

794 Bradypus, Peltephilus and Stegotherium. Its presence in the Proeutatus, pampatheres, Miocene

795 glyptodonts and many other cingulates suggests that it has been lost in Glyptodon. Apart from this

796 potential loss, the distribution on the baseline cladogram of the character corresponding to the

797 orientation of the branch directly connected to the transverse canal foramen may support the

798 common morphological hypothesis of a close relationship among Proeutatus, pampatheres and

799 glyptodonts (character 5 – Figure 13; see also Engelmann, 1985; Gaudin & Wible, 2006; Billet et

800 al., 2011; Gaudin & Lyon, 2017). Moreover, our work is congruent with the matrix of Gaudin &

801 Wible (2006) regarding the presence/absence of the transverse canal foramen for most taxa

802 (character 111) with the exceptions of Tamandua (coded as absent in Gaudin & Wible, 2006),

803 Stegotherium (coded as present in Gaudin & Wible, 2006) and Doellotatus. In the case of the latter,

804 the specimen available for our study was poorly preserved for this character (coded as present in

805 Gaudin & Wible, 2006). Our study also allows us to confirm the hypothesis of Wible & Gaudin

806 (2004), which suggested that the canal crosses the midline of the cranium in Euphractus

807 sexcinctus. In their fetuses, they did not observe this transverse pattern, and doubted whether it

808 existed in adult specimens (Wible & Gaudin, 2004). We can confirm this pattern in our specimen

809 (Figure 8). This well-known circulation pattern in several marsupials is much less clear in

810 placentals, for which the occurrence of a foramen for the transverse canal (often without knowing

811 whether it crosses the cranium midline) is most often interpreted as a case of convergence

812 (Sánchez-Villagra & Wible, 2002). In addition, our analysis of the youngest specimen of Zaedyus

813 also suggests that the transverse canal is not formed in young euphractine individuals, in

814 accordance with the observations of Wible & Gaudin (2004). However, in young dasypodines, we

815 clearly observe this feature (Figure 11). For a large majority of taxa in our sample, we can confirm

816 that a transverse canal crossing the midline is present in cingulates.

817

818 The distribution on the baseline cladogram of the character corresponding to the anterior

819 course of the orbitotemporal canal also provided interesting information (character 6 – Figure 13).

820 Calyptophractus, Proeutatus and glyptodonts share a strong downward trajectory of this canal,

821 with an anterior opening located much lower in lateral view than its posterior connection of the

822 orbitotemporal canal to the posttemporal canal. The evolutionary scenario for this character is,

823 however, unclear for glyptodonts and their close allies, and homoplasy seems to be present (Figure

824 13). Our study also highlights the presence of a foramen for the anterior opening of the

825 orbitotemporal canal in all cingulates except Priodontes whereas this foramen was scored as absent

826 in Vassallia and Chlamyphorus in Gaudin & Wible (2006, character 78), and is often unknown for

827 other cingulate taxa. Based on our observation, there is no doubt that the canal opens in the

828 orbitotemporal region in Vassallia, while this opening is described as absent in Holmesina

829 floridanus Robertson, 1976 by Gaudin & Lyon (2017). The opposite discrepancy exists regarding

830 the foramen for the frontal diploic vein, absent in Vassallia and described as present in Holmesina

831 floridanus by Gaudin & Lyon (2017). As these two foramina are usually located relatively close

832 to each other in the orbitotemporal region (bearing many foramina), we suggest that

833 misidentifications may have occurred between the opening of these two canals, if they are present,

834 or with ethmoidal foramina (Figure S4). The only way to confirm this hypothesis would be to scan

835 Gaudin & Lyon (2017) specimens of Holmesina floridanus.

836

837 Another character we investigated concerned the inclination of the canal for the

838 capsuloparietal emissary vein in lateral view (character 7 – Figure 13). All tolypeutines,

839 Calyptophractus, Vassallia and glyptodonts share a less steep inclination than that observed in

840 other cingulates, with a part close to the anterior opening oriented almost directly to the anterior

841 direction. The distribution of this character could provide support for the molecular hypothesis of

842 a closer relationship of the glyptodonts with chlamyphorines and tolypeutines (Delsuc et al., 2016;

843 Mitchell et al., 2016; Figure 13). However, the condition is reversed in Chlamyphorus and

844 Proeutatus, creating homoplasy that casts doubt on the evolution of this trait. The trajectory of this

845 canal has never been scored in prior phylogenetic analyses of the Cingulata. In the literature, only

846 two characters have been scored that indirectly concern this canal, characters 119 and 120 of

847 Gaudin & Wible (2006), related to the presence/absence of the postglenoid foramen and

848 suprameatal foramen, respectively. These characters deliver contrasting grouping among

849 cingulates (Gaudin & Wible, 2006).

850

851 Finally, the internal inclination of the cranial vault relative to the anteroposterior axis of

852 the cranium also helps identify some cingulate taxa that may resemble glyptodonts in this regard

853 (character 8; Figure 13). The distribution of this quantitative trait on the baseline cladogram

854 indicates that the dasypodines, chlamyphorines, Proeutatus and glyptodonts exhibit a strong IVI

855 angle, whereas Vassallia possesses a very weak angle. This strong difference between glyptodonts

856 and pampatheres was already highlighted by Tambusso & Fariña (2015b). The variation of this

857 trait was not explained by allometry in our sample. A highly inclined vault may have been evolved

858 independently in the dasypodines and in glyptodonts and their allies. Its distribution could provide

859 support for a relationship among chlamyphorines, Proeutatus and glyptodonts to the exclusion of

860 pampatheres or the latter may have undergone a reversal (Figure 13). The vault inclination in these

861 taxa seems to be partly congruent with the distribution of a character proposed by Billet et al.

862 (2011) and discussed by Delsuc et al. (2016), i.e., the dorsal position of the ventral surface of the

863 auditory region relative to the palate (character 78 – Billet et al., 2011). This is a characteristic of

864 chlamyphorines, eutatines, pampatheres, and glyptodonts in Billet et al.’s (2011) analysis. The

865 potential relationship of these two aspects of the braincase should be tested in future studies.

866

867 In conclusion, our investigation of the cranial canals and alveolar cavities highlighted

868 several endocranial characters that support a resemblance of glyptodonts with chlamyphorines,

869 Proeutatus and pampatheres. Except for character 7, our investigation did not bring to light new,

870 and strong resemblances between tolypeutines and glyptodonts that would support their close

871 relationship as suggested by molecular studies (Delsuc et al., 2016; Mitchell et al., 2016). In short,

872 our study of internal anatomy lends further credence to recent reports of a greater morphological

873 resemblance between glyptodonts and chlamyphorines than tolypeutines (Delsuc et al., 2016;

874 Mitchell et al., 2016). In this regard, it is worth noting that the chlamyphorines + tolypeutines

875 relationship received distinctly lower statistical support than most other clades in mitogenomic

876 analyses of cingulate phylogeny (Delsuc et al., 2016; Mitchell et al., 2016).

877 The congruence of these new internal characters with past morphological phylogenetic

878 analyses of the group is difficult to evaluate since the results of the latter have been rather unstable

879 (e.g., Engelmann, 1985; Abrantes & Bergqvist, 2006; Gaudin & Wible, 2006; Billet et al., 2011).

880 However, a close resemblance of glyptodonts to the eutatine Proeutatus and the pampatheres is

881 supported by several characters in our study, which would be congruent with several recent

882 phylogenetic hypotheses based on morphological data (Engelmann, 1985; Gaudin & Wible, 2006;

883 Billet et al., 2011; Gaudin & Lyon, 2017). More generally, internal cranial anatomy seems to show

884 similarities among chlamyphorines, Proeutatus, pampatheres, and glyptodonts (see also Tambusso

885 et al., 2021), but new analyses are needed that incorporate this new data before firmer phylogenetic

886 conclusions can be reached. Our study provides a non-exhaustive account of internal canals of the

887 cranium. Internal structures still need to be studied to select new characters in particular for

888 endocranial traits that we briefly describe but do not explore in detail. This is notably the case of

889 the canal for the frontal diploic vein or the relative position of the sphenopalatine canal in relation

890 with the nasopharyngeal canal, whose patterns of variation remain unclear at the moment. Another

891 promising way forward was also revealed by our developmental series in which Cabassous varies

892 in a manner different from that of Dasypus and Zaedyus as far as the inclination of the cranial roof

893 is concerned (Figure 11). A better exploration of the developmental series with more specimens

894 per species and more species sampled could provide a better understanding of their ontogenetic

895 trajectories, which can be coded for phylogenetic analyses (e.g., Bardin et al., 2017). Further

896 studies are also needed to better understand the patterns of variation of the internal characters

897 highlighted here, which in some respects may be affected by allometry as we have highlighted for

898 alveolar cavities and the canal for the capsuloparietal emissary vein.

899

900

901 ACKNOWLEDGMENTS

902

903 We are grateful to Christiane Denys, Violaine Nicolas, and Géraldine Véron, (Muséum

904 National d’Histoire Naturelle, Paris, France), Roberto Portela Miguez, Louise Tomsett, and Laura

905 Balcells (British Museum of Natural History, London, UK), Neil Duncan, Eileen Westwig,

906 Eleanor Hoeger, Ross MacPhee, Marisa Surovy and Morgan Hill Chase (American Museum of

907 Natural History, New York, USA), Nicole Edmison and Chris Helgen (National Museum of

908 Natural History, Washington, DC, USA), Jake Esselstyn (Louisiana State University, Museum of

909 Natural Sciences, Baton Rouge, USA), Manuel Ruedi (Muséum d’Histoire Naturelle, Geneva,

910 Switzerland), Pepijn Kamminga, Arjen Speksnijder and Rob Langelaan (Naturalis Biodiversity

911 Center, Leiden, Holland), April Isch and Zhe-Xi Luo (University of Chicago, Chicago, USA),

912 Adrienne Stroup and Bill Simpson (Field Museum of Natural History, Chicago, USA), Steffen

913 Bock, Christiane Funk, Frieder Mayer, Anna Rosemann Lisa Jansen, Kristin Mahlow, Johannes

914 Müller and Eli Amson (Museum für Naturkunde, Berlin, Germany), and Camille Grohé

915 (University of Poitiers, Poitiers, France) for access to comparative material and/or to CT-scans.

916 We would like to warmly thank Daniel Brinkmann (Yale Peabody Museum, New Haven, USA)

917 for his precious help in organizing KLV’s visit to the collections of the Yale Peabody Museum.

918 Many thanks also to Sergio Ferreira-Cardoso (Institut des Sciences de l’Evolution) for his help

919 during the trips of KLV for data acquisition. We thank Benoit de Thoisy (Institut Pasteur de la

920 Guyane) and Clara Belfiore for their help with the data acquisition, Olivia Plateau (University of

921 Fribourg, Switzerland) for her help on the R script and Cyril Le Verger for his help with

922 segmentation. We thank Renaud Lebrun (Institut des Sciences de l’Evolution), Farah Ahmed

923 (British Museum of Natural History), Miguel García-Sanz, Marta Bellato, Nathalie Poulet and

924 Florent Goussard (Platform AST-RX – Muséum National d’Histoire Naturelle) who generously

925 provided help with CT-scanning. Some of the experiments were performed using the µ-CT

926 facilities of the Montpellier Rio Imaging (MRI) platform of the LabEx CeMEB. KLV

927 acknowledges the financial support provided by the Sorbonne Universities/ED227 transhumance

928 international grant program. Finally, we would like to warmly thank Christian de Muizon (Centre

929 de Recherche en Paléontologie – Paris), Timothy Gaudin (University of Tennessee), Robert J.

930 Asher (University of Cambridge), Sophie Montuire (University of Bourgogne), Isabelle Rouget

931 (Centre de Recherche en Paléontologie – Paris), Allowen Evin and Lionel Hautier (Institut des

932 Sciences de l’Evolution) for reviewing a previous version of this work in the PhD dissertation of

933 KLV.

934

935 AUTHOR CONTRIBUTIONS

936

937 KLV contributed to data acquisition, data analyses/interpretations, drafting of the manuscript, and

938 study design. LRG contributed to data acquisition and critical revision of the manuscript. GB

939 contributed to data acquisition, study design, and critical revision of the manuscript.

940

941 REFERENCES

942

943 Abba, A.M., Cassini, G.H., Valverde, G. et al. (2015) Systematics of hairy armadillos and the

944 taxonomic status of the Andean hairy armadillo (Chaetophractus nationi). Journal of Mammalogy,

945 96(4), 673–689.

946

947 Abrantes, E.A.L. & Bergqvist, L.P. (2006) Proposta filogenetica para os Dasypodidae (Mammalia:

948 Cingulata). In: Gallo, V., Brito, P.M., Silva, H.M.A. & Figueirido, F.J. (Eds) Paleontologia

949 Vertebrados: Grandes Temas e Contribuiçoes Científicas. Rio de Janeiro: Interciências, pp. 261–

950 274.

951

952 Ameghino, F. (1884) Filogenia: Principios de clasificación transformista basados sobre leyes

953 naturales y proporciones matemáticas. Buenos Aires: Lajouane, F.

954

955 Ameghino, F. (1887) Enumeración sistemática de las especies de mamíferos fósiles coleccionados

956 por Carlos Ameghino en los terrenos eocenos de Patagonia austral y depositados en el Museo La

957 Plata. Extracto del Boletín del Museo La Plata, 1, 1–26.

958

959 Ameghino, F. (1889) Contribución al conocimiento de los mamíferos fósiles de la República

960 Argentina. Actas de la Academia Nacional de Ciencias en Córdoba, 6, 1–1027.

961

962 Ameghino, F. (1891) Nuevos restos de mamíferos fósiles descubiertos por Carlos Ameghino en el

963 Eoceno inferior de la Patagonia austral. Especies nuevas, adiciones y correcciones. Revista

964 Argentina de Historia Natural, 1, 289–328.

965

966 Bardin, J., Rouget, I. & Cecca, F. (2017) Ontogenetic data analyzed as such in phylogenies.

967 Systematic biology, 66(1), 23–37.

968

969 Billet, G., Hautier, L., Muizon de, C. & Valentin, X. (2011) Oldest cingulate skulls provide

970 congruence between morphological and molecular scenarios of armadillo evolution. Proceedings

971 of the Royal Society B: Biological Sciences, 278(1719), 2791–2797.

972

973 Billet, G., Hautier, L. & Lebrun, R. (2015) Morphological diversity of the bony labyrinth (inner

974 ear) in extant Xenarthrans and its relation to phylogeny. Journal of Mammalogy, 96(4), 658–672.

975

976 Billet, G., Hautier, L., Thoisy de, B. & Delsuc, F. (2017) The hidden anatomy of paranasal sinuses

977 reveals biogeographically distinct morphotypes in the nine-banded armadillo (Dasypus

978 novemcinctus). PeerJ, 5, e3593.

979

980 Boddaert, P. (1768) Dierkundig Mengelwerk in Het Welke de Nieuwe of nog Duistere Zoorten Van

981 Dieren. Utrecht: Abraham van Paddenburg en J. Van Schoonhoven (Volume 2).

982

983 Bollback, JP. (2006) SIMMAP: stochastic character mapping of discrete traits on phylogenies.

984 BMC Bioinformatics, 7(1), 1–7.

985

986 Bordas, AF. (1932) Proposición de un nuevo género para “Eutatus inornatus”. Physis, 11(38),

987 167–168.

988

989 Boscaini, A., Iurino, D.A., Sardella, R., Tirao, G., Gaudin, T.J. & Pujos, F. (2018) Digital cranial

990 endocasts of the extinct sloth Glossotherium robustum (Xenarthra, Mylodontidae) from the late

991 Pleistocene of Argentina: description and comparison with the extant sloths. Journal of

992 Mammalian Evolution, 27(1), 55–71.

993

994 Boscaini, A., Iurino, D.A., Mamani Quispe, B. et al. (2020) Cranial anatomy and paleoneurology

995 of the extinct sloth Catonyx tarijensis (Xenarthra, Mylodontidae) from the late Pleistocene of

996 Oruro, Southwestern Bolivia. Frontiers in Ecology and Evolution, 8, 1–16.

997

998 Burmeister, H. (1863) Ein neuer Chlamyphorus. Abhandlungen Naturforschende Gesellschaft zu

999 Halle, 7, 165–171.

1000

1001 Burmeister, H. (1874) Monografía de los glyptodontes en el Museo Público de Buenos Aires.

1002 Anales del Museo Público de Buenos Aires, 2, 1–412.

1003

1004 Cardini, A. (2019) Craniofacial allometry is a rule in evolutionary radiations of placentals.

1005 Evolutionary Biology, 46(3), 239–248.

1006

1007 Cardini, A. & Polly, P.D. (2013) Larger mammals have longer faces because of size-related

1008 constraints on skull form. Nature communications, 4(1), 1–7.

1009

1010 Carlini, A.A. & Zurita, A.E. (2010) An introduction to cingulate evolution and their evolutionary

1011 history during the great American biotic interchange: biogeographical clues from Venezuela. In:

1012 Sánchez-Villagra, M., Aguilera, O. & Carlini, A.A. (Eds) Urumaco and Venezuela paleontology.

1013 The fossil record of the northern neotropics. Bloomington: Indiana University Press, pp 233–255.

1014

1015 Carlini, A.A., Soibelzon, E. & Glaz, D. (2016) Chaetophractus vellerosus (Cingulata:

1016 Dasypodidae). Mammalian Species, 48(937), 73–82.

1017

1018 Castellanos, A. (1932) Nuevos géneros de gliptodontes en relación con su filogenia. Physis,

1019 11(38), 92–100.

1020

1021 Castellanos, A. (1946) Un nuevo gliptodontoideo del Araucanense del valle de Yocavil (Santa

1022 María) de la Provincia de Tucumán. Publicaciones del Instituto de Fisiografía y Geología, 6, 1–

1023 19.

1024

1025 Castellanos, A. (1959) Trascendencia de la obra de Florentino Ameghino. Revista de la Facultad

1026 de Ciencias Naturales de Salta, 1, 35–56.

1027

1028 Ciancio, M.R., Castro, M.C., Galliari, F.C., Carlini, A.A. & Asher, R.J. (2012) Evolutionary

1029 implications of dental eruption in Dasypus (Xenarthra). Journal of Mammalian Evolution, 19(1),

1030 1–8.

1031

1032 Claude, J. (2008) Morphometrics with R. New York: Springer-Verlag.

1033

1034 Clavel, J., Merceron, G. & Escarguel, G. (2014) Missing Data Estimation in Morphometrics: How

1035 Much is Too Much? Systematic biology, 63(2), 203–218.

1036

1037 Clavel, J., Escarguel, G. & Merceron, G. (2015) mvMORPH: an R package for fitting multivariate

1038 evolutionary models to morphometric data. Methods in Ecology and Evolution, 6(11), 1311–1319.

1039

1040 Cuvier, G. (1798) Tableau élémentaire de l’histoire naturelle des animaux. Paris: Baudouin.

1041

1042 Delsuc, F., Gibb, G.C., Kuch, M. et al. (2016) The phylogenetic affinities of the extinct

1043 glyptodonts. Current Biology, 26(4), 155–156.

1044

1045 Desmarest, A.G. (1804) Tableau méthodique des mammifères. Nouveau dictionnaire d'histoire

1046 naturelle, 24, 5–58.

1047

1048 Engelmann, G.F. (1985) The phylogeny of the Xenarthra. In: Montgomery, G.G. (Ed) The

1049 evolution and ecology of armadillos, sloths and vermilinguas. Washington: Smithsonian

1050 Institution Press, pp. 51–64.

1051

1052 Evans, H.E. & De Lahunta, A. (2012) Miller’s Anatomy of the Dog. St Louis: Saunders.

1053

1054 Fariña, R.A., Vizcaíno, S.F. & De Iuliis, G. (2013) Megafauna: giant beasts of Pleistocene South

1055 America. Bloomington: Indiana University Press.

1056

1057 Ferigolo, J. (1985) Evolutionary trends of the histological pattern in the teeth of Edentata

1058 (Xenarthra). Archives of Oral Biology, 30(1), 71–82.

1059

1060 Fernicola, J.C. (2008) Nuevos aportes para la sistemática de los Glyptodontia Ameghino 1889

1061 (Mammalia, Xenarthra, Cingulata). Ameghiniana, 45(3), 553–574.

1062

1063 Fernicola, J.C., Toledo, N., Bargo, M.S. & Vizcaíno, S.F. (2012) A neomorphic ossification of the

1064 nasal cartilages and the structure of paranasal sinus system of the glyptodont Neosclerocalyptus

1065 Paula Couto 1957 (Mammalia, Xenarthra). Palaeontologia Electronica, 15, 1–22.

1066

1067 Fernicola, J.C., Rinderknecht, A., Jones, W., Vizcaíno, S.F. & Porpino, K. (2017) A new species

1068 of Neoglyptatelus (Mammalia, Xenarthra, Cingulata) from the late Miocene of Uruguay provides

1069 new insights on the evolution of the dorsal armor in cingulates. Ameghiniana, 55(3), 233–252.

1070

1071 Flower, W.H. (1882) On the mutual affinities of the animals composing the order Edentata.

1072 Proceeding of the Zoological Society of London, 50, 358–367.

1073

1074 Gaudin, T.J. (1995) The ear region of edentates and the phylogeny of the Tardigrada (Mammalia,

1075 Xenarthra). Journal of Vertebrate Paleontology, 15(3), 672–705.

1076

1077 Gaudin, T.J. (2004) Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardigrada):

1078 the craniodental evidence. Zoological Journal of the Linnean Society, 140(2), 255–305.

1079

1080 Gaudin, T.J. & Wible, J.R. (2006) The phylogeny of living and extinct armadillos (Mammalia,

1081 Xenarthra, Cingulata): a craniodental analysis. In: Carrano, M.T., Gaudin, T.J., Blob, R.W. &

1082 Wible, J.R. (Eds) Amniote Paleobiology: Perspectives on the Evolution of Mammals, Birds, and

1083 Reptiles. Chicago: University of Chicago Press, pp. 153–198.

1084

1085 Gaudin, T.J. & Lyon, L.M. (2017) Cranial osteology of the pampathere Holmesina floridanus

1086 (Xenarthra: Cingulata; Blancan NALMA), including a description of an isolated petrosal bone.

1087 PeerJ, 5, e4022.

1088

1089 González Ruiz, L. & Scilalto-Yané, G.J. (2008) Una nueva especie de Stegotherium Ameghino

1090 (Xenarthra, Dasypodidae, Stegotheriini) del Mioceno de la provincia de Santa Cruz (Argentina).

1091 Ameghiniana, 45(4), 641–648.

1092

1093 González Ruiz, L. & MacPhee, R.D. (2014) Dental anomalies in Tolypeutes matacus (Desmarest,

1094 1804) (Mammalia, Xenarthra, Cingulata). XXVII Jornadas Argentinas de Mastozoología. 4 al 7

1095 de Noviembre de 2014. Esquel (Chubut), Argentina. Libro de Resúmenes: 94.

1096

1097 González Ruiz, L., Ladevèze, S. & MacPhee, R.D. (2014) Dental anomalies in Euphractus

1098 sexcinctus Wagler (Mammalia: Xenarthra: Dasypodidae). 94th Annual Meeting of the American

1099 Society of Mammalogist. 6 al 10 de Junio de 2014. Oklahoma City (Oklahoma), USA. Abstract

1100 Book: 59-60.

1101

1102 González Ruiz, L., Ciancio, M.R., Martin, G.M. & Zurita, A.E. (2015) First record of

1103 supernumerary teeth in Glyptodontidae (Mammalia, Xenarthra, Cingulata). Journal of Vertebrate

1104 Paleontology, 35(1), e885033.

1105

1106 González Ruiz, L., Aya-Cuero, C.A. & Martin, G.M. (2017) La dentición de Priodontes maximus

1107 (Kerr, 1972): formula, morfología y anomálias. XXVII Jornadas Argentinas de Mastozoología. 14

1108 al 17 de Noviembre de 2017. Bahía Blanca (Buenos Aires), Argentina. Libro de Resúmenes: 135.

1109

1110 González Ruiz, L., Brandoni, D., Zurita, A.E. et al. (2020) Juvenile Glyptodont (Mammalia,

1111 Cingulata) from the Miocene of Patagonia, Argentina: Insights into Mandibular and Dental

1112 Characters. Journal of Vertebrate Paleontology, 40(1), e1768398.

1113

1114 Harlan, R. (1825) Description of a New Genus of Mammiferous Quadrupeds of the Order

1115 Edentata. Annals of the Lyceum of Natural History of New York, 6, 235–246.

1116

1117 Hayssen, V. (2014) Cabassous unicinctus (Cingulata: Dasypodidae). Mammalian Species,

1118 46(907), 16–23.

1119

1120 Herrera, C.M.R., Powell, J.E., Esteban, G.I. & Del Papa, C. (2017) A new Eocene dasypodid with

1121 caniniforms (Mammalia, Xenarthra, Cingulata) from northwest Argentina. Journal of Mammalian

1122 Evolution, 24(3), 275–288.

1123

1124 Hoffstetter, R. (1958) Xenarthra. In: Piveteau, J. (Ed) Traité de Paléontologie. Paris: Masson &

1125 Cie.

1126

1127 Huxley, T.H. (1864) II. On the osteology of the genus Glyptodon. Philosophical Transactions of

1128 the Royal Society of London, 155, 31–70.

1129

1130 Kerr, R. (1792) The animal kingdom or zoological system, of the celebrated Sir Charles Linnaeus.

1131 class I. Mammalia: contain a complete systematic description, arrangement, and nomenclature,

1132 of all the known species and varieties of Mammalia, or animals which give suck to their young;

1133 being a translation of that part of the Systema Naturae, as lately published, with great

1134 improvements, by Professor Gmelin of Goettingen, together with numerous additions from more

1135 recent zoological writers, and illustrated with copperplates. London/Edinburgh: Strahan, A.,

1136 Cadell, T. & Creech, W. (Eds).

1137

1138 Le Verger, K., Hautier, L., Bardin, J., Gerber, S., Delsuc, F. & Billet, G. (2020) Ontogenetic and

1139 static allometry in the skull and cranial units of nine-banded armadillos (Cingulata: Dasypodidae:

1140 Dasypus novemcinctus). Biological Journal of the Linnean Society, 131(3), 673–698.

1141

1142 Linnæus, C. (1758) Systema naturae per regna tria naturæ, secundum classes, ordines, genera,

1143 species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

1144 Homiae: Laurentii Salvii.

1145

1146 McBee, K. & Baker, R.J. (1982) Dasypus novemcinctus. Mammalian species, 162, 1–9.

1147

1148 Messineo, P.G. & Politis, G.G. (2009) New radiocarbon dates from the Campo Laborde site

1149 (Pampean Region, Argentina) support the Holocene survival of giant ground sloth and

1150 glyptodonts. Current Research in the Pleistocene, 26, 5–9.

1151

1152 Mitchell, K.J., Scanferla, A., Soibelzon, E., Bonini, R., Ochoa, J. & Cooper, A. (2016) Ancient

1153 DNA from the extinct South American giant glyptodont Doedicurus sp. (Xenarthra:

1154 Glyptodontidae) reveals that glyptodonts evolved from Eocene armadillos. Molecular Ecology,

1155 25(14), 3499–3508.

1156

1157 Muizon de, C. & Marshall, L.G. (1987) Le plus ancien Pantodonte (Mammalia) du Crétacé

1158 supérieur de Bolivie. Comptes rendus hebdomadaires des Séances de l'Académie des Sciences,

1159 Paris, 304, 205–208.

1160

1161 Muizon de, C., Billet, G., Argot, C., Ladevèze, S. & Goussard, F. (2015) Alcidedorbignya

1162 inopinata, a basal pantodont (Placentalia, Mammalia) from the early Palaeocene of Bolivia:

1163 anatomy, phylogeny and palaeobiology. Geodiversitas, 37(4), 397–634.

1164

1165 Owen, R. (1839) Description of a tooth and part of the skeleton of the Glyptodon, a large quadruped

1166 of the edentate order, to which belongs the tessellated bony armour figured by Mr. Clift in his

1167 memoir on the remains of the Megatherium, brought to England by Sir Woodbine Parish, F.G.S.

1168 Proceedings of the Geological Society of London, 3, 108–113.

1169

1170 Paradis, E. & Schliep, K. (2019) ape 5.0: an environment for modern phylogenetics and

1171 evolutionary analyses in R. Bioinformatics, 35(3), 526–528.

1172

1173 Patterson, B. & Pascual, R. (1972) The Fossil Mammal Fauna of South America. In: Keast, A.,

1174 Erk, F.C. & Glass, B. (Eds) Evolution, Mammals, and Southern Continents. Albany: State

1175 University of New York Press, pp. 247–309.

1176

1177 Patterson, B., Segall, W. & Turnbull, W.D. (1989) The ear region in xenarthrans (=Edentata,

1178 Mammalia). Part I. Cingulates. Fieldiana Geology, 18, 1–46.

1179

1180 Porpino, K.D.O., Fernicola, J.C. & Bergqvist, L.P. (2010) Revisiting the intertropical Brazilian

1181 species Hoplophorus euphractus (Cingulata, Glyptodontoidea) and the phylogenetic affinities of

1182 Hoplophorus. Journal of Vertebrate Paleontology, 30(3), 911–927.

1183

1184 Revell, L.J. (2012) phytools: a R package for phylogenetic comparative biology (and other things).

1185 Methods in ecology and Evolution, 3(2), 217–223.

1186

1187 Robertson, J.S. (1976) Latest Pliocene mammals from Haile XV A, Alachua County, Florida.

1188 Bulletin of the Florida State Museum, Biological Sciences, 20(3), 111–186.

1189

1190 Sánchez‐Villagra, M.R. & Wible, J.R. (2002) Patterns of evolutionary transformation in the

1191 petrosal bone and some basicranial features in marsupial mammals, with special reference to

1192 didelphids. Journal of Zoological Systematics and Evolutionary Research, 40(1), 26–45.

1193

1194 Scott, W.B. (1903) Mammalia of the Santa Cruz beds. I. Edentata. Reports of the Princeton

1195 University Expeditions to Patagonia. Princeton/Stuttgart: Princeton University.

1196

1197 Simpson, G.G. (1930) Holmesina septentrionalis, extinct giant armadillo of Florida. American

1198 Museum Novitates, 422, 1–10.

1199

1200 Smith, P. & Owen, R.D. (2017) Calyptophractus retusus (Cingulata: Dasypodidae). Mammalian

1201 Species, 49(947), 57–62.

1202

1203 Superina, M. & Loughry, W.J. (2015) Why do Xenarthrans matter? Journal of Mammalogy, 96(4),

1204 617–621.

1205

1206 Swofford, D.L. (2002) PAUP: Phylogenetic analysis using parsimony (and other methods).

1207 Version 4.0a167. Sunderland: Sinauer Associates.

1208

1209 Tambusso, P.S. & Fariña, R.A. (2015a) Digital cranial endocast of Pseudoplohophorus absolutus

1210 (Xenarthra, Cingulata) and its systematic and evolutionary implications. Journal of Vertebrate

1211 Paleontology, 35(5), e967853.

1212

1213 Tambusso, P.S. & Fariña, R.A. (2015b) Digital endocranial cast of Pampatherium humboldtii

1214 (Xenarthra, Cingulata) from the Late Pleistocene of Uruguay. Swiss Journal of Palaeontology,

1215 134(1), 109–116.

1216

1217 Tambusso, P. S., Varela, L., Góis, F., Moura, J. F., Villa, C. & Fariña, R. A. (2021) The inner ear

1218 anatomy of glyptodonts and pampatheres (Xenarthra, Cingulata): Functional and phylogenetic

1219 implications. Journal of South American Earth Sciences, 108, 103189.

1220

1221 Thewissen, J.G.M. (1989) Mammalian frontal diploic vein and the human foramen caecum. The

1222 Anatomical Record, 223(2), 242–244.

1223

1224 Vizcaíno, S.F. (2009) The teeth of the “toothless”: novelties and key innovations in the evolution

1225 of xenarthrans (Mammalia, Xenarthra). Paleobiology, 35(3), 43–366.

1226

1227 Vizcaíno, S.F. & Loughry, W.J. (2008) Biology of the Xenarthra. Gainesville: University Press of

1228 Florida.

1229

1230 Wake, D.B., Wake, M.H. & Specht, C.D. (2011) Homoplasy: from detecting pattern to

1231 determining process and mechanism of evolution. Science, 331(6020), 1032–1035.

1232

1233 Wetzel, R.M. (1985) Taxonomy and distribution of armadillos, Dasypodidae. In: Montgomery,

1234 G.G. (Ed) The evolution and ecology of armadillos, sloths, and vermilinguas. Washington DC:

1235 Smithsonian Institution Press, pp. 23–46.

1236

1237 Wetzel, R.M., Gardner, A.L., Redford, K.H. & Eisenberg, J.F. (2007) Order cingulata. In: Gardner,

1238 A.L. (Ed) Mammals of South America: Marsupials, Xenarthrans, Shrews, and Bats. Chicago:

1239 University of Chicago Press, pp. 128–156.

1240

1241 Wible, J.R. (1993) Cranial circulation and relationships of the colugo Cynocephalus (Dermoptera,

1242 Mammalia). American Museum Novitates, 3072, 1–27.

1243

1244 Wible, J.R. (2010) Petrosal anatomy of the nine-banded armadillo, Dasypus novemcinctus

1245 Linnaeus, 1758 (Mammalia, Xenarthra, Dasypodidae). Annals of the Carnegie Museum, 79(1), 1–

1246 28.

1247

1248 Wible, J.R. & Gaudin, T.J. (2004) On the cranial osteology of the yellow armadillo Euphractus

1249 sexcintus (Dasypodidae, Xenarthra, Placentalia). Annals of the Carnegie Museum, 73(3), 1–117.

1250

1251 Wible, J.R. & Spaulding, M. (2013) On the cranial osteology of the African palm civet, Nandinia

1252 binotata (Gray, 1830) (Mammalia, Carnivora, Feliformia). Annals of the Carnegie Museum, 82(1),

1253 1–114.

1254

1255 Zurita, A.E., Scarano, A.C., Carlini, A.A., Scillato-Yané, G.J. & Soibelzon, E. (2011)

1256 Neosclerocalyptus spp. (Cingulata: Glyptodontidae: Hoplophorini): cranial morphology and

1257 palaeoenvironments along the changing Quaternary. Journal of Natural History, 45(15-16), 893–

1258 914.

1259 TABLE 1. List of specimens. Symbol: †, extinct species; *, perinatal stage; **, juvenile; ***, subadult; ****, adult; (i), author of the genus. 1260 Family/Subfamily Species Institutional number Locality Period References Bradypodidae Bradypus tridactylus MNHN ZM-MO-1999-1065 French Guiana; Petit saut rive droite Extant Linnaeus, 1758 Myrmecophagidae Tamandua tetradactyla NHM 3-7-7-135 Brazil; Mato Grosso; Chapada Extant Linnaeus, 1758 Argentina; Santa Cruz; Santa Cruz Formation; Peltephilidae Peltephilus pumilus† YPM-VPPU 15391 Early Miocene Ameghino, 1887 Coy Inlet Dasypodinae Dasypus novemcinctus* AMNH 33150 Colombia; Quindui; Salento Extant Linnaeus, 1758 Dasypodinae Dasypus novemcinctus** AMNH 133261 Brazil; Goias; Anapolis Extant Linnaeus, 1758 Dasypodinae Dasypus novemcinctus*** AMNH 133328 Brazil; Mato Grosso do Sul; Maracaju Extant Linnaeus, 1758 Dasypodinae Dasypus novemcinctus**** AMNH 255866 Bolivia; Beni; Cercado Extant Linnaeus, 1758 Argentina; Santa Cruz; Santa Cruz Formation; González y Scillato- Dasypodidae Stegotherium tauberi† YPM-VPPU 15565 (type) Early Miocene Killik Aike Norte Yané, 2008 Argentina; Santa Cruz; Santa Cruz Formation; Euphractinae Prozaedyus exilis† YPM-VPPU 15579 Early Miocene Ameghino, 1887 Killik Aike Norte Argentina; Santa Cruz; Santa Cruz Formation; Euphractinae Prozaedyus proximus† YPM-VPPU 15567 Early Miocene Ameghino, 1887 Coy Inlet Euphractinae Euphractus sexcinctus AMNH 133304 Brazil; Goias; Anapolis Extant Linnaeus, 1758 Euphractinae Chaetophractus villosus AMNH 173546 South America; No more precision Extant Desmarest, 1804 Euphractinae Zaedyus pichiy* ZMB 49039 Argentina; Oso Marino Extant Desmarest, 1804 Euphractinae Zaedyus pichiy** MHNG 1627.053 Argentina; Chubut; Punta Ninfas Extant Desmarest, 1804 Euphractinae Zaedyus pichiy*** MHNG 1276.076 Argentina; Chubut; Fofo Cahuel Extant Desmarest, 1804 Euphractinae Zaedyus pichiy**** FMNH 23810 Argentina; Chubut; No more precision Extant Desmarest, 1804 Bolivia; unnamed formation; Potosí; Quebrada Euphractinae Doellotatus sp.† UF 260533 Middle Miocene Bordas, 1932 (i) Honda Tolypeutinae Cabassous unicinctus** NBC 26326.B Suriname; No more precision Extant Linnaeus, 1758 Tolypeutinae Cabassous unicinctus*** AMNH 133386 Brazil; Mato Grosso do Sul; Maracaju Extant Linnaeus, 1758 Tolypeutinae Cabassous unicinctus**** MNHN 1999-1044 French Guiana; No more presicion Extant Linnaeus, 1758 Tolypeutinae Tolypeutes matacus FMNH 28345 Brazil; Mato Grosso; Descalvado Extant Desmarest, 1804 Tolypeutinae Priodontes maximus AMNH 208104 Zoo; No more precision Extant Kerr, 1792 Chlamyphorinae Chlamyphorus truncatus AMNH 5487 Argentina; Mendoza; No more precision Extant Harlan, 1825 Chlamyphorinae Calyptophractus retusus NMNH 283134 Bolivia; Santa Cruz; No more precision Extant Burmeister, 1863 Argentina; Santa Cruz; Santa Cruz Formation; Eutatini Proeutatus lagena† YPM-VPPU 15613 Early Miocene Ameghino, 1887 Coy Inlet Argentina; Catamarca; Andalhuala Formation; Pampatheriinae Vassallia maxima† FMNH P14424 Late Miocene Castellanos, 1946 Puerta del Corral Quemado Argentina; Santa Cruz; Santa Cruz Formation; Glyptodontinae Propalaehoplophorus minus† AMNH-FM 9197 Early Miocene Ameghino, 1891 Cañadón de las Vacas Argentina; Santa Cruz; Santa Cruz Formation; Glyptodontinae "Cochlops" debilis† YPM-VPPU 15592 Early Miocene Ameghino, 1891 Cañadón Silva Argentina; Santa Cruz; Santa Cruz Formation; Glyptodontinae Eucinepeltus complicatus† AMNH-FM 9248 (type) Early Miocene Brown, 1903 Killik Aike Norte Argentina; Santa Cruz; Santa Cruz Formation; Glyptodontinae "Metopotoxus" anceps† YPM-VPPU 15612 Early Miocene Scott, 1903 Lago Pueyrredón Glyptodontinae Glyptodon sp.† MNHN PAM-759 Argentina; Buenos Aires; No more precision Pleistocene Owen, 1839 (i) Glyptodontinae Glyptodon sp.† MNHN PAM-760 Argentina; Buenos Aires; No more precision Pleistocene Owen, 1839 (i)

1261

1262 TABLE 2. Data matrix with character scores for each genus. Character 1 and 7 are discrete and character 8 is continuous (see text). Symbols: -, not applicable; ?, 1263 missing data; †, extinct species. 1264 Taxa Character 1 Character 2 Character 3 Character 4 Character 5 Character 6 Character 7 Character 8 Bradypus 1 1 0 0 2 0 0 3.66 Tamandua - - 0 0 0 0 0 11.06 Peltephilus † 1 0 0 1 2 1 1 -4.85 Dasypus 0 2 1 1 0 1 1 17.73 Stegotherium † 0 1 1 1 2 1 1 20.83 Prozaedyus † 3 1 ? ? 0 1 1 ? Doellotatus † 2 0 ? ? ? 1 1 8.08 Euphractus 2 1 1 1 0 1 1 6.58 Chaetophractus 2 1 1 1 0 1 1 3.96 Zaedyus 3 1 1 1 0 1 1 1.67 Chlamyphorus 3 0 1 2 2 1 1 18.29 Calyptophractus 3 0 1 2 2 2 2 11.68 Cabassous 0 1 1 1 0 1 2 8.57 Tolypeutes 2 0 1 1 2 1 2 -1.04 Priodontes 0 1 1 1 0 0 2 -2.11 Proeutatus † 1 1 0 ? 1 2 1 17.92 Vassallia † 3 0 0 ? 1 1 2 0.08 Propalaehoplophorus † 3 0 0 ? 1 2 2 18.56 "Metopotoxus" † 3 0 0 ? 1 2 2 19.45 "Cochlops" † 3 0 0 2 1 2 2 21.2 Eucinepeltus † 3 0 0 ? 1 2 2 ? Glyptodon † 3 0 0 2 2 2 2 35.84

1265

1266 1267 1268 FIGURE 1. Illustration of the selected internal canals on the transparent cranium of Euphractus sexcinctus AMNH 1269 133304 in right lateral (A) and ventral (B) views. Scale = 1 cm.

1270 1271 1272 FIGURE 2. Diversity of the dental alveolar cavities in our cingulate sample in lateral (red square), ventral (yellow 1273 square) and anterior (green square) view. Crania are reconstructed with transparency to leave the cavities apparent. 1274 Colors of species names refer to their attribution at the subfamilial level according to molecular analyses (lower right 1275 panel); extinct species not allocated to one of these subfamilies are shown in black. † represents an extinct taxon. Scale 1276 = 1 cm.

1277 1278 1279 FIGURE 3. Ontogenetic variation of internal canals selected in this study viewed on transparent crania in each 1280 developmental series (Dasypus, Zaedyus and Cabassous). Note that early postnatal stages for Cabassous are not 1281 documented in our sample. See Le Verger et al. (2020) for the determination of stages. Phylogenetic relationships are 1282 indicated with colors following Figure S3. The color of canals follows that of Figure 1. Abbreviations: pbplc, posterior 1283 branch of the palatine canal. Scale = 1 cm. 61

1284 1285 1286 FIGURE 4. Distribution of the ratio of greatest dental row height (GDRH) to greatest cranium height (GCH) with 1287 respect to cranial size (= log(geometric mean); see Materials & Methods). For each of the three developmental series, 1288 A, symbolizes the adult specimen. Crania of specimens marked with an asterisk are illustrated in the graph. Scale = 1 1289 cm.

1290 1291 1292 FIGURE 5. Interspecific variation of the canal for the frontal diploic vein in our sample, all illustrated in dorsal view. 1293 Red arrows mark the main external opening of the canal. Blue arrows mark the main internal path of the canal on the 1294 cranial midline. Colors of species names follow Figure 2. Scale = 1 mm.

1295 1296 1297 FIGURE 6. Interspecific variation in our sample of the reconstructed nasolacrimal (= red), sphenopalatine (= yellow) 1298 and palatine (= orange) canals shown in lateral view. Crania are reconstructed with transparency. Colors of species 1299 names follow Figure 2. Abbreviations: cfpb, caudal foramen for palatine canal branch; pbplc, posterior branch of 1300 palatine canal. Scale = 1 cm.

1301 1302 1303 FIGURE 7. Interspecific variation in our sample of the reconstructed nasolacrimal (= red), sphenopalatine (= yellow) 1304 and palatine (= orange) canals shown in ventral view. Crania are reconstructed with transparency. Colors of species 1305 names follow Figure 2. Abbreviations: cfpb, caudal foramen for palatine canal branch; pbplc, posterior branch of 1306 palatine canal. Scale = 1 cm.

1307 1308 1309 FIGURE 8. Interspecific variation of the transverse canal in ventral view in our sample. Red arrows mark the main 1310 external opening of the canal. Blue arrows mark the branch crossing the midline. Green arrows mark the main posterior 1311 branch which connects to the inferior petrosal sinus (see text). Colors of species names follow Figure 2. Scale = 1 1312 mm.

1313 1314 1315 FIGURE 9. Interspecific variation in our sample of the orbitotemporal (= red), posttemporal (= pink) and 1316 capsuloparietal emissary vein (= blue) canals shown in lateral view. Caudal part of the cranium is transparent. Parts 1317 of the canals showing transparency symbolize a groove instead of a fully enclosed canal. Colors of species names 1318 follow Figure 2. Scale = 1 cm.

1319 1320 1321 FIGURE 10. Interspecific variation in our sample of the orbitotemporal (= red), posttemporal (= pink) and 1322 capsuloparietal emissary vein (= blue) canals shown in ventral view. Transparent parts of the canals indicate a groove 1323 instead of a fully enclosed canal. Colors of species names follow Figure 2. Scale = 1 mm.

1324 1325 1326 FIGURE 11. Distribution of the internal vault inclination (IVI) with respect to cranial size (= log(geometric mean)) 1327 in our sample. For the three developmental series, A symbolizes the adult specimen. Specimens marked with an 1328 asterisk are illustrated by cranial reconstructions in sagittal view in the graph. Scale = 1 cm.

1329 1330 1331 FIGURE 12. Reconstructed evolutionary scenarios for the endocranial characters 1 – 4 plotted on the reference 1332 cladogram with ancestral state estimation for internal nodes (see Materials & Methods, Supporting information 1 and 1333 Figure S3). Each character is illustrated, and the relationship between color and coding is indicated within the figure 1334 itself. † represents extinct genera. Scale = 1 cm.

1335 1336 1337 FIGURE 13. Reconstructed evolutionary scenarios for the endocranial characters 5-8 plotted on the reference 1338 cladogram with ancestral state estimation for internal nodes (see Materials & Methods, Supporting information 1 and 1339 Figure S3). Each character is illustrated and the relationship between color and coding is explained within the figure. 1340 † represents extinct genera. For character 8 (= IVI), the angle between the anteroposterior axis of the cranium (defined 1341 by the line connecting the most posterior (a) and anterior (b) edges of the tooth row) and the straight line connecting 1342 the most dorsal point of the annular ridge (c) and the most ventral point of the tentorial process (d). Scale = 1 cm.

1343 SUPPLEMENTARY DATA 1344 1345 SUPPORTING INFORMATION 1: Matrix and Analytical Parameters. 1346 1347 For de description of each characters and the previous coded taxa see Billet et al. (2011). 1348 1349 Parameters: 1350 - Dimensions ntax = 22 nchar = 125; 1351 - Format datatype = standard; 1352 - Gap = -; 1353 - Missing = ?; 1354 - States = "0 1 2 3 4 5 6". 1355 - Heuristic search settings: Optimality criterion = parsimony; 1356 - Character-status summary: Of 125 total characters: 27 characters are of type 'ord' (Wagner); 98 characters 1357 are of type 'unord'; All characters have equal weight; All characters are parsimony-informative; Gaps are 1358 treated as "missing"; Multistate taxa interpreted as polymorphism. 1359 - Starting tree(s) obtained via stepwise addition; 1360 - Addition sequence: random; 1361 - Number of replicates = 1000; 1362 - Starting seed = generated automatically; 1363 - Number of trees held at each step = 10; 1364 - Branch-swapping algorithm: tree-bisection-reconnection (TBR) with reconnection limit = 8; 1365 - Steepest descent option not in effect; 1366 - Initial 'Maxtrees' setting = 100; 1367 - Branches collapsed (creating polytomies) if maximum branch length is zero; 1368 - 'MulTrees' option in effect; 1369 - Keeping only trees compatible with constraint-tree "kevin"; 1370 - Trees are unrooted. 1371 1372 New coded taxa: 1373 1374 Calyptophractus retusus 1375 3210? 1???? 10611 12020 10012 01211 11010 12112 ??011 10000 0000? 00010 10221 11121 01011 111?0 00110 1376 10111 110?0 0?10? 01011 2300? ???01 10101 10110 1377 1378 “Cochlops” debilis 1379 3?1?? 2???? ????? ????? ???0? ??201 ?0010 13113 ?0021 10000 0?00? 110?? ??121 21121 1380 01111 111?1 01100 10210 11010 120-? 001?? 0??1? ????1 1211? (01)0111 1381 1382 Eucinepeltus complicatus 1383 3211? 21101 206?? ????? ?0?0? 10201 10010 13113 ?0021 1?000 0?0?? 110?? 1?122 21121 00111 111?1 011?0 1384 10210 1???0 ????? 001?? ???1? ????1 12111 10111 1385 1386 Glyptodon sp. 1387 3211? 21101 20601 02321 10?0? 10201 10010 13113 10021 10000 0?0?? 110?? 1?121 21121 00111 111?1 0?1?0 1388 10210 11010 120?1 001?? 0??1? ???01 12111 10111 1389 1390 “Metopotoxus” anceps 1391 3???? 2???? ????? ????? ???0? ??20? ?0010 13??? ?0011 10000 ??00? 110?? ???21 21121 01111 111?1 1?1?? 1392 ?0210 ????? ????? 0???? ????? ????1 1211? 0011?

1393 TABLE S1. List of adult specimens used for assessing the intraspecific variation in Dasypus, Zaedyus and Cabassous. 1394 Family/Subfamily Species Institutional number Locality Dasypodinae Dasypus novemcinctus AMNH 255866 Bolivia, Beni, Cercado Dasypodinae Dasypus novemcinctus AMNH 211668 Bolivia, Beni, Cercado, ca. 23 kilometers west of San Javier Dasypodinae Dasypus novemcinctus AMNH 262658 Bolivia, Pando, Nicolas Suarez, 5 kilometers upstream from Cachuela Dasypodinae Dasypus novemcinctus AMNH 263287 Bolivia, Santa Cruz, Andres Ibanez, Ayacucho Dasypodinae Dasypus novemcinctus AMNH 205727 Uruguay, Lavalleja, Zapican, 12 kilometers west southwest of Zapican Euphractinae Zaedyus pichiy FMNH 23810 Argentina, Chubut Euphractinae Zaedyus pichiy AMNH 94327 Argentina, Chubut, Sarmiento, Colhue Huapi Lake Euphractinae Zaedyus pichiy MNHN 1883-158 Argentina, Santa Cruz Euphractinae Zaedyus pichiy ZMB 46103 South America, Argentina, Puero Jenkins, -47,75779, -65,90836 Euphractinae Zaedyus pichiy ZMB 46104 South America, Argentina, Oso Marino, -47,9237, -65,83145 Tolypeutinae Cabassous unicinctus MNHN 1999-1044 French Guiana Tolypeutinae Cabassous unicinctus MNHN 1998-2255 French Guiana, Petit-Saut Tolypeutinae Cabassous unicinctus AMNH 137196 South America, Brazil, Para, Tapajos River, Igarape Brabo Tolypeutinae Cabassous unicinctus AMNH 74113 South America, Peru, Loreto, Maynas Tolypeutinae Cabassous unicinctus MVZ 155192 Peru, Rio Cenepa

1395

1396 TABLE S2. List of scanned specimens available online or under request (see Materials & Methods). Symbol: †, extinct species; *, perinatal stage; **, juvenile; 1397 ***, subadult; ****, adult; (i), author of the genus. 1398 Species Institutional number Scanned by or under the care of Bradypus tridactylus MNHN ZM-MO-1999-1065 GB Tamandua tetradactyla NHM 3-7-7-135 Sergio Ferreira Cardoso (see Acknowledgment) Peltephilus pumilus† YPM-VPPU 15391 LRG Dasypus novemcinctus* AMNH 33150 Lionel Hautier (see Acknowledgment) Dasypus novemcinctus** AMNH 133261 Lionel Hautier (see Acknowledgment) Dasypus novemcinctus*** AMNH 133328 Lionel Hautier (see Acknowledgment) Dasypus novemcinctus**** AMNH 255866 LGR Stegotherium tauberi† YPM-VPPU 15565 (type) LGR Prozaedyus exilis† YPM-VPPU 15579 LGR Prozaedyus proximus† YPM-VPPU 15567 LGR Euphractus sexcinctus AMNH 133304 LGR Chaetophractus villosus AMNH 173546 LGR Zaedyus pichiy* ZMB 49039 Eli Amson (see Acknowledgment) Zaedyus pichiy** MHNG 1627.053 KLV Zaedyus pichiy*** MHNG 1276.076 KLV Zaedyus pichiy**** FMNH 23810 LRG Doellotatus sp.† UF 260533 LRG Cabassous unicinctus** NBC 26326.B KLV Cabassous unicinctus*** AMNH 133386 KLV Cabassous unicinctus**** MNHN 1999-1044 KLV Tolypeutes matacus FMNH 28345 LRG Priodontes maximus AMNH 208104 LRG Chlamyphorus truncatus AMNH 5487 LRG Calyptophractus retusus NMNH 283134 LRG Proeutatus lagena† YPM-VPPU 15613 LRG Vassallia maxima† FMNH P14424 KLV Propalaehoplophorus minus† AMNH-FM 9197 LRG "Cochlops" debilis† YPM-VPPU 15592 LRG Eucinepeltus complicatus† AMNH-FM 9248 (type) LRG "Metopotoxus" anceps† YPM-VPPU 15612 LRG Glyptodon sp.† MNHN PAM-759 KLV Glyptodon sp.† MNHN PAM-760 KLV

1399 TABLE S3. List of specimens with specific dental formula. Symbol: †, extinct species; *, perinatal stage; **, juvenile; ***, subadult; ****, adult; (i), author of 1400 the genus; C, canine; dPM, decidious premolar; M, molar; Mf, molariform; Mfp, molariform in premaxillary; PM, premolar; pmx, premaxilla; Ust, unfunctional 1401 supernumary teeth. 1402 Family/Subfamily Species Institutional number Dental formula Bradypodidae Bradypus tridactylus MNHN ZM-MO-1999-1065 1 C + 4 Mf Myrmecophagidae Tamandua tetradactyla NHM 3-7-7-135 no teeth Peltephilidae Peltephilus pumilus† YPM-VPPU 15391 1 Mfp + 6 Mf Dasypodinae Dasypus novemcinctus* AMNH 33150 7 dPM Dasypodinae Dasypus novemcinctus** AMNH 133261 7 dPM Dasypodinae Dasypus novemcinctus*** AMNH 133328 7 dPM/PM + 1 M Dasypodinae Dasypus novemcinctus**** AMNH 255866 7 PM + 1 M Dasypodidae Stegotherium tauberi† YPM-VPPU 15565 (type) 6 Mf Euphractinae Prozaedyus exilis† YPM-VPPU 15579 8 Mf Euphractinae Prozaedyus proximus† YPM-VPPU 15567 8 Mf Euphractinae Euphractus sexcinctus AMNH 133304 1 Mfp + 1 Ust + 8 Mf Euphractinae Chaetophractus villosus AMNH 173546 1 Mfp + 1 Ust + 8 Mf Euphractinae Zaedyus pichiy* ZMB 49039 6 Mf Euphractinae Zaedyus pichiy** MHNG 1627.053 8 Mf Euphractinae Zaedyus pichiy*** MHNG 1276.076 8 Mf Euphractinae Zaedyus pichiy**** FMNH 23810 8 Mf Euphractinae Doellotatus sp.† UF 260533 Incomplete specimen bearing 7 Mf (9 Mf in Gaudin & Wible, 2006) Tolypeutinae Cabassous unicinctus** NBC 26326.B 9 Mf Tolypeutinae Cabassous unicinctus*** AMNH 133386 9 Mf Tolypeutinae Cabassous unicinctus**** MNHN 1999-1044 9 Mf Tolypeutinae Tolypeutes matacus FMNH 28345 1 Ust on pmx + 9 Mf Tolypeutinae Priodontes maximus AMNH 208104 19 Mf Chlamyphorinae Chlamyphorus truncatus AMNH 5487 8 Mf Chlamyphorinae Calyptophractus retusus NMNH 283134 8 Mf Eutatini? Proeutatus lagena† YPM-VPPU 15613 1 Mfp + 8 Mf Pampatheriinae Vassallia maxima† FMNH P14424 1 Mfp + 8 Mf Glyptodontinae Propalaeohoplophorus minus† AMNH-FM 9197 8 Mf Glyptodontinae "Cochlops" debilis† YPM-VPPU 15592 Incomplete specimen bearing 7 Mf (8 Mf in Scott, 1903) Glyptodontinae Eucinepeltus complicatus† AMNH-FM 9248 (type) 8 Mf Glyptodontinae "Metopotoxus" anceps† YPM-VPPU 15612 Incomplete specimen bearing 7 Mf (8 Mf in Scott, 1903) Glyptodontinae Glyptodon sp.† MNHN PAM-759 8 Mf Glyptodontinae Glyptodon sp.† MNHN PAM-760 8 Mf

1403 TABLE S4. Cranial measurements in mm for GCL, GCW, GCH, GDRH and Geometric mean, and in degree for IVI (see Figure S2). Symbol: ?, missing data; †, 1404 extinct species; *, perinatal stage; **, juvenile; ***, subadult; ****, adult. 1405 Species GCL GCW GCH GDRH IVI Geometric mean Bradypus tridactylus 75.67 49.15 42.92 13.79 3.66 54.25 Tamandua tetradactyla 124.82 41.56 50.71 0 11.06 64.07 Peltephilus pumilus † 93.9 49.04 42.17 22.76 -4.85 57.91 Dasypus novemcinctus * 38.69 19.28 17.77 0.8 0.8 23.67 Dasypus novemcinctus ** 54.14 24.89 20.04 3.02 10.26 30.00 Dasypus novemcinctus *** 79.36 33.52 26.28 4.61 10.18 41.19 Dasypus novemcinctus **** 89.04 39.07 37.65 5.78 17.73 50.78 Stegotherium tauberi † 138.9 49.29 46.11 3.05 20.83 68.09 Prozaedyus † 66.71 30.45 29.34 7.16 ? 39.06 Euphractus sexcinctus 105.97 66.55 47.09 15.17 6.58 69.25 Chaetophractus villosus 89.39 58.46 37.48 14.07 3.96 58.07 Zaedyus pichiy * 29.31 18.31 13.86 0.55 ? 19.52 Zaedyus pichiy ** 56.43 33.47 24.76 6.39 3.04 36.03 Zaedyus pichiy *** 63.56 39.03 27.18 7.2 2.4 40.70 Zaedyus pichiy **** 71.65 42.59 29.18 8.52 1.67 44.65 Doellotatus sp. † ? ? 37.35 15.36 8.08 ? Cabassous unicinctus ** 69.94 40.62 35.69 8.24 16.79 46.63 Cabassous unicinctus *** 77.96 38.79 34.72 6.19 12.85 47.17 Cabassous unicinctus **** 87.41 47.09 37.78 9.53 8.57 53.77 Tolypeutes matacus 69.16 31.89 28.95 8.46 -1.04 39.96 Priodontes maximus 189.35 80.34 53.58 7.12 -2.11 93.41 Chlamyphorus truncatus 36.56 24.3 20.41 6.35 18.29 26.27 Calyptophractus retusus 42.86 27.38 23.41 8.22 11.68 30.17 Proeutatus lagena † 110.98 61.64 50.89 17.86 17.92 70.35 Vassallia maxima † 243.85 138.42 105.18 63.82 0.08 152.55 "Metopotoxus" anceps † 138.22 98.17 76.17 38.95 19.45 101.11 Propalaehoplophorus minus † 141.27 117.01 80.33 44.41 18.56 109.91 "Cochlops" debilis † 145.82 102.54 89.25 45.64 21.2 110.10 Eucinepeltus complicatus † 180.25 139.63 93.44 54.93 ? 132.98 Glyptodon sp. † 331.59 336.88 209.27 124.07 35.84 285.93

1406 76

1407 1408 1409 FIGURE S1. Illustration of the internal and external openings of each selected canal on a specimen of Euphractus 1410 sexcinctus (AMNH 133304) in transparent and non-transparent views. A, B, F and H, lateral view; C, ventral view; D 1411 and E, oblique internal view; G, lateral view of the braincase inner part; I, occipital view. Colors of the canals follow 1412 Figure 1. Abbreviations: afdv, accessory frontal diploic vein internal opening; aospc, anterior opening of the 1413 sphenopalatine canal; aotc, anterior opening of the orbitotemporal canal, asmf, accessory suprameatal foramen; fdv, 1414 foramen for the frontal diploic vein; ifdv, internal foramen for the frontal diploic vein; iocev, internal opening of the 1415 capsuloparietal emissary vein canal; lacf, lacrimal foramen; nlc, nasolacrimal canal; oncpl, opening in nasopharyngeal 1416 canal of palatine canal; otg, orbitotemporal groove; pf, palatine foramina; poptc, posterior opening of the posttemporal 1417 canal; ptgf, postglenoid foramen; ramus temporalis canal; rtotc, rami temporales foramina from the orbitotemporal 1418 canal; rtptc, rami temporales foramina from the posttemporal canal; smf, suprameatal foramen; spf, sphenopalatine 1419 foramen; tc, tranverse canal; tcf, tranverse canal foramen. Scale = 1 cm. 77

1420 1421 1422 FIGURE S2. Cranial measurements (Table S2) illustrated on a transparent cranium in lateral (top) and dorsal (bottom) 1423 view of Glyptodon sp. MNHN.F.PAM 760. Abbreviations: GDRH, greatest dental row height; GCH, greatest cranium 1424 height; GCL, greatest cranium length; GCW, greatest cranium width; IVI, internal vault inclination (= angle between 1425 the anteroposterior axis of the cranium (defined by the line connecting the most anterior and posterior edges of the 1426 dental row) and the straight line connecting the most dorsal point of the annular ring and the most ventral point of the 1427 tentorial process). Scale = 1 cm.

1428 1429 1430 FIGURE S3. A, modified backbone constraint from Mitchell et al. (2016) used for our phylogenetic analysis (see 1431 text). Proeutatus is enforced as the sister group of glytptodonts in accordance with most phylogenetic analyses using 1432 morphology (Engelmann, 1985; Gaudin & Wible, 2006; Billet et al., 2011; Herrera et al., 2017). B. Topology of the 1433 baseline cladogram. C. Topology of the strict consensus from the same analysis without constraint. See Supporting 1434 information 1 for phylogenetic analysis.

1435 1436 1437 FIGURE S4. Internal/external opening and canal trajectory for the right and left frontal diploic vein in Euphractus 1438 sexcinctus (AMNH 133304). A. Dorsal view in transparency with the two canals for the frontal diploic vein. The two 1439 canals do not cross the cranium midline. B. Occipital view of the conserved cranium part with internal opening. C. 1440 Oblique (more ventral) occipital view to facilitate the visibility of internal openings. Colors of the canals follow Figure 1441 1. Abbreviations: afdv, accessory frontal diploic vein internal opening; cfdv, canal for the frontal diploic vein; fdv, 1442 foramen for the frontal diploic vein; ifdv, internal foramen for the frontal diploic vein. Scale = 1 cm.

1443 1444 1445 FIGURE S5. Identification of the bones enclosing the nasolacrimal canal in Euphractus sexcinctus (AMNH 133304) 1446 illustrated by a cranium in right lateral view (top). The slices analyzed are indicated on the cranium by their number 1447 in the image stack and illustrated below. The nasolacrimal canal is reconstructed in red on each slice, on the left side 1448 of the image. Abbreviations: lac, lacrimal; mx, maxillary; nlc, nasolacrimal canal; pmx, premaxillary. Scale = 1 cm.

1449 1450 1451 FIGURE S6. Comparative illustration of the trajectory of the palatine canal in glyptodonts and other cingulates 1452 (illustrated here by Euphractus sexcinctus (AMNH 133304)). A, lateral internal view on a cranium sectioned on the 1453 midline. B, same view as A but with the palatine canal reconstructed. C, same view as A with cranium transparency 1454 and with the sphenopalatine and palatine canals reconstructed. Abbreviations: aospc, anterior opening of the 1455 sphenopalatine canal; ioplc, internal opening of the palatine canal; npc, nasopharyngeal canal; plg, palatine grove; 1456 spc, sphenopalatine canal. Scale = 1cm. 1457 1458

1459 1460 1461 FIGURE S7. Illustration of the position of the sphenopalatine and palatine canals in relation to the nasopharyngeal 1462 canal in Euphractus sexcinctus (AMNH 133304), Vassallia maxima (FMNH P14424) and Glyptodon sp. 1463 (MNHN.F.PAM 760). A. Selected slides (numbered according to their position in the image stack) indicated on the 1464 cranium in lateral view. B. Slides in coronal view. C. Canals are indicated on cranium in transparency in lateral view 1465 (same as A). The same colors were used for canals: orange, palatine canal; yellow, sphenopalatine canal. 1466 Abbreviations: npc, nasopharyngeal canal; plc, palatine canal; plg, palatine groove; spc, sphenopalatine canal. Scale 1467 = 1 cm.

1468 1469 1470 FIGURE S8. Identification of the canal for the ramus superior of the stapedial artery in Tolypeutes matacus (FMNH 1471 28345). External opening is illustrated on a cranium in ventral view with a focus on the auditory region. Canal 1472 trajectory in relation to the other braincase canals is representing on a transparent cranium in lateral view with a focus 1473 on the neurocranium. Several parts of the canal (external opening, contact with the orbitotemporal and posttemporal 1474 canal, etc.) are also illustrated by numbered slides (in relation to the total number of slides) and indicated on the crania. 1475 Abbreviations: cevc, capsuloparietal emissary vein canal; crsu, canal for the ramus superior of the stapedial artery; 1476 otc, orbitotemporal canal; otg, orbitotemporal groove; ptc, posttemporal canal. Scale = 1 cm.

1477 1478 1479 FIGURE S9. 3 Different cases of contact/non-contact between the three braincase canals analyzed in our study 1480 (including the region of confluence) in Tolypeutes matacus (FMNH 28345), Euphractus sexcinctus (AMNH 133304) 1481 and Glyptodon sp. (MNHN.F.PAM 760). Selected slides (numbered according to the total slide number) are indicated 1482 on cranium in lateral view and canals are colored on one side of each slide. Abbreviations: cevc, capsuloparietal 1483 emissary vein canal; cevg, capsuloparietal emissary vein groove; ptc, posttemporal canal; rc, region of confluence; 1484 rtc, ramus temporalis canal. Scale = 1 cm.