Endocast measurements for <i>Hyopsodus</i> (given in mm, and mm³ for endocast volume).

<p>R = right side of specimen; L = left side of specimen;</p><p>* = <i>H. paulus</i> (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030000#pone.0030000-Gazin2" target="_blank">[35]</a>, pl. 1);</p><p>** = <i>H. miticulus</i> (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030000#pone.0030000-Gazin2" target="_blank">[35]</a>, pl. 5).</p

Data for brain size estimate of basal ungulates.

<p>EV, endocast volume; EBM, estimated body mass; EQ1, encephalization quotient using Radinsky's <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030000#pone.0030000-Radinsky2" target="_blank">[20]</a> equation; EQ2, encephalization quotient using Eisenberg's <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030000#pone.0030000-Eisenberg1" target="_blank">[39]</a> equation.</p

Illustration of the protocol used to quantify the endocranial petalias.

<p>A: 3D models of the skull (grey) and of the virtual endocast (yellow) of Cro-Magnon 1 displayed at different levels of transparency. 3 landmarks are positioned on the skull (G: glabella, B: basion, I: inion) and 4 on the endocranial surface (RFP, LFP: right and left frontal poles, ROP, LOP: right and left occipital poles). B: superior view showing a line (L1) traced through glabella and inion. Frontal and occipital poles are orthogonally projected on this line. The distance between the projected images of the points corresponds to the antero-posterior component of petalia (see details for the frontal poles). C: lateral view showing a second line (L2) traced through basion orthogonally to the first line. The 4 endocranial points are projected orthogonally on L2 and the distance between the projected images of the points corresponds to the vertical component of petalia. D: the 4 points are projected orthogonally on the plane defined by the two lines and the difference between the right and left side for this lateral distance constitutes the lateral component of petalia.</p

Dorsal view of some basal ungulates.

<p>Reconstructions made after the original cranial endocasts of: (A) <i>Phenacodus</i> (AMNH 4369), (B), <i>Meniscotherium</i> (AMNH 49082), (C) <i>Hyopsodus</i> (AMNH 143783), (D) <i>Pleuraspidotherium</i> (MNHN CR 252, 963), (E) <i>Arctocyon</i> (MNHN CR 700), (F) <i>Cebochoerus</i> (MNHN 34–1967), (G) <i>Hyracotherium</i> (AMNH 55267). All specimens normalized on the neopallium length. Proportions of the different parts indicated in percent of the total endocast length: black, rhinencephalon; red, neopallium; blue, mesencephalon; green, cerebellum. Not to scale.</p

Labelled endocast and basicranium of <i>Hyopsodus lepidus</i> (AMNH 143783).

<p>Reconstruction illustrated in left lateral (A), dorsal (B), right lateral (C), ventral with basicranium (D), ventral without basicranium (E), and posterior views. Abbreviations: cas, cavernous sinus; cc, condyloid canal; cdf, condyloid foramen; ci, colliculi inferior; cf, condylar foramen; cs, colliculi superior; fl, paraflocculus; flm, foramen lacerum medium; flp, foramen lacerum posterius; fo, foramen ovale; fp, fissure prima; hy, hypophysis; ips,inferior petrosal sinus; lal, lateral lobe of cerebellum; las, lateral sinus (or transverse sinus); los, longitudinal sinus; mf, mastoid foramen; mo, medulla oblongata; ms, mesencephalon; mv, mastoid vein; np, neopallium; ob, olfactory bulb; oc, occipital condyle; op, olfactory peduncle; os, occipital sinus; ot, olfactory tubercle; pb, petrosal bone; pgf, postglenoid foramen; pil, piriform lobe; rhp, rhinal fissure; sc, sinusal canal; tf, temporal foramen; ts, temporal sinus; vc, vermis cerebelli. Scale bar = 1 cm.</p

Reconstruction of the lateral view of <i>Hyopsodus lepidus</i> compared with other basal ungulates.

<p>Reconstructions made after the original cranial endocasts of: (A) <i>Hyopsodus lepidus</i> (AMNH 143783), (B) <i>Pleuraspidotherium</i> (MNHN CR 252, 963; cast AMNH 39266); (C) <i>Phenacodus</i> (AMNH 4369); (D) <i>Meniscotherium</i> (AMNH 49082; USNM 19509); (E) <i>Arctocyon</i> (MNHN CR 700), modified after Russell and Sigogneau (1965). Not to scale. Abbreviations: same as <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030000#pone-0030000-g002" target="_blank">Figure 2</a>.</p

Simplified phylogenetic relationships among basal ungulates, modified after [<b>36, fig. 11B</b>].

<p>Simplified phylogenetic relationships among basal ungulates, modified after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030000#pone.0030000-Ladevze1" target="_blank">[<b>36, fig. 11B</b>]</a>.</p

Working hypotheses on the relationships between OES/EDJ morphologies

<p>OES, occlusal enamel surface; EDJ, enamel-dentine junction; OPC, orientation patch count The four hypotheses on how the OES echoes EDJ morphology are considered Following hyp^#1 the correlation between the EDJ and the OES is expected to be total and both organs are expected to show the same amount of occlusal complexity (OPC); hyp^#2, the correlation between the EDJ and the OES is expected to be high and both organs are expected to show different amount of occlusal complexity; hyp^#3, the correlation between the EDJ and the OES is expected to be low and the OES is expected to show greater amount of occlusal complexity; hyp^#4, the correlation between the EDJ and the OES is expected to be low and the OES is expected to show lower amount of occlusal complexity.</p

Level of correlation between EDJ and OES for topometrical signifiers within the primate sample

<p>The correlation coefficient (r) is displayed for elevation (black profile), inclination (red), orientation (orange) and mean curvature (yellow) for each specimen (black dot) Dotted lines correspond to the average correlation level for each topometrical signifier.</p

Topometrical individual OES/EDJ correlations relative to average occlusal enamel thickness (mm) of size standardized molars

<p>(A) Elevation (B) Mean Curvature (C) Orientation (D) Inclination The tridimensional maps (upper row) illustrate OES (right) and EDJ (left) topometrical data and enamel thickness data (left corner box) used for computing correlations (gorilla molar is shown). For visualization purpose, only extreme concave and convex values are shown on Mean Curvature tridimensional maps. Convex hulls delimit respectively platyrrhines (circles), cercopithecoids (triangles), non-human hominoids (diamonds) and modern humans (black diamonds) The coefficients of determination (R2), correlation (r) and p-value are given for each regression line between the EDJ/OES correlation and 3DET^STD (blue) 3DET^STD, average occlusal enamel thickness of size standardized molars.</p