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

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

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

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

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