Boa aa eon oe 2.5 7 a 2 $ * . 4 ™. Sieg. Wes a Fo ied Vee tot Pores pees . . Siw 3 . 2 . Te oan ae oe ae er ee iis Peery . . a ee Sa Sa Cai ie iy - HARVARD UNIVERSITY EEL Ash LIBRARY OF THE Museum of Comparative Zoology a ar : . i THE PEABODY MUSEUM OF NATURAL HISTORY BULLETIN 2 1b,3 67 THE OSTEOLOGY OF ||. EPOREODON SOCIALIS MARSH BY MALCOLM RUTHERFORD THORPE, Px.D. NEW HAVEN _ THE PEABODY MUSEUM OF NATURAL HISTORY YALE UNIVERSITY 1931 PEABODY MUSEUM OF NATURAL HISTORY TRUSTEES JAMES Rowianpd ANGELL, Pu.D., Lirr.D., LL.D. ALFRED LAWRENCE Ripiey, M.A. JouHN VituierRs Farwei, M.A. Epwin Musser Herr, Sc.D. CLARENCE BuakesLer, M.A. Rev. Winwiam Apams Brown, Pu.D., D.D. DIRECTOR Ricuarp Swann Lut, Pu.D., Sc.D. CURATORS Epwarp Sauispury Dana, Pu.D., Curator of Mineralogy, Emeri- tus. Cuartes Scuucnert, LL.D., Sc.D., Curator of Invertebrate Paleontology, Emeritus. Srantey CritTENDEN Batu, Pu.D., Curator of Zoology. Cart Owren Dunsar, Px.D., Curator of Invertebrate Paleon- tology. Witiiam Esenezer Forp, Pu.D., Curator of Mineralogy. Grorce Grant MacCurpy, Pu.D., Curator of Anthropology. Cornetivus Berrien Oscoop, Pu.D., Assistant Curator of An- thropology. Axsert Emr Parr, M.A., Curator of the Bingham Oceano- graphic Collection. Matcotm RutrHerrorp TxHorrr, Px.D., Curator of Vertebrate Paleontology. DOCENTS Dorotuy Emma Arno;p, B.A. GertruvE Horcurtss Ciark. Miuprep Cyntruia Bevan Porter, M.A. RESEARCH ASSOCIATES Grorcr Grant MacCurpy, Pu.D., Research Associate in Prehis- toric Archeology. Matcotm Ruruerrorp Tuorrr, Pu.D., Research Associate in Vertebrate Paleontology. ui nin ; i - | adi | THE PEABODY MUSEUM OF NATURAL HISTORY BULLETIN 2 THE OSTEOLOGY OF EPOREODON SOCIALIS MARSH BY MALCOLM RUTHERFORD THORPE, Pux.D. NEW HAVEN THE PEABODY MUSEUM OF NATURAL HISTORY YALE UNIVERSITY 1931 oe eh Tote \ iy Aa: ‘ish vA eo a i Ts ok. 1 4 i yn 1 CONTENTS Page Introduction and summary OSE ranting OF ons tanene Ine 5 BEEOMOSC HORIZON o's) es me se “4 2 SEVEIL G3) (0) SAP oe gn a Skull er a bas eae a rahe ey mad eae Vertebre 4 de AON i a RO & SOS eT Ua OES ema | fpr Oe kee ees ek wa Oe eg ll et te a@ Eependicular SkeletOnys “owe aie eee te | ey ae OO G/U CARR ecg ae ane es SC ee a ere Humerus PR ore, thd Cat ay ode ANC nS miso 8 MR peaepibs TN Cly UUbTPER SS 9. vor es hee terauhen tt porn Besa tite Re eee. Un OS STDS SE en ee ee ean merce alee mY abs Red? 1) Pelvis 1g gle A ge SRC CYPRUS reall tr i ome RAY NES | 6 LO STIEULS = | SN aps emily Seo gE A Paar Same de” J Ub neat RR ES 3 Mbitamatily Mba gc. ee eh |, Mage eee halve eo = Nee ee SEE gree sytem Al Baath 9 a thd! ibs beatin aimed (ORC MC STAN NS Se ator’ Mee M4 4 : HY. i (tanh Bayt r @ T ‘ INTRODUCTION AND SUMMARY ROFESSOR Marsh’ established the genus Eporeodon in March, 1875, upon the presence in the skull of prominent auditory bulle, a larger bodily size, and characteristic of a higher geologic horizon, as distinguished from Merycoidodon. He could have used the loss of the pollex on the manus and the total absence of the foramen rotundum in the skull as addi- tional distinguishing characters. Of the thirteen species of Eporeodon already described, two were erected by Professor Marsh, the type specimens of each being in the Peabody Museum of Natural History at Yale Uni- versity. These species are E. occidentalis (the genotype) and E. socialis. Except for occasional references by the author in earlier pa- pers, no description of E. socialis has been written, and it is now proposed to describe in detail the various skeletal elements of this form. Professor Marsh figured the superior view of the skull, with the brain in position and the fore and hind feet, in 1884, and the feet again in 1885, but with no text description in either instance. The cotypes on which E. socialis Marsh is founded were col- lected for Professor Marsh on August 17, 1874, at Scotts Bluff, Nebraska, by M. H. Clifford and A. S. Shelley. The two skeletons lay side by side, the skulls being three inches apart and the vertebral columns nearly parallel. These and other specimens collected at that locality were transported overland to Julesburg, Colorado, and from thence to North Platte, the nearest railway shipping point at that time. These two cotypes are numbered 13118 and 13119, Y.P.M., and the latter was mounted a few years ago. Cat. No. 13118 is about one-third smaller; the leg bones are slightly smaller and shorter, and the length of each individual vertebral centrum is less than those of the other skeleton. The 1 Marsh, O. C. Am. Jour. Sci. (3), vol. IX, 1875, p. 249. 6 PEABODY MUSEUM OF NATURAL HISTORY skulls show almost no differences. Both animals were fully adult, and the smaller may have been a female. The bones of both cotypes were enclosed in Brule clay. The skeletal elements have been compared with those of a specimen of Sus scrofa, Cat. No. 01580 Y.P.M., with which Eporeodon socialis corresponds very closely, except in the skull and dentition. These Oligocene forms must not be considered as the direct ancestors of the modern Suide, for in many respects the Merycoidodontide are more like T'ragulus (chevrotain) than the Suide, though in others they resemble the suillines. Therefore, while it was more convenient in the preparation of this paper to compare Eporeodon with Sus, a form available to all students, it must not be considered that its affinities are necessarily all with the Suide. These eporeodonts were gregarious and roamed the plains and forests in herds. They must have been well able to protect themselves, fighting other animals after the manner of the modern peccaries, which are known to tree animals as large and ferocious as the jaguar. Undoubtedly the eporeodonts drew their sustenance mainly from grasses and roots, as indicated by their selenodont dentition. Their canine teeth in both upper and lower dental batteries were well adapted to cutting, and their almost claw-like distal phalanges could have dug up roots easily. The climate in the late Oligocene, when these animals lived, was equable and warm. Dr. G. R. Wieland personally stated that in his opinion, the climate of Wilmington, Dela- ware, approximates very closely that of the upper Oligocene period in the Great Plains area. In connection with this paper I am very appreciative of the friendly criticism of Professor Lull, and I am greatly assisted by Mr. R. Weber’s illustrations which admirably show the de- tails of the various skeletal elements. “4X (adaoyy, 1233 Vv ) ‘SIIEL “ON “}eD addjoy jo [[Nys Jo ysvo YM “W'd'A GLISL ON “WO eddqoD ‘ysaey syym008 uopoasodgy Jo uoxEYs payunoy, “fT ‘BI “AX ‘adAjoRd “| “SI JO aSloaoy “Ysaey s2yyQ008 uopoasod sy JO UOIZBALOYSat YSoT '°Z “SIA GEOLOGIC HORIZON HE White River deposits, divided into a lower, the Chadron formation, and an upper, the Brule clay, com- prise the strata in the Scotts Bluff area. They are both fresh- water deposits. The sandy coarse sediments of the Chadron in- dicate a more rapid flow of the streams, while the Brule clays, of much finer material, show that the currents were less strong and that the local lakes and flood plains were of much greater extent. At Scotts Bluff the Chadron is scarcely exposed and the Brule formation is about 500 feet thick, forming the outcrop- ping rock on all sides of the Bluff. These sediments consist chiefly of pinkish to buff-colored clays, with thin-bedded sand- stone and limestone strata near the bottom, while near the top are two beds of volcanic ash, separated by about 100 feet of pinkish to buff clays. The volcanic material was probably transported from the Rocky Mountain or Black Hills regions, either by wind or stream action or by both, and deposited in the lakes. In the Scotts Bluff area this fine-grained clay holds its typical character to the top of the formation and does not carry the sandstone strata which are found farther north and charac- terize the Protoceras beds. AXIAL SKELETON SKULL HE greatest differences between Eporeodon socialis and Sus scrofa are found in the skull. The skeletal parts of the Suid have remained fairly uniform and their characters very persistent, exclusive of the skull, from the Eocene to the pres- ent. Likewise the various genera of the Merycoidodontide show a great similarity in their skeletal elements, with the exception of the skulls, where the effects of evolution are chiefly centralized. The skull of the larger individual, Cat. No. 13119, is not so well preserved as that of the other, Cat. No. 13118, which will be used for descriptive purposes. A cast of the latter skull has been placed on the mount. All of the other skeletal elements de- scribed are in the mounted skeleton of the larger animal. The skull of Eporeodon is similar in general aspect to that of the oreodonts which have been so accurately described by Leidy, Cope, and Scott. Lateral view. With the mandible, the lateral surface is rec- tangular in Eporeodon (Fig. 3) ; in Sus (Fig. 4), triangular. The upper contour is nearly straight, whereas in Sws there is a gentle slope upward to the supraorbital foramina, from which point the frontoparietal slope is straight and sharply upcurved to the occipital crest. The skull of Sws is long with a greatly lengthened facial section, while in Eporeodon the skull is a lit- tle shorter with the facial segment very much shorter abso- lutely. The zygomatic arches are stronger and higher than in Eporeodon; in both they are flattened from side to side. The zygomatic process of the temporal bone curves sharply upward posteriorly and forms a rounded recurved projection above and anterior to the meatus acusticus externus, similar to that found in Promerycocherus, whereas Eporeodon differs materially from this in that the zygomatic process does not trend upward but is nearly straight, terminating posteriorly above the pos- terior margin of the postglenoid tubercle. The orbits are closed, AXIAL SKELETON 9 but those of Sus are open, as in Protoreodon and Agriocherus. The orbits of Eporeodon are relatively slightly larger, but the position in both is about the same with respect to the line of vi- sion. They are placed very near to the center in proportion to the total skull length in Eporeodon, but in Sus their position is very much farther back, being approximately two thirds the distance from the prosthion. This difference is due to the greater absolute lengthening of the face in Sus. The anterior orbital margin is very thin in Eporeodon, due to the deep lac- rimal pit (fossa) ; in Sws it is thick and rounded. The lacrimal fossa in the former is deep and circular; in the latter there is no corresponding pit but rather a broad shallow depression, formed in contiguous parts of the lacrimal, malar, and maxil- lary bones. Neither Agriocherus nor Protoreodon possesses a lacrimal fossa. The fossa for the attachment of the ventral oblique muscle of the eyeball is situated just inside of the an- teroinferior orbital margin and is much more pronounced in Sus. The infraorbital foramen of the latter, relatively a little larger than that of Eporeodon, is located above the anterior portion of the fourth premolar ; that of the other genus, nearly above the center of the third premolar. The posterior edge of M? is almost directly below the temporal process of the malar bone, while that of Sus has a position below and only slightly posterior to the anterior border of the orbit. The canine of Sus stands about midway between the premaxillary border and the infraorbital foramen. It is directed sharply outward, downward, and then upward and is much flattened. In Eporeodon this tooth is located beneath the anterior tip of the ossi nasi, is di- rected straight downward, and is trihedral in shape with the inner flat side at right angles to the sagittal plane. Owing to the much greater relative size of the premaxilla in Sus, the three incisors are plainly visible from the side view, but in Eporeodon the third incisors are seen, while the second are very slightly visible and the first not at all. In the latter they in- crease in size from first to third, while in the former they de- crease from first to third. In Sus the temporal fossa is entirely 10 PEABODY MUSEUM OF NATURAL HISTORY PotSof m Ss * ~\ Wy W < “ wv SS SS 4 \\ i RN | Zs Yj Ni \\ a A\\\i, ! ao Yom,” ( aly Fig. 3. Lateral view of skull and jaws of Eporeodon socialis Marsh. (am, angle of mandible; cp, Pm, or caniniform premolar; eam, external auditory meatus; f, frontal; if, infraorbital foramen; /f, lacrimal fossa; m, malar or jugal; mf, mental foramen; mp, mental prominence; mx, maxilla; n, nasal; 0, occipital; oc, occipital condyle; p, parietal; pce, parietal crest; pg, postglenoid process or tubercle of squamosal; pmax, premaxilla; pof, postorbital process of frontal; pp, paramastoid process; s, squamous temporal bone; sof, supraorbital foramen; zpt, zygomatic process of temporal bone.) Cotype Cat. No. 13118 WPS MoSc: lateral and its long axis nearly vertical, but in the other genus this fossa is lateral only in the squamous portion of the tem- poral bone and its long axis is very nearly horizontal. The length of the fossa along its greater axis is, relatively, con- siderably more than in Eporeodon. The postglenoid tubercle in Sus is extremely small and unimportant, but in Eporeodon it is very large and robust, being 13 mm. in length below the ven- tral surface of the temporal condyle, while its anteroposterior diameter is 10 mm. The horizontal ramus of Sws is broader and transversely heavier but has a smaller vertical diameter; the angle of the condyle is relatively weaker and does not have the rugosities for AXIAL SKELETON 11 eamaft * tt ek ie Fig. 4. Outline of lateral view of skull and jaws of Sus scrofa Linnezus. (For legend, see Fig. 3.) x14. muscle attachment so well developed as in Eporeodon. 'The condyles are ridge shaped, but in Sus they are rounded and knob-like. The ascending ramus is broader anteroposteriorly than in Sus. The slope of the symphysis is nearly the same in both. The inferior canine (P,) is vertically triangular and not at all recurved, while that of Sus is strongly recurved back- ward. The incisors are very much heavier and very much more laterally placed than in Eporeodon. Their direction is nearly 45 degrees from the alveolus, but those of Eporeodon are slightly more nearly vertical. There is a short diastema between the true canine and the first premolar (caniniform premolar) and none between that and P., but a relatively large one be- tween the true canine and P, in Sus. The last three premolars are crowded so that their long diameters are oblique to the line of the mandible. Such is not the case in the other genus. 12 PEABODY MUSEUM OF NATURAL HISTORY toc poe ff \s AW, SUNN y WX * Lyi puel'¥ Hg Cad, 7. vy, TIF, ‘ ee . WD S .. > EL? Ls MUD Ze COUT: s Za. sof Fig. 5. Superior view of skull of Eporeodon socialis Marsh. (apf, anterior palatine foramen; f, frontal; if, infraorbital foramen; /f, lacrimal fossa; mz, maxilla; n, nasal; me, supraoccipital or nuchal crest; p, parietal; pce, parietal crest; pma, premaxilla; poc, postorbital constriction; pof, postorbital or su- praorbital process of frontal; s, squamosal; sof, supraorbital foramen; za, zygomatic arch. Cotype Cat. No. 13118 Y.P.M. x. Superior view (Figs. 5 and 6A). The most apparent differ- ence between the skulls of Sws and Eporeodon is that the former has a great lengthening of face. The nasals form a narrow ridge, with a slightly concave crest throughout their entire length. The maxillary bones flare along the alveolar border. In Eporeodon the face is filled out so that in cross section it is ovate with the end truncated. The supraorbital foramina in Sws are on a transverse line with the anterior rim of the orbits; in the other they are situated nearly on a line drawn trans- versely through the middle of the orbits. The grooves leading from these foramina in Sus are directed slightly inward and forward to the nasals, and then they turn ventrolaterally above the infraorbital foramina; those of Eporeodon are less pro- nounced and follow the same general course, but they vary somewhat in different specimens. In the latter the parietal bones terminate in a medial crest, forming a sharp ridge be- tween the junction of the frontals and the nuchal crest 57 mm. AXIAL SKELETON 13 mes yp pe f fof za sof Pale ape ee Fig. 6A. Outline of superior view of Sus scrofa Linneus. (For legend, see Fig. 5.) x. long, but in Sus the parietal crest, broad and flat, forms the continuation of the frontal ridge from the supraorbital proc- esses of the frontals to the nuchal crest, and the two sides do not meet. The length of the parietal crest, including the frontal crest, is 63 mm. The superior view of the Sus cranium shows a nearly equilateral triangle, whose base is a transverse line between the supraorbital processes of the frontals and whose sides are formed by the parietal crests. The apex of the triangle is truncated by the nuchal crest. In Eporeodon the cranial area is very differently shaped, being more like that of the White River Felide and not at all hog-like. There is no postorbital constriction, or, if any, it is but extremely ill de- fined, in Sus, while in Eporeodon it is as well marked as in the Carnivora. The wings of the nuchal crest of Sus are approxi- mately 32 degrees from the sagittal plane, and those of Eporeo- don are about 48 degrees. The zygomata are slightly more out- wardly curved in Sus than in Eporeodon, where they are nearly straight. The glenoid portion of the temporal is considerably heavier than in Sus. The lacrimal fosse produce a marked pre- orbital constriction not found in the former. The outline of the Sus skull, as seen from above anteroposteriorly, is oblongate to the infraorbital foramina, then roughly triangular with the base a little posterior to the temporal condyles, while with the other genus it is triangular to the anterior border of the orbits, then oblong to the temporal condyles, ending in a small triangle whose apex is the nuchal crest. As stated above, the temporal 14 PEABODY MUSEUM OF NATURAL HISTORY Fig. 6B. Outline of inferior view of Sus scrofa Linnzus. (For legend, see Fig. 7.) x4. fossa in Eporeodon is very much larger than in Sus. The ca- nine alveolus is very much heavier and more prominent in Sws. The total length of the parietal bone, measured along the sagit- tal plane, is 44 mm., and in Eporeodon it is 69 mm. The pre- maxillaries are well developed and separate, although in con- tact in the median line. The other species of the Merycoido- dontide, except Agriocherus, where the premaxillaries are re- duced and not in contact in the median line, either have them separate but in contact or codssified at their tips. Inferior view (Figs. 6B and 7). The distance from the prosthion to the maxillary-palatine suture, measured along the sagittal plane, is 130 mm., but in Eporeodon it is only 92 mm. The tooth rows in both are parallel and about the same distance apart. The molars of both increase in size from first to third. The length of the tooth row from C to M® inclusive is 116 mm., and in Eporeodon it is 100.5 mm. The pterygoid process of the palatine terminates in a very small knob, and the whole process extends backward and slightly downward, while that of Sus turns abruptly downward, ending in a heavy knob (hamular process). The sphenoid bone is quite prominent and extends laterally for 12 mm. in Sus, thus being dissimilar to Eporeo- don. The basicranial axis is nearly parallel to the plane of the palate, but in the latter genus it is directed upward from the basion and obliquely to the plane of the palate. The bulle are AXIAL SKELETON 1 Or “2.0 ae ay KLIN oe 4 hee it ' ANWR ' ; it st qgfsth) sf eR oc pp te fim fo jp Fig. 7. Inferior view of skull of Eporeodon socialis Marsh. (apf, anterior palatine foramen; 6, tympanic bulla; ba, basion; bo, basioccipital; cf, condylar or hypoglossal foramen; flm, foramen lacerum medius and anterior opening of carotid canal; flp, foramen lacerum posterius; fm, foramen magnum; fo, fora- men ovale; gf, glenoid fossa; oc, occipital condyle; p, prosthion; pg, post- glenoid process of squamosal or glenoid tubercle; pgf, postglenoid fossa; pp, paroccipital or paramastoid process; ppf, posterior palatine foramen; ptp, pterygoid process of palatine; sf, sphenoidal fissure or foramen lacerum an- terius; sm, stylomastoid foramen; sph, sphenoid or basisphenoid bone; te, point of articulation of tympanohyal element of hyoid arch. Cotype Cat. No. 13118 Y.P.M. x. much inflated, this being the major factor on which Professor Marsh erected the genus Eporeodon. These bulle are oval shaped, occupying the area bounded by the foramen ovale, glenoid tubercle, paramastoid (paroccipital) process, and parts of the basioccipital and basisphenoid bones. The bulle of Sus are triangular in outline with the base set slightly ob- liquely to the basisphenoid bone. They do not occupy relatively as much area as in Eporeodon. The postglenoid tubercles are prominent in this latter, extending 14 mm. below the inferior surface of the temporal condyles. The paroccipital processes are transverse but laterally compressed in their inferior por- tions. The external auditory meatus is relatively large and situated just anterior to the base of the paroccipital process. In some specimens of Eporeodon the anterior portion of the 16 PEABODY MUSEUM OF NATURAL HISTORY meatus is expanded to form a wing, but in the cotypes this part is imperfectly preserved. Foramina. The tympanohyal pit is deep, and the stylomas- toid foramen is situated externoposteriorly to it. These fora- mina are separated by a thin ridge of bone, and the latter is very much smaller than the former. The opening of the stylo- mastoid is a groove rather than a pit. There is a deep pit for the postglenoid foramen. The condylar foramen and the fora- men lacerum posterius are in their normal position. The carotid canal is very small, while the foramen lacerum medius is large and located slightly anterointernally to the bulla. The foramen ovale is small and lies just anterior to the bulla. The foramen lacerum anterius (sphenoidal fissure) is relatively large. Osborn and Wortman first stressed the fact that the foramen rotundum is entirely lacking. Merycoidodon possesses this foramen very well developed. In Eporeodon bullatus Leidy “the foramen rotundum is represented by two very minute vestigial foramine at the sides of the pterygoid plate, between the sphenoidal fissure and the ‘foramen ovale.’ ”* The authors further state: “It is more than probable that these will be found wanting in many specimens of this species. In our speci- mens they certainly could not have been functional, and there can be little doubt that the superior maxillary nerve made its exit through the sphenoidal fissure. The foramen rotundum therefore may be said to be practically absent.” Eporeodon bullatus is a transitional form, both in its structure and in its stratigraphic position, between Merycoidodon and the true Eporeodon. The complete loss of the foramen rotundum in the latter indicates a very wide gap in the evolutionary series be- tween this genus and the former, in which this foramen is al- ways present. Dentition. The formula of the permanent dentition of Eporeodon and of Sus is 13, C1, P4, M3, forty-four teeth 1 Osborn, H F., and Wortman, J. L. Fossil Mammals of the Lower Miocene White River Beds. Collection of 1892. Bull. Am. Mus. Nat. Hist., vol. VI, art. vii, p. 218, 1894. AXIAL SKELETON a7 in all. The apparent fourth lower incisor is about twice the size of the third true incisor and is the true canine with incisi- form characteristics. The inferior incisors extend obliquely upward and forward, while the superior ones extend slightly forward and downward, with their crowns pointing wholly downward. The shape of the superior ones is that of an ovoid, convex externally and excavated internally, with sharp edges, while that of the inferior incisors is more like a trapezoid, with nearly flat external outer surfaces and convex inner ones. ‘There is no diastema in the lower mandible between the incisors and true canine and but a slight one between the canine and the caniniform premolar, and none, or only an extremely small one, in the upper jaw between the incisors and canine. The superior canine curves slightly backward and outward, but strongly downward. Its shape is trilateral, sharp pointed, with its sides nearly equal and almost straight. One side is set transversely to the sagittal plane. The inner face has a deep median groove, starting at the base of the crown and gradually dying out downward. The angular interval between the inferior canini- form premolar and true canine received the superior canine. The inferior canine (P,) is directed forward, outward, and up- ward. It is placed obliquely in the jaw, strongly convex on its outward face and but slightly convex inwardly. It is laterally compressed, and its edges are acute. The tips are truncated obliquely forward from wear. The crown resembles that of the second premolar, except that the latter is smaller and has an internal ridge. This premolar is also obliquely placed in the jaw. From the position of this functional canine and its close resemblance to the premolar, as well as the presence otherwise of an excess number of incisors, it is without doubt a canini- form premolar and is so considered in this paper. Both upper and lower functional canines are of about the same length but of different shape in each set. The superior canine is separated from the first premolar by a short diastema which received the point of the inferior canine. There are four premolars above and four below. The upper 18 PEABODY MUSEUM OF NATURAL HISTORY ones increase successively in size from first to fourth. The an- terior three are of the same pattern—oblong in basal outline, medially divided in an anteroposterior direction by an acute ridge, terminating in an apex. An internal medial transverse ridge joins the apex with the base of the crown. The external face is slightly convex, and the internal is excavated on each side of the median transverse ridge, the posterior excavation be- ing the larger. The posterior transverse diameter is greater than the anterior in all of these three superior premolars. In these same teeth the anterointernal excavation is divided an- teriorly by a short ridge connecting the main fore and aft ridge and the cingulum, forming a very small anterior pit above the cingulum. The posterior excavation of the third premolar re- sembles an additional lobe, similar to the internal lobes of the molars. The fourth premolar consists of two transversely placed crescent-shaped demiconoidal lobes quite similar to the molars, but relatively larger. The outer face is concave, divided by a very slight ridge. A minute diastema exists between the first and second premolars on the right but not on the left. The lower premolars are of a somewhat different pattern. The second and third are obliquely placed in the mandible, com- pressed oval shaped, with an anteroposterior acute median ridge terminating in an apex. A median internal ridge connects the apex and cingulum. This ridge is not transverse to the main one, but forms an acute angle posteriorly, surrounding a shal- low fossa. The anterior fossa is shallower and larger. The fourth premolar is more oblong shaped, and the internal me- dian ridge is situated nearly at right angles to the anteropos- terior one. Its internal border is approximately as high as the main apex, thus forming a deep pit in the posterointernal part of the tooth and a deep concavity on the anterointernal part. The true molars are three in number. Among recent rumi- nants they resemble those of the deer more closely and are in- serted by fangs only. In both series they increase in size from first to last and consist of four crescent-shaped demiconoidal lobes. The superior molars are nearly square, while the inferior AXIAL SKELETON 19 are slightly greater anteroposteriorly, except M;, which has an extra posterior lobe, producing a greater length in the antero- posterior diameter over the transverse. The pattern of both series of molars is essentially the same. Anteroexternally the lobes form prominent buttresses, laterally compressed at their outer extremities and expanded near the base of the crown. The line of the lower molars is situated well within the outer portions of the upper. The teeth of Sws are so unlike those of Eporeodon in pattern that a comparison would be of no value here, since their struc- ture is so well known. The teeth of Agriocherus also show wide departures from the true selenodont type, resembling those of Hyopotamus, except for the absence of the anterior interme- diate cusp of the molars. MEASUREMENTS OF SKULL OF EPOREODON mm. PersrMOMuete DASLOR “ye sah es ne ec te, LOB: Prastiaon to occipital condyles’ 29-20 2 ws ts lw «GD BSEGNEMGULLOMMASION TY ii ,0 hy nash oes SS a eh a ee LOOSE Pease Mion tor bregma. 6 Sac ae eo fe) el he ore Vee oa DBS Masinhat Gr pTegmMa ie Want. eta ee ie er RO me ee a GS PREC EON BRECON cH ro tas ind Pisa eta baie ds Ms og peace a ec NL Oe Eee OM or CISCO KR | 6.4.) sb sr be Sais us hag lh Re vee Ae ask BME Eee ISL Ot SOLLINCLED, gir ior ta y dsicgrie: es Nesy ueteten pha Daremineeao OOk Biparamastoid diameter at inferior border of occipital condyles 43.5 Nvidth-of ocetput above basion: 24.6006) 3 on ee a Be GD Pviatheot postorbital constriction. (oo. oe ese. sn SDT Maximum transverse diameter at postorbital arches . . . 86.7 Maximum transverse diameter of cranium . . . . . . Oi. Maximum transverse diameter at infraorbital foramina . . 50. hima anterorbital bréeddth:’ 20. a 1 Prosthion: The most prominent part on the alveolar border between the two upper median incisors. 2 Basion: The mid-point on the anterior margin of the foramen magnum. 3 Nasion: The highest point on the internasal suture. 4 Bregma: The point at which the sagittal and coronal sutures meet. 20 PEABODY MUSEUM OF NATURAL HISTORY mm. Anteroposterior diameter of bulla 24.7 Transverse diameter of bulla . 15. Depth of bulla below inferior border of piesoid tabenee 14.2 Depth of paramastoid below inferior border of glenoid tu- bercle ee ey Fo oe 20. Maximum diameter across outside of glenoid tubercle 70.6 Anterior palatal breadth between roots of canines . 25. Anterior palatal breadth at first premolar 30. Posterior palatal breadth at third molar . er ke ULE Length of superior tooth-row, canine to third molar, inclusive 102.7 Length of superior molar series 49, Length of superior premolar series 43.5 Palatal length,°® axial . 112.4 Vertical diameter of orbit 29.2 Transverse diameter of orbit . 27.9 Length of mandibular ramus . 159.5 Length of mandibular symphysis AT 4: Height of coronoid above ramus, vertical 94.5 Height of condyle above ramus, vertical . ‘ 82.2 Length of inferior tooth-row, canine to third molar, inclusive 99.4 Depth of mandible below center of third molar . 38. Width of ascending ramus posterior to third molar . 53. ; Anteroposterior Transverse Superior tooth-row: a ei Tncisor ali.) ree ee Peer 3.7 Incigor 2" Gre savin Wah tea ae ee eae A, 4.7 Tneisorvs? ss “a cep eae ee ees om 5.5 Ganine:. . 4773) Aba eee ee ee 8. 8.5 Premolar 1 at 2-9 pen Poh he i ee an Premolar /2%.5.).20 oP oe Au + ae Oe 8.6 Premolar’8) 20). y 20) a. ue ee el 10.9 Premolar' 4) 5; =.) 92) ne) toe ios oe eee 13.3 Molar 1 ee es ae tee by ryt 25) 15.7 Molar 2 zijlivt ist hae WE oie Loumialigee 19. Molar 3 2 bis 6 he) See ee eee ad 20. 5 Palatal length: Prosthion to posterior surfaces of the maxillary parapets, in axial projection, including the pterygoid processes of the maxille, if present. AXIAL SKELETON 21 4 Anteroposterior Transverse Inferior tooth-row: an, pay Incisor 1 SC eke aks Weck Scenes Bis 4, 3.2 Incisor 2 Se ae ie Sis eae 4.5 3.3 Incisor 3 Sfgeerd acne pu rat) Ra te 4.7 4. CCABIDETT eas sagt Iie Ss lalie las a 6. 6.4 Canmiform premolar’ 5 3. 3 . ALS Ce ipremolare2 siti x6 Gh ee Be 5.7 IPSeMOINr Ge ke nal wast et ae ee EBS 7.3 Rrcmolars aie! hk eS cs A oe oe ATOR 9.8 Molar 1 SOL Coen ar eterno ee oti 11.2 Molar 2 : SP ee ee nA Bae Tae 7 13.2 Molar 3 Bok eth ed = Rorschach en) One 138.5 VERTEBRE The vertebral formula of Eporeodon is C'7, D 13, L6, S 4, Ca 20+ ; that of Sus, C'7, D 14-15, L 6-7, S 4, Ca 20-23. The cervicals of the former are nearly square and those of the latter, short and wide. The anterior articular surfaces of the centra of both genera are slightly convex and their bodies elliptical in cross section, with the greater diameter transverse. Also in both, the posterior articular surfaces are slightly concave, that is, the vertebre are opisthoccelous but not markedly so. A well- developed ventral spine is present in Eporeodon, with none in Sus. The neural canal of the former is nearly circular with a slight convexity of the floor ; of the latter it is wide transversely, and the floor is slightly concave. In addition to the foramen transversarium, which is present in both genera, Sus has an additional foramen (not found in Eporeodon) puncturing the pedicle. The transverse process consists of two branches in both. The small superior branch projects backward and ends in a knobby process, while the ventral branch is an osseous plate extending outward and downward, but in Eporeodon this pro- jects downward, outward, and forward, with its free end con- siderably thickened. The spines increase in size in both from third to last inclusive, but those of Eporeodon are relatively a little longer. In the latter all of them project forward, except 22 PEABODY MUSEUM OF NATURAL HISTORY the seventh (Fig. 8) which is vertical, but the anterior ones of Sus project backward and the posterior, forward. The spine of the last cervical is of great comparative length in Sus, but in Eporeodon it is but little longer and stouter than that of the sixth. Both do not possess the ventral transverse process, but they do have a pair of small facets on the lateral borders of the posterior articular surface for the heads of the first ribs. Fig. 8. Seventh cervical vertebra of Eporeodon socialis Marsh. Fig. 9. Atlas of Eporeodon socialis Marsh. Fig. 10. Axis of Eporeodon socialis Marsh. Cotype Cat. No. 13119 Y.P.M. x. The atlas (Fig. 9) is more nearly square from a superior view than that of Sus, which has a much greater transverse diameter. The articular cavities for the condyles of the skull are relatively shallow in Sus, whereas those of the older genus are deep and large, and the anterosuperior part of the arch overhangs them. The facets for the axis are like those of the deer. The large, round dorsal tuberosity of Sus occupies a cen- tral position in both diameters, but in Eporeodon the tuberos- ity, which is heavy, terminates in a sharp point located nearly over the anteromedial margin. The alar and intervertebral foramina occupy relatively the same position in both genera. The wings are flattened with a heavy posterior tuberosity. The ventral tubercle of HE poreodon is a thick, short, rounded spine, projecting back under the axis, but that in Sus is long and laterally compressed. The posterior articular surfaces of Eporeodon are larger and the anterior more deeply situated than in the other genus. AXIAL SKELETON 23 Exclusive of the dorsal spine of the axis, the larger diameter of this vertebra is transverse, but in E:poreodon it is antero- posterior. The posterior articular surfaces and the dorsal spine are similar in both genera. The anterior articular surfaces of Sus stand nearly vertical to the horizontal plane of the cen- trum, but those of Eporeodon are markedly convex, standing at an angle of about 30 degrees from the perpendicular. E poreo- don has a well-marked ventral spine which Sus lacks. The pos- terior end of the spine is considerably thickened. The floor of the neural canal is medially divided by a ridge of bone 2.2 mm. high, which is not so in Sus. The odontoid process of the axis of Sus is a thick cylindrical rod, whereas that of Eporeodon (Fig. 10) is oval with the longer diameter transverse. Its shape is therefore quite different from that of Sws. The neural canal is oval with the greater diameter vertical, but in the other it is nearly square. The dorsal spine is restored and may be sub- ject to a slight revision. However, I think it was not prolonged so far anteriorly as in Agriocherus, but was rather more like that of Merycoidodon. Eporeodon Sus mm, mm. eneth of atlas, anteroposterior « 9. 2 °s. = 40. 39. Width Ps ree oP iee sh esi Whey y tare ee iy 5d. 67. Heipht of dorsal tuberosity. =. 4. '. 20% a )0e) te oe | 20:6 ay. 38 PEABODY MUSEUM OF NATURAL HISTORY Eporeodon Sus mm. mm. Length of centrum-of saeral3.... : =. . Bz 21.5 Length of centrum of sacrali.4-. .->. 5 3 «. =| AB 22. Width of sacral 1, including transverse process . 64. 68.4 Width of sacral 2, including transverse process . 38. 40. Width of sacral 3, including transverse process . 35. 27. Width of sacral 4, including transverse process . 388. 26. Width across articular surfaces of sacral 1 . . 84. 42. Height, inferior edge of centrum to top of spine, Sacra Ws ahh cee eel aa pk ey eee ra aimee 20.9 Height, inferior edge of centrum to top of spine, Sacha? "4: ke eleeroe Ue ae Gch ace ik eae eee es 14.4 Height, inferior edge of centrum to top of spine, sacral 3 Bah Poh Sy Nt cn Se meta mm LU) 13. Height, inferior edge of centrum to top of spine, sacral Ang sees! £7 shake Ayees Pek att ee ee 19. 12.7 Femur The head of the femur is hemispherical and more exserted from the neck than that of any recent ungulate. The oval de- pression for the attachment of the ligamentum teres is well de- fined. The neck is elongate and constricted, and the great trochanter rises about as high as the proximal end of the articu- lar surface. There is no third trochanter. In fact, these fea- tures resemble those of the carnivore more than of the ungulate type of femur. The digital fossa is deep, which presupposes a relatively large obturator externus muscle. The lesser trochan- ter, situated slightly on the preaxial side, is conical and rela- tively rugose. The intertrochanteric lines are rather indistinct, as well as the linea quadrati. The shaft (Fig. 21) is almost straight and nearly circular in cross section. The linea aspera are faintly indicated. The distal end has a considerable antero- posterior diameter. The outer tuberosity is much more promi- nent than the inner. The internal condyle is the larger and is more rounded than the external. Its articular facet is trans- versely convex. The articular surface of the external condyle is APPENDICULAR SKELETON 39 Fig. 21. Femur of Eporeodon socialis Marsh. Fig. 22. Tibia and fibula of Eporeodon socialis Marsh. Cotype Cat. No. 13119 Y.P.M. x. Fig. 23. Left pes of Eporeodon socialis Marsh. Cotype Cat. No. 13119 Y.P.M. (After Marsh.) x. inclined toward the median line, and the intercondyloid notch is deep. Anteriorly the condyles are continuous with each other, forming a concave depression or trochlea for the patella, which is shield shaped, flattened on top and on its posterior side, and convex anteriorly. TrBIA AND FIBULA The fibula (Fig. 22) is missing, except for its distal end. The shaft is restored and extended the entire length of the tibia, from which it is separated by a narrow interosseous space. The 40 PEABODY MUSEUM OF NATURAL HISTORY external malleolus is larger and wider than the internal and articulates with the astragalus by a triangular facet. It is ex- ternally deeply grooved for the tendons of the peroneus longus and brevis muscles. Its edge is very rugose, affording attach- ment to the external lateral ligament of the ankle joint. The tibia is similar to that of the artiodactyle type, although somewhat suggestive of that of Canis. The spine is prominent and bifid, affording attachment to the semilunar fibro-carti- lages and, by clearly marked depressions in front and behind its base, to the crucial ligaments of the joint. The shaft has three sharp ridges. The internal malleolus projects downward below the external, and it is of peculiar shape, bemg long, stout, and somewhat hook shaped. This hook is received in a deep depression in the astragalus. It has well-marked grooves for the tendons of the tibialis posticus and flexor longus digi- torum muscles and also affords attachment to the internal lat- eral ligaments. Eporeodon Sus mm. mm, Maximum length of pelvis); = =<) = 9a) =) 2» Lolee 182. Length from tuber coxe to tuber sacrale . . . 57.2 78.5 Minimum vertical diameter of illum . . . . Ly: 18.2 Anteroposterior diameter of acetabulum . . . 22.3 26. Transverse diameter of acetabulum . . . . 21.4 26.2 Minimum horizontal diameter of pubis (acetabu- Lary) '.o.ce to Cee beta re ee: on ee re 14.4 10. Minimum vertical diameter of pubis (acetabular) 6.3 6. Length of pubic suture’. 9.7 2 Ne a oe Woe ae 52.7 Maximum width across acetabuli . . . . . 80.8 96. Maximum width across posterior end. . . . 96. 94. Length of left femur from head to medial condyle 168. Pils Maximum diameter across proximal end . . . 40. 4A, Mimimum diameter across proximalend . . . 238. 28. Maximum diameter’across head = =~ 3.) ; )e2ilke 22. Maximum diameter across distalend . . . . 41.5 AT. Maximum diameter across distal end at right an- gles to first.abovye? {si \jie, bo) ae ee eee Oe 37. APPENDICULAR SKELETON 41 Eporeodon Sus mm. mm. Maximum diameter across center of shaft. . . We 25. Minimum diameter across center of shaft. . . 14.5 16. Watavn or, left patella i254 .rioe)