The materials from Clark Fork and the lower Gray Bull are largely in the collections of the American Museum and Princeton University. Text figures and 34 were provided to me by the kindness of the American Museum of Natural History, most of which had been prepared for Granger's study.
HISTORY OF INVESTIGATION
87 1, and was described in November of that year as Trogosus vetulus
The true affinities of ''P." minor were not recognized until some time later when Leidy saw the tooth. In June of that year Marsh (p. 485) described a fragmentary upper jaw section (fig. 15 of this paper) , not associated Vv'itli lower teeth, to which he gave the name Tillotherimn hyracoides.
NO. 10 TILLODONTIA — GAZIN 5
6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 and considered the lower molars as not unlike those in Ectogamis,
Wortman (1897) was the first to correct the confusion between the genera of tillodonts and taeniodonts, and although his conclusions regarding the edentate relationships of taeniodonts are not in agreement with most later investigators, he laid the foundations of the orders now. This briefly reported the discovery of a nearly perfect atillodont skull in the Huerfanobeds of Colorado, a description of which forms part of this article.
8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121
GEOGRAPHIC AND GEOLOGIC OCCURRENCE
The Bridgerian horizon in the Huerfano, although relatively arid, has yielded a surprisingly large proportion of totillodont remains, including two of the four known slalls and a large number of isolated fragments. From all available evidence, including observations from different seasons in the Bridger, it seems likely that tillodonts are restricted to the lower horizons of the Bridger.
ENVIRONMENT
Although the deposition of a significant portion of the Green River lake beds was placed in the time interval between Era. In the work of Sears and Bradley (1924) and Bradley (1926) the nature of the relationship between lacustrine and older fluvial deposits was clearly demonstrated.
NO. 10 TILLODONTIA — GAZIN II
121 Eventually, during later Green River time, the fluvial phase Eventually, during later Green River time, the fluvial phase, encroaching from the north and west over the former lake beds, bounded the lake area and finally , possibly accompanying diastrophic change. , Green River deposition ended and only the Bridger facies continued.
CLASSIFICATION
NO, 10 TILLODONTIA GAZIN 1
ESTHONYCHIDAE
14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 Trogosinae
SYSTEMATIC REVISION OF THE TILLODONTIA Family ESTHONYCHIDAE Cope, 1883
NO. 10 TILLODONTIA — GAZIN 15
Particularly characteristic of tylodont lower molars is the presence of a metastylid, a small dome about the middle vertically on the posterior slope of the metaconid. However, a large overlap or partial parallel arrangement of subfamilies occurs in the Cathedral Bluff phase of Wind River time.
NO. 10 TILLODONTIA — GAZIN I9
20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121
It is also worth noting that the type of Esthonyx bisitlcatus is the largest of the San Jose species. Type.—Eight separate teeth, including M3 and questionably connected incisors, canine, premolar, and a molar fragment, A.M.
22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121
NO. 10 TILLODONTIA — GAZIN 23
17156 is even less important in the New Mexico collections than the proportions of type E. The Clark Fork specimen included in the above provisional assignment, and to some extent the type, shows the almost intangible condition more typical in large E.
26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 eludes a lower jaw portion with a single molar from the Lost Cabin
Wear occurred only along the front slope of the ridge and at the top. On the other hand, the latter bear a striking resemblance to the much larger, loose teeth, which are interpreted as the third incisors of Tillodon and to some extent PinTrogosushyracoides, although here it appears more hippsodont.
28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121
10 TILLODONTIA — GAZIN 29Discussion.—This particularly large species of Esthonyx is known Discussion.—This particularly large species of Esthonyx is known. This is shown in the lower dentition by the lack of development of the metastylid, the less pronounced hypsodonty of the outer lobes, as well as by the bulging of the cusp, the latter affecting somewhat shallower, significantly less concave basins.
30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121
NO, 10 TILLODONTIA — GAZIN 3I sulcatus specimen the hypocone base has an ahnost periptychid appear-
In these forms, the enamel on the front of the second incisors is not limited to the crown portion and these teeth grow from persistent pulp. The enamel is well distributed over the outer surface of the tooth to a point well below the maximum width of the strongly convex columns.
NO. 10 TILLODONTIA — GAZIN 35
36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121
NO. 10 TILLODONTIA — GAZIN 37
121 Discussion.- The diameter of the incisor in Bridger tillodonts Discussion.- The diameter of the incisor in Bridger tillodonts changes markedly with increased age and wear. 34;B." Although the preserved teeth in this specimen retain their natural form and something of their relative positions in the jaws, the bony portions are much disintegrated, and except for a small portion of the right premaxilla, little can be ascertained about the character of the specimen between I- and Whether such difference can logically be attributed to adimorphic condition is debatable, and with scarcely more than one truly diagnostic specimen representing each of the forms in question, the power of demonstration is lacking, and indeed may be impossible to demonstrate, so that the differences here are asatasonomically preserved.
42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121
10 TILLODONTIA — GAZIN 43 Discussion.- The above isolated tooth is the second type Discussion.- The above isolated tooth is the second type. The main characters attributed to T. latidens resulted from a misunderstanding of the position of the tooth in the dental series. This species is preserved as distinct from Trogosus hyracoides because of the unusually large size of the teeth.
44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121
10 TILLODONTIA — GAZIN 45MEASUREMENTS IN MILLIMETERS OF TYPE SPECIMENS OF TrogOSllS graugeri, MEASUREMENTS IN MILLIMETERS OF TYPE SPECIMENS OF TrogOSllS graugeri,.
46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 Lower dentition
The material was sent to Marsh for study in 1889 and in 1899 the collection was donated by Hills to the National Museum. The crowns of the teeth are missing from the skull and jaws, but casts of P^, M-, and AP have been obtained from impressions in the accompanying matrix. Nevertheless, the basal region, posterior to the pterygoids, is slightly narrower and longer than in the T.
48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 MEASUREMENTS IN MILLIMETERS OF TYPE SPECIMEN OF TrogOSUS hillsH,
NO. 10 TI LLODONTI A — GAZI
49 apparently Ii absent. Marked diastemata separating upper canine from
50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 was found by the writer in beds considered to be low in Bridger B,
THE TILLODONT SKELETON SKULL
The anterior margin of the maxillae and the anterior palatine foramen are far forward on the palatal surface, in a position median to the third incisors, nearly as far forward as in Erinaceus.'^. The nasal wing of the upper jaw is in short contact with the nasal bone and is excluded from cooperation on the anterior edge of the orbit with the lacrimal and cervical bones, except in T. Posteriorly, its opening into the orbital fossa is very large and bounded above by the lacrimal and below by the orbital plate of the maxilla .
NO. 10 TILLODONTIA — GAZIN 55
56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 the posterolateral extremity of the broad lateral portion of the surface
Well posterior to the infraorbital canal, within the ascending plate of the palatine and completely posterior to the orbital plate of the maxilla, is the large posterior opening of the palatine foramen, including the sphenopalatine foramen, as seen in the septum seen in the skull of Trogosus hyracoides. In addition to the nerves listed above, the opening of the sphenoidal fissure apparently also transmitted the external carotid. The foramenovale is of good size and normal position just above and lateral to the external ridge of the alisphenoid, but well separated from the glenoid articular surface.
58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 well-marked sulcus between the basisphenoid and the pterygoid plate
ENDOCRANIAL CAST
NO. 10 TILLODONTIA — GAZIN 59
The cast, extrapolated from the probable size of the olfactory lobes, is about 30 to 33 percent of the length of the skull. Posteriorly, on the lateral edge of the medulla oblongata, the position where the hypoglossal emerges is indistinct, as the foramen was not prepared before casting. On the right side (left of the illustration), anteroventral to the filling of the internal opening of the foramen lacerummedium,.
MANDIBLE
This is followed by an incomplete lateral protrusion near the posterior edge of the cast, which is the filling of an opening of a venous canal in the occiput, just within the foramen magnum. In the ventral view, in addition to the anterior positions of the view of the optic nerve and the contents of the sphenoidal fissure, below a position just posterior to the center of the cerebrum there is a subdued but elongated-oval prominence, interpreted as the position of the pituitary gland. Also in the lateral view, the indication of the hypoglossa and the vein leaving the exoccipital can be seen posterior to the foramen lacerum posterius, on the lateral margin of the right side of themedullaoblongata.
62 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 almost or quite to below the anterior margin of M2, accommodating the
NO. 10 TILLODONTIA — GAZIN 63 The ascending ramus of the middle Eocene jaws shows some small
04 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 sulcus mylohyoideus is stated by Zittel to be especially characteristic
DENTITION
In the particular specimen in which this tooth was observed, the enamel was preserved around the lateral and anterior surfaces, apparently in a stage of wear in which only the basal part of the crown remained. The paraconid is lingual in position, and the anterior and posterior transverse ridges of the trigonid are nearly parallel. In the lower series, Dpg does not differ much from P3 except for the compressed ridges down the paraconid and the metaconidal section of the protoconid observed in E .
HYOID ARCH
10 TILLODONTIA — GAZIN 69noticeable in Paleocene and Sand Coulee materials, but are climacteric noticeable in Paleocene and Sand Coulee materials, but are climacteric in the Bridger. Very few specimens that have deciduous teeth are known from Esthonyx and so farnones have been observed from Trogosus. The paraconid is well forward of the metaconid than in P4, but the talonid pelvis is larger and more elongated as in Mi.
70 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 VERTEBRAE
NO. 10 TILLODONTIA — GAZIN 7I
7^ SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 121
NO. 10 TILLODONTIA — GAZIN 73
74 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 RIBS
CLAVICLE
SCAPULA
10 TILLODONTIA — GAZIN 75anterior limb of the glenoid surface and, although fused to the anterior limb of the glenoid surface and, although fused to the scapula, it is quite distinctively separated from the glenoid surface. The scapula of Trogosus is quite different from that of any other animal with which it can be compared. The anterior margin expands somewhat near the lower extremity as in Phenacodus, but no other special similarities were noted with Cope's figure (1884a, p. 57c).
HUMERUS
2g.-Trogosiis, species: Left humerus (A.M. No. 17011, restored proximally from specimen associated with U.S.N.M. No. 17157), proximal, lateral, posterior and distal views, Xi-Huerfano (B) middleEocene, Colorado.
78 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121
NO. 10 TILLODONTIA — GAZIN 79 the supinator ridge extends rather smoothly upward a greater distance
RADIUS
ULNA
The sigmoid notch or fossa is widespread distomedially and laterally the lesser sigmoid fossa presents two well separated surfaces for the head of the radius. Trogosus, species: Left ulna (associated with U.S.N.M. No. 17157, tj-peof Trogostts hillsii. new species; olecranon restored from second specimen associated with type T. hilhii: distal limb restored from U.S.N.M. Hyracoid No. 178, its lateral 8 -6 ,endistal views,Xi- Huerfano The distal limb shows a convex facet on the anterior and medial margin for the radius, and a small saddle-shaped surface between it and the styloid process, which articulates with the styloid process with the cuneiform .
NO. 10 TILLODONTIA — GAZIN
MANUS
82 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 the distal portions of two phalanges, is that associated with the skull
NO. 10 TILLODONTIA — GAZIN 83
Cuneiform. The Trogosuscuneiforme is roughly triangular when viewed proximally (Fig. 33a), and has a broad anterior surface that extends widely around the lateral side of the palmar end. The Tillodonpisiform is noticeably larger, especially in limb diameter; the facet of the ulna also appears larger compared to that of the cuneiform. The distal surface of the trapezium is convex from left to right and covers the proximal end of the second metacarpal, except where the latter has a small facet at the palmar end of the medial edge of the trapezium.
NO. 10 TILLODONTIA — GAZIN 87
Metacarpals.— Trogosus metacarpals (Fig. 32) are moderately short and robust, increasing in length from the first to the third and decreasing again to the fifth. The proximal extremity of the first metacarpal is set distinctly distal to the second metacarpal, while the second and third are straight. Also the distal extremities, at their widest points, are more expanded transversely than the proximal extremities, except in the first and fifth.
NO. 10 TILLODONTIA — GAZIN 89
90 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 cut dorsally so that the fourth metacarpal rides over a small knoblike
NO. 10 TILLODONTIA — GAZIN QI
92 SMITHSONIAN MISCEXLANEOUS COLLECTIONS VOL. 121 widest; it is gently concave forward and makes a very acute angle
FEMUR
94 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121
10 TILLODONTIA — GAZIN 95and shortened, and is bounded high externally by the lower border and shortened, and is bounded high externally by the lower border of the small, postero-externally facing facet for the fibula. Trogosus, species: Left tibia and fibula (Y.P.M. No. 11088), proximal, anterior, lateral and distal views, Xi- Bridger Middle Eocene,. The Esthonyx tibia, if properly connected, appears to be relatively longer and more slender with the outer condyle off.
96 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 proximal extremity supported below by a more prominent, though
FIBULA
The composite hind leg illustrated here (fig. 37) consists of elements from four different individuals, representing two sexes. Trogosus, species, left cuboid (Y.P.M, No. 11088), distal view; g, Trogosus hyracoides, left astragalus (A.M. No. 18982), plantar view; h andi, Tillodonfodicns, new genus, left (from right side) metatarsals 3 and 4 (No. Y.P.M. 11087), type specimen, close-up view; XI- a, Huerfano (B) Middle Eocene, Colorado; b-i, Middle Bridger Eocene, Wyoming. The amount of rotation between the astragalus on the one hand and the tibia and fibula on the other was decidedly established, as-.
NO. 10 TILLODONTIA — GAZIN 99
100 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 exhibits a very prominent and widely extended peroneal process
The articulation with the external cuneiform is shown from one side along the proximal edge of the lateral surface. The distal articulation is L-shaped, or almost T-shaped, for the proximal extremity of the third metatarsal. The proximal surface of the cuboid has a ridge-like ridge that separates the concave face for the stragalus from the more convex, proximolateral surface for the calcaneum.
102 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 a second in material associated with the skull of Trogosus hyracoides
NO. 10 TILLODONTIA — GAZIN IO3
RELATIONSHIPS OF ORDER AND CONCLUSIONS
On the other hand, much can be said in favor of the Pantolambda type of tooth set. The stylar development of the upper molars, except for the presence of a small mesostyle, is comparable to that of Trogosus; However, Pantolambda lacks the pervasive hypoconal ridge seen in both Trogosus and Esthonyx. The correspondence between the lower molars and Trogosus is quite striking, even for the metastylid; however, the outer walls are distinctly less hypsodont and more compressed anteroposteriorly.
NO, 10 TILLODONTIA — GAZIN IO5
I06 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 Brown, Roland W
NO. 10 TILLODONTIA — GAZIN IO7
I08 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 121 Hay, Oliver P
NO. 10 TILLODONTIA — GAZIN IO9
TiLLODONT MANDIBE FROM HUERFANO MIDDLE LAKES Trognsus graiigeri, new species: Mandible (A.AI. No. 17008), type specimen,. TiLLODONT SKULL FROM HUERFANO MIDDLE MOCEAN Trogosus hillsii, new species: Skull (U.S.X.M. No. 17157), type specimen,. TiuLODONT Skull from Bridger Middle Eocene TiUodon jodicns (Marsh), new genus: Skull (Y.P.M. No. 11087), type.
