Trachodon (Pteropelyx) marginatus, Lambe, 1902

Lambe L. M., 1902, New genera and species from the Belly River Series (mid-Cretaceous), Geological Survey of Canada Contributions to Canadian Palaeontology 3, pp. 25-81 : 71-75

Trachodon (Pteropelyx) marginatus . Sp. nov.

Plate III, fig. 1 , plate IV, figs. 1, 5 and 6 , and plates V , VI , VII , VIII , IX and X .

Excellently preserved remains, of a large herbivorous dinosaur, met with in abun- dance in the Red Deer river district, arc referred to the above species. Although the various bones of the skeleton were generally found distributed, a number Were discovered associated with each other, the remains of one individual. These consisted of the hunie- Tus, ulna and radius of the left fore limb, a metatarsal and phalanges of the pes, the zygapophyses of cervical vertebrtc, ribs, fragments of teeth, broken ossilied tendons and impressions of the integument. The species is represented further by disassociated femora, tibize, inetacarpals and phalanges of the manus, rami ofthe lower jaw and maxillte with remarkably well preserved teeth in place, dorsal and caudal vertebrtc, a pubic bone, ischia, ilia, chevron bones and numerous teeth as Well as other remains probably referable te the same species.

Of the bones, of one individual, found in association, the humerus with the ulna and radius are figured on plates VI and VII.

The humerus, figs. 1 and 2, has a prominent radial crest that extends, from the external tuberosity above to slightly more than half way down the shaft externally and is roughly striated at its lower end ior the attachment of the deltoid muscle. The head is small and is supported below by a strong rounded ridge. The proximal end, seen from above, is roughly triangular in shape, the front face broadly excavated with conspicuously concave surfaces on either side of the head behind that continue forward to meet the inner and outer‘ tuberosities. The condyles are separated by a deep depression behind, that extends up the shaft for a short distance; in front they are not so conspicuously divided.

An archaic feature is expressed in the great downward extension and conspicuous singularity of the radial crest. In comparing this humerus with that of Hadrosaurus Foulkii, * Leidy, from the Cretaceous of the east, a form allied to this species, a marked difference is noticeable in their proportions.

Measurements af humerus.
	M.
Extreme LL / LAD length u.. \ y 27ı inches	.683
Breadth at lower end of radial crest.	.165
Circumference midway between lower end of radial crest and distal end	.265
Breadth across head and outer tuberosity.	140
“ “ inner tuberosity.	.130
Breadth across inner anrl outer tuberosities..	145
Breadth of outer condyle.	100
Breadth of inner condyle (imperfect).	.080
Thickness at centre of condyles	.092
Thickness of radial crest near lower end.	.034

The ulna and radius, belonging to the same fore limb as the humerus, are figured as they Were found,

The ulna has a strongly developed olecranon process terminating its expanded proximal end which is concave on three sides so as to be subtriangular in section. From the middle ofits shaft downward, it increases in size very little.

The radius is a comparatively slender" bone but terminates below in a carpal articu- lating surface slightly larger than that of the distal end of the ulna.

Measurements of
	M.
Extreme length of ulna (28 inches)	.708
Circumference at middle of shaft.	.190
Greatest breadth across coronoid process.	.145
Greatest thickness at proximal end.	.094
Greatest diameter of carpal end	.074
Shortest diameter of carpal end.	.057
Extreme length of radius (25 inches).	.632
Circumference at middle of shaft.	155
Long diameter of head	.086
Short diameter of head	.054
Long diameter of carpal end.	.087
Short diameter of carpal end.	.050

The right femur, plate VIII , provisionally associated with T marginatus , is interesting in many particulars, notably, its slenderness, the prominence of the head, the backward extension of the condyles and the marked development of the third trochanter. The inner condyle is larger than the outer one,‘ they are both, viewed from the side, broadly rounded posteriorly and pointed in front. From the great trochanter, a prominent ridge extends dowrrward, for some distance on the outer front face of the bone.

Measurements of femur.
	M.
Length from top of trochanter to bottom of outer condyle..	l 1825
Length from top of head to bottom of inner condyle ...	1 1698
Breadth of upper extremity‘.	.2464
Breadth of lower‘ extremity ...	.2497
Transverse diameter at middle of shaft..	.145
Antero-posterior diameter at middle of shaft.	.134
Circumference below third trochanter.	.4048
Circumference above third trochanter.	.4774
Anter‘o-posterior‘ diameter of head (imperfect).	127
Antero-posterior diarneter‘ of trochanter.	.209
Antero-posterior diameter of inner condyle.	.300
Length of third trochanter.	.377
Height at centre of third trochanter..	.047

A comparison of this femur with that of Hadrosaurus foulkii, Leidy reveals a great similarity in their general proportions. If anything, the Red Deer‘ river‘ specimen is more slender but otherwise there are no very marked differences.

The tibia ( plate IX , figs. 1 and 2), Was probably not as long as the femur‘ but was a decidedly robust bone. Unfortunately no specimens were secured associated With femora that might be supposed to belong' to the same individual.

Of the two right tibiae figured on plate IX (provisionally referred to T. rnarginatus), the one on the right, seen fr‘orn behind, is considerably crushed so as to exaggerate the breadth of the proximal end; the other specimen is remarkably Well preserved.

This bone of the leg, cylindrical at mid-length, expands rapidly toward either‘ end. The longer axis of the distal end is nearly at right angles to that of the proximal end. Viewed from behind, the proximal end is seen to be broadly concave, the outer‘ side consisting of a backwardly directed flange. On the inner side the head is divided into two parts by a deep furrow.

Measurements of tibia.
	‘nI.M.
Length of tibia externally.	1.018
Length in front.	.980
Circumference at narrowest part of shaft, just below the middle..	.379
Breadth of upper extremity	.272
Diameter of middle of head antero-posteríoriy.	.2024
Breadth of tarsal extremity.	.337
Diameter‘ at middle of tarsal surface.	123

Ramus of lower jaw, plates III and IV, long and narrow, with teeth occupying a deep, narrow chamber or magazine in the posteriortwo-thirds of the length. Cororroid process high, rising abruptly from the outer‘ side, of the posterior end; laterally compressed above, deeply excavated below posteriorly. An edentulous prolongation in front curves obliquely downward and inward with a symphyseal surface at the: inner forward end. Upper and lower borders nearly parallel. Outer wall of dental chamber thick and strong, with shallow, vertical, alveolar‘ grooves occupying its inner side. Inner‘ wall,.very thin, averaging about 2 mrn. in thickness, Without alveolar‘ grooves proper; seldom preserved. Coronoid process below, produced backward externally as a thin plate of bone continuous With the outer surface of the jaw; on its inner‘ side it unites with the outer‘ alveolar‘ wall in advance of the posterior end of the dental chamber. Derrtary canal leading from the upper‘ part of the posterior cavity forward between the outer‘ surface of the jaw and the dental chamber‘. Mandibular groove passing forward under the lower‘ border‘ of the chamber‘. A row of foramina occurs on the inner side, one foramen at the base of each vertical series of teeth. A number of foramina also present on the outer‘ suface. Teeth replaced from within, their keeled, erranrelled surfaces of the crown inside occurring in a vertical series of three or four near the middle of the jaw with two or three ofa series in use in the grinding surface at the same time. Their lateral margins decorated with small, rounded projections fr‘om near the apex downward to where the crown begins to narrow again.

Measurements of left ramus of lower jaw.
	M.
Extreme length	630
Depth at middle of magazine.	095
\Virlth at base of magazine.	.034

Length of nngazine	"400
Depth of same at its mid-length	' 088
Width through magazine at middle of magazine	" 068
Elevation of coronoid process above lower border	232
Elevation of coronoid process above upper border	158
Antero-posterior diameter of coronoid process above. -.	080
Transverse diameter of coronoid process above	' 015
Thickness of inner alveolar wall	' 002
Forty-six alveolar grooves.
Diameter of dental foramina (largest)	' 0C5
Diameter of dental foramina at ends of series ...	040
Elevation of grinding surface of teeth above edge of outer wall	075
Distance from front of magazine to anterior end of symphyseal surface.. ......	182

Maxilla, plate V , robust, high at the centre, sloping downward toward either end, the dental chamber occupying nearly the whole of its length. Seen from above, the posterior half slopes obliquely forward and outward, while the reverse is the case in front; at the extreme anterior end there is a limited slope inclined obliquely outward. Also, viewed irom above, the posterior half is straight and broader than the front half which narrows to a- rounded, outwardly turned point. Inner surface rather flat. Outer surface with a rounded ridge running horizontally from the posterior end to meet the facet for the articulation of the anterior end of the jugal. On the inner, upper side behind mid-length, a facet, probably for the palatine, is present. Teeth replacing each other from the inner side, apparently not more than two, of a series in v;se in the grinding surface at the same time; the carinated, enamelled faces of the crowns facing outward. A row of foramina, similar to that of the lower jaw, conspicious in the upper part of the inner side. Several large foramina occur in the anterior half of the outer side.

Measurements of right maxilla
	M.
Extreme length	300
Extreme depth of same (imperfect above)	1 1
Length of dental series	316
Tliickness of maxilla at mid length	078
Distance apart of lower edges of alveolar walls at mid-length ...	025
Distance apart of same near anterior end	016
Distance apart of same near posterior end ...	015
Distance of row of foramina (forty in number) above edge of inner alveolar wall at centre	055
Projection of outer edge of grinding surface of teeth below edge of outer alveolar wa'l at centre	-019
Projection of inner edge of same below edge of inner alveolar wall at centre ...	007
Average horizontal diameter of foramina in inner alveolar wall	047

Pubis, plate X, fig. 1 (provisionally associated with T.marginatus ), produced forward into a broad, thin, transversely compressed, spatulate expansion that is slightly concave on its outer surface. Posteriorly a slender postpubic process, springing from a point inside and in advance of the base of the pedestal bearing the ischiac facet, is directed backward on the lower border of the ischium with which it effects a ligamental union.

Iliac facet small, separated from the isehiac facet by a wide, concave, acetabular emargination that forms about one-third of the whole acetabular‘ border.

Measurements of pubis.
	M.
Length of acetabular border along curve	.235
Distancc from centr‘c of ischiac facct to centre of iliac facet.	.205
Breadth at narrowest part of anterior‘ expansion.	.092
Thickness at centre of narrowest part	.027
Breadth of specimen anteriorly (imperfect).	174
Circumference of base of postpubic process.	.092
Vertical diameter of ischiac facet.	.045
Greatest thickness slightly in advance of acetabular border. z	.022
Greatest thickness at centre of anterior end (imperfect) of specimen.	.018
Length of specimen frorn ischiac facet to anterior end.	.485
Estimated length of pubis, when perfect, from anterior end to posterior end of postpubic process (37 inches).	.940

Isehium long, plate X, fig. 2 (provisionally associated with T. marginatus ), laterally compressed, broadly expanded proximally and ending distally in a loot-shaped extremity pointing downward. Shaft almost straight, its upper‘ edge curving concavely and broadly upward to meet the iliac facet Upper expanded part very thin, plate-like, thickened abruptly, on either side of the thin, concave edge of the acetabular border, to form well developed iliac and pubic facets. The surfaces of the facets very rugose. A narrow postpubic facet extends, downward and backward at right angles to the pubic facet along the lower front border of the proximal end. Below this facet and separated from it by a concavity in the thin margin is a flange of bone for the further support of the postpubis. Inner surface of distal half, striated longitudinally for a ligamental union with its mate of the opposite side.

Measurements of ischium.
	M.
Extreme length from iliae facet	1.050
Distance from upper‘ end of iliac facet to lower end of pubic facet.	.332
Length of acetabular border measured on concavity.	140
Length of iliac facet.	135
Breadth of	.060
Length of pubic facet.	.040
Breadth of same.	.020
Length *of postpubic facet.	122
Breadth of same.	.013
Circumference at mid-length	.162
Breadth of expanded distal end.	.0217
Thickness of lower part of same	.070
Thickness of upper part of same.	.040
Thickness of proximal 'expansion at centre	.016

A number of ilia, representing difierent types of herbivorous dinosaurs, are included in the collections. In fig. 23, three of these are shown. The upper one, A, is of the Monoclonius type and is arbitrarily associated with M. dawsoni . another, B, is referred to Trachodon marginatus (provisionally), Whilst the lower one; C, Stegosauroid in its character, may belong to Stereocepltalus tutus .

Figures

PLATE III. Fig. 1. Trachodon (Pteropelyx) marginatus, Lambe, inner side of left ramus of lower jaw, showing the teeth; one-half the natural size. Page 73. e, coronoid process; a, symphyseal surface; b, inner wall of dental chamber; c, mandibular groove; d, foramen. Fig. 2. Trachodon (Pteropelyx) sclwyni, Lambe, inner surface of teeth of lower jaw, to show succession natural size. Page 69. Fig. 3. Grinding surface of teeth of same specimen; natural size. Fig. 4. Scapherpeton tectum, Cope, dorsal vertebra, from the left side; twice the natural size. Page 31. Fig. 5. View from the front, same specimen. Fig. 6. Scaplıerpeton tectuııı, atlas, front view; twice the natural size. Fig. 7. The same, viewed from behind. Fig. 8. The samc, side view from the lcft. y, diapophysis _; z, prezygapophysis; ê, postzygapophysís l; s, neural spine 5 x, anterior articural cup; w, neural canal; v, facet for occipital condyle of skull.

PLATE IV. Fig. 1. Trachodon (Pteropelyx) marginatus, Lambe, outer side of the same mandibular rainus figured on plate III; one-half the natural size. Page 73. Fig. À Trachodon (Pteropelyx) altidens, Lambe, outer side view of left maxilla, one-lialf natural size. The speciman was drawn upside down so as to have a better light on the teeth. Page 76. Fig. 3. Inner view of the same specimen, with part of the inner wall removed to show successional teeth; one-half natural size. Fig. 4. Two teeth from the same specimen, showing the characteristic border sculpture, with the crown of the worn tooth restored, in dotted outline, to show the proportion of length to breadth; twice the natural size. Fig. 5. Trachodon (Pleropelyx) marginatus, Lambe, outer view of apical part of crown of tooth from the maxilla represented on plate V, for comparison with fig. 4; twice the natural size. Page 74. Fig. 6. Trachodon (Pteropclynf) marginatus, crown of one of the teeth of the ramus shown in fig. l of this plate and fig. 1 0 f the preceding plate; twice the natural size. Page 73. Fig. 7. Pteropelyx grallllipes, Cope, crown of tooth of lower jaw, t) show border sculpture; twice the natural size. Introduced for comparison. Page 77. f, grinding surface of teeth a, facet for jugal.

PLATE V Fig. 1. Trac/radon (Pleroııelıııc) ııuırfıivıatım Lainbe. right inaxillarv bone. external view: reduced one- 1¬¬1. ¢_ um» 7.1-.. -..De Fig. 2. The same, internal view. Fig. 3. The same, superior view. a, facet for jugal; b, facet for palatine.

PLATE VI. Fig. 1. Trachodon (Pteropelyx) marginatus, Lambe, left humerus, viewed obliquely from inner front,' one-third natural size. Page Tl. Fig. 2. The same, from outer rear. Fig. 3. Trachodon (Pteropelyx) marginatus, impression of epidermis, from the sandstone in which the above specimen was embedded; natural size. r, radial crest; lı, head; i, inner tuberosity; 0, outer tuberosity; c, outer condyle.

PLATE VII. Fig. 1. Trachodon (Pteropelyx) marginatus, Lambe, left ulna and radius, anterior view; one-third natural size. From the S 8.l119 lll(ll \’l(ll 1{1l as that to which the humerus, figured on plate VI, belonged. Page 72. Fig. 2. The same, posterior view. 11, ulna r, radius; o, olecranon process.

PLATE VIII. Fig. l. Trachodon (Pteropelyx) marginatus, Lambe, right femur, anterior view; one-fifth the natural size. (Provisionally associated with T. marginatus). Page ÎÎZ. Fig. 2. The same, internal view. Fig. 3. The same, posterior view. h, head; l, great trochanter; m, third trochanter; e, inner condyle.

PLATE IX. Fig. 1. Trachodon (Pteropelyx) marginatus, Lambe, right tibia, external view; fi-ve twenty-thirds the natural size. (Provisionaliy associated with T marginatus). Page 73. Fig. 2. Another tibia of the same species, posterior view; similarly reduced. (Provisionally associated with T. marginatus)

PLATE X. Fig. 1. Trachodon (Pteropelyx) marginatus, Lambe, left pubis, external view; one-third the natural size. (Provisionally associated with T. marginatus). Page 74. Fig. Ê. Trachodon (Pteropelyx) marginatus, left ischium, external view, " one-fifth the natural size. (Provisionaily associated with T. marginatus). Page 75. i, iliac facet; b, acetabular border; g, ischiac facet; ÍL, postpubic process; p, pubic facet; pp, postpubie facet; j, flange.