Trachodon (Pteropelyx) altidens, 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 : 76-78

Trachodon (Pteropelyx) altidens . Sp. nov.

Plate IV, figs. 2, 3 and 4.

A lelt maxilla, With the teeth preserved, reveals a hitherto undeseriliccl species of Trachodon. The teeth are distinctly narrow in proportion to their length and are beauti- fully marked, for a short distance above the apex of the crown, on the raised edges of the outer enainelled face by a few, obliquelv placed, transversely elongated embossments, which decrease in size gradually, from the apex of the tooth upward until they become ineonspicuous as a few marginal denticles or projections. The name of the species is suggested by the height of the teeth relative to their breadth and the distance they project beyond the alveolar border.

The maxilla indicates an animal of comparatively small size and slender proportions. Three rows of teeth, more generally two, were in use.in the grinding surface at the same time, with at least two or three series of successional teeth following, to replace those in use from the inside, the stumps of the old teeth falling out on the outside of the javv. In fig. 3, the mode of succession of the teeth downward is shown, the bone having been removed for a short distance from the anterior end of the speeimen. About one-fifth of the maxilla is missing anteriorly, as Well as a considerable part of the superior border above the row of lbraınin-a. A prominent, overhanging ridge, runs forward, on the outer side, from the posterior end, forming the outer and lower border of the facet for the front part of thejugal. A notieeable feature is the distance the teeth project beyond the borders of the alveolar walls. Four nellro-vasclllar foramina are conspicuous in the outer wall in front of the ridge lust mentioned. The enamelled surface of the crown of each tooth bears a strong median carination. The teeth from which the apices have been removed by use are quite smooth and do not show the characteristic border markings.

COMPARATIVE TABLE OF TEETH OF SPECIES 0F TRACHODON AND PTEROPELYX.

Trachodon mirabilis, Leidy.	Teeth pointed above; margins smooth.
Trachodon (Pteropelyx) selwyni , Lambe.	Teeth rounded oval above,' margins smooth or with the faintest indications of oblique transverse striaz. Fig. 2, plate III .
Trachodon (Pleropelyx) marginatus , Lambe.	Teeth rounded above; with a marginal sculpture. Figs. 5 and 6 , plate IV .
Pteropelyx grallipes, Cope.	Teeth rounded above; with a border sculpture. Fig. 7, plate IV
Trachodon (Pteropelyx) altidens , Lambe.	Teeth of small size, long in proportion to the breadth, and pointed above; with a border sculpture near theapex. Fig. 4, plate IV .

A large series of rami of lower jaws of species of Trachodon Were collected in the Red Deer river district. Unfortunately in most of the specimens the teeth are missing, making their specific identification somewhat conjectural. In fig. 24 , three of the rami are figured to show size and form.

Figures

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 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. Scapherpeton tectum, 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.

Fig. 6. Anterior half of the shell of Adocus variolosun, from Red Deer river; ventral aspect showing the front margin of the carapace, One-fifth natural size

FIG. 24. Right mandibular rami of species of Trachodon from Red Deer river, A, ramus of lower jaw of T. selwyni R and C, rami probably referable to T. marginatus2 d, alveolar grooves from which the teeth have fallen e, coronoid process symphyseal surface. One-sixth the natural size.