Ptilodus primaevus, 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 : 79

Ptilodus primaevus . Sp. nov.

Plate XV, figs. 13 and 14.

I`he speeimen on which this species is based consists of an imperfect right mandibular ramus in which the fourth premolar and the first molar are preserved. The fracture in front exposes the large anterior root of the premolar and the small posterior root is seen from the outer side. The lower front border of the crown ofthe premolar is slightly excavated apparently for the accommodation of the posterior edge of a very small, closely fitting third premolar. The socket for the base of the root of the incisor is seen 011 the inner side and indicates a tooth of comparatively robust proportions. Behind the first molar, the socket of the second molar is preserved, which, judging from its size, held a tooth considerably smaller than the first molar.

The characters of the teeth are as follows: —Fourth premolar with eleven serrations on its edge; on its inner side, five complete grooves preceded by three half grooves; on its outer side, five complete grooves preceded by one half groove. First molar with four tubercles on its inner side and six tubercles on the outer side.

Ptilodus primaevus is especially interesting on account of the small number of grooves on the large cutting fourth premolar (approching the genus Meníscoëssus ill this respect) and the slightly backward curve of the tubercles on the outer side of the first molar, also suggestive of Meníscoëssus.

In the figures of the type of the species, the teeth are shown as they appear in the specimen, but the first molar is evidently somewhat out of its true position of close proximity to the fourth premolar.

Belly River series, Red Deer river, 1901.

Figures

PLATE XV. Fig. 1. Ornithomimus altus, Lambe, caudal vertebra, superior view, natural size. Page 52. Fig. 2. View of right side of same. Fig. 3. Ornithomimus altus, caudal vertebra, superior view natural size. Page 52. Fig. LL. The same, inferior view. Fig. 5. The same, right side. Fig (S. Ornithomimus altus, left sidc of lumhar vertebra of small individual natural size. Fig. 7. The same, superior view. Fig. S. The same, anterior view. Fig. Ü. Terminal phalanx of megalosauroid dinosaur, lateral view; natural size. Fig. 10. The same, proximal view. z, prezygapophysis i, postzygapoplıysis; s, neural spine e, transverse process. Fig, ll. Tooth of Deinorloıı cnrplanatus‘, Cope, side view; four times the natural size. Page 45). Fig. 12. Transverse section of the same. Fig. 13. Ptilodus primaevus, Lambe, right man libular rztmus,c.\' ternal view; enlarged four times. Page 79. Fig. 1 -1. The same, internal view. pflf, fourtli prernolar; mf, first molar i, socket for incisor; n, socket for second molar. Fig. 15. Boreodon matutinus, Lambe, premolar. side view, four times natural size. Page TQ c, cingulum. Fig. 16. Right maxillary bone, (provisionally associated with Scapherpelnu tectmn), external view, four times thc natural size. Fig. ii. Inferior' view of the samc, similarly cnlargcd. Page 32. Fig. is. Prcınaxillary bone of Diphyodus longirostris, Lambe, inferior view; enlarged four times. Page 30. Fig. 19. Transverse section of samc, similarly enlarged. t, tooth-base m, interspace.