Stegoceras validus, 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 : 68-69

Stegoceras validus . Sp. nov.

Plate XXI, figs. 1 - 5 .

The two s mmetrical, com act bones 7 re P resented on plate XXI I were found se mratel. The lower portions of their sides, as well as their ends, consist of sutural surfaces, indicating that other bones were firmly united to them and completely surrounded them. A transverse suture divides each almost equally into an anterior and a posterior half. On the lower surface there is evidence of a line of coalescence in a longitudinal direction and extending from end to end. The upper surface of each specimen is dome shaped. In the larger specimen the anterior end is produced forward and is slightly elevated terminating in two projections; the surface is here distinctly nodose. In the lateral, posterior, upper surface a similar rugosity is apparent. The surface of the central convexity is smooth.

In the smaller specimen the upper surface is smooth and pittcd throughout. It is trilobed posteriorly and is not produced forward in front where, however, two small nodes occur, one on each side of the median lino.

The structure of the lower surface is marked by a number of smooth, concave areas, as represented in the reproductions, from photographs of the specimens, in figs. 2 and 5 of plate XXI .

It is probable that these bones were situated in the median lino of the head, in advance of the nasals. They may have belonged to a species of dinosaur not otherwise represented in the collections from Red Deer river and, judging from the difference in shape ofthe two specimens, more than one species may be indicated. Marsh in his figurc ofthe head of Triceratops serratzós* shows a nasal horn core (divided both transversely and longitudinally by sutures) that may correspond to the specimens from Red Deer river.

A third specimen, similar to the anterior half of the larger of the two bones was collected in 1901. It has separated from its posterior half along the lino of the transverse suture.

For these bones the name Stegoceras validas is proposed with the hope that future discoveries may aid in a clearer understanding of their aflinities.

Belly River series, Red Deer river. 1898, 1901.

Figures

PLATE XXI. Fig. 1. Stegoceras validus, Lambe, prenasal bone; side view. Natural size. Page 63. Fig. 2. The same, inferior aspect. Fig. 3. Superior view of another specimen; natural size. Fig. 4. The same; side view. Fig. 5. The same; inferior view. Fig. 6. Stereocephalus tutus, Lambe, symmetrical plate, superior aspect; one-half the natural size. (Pro. visionally associated with S. tutus). Figs. 7 and S. Similar keeled plates one-half the natural size. Fig. 9. Shield of Acipenser albertensis, Lambe, viewed from above. Natural size. Page 29 .

PLATE XXI. Fig. 1. Stegoceras validus, Lambe, prenasal bone; side view. Natural size. Page 63. Fig. 2. The same, inferior aspect. Fig. 3. Superior view of another specimen; natural size. Fig. 4. The same; side view. Fig. 5. The same; inferior view. Fig. 6. Stereocephalus tutus, Lambe, symmetrical plate, superior aspect; one-half the natural size. (Pro. visionally associated with S. tutus). Figs. 7 and S. Similar keeled plates one-half the natural size. Fig. 9. Shield of Acipenser albertensis, Lambe, viewed from above. Natural size. Page 29