Fio. 14. A supposed frill spike of a cetatopsian, possibly Pachyrhinosaurus, NMC 8863 (left). Portion of ?parietal frill, possibly Puchyrhinosaurus, NMC 10644 (right), anterior aspect, Scale: 10 cm.

CAN. J. EARTH SCI. VOI., 12, 1975

cesses on the Centrosaurus frill may be recalled (see, for example, Brown 1914h). It is interesting, though probably of no great significance, that the big spike on NMC 9602 resembles the forward process on the left side of the frill in Lambe's type of Centrosaurus apertus (NMC 971) â€” which was originally mistaken for a nasal horn (Lambe 1904; 1910).

A puzzling horn-like bone (NMC 8863) was collected by C. M. Sternberg at Scabby Butte in 1946. In lateral outline (Fig. 14) it resembles the curved nasal horns of some centrosaurs, but it is heavier and longer than in any known species. Unlike nasal horn cores, the surface texture appears to be asymmetrical, with longitudinal sulci better developed on one side than the other. A section is missing, and something has been lost from the tip, but the complete bone must have been in the neighborhood of 55 cm long. It is Aattened, with proximal diameters of 18.5cm and 7.S cm, but does not appear to be distorted. The shape is suggestive of the frill spike on NMC 9602; at the base there is the merest suggestion of a smooth surface reminiscent of the finished lining of the sinus in the pariietal bars described above.

The form and arrangement of the spikes in NMC 9602 can be compared with the frill of Styracosaurus ovatus Gilmore from the Two Medicine Formation of Montana (Gilmore 1930, Pl. 10, Fig. 2). However, the Scabby Butte specimen is less massive, and a medial pair of spikes (if present) may have been diA'erentiy oriented than those of S. ovatus. The single spike of NMC 9602 was relatively shorter than the similarly placed spike in S. ooatus, but the supposed spike NMC 8863 is almost twice as large as the largest one in the Two Medicine specimen. Gilmore's material includes a separate fragment bearing a smaller spike, which he believed belonged considerably farther forward than the larger spikes. The attached part of the frill in this specimen is more massive than any part of the frill anterior to the spike in NMC 9602, and I find no evidence of another spike in this specimen. The resemblance between NMC 9602 and the frill of S. albertensis is less obvious, but there is a fundamental similarity in the general shape of the bone and the arrangement of the lateral epoccipital processes. If under my alternative interpretation (Fig. 13) the Scabby Butte frill possessed long medial spikes, these may have been oriented more as in S. aibertensis than in S. ooatus.

ct 0

U 0

~ 0

vi M

V 0 rA D 0

2 4

exterior) surface is deeply sculptured. 1 have not seen such an opening in any other ceratopsian frill. That the cavity was not of pathological origin seems clear from the fact that its lining is mostly smooth and shows no evidence of necro- tic erosion. One might suppose that voids developed at the bases of frill spikes, thereby lightening a rather weakly supported frill struc- ture. But a fracture close to the base of the large preserved spike shows only a slight increase in cancellous bone and nothing resembling the finished surfaces within the sinus. The edge of the frill remains thick laterally along the side of the parietal, but nevertheless seems relatively weak in view of the heavy structure that it had to support. Anterior to the spike, the edge of the frill carries three broad lateral undulations

Because of their occurrence in the same restricted area with skulls in Pachyrhinosaurus, whose frill is largely unknown, the question naturally arises: can these unusual frills belong to that genus 9 What evidence there is, is circum- stantial, but it seems convincing that:

(1) the frill of Pachyrhinosaurus was fenes- trated, as are these frills;

(2) Pachyrhinosaurus had a remarkably short

squamosal, implying unusual architecture for the frill as a whole;

(3) a short squamosal is associated with a

spiked frill in Styracosaurus;

(4) the frill resembles the frills of Styracosaurus

and Centrosaurus more than any other ceratopsians, and Pachyrhinosaurusi s clearly related to these genera;

(5) NMC 9602 was found about midway be- tween the two I'achyrhinosaurus skulls at Site 2, and NMC 10644 was only a few feet removed from skull NMC 9485;

(6) although Site 2 may contain remains of

another ceratopsian, Anchiceratops, the frill in this genus is entirely different from these specimens; and

(7) NMC 8860, the fragmentary skull col- lected by Sternberg at Scabby Butte, includes a small piece of bone some 87 mm long that seems to agree with the bone comprising the presumed lateral bars of the frills from Site 2.

There is, on the other hand, no direct evidence that these frills (or, for that matter, the frill of S. ooatus) belong to Styracosaurus. I suspect that they pertain to Pachyrhinosaurus and offer the accompanying reconstruction (Fig. 15) with some confidence.

Nun-Cerattiysian Vertebrates from SeabbySutte

Curiously, non-ceratopsian bones are very rare at Scabby Butte outside the Site 2 bonebed. Fish and amphibian remains occur in quantity only in the bonebed at Site 3, but every taxon recognized at Scabby Butte is represented at that locality. Hadrosaurs are abundant at Site 2 but nowhere else. The poor representation of some common Edmonton (= Horseshoe Can- yon) forms â€” for example, Charnpsosaurus, had- rosaurs, carnosaurs, and ankylosaurs â€” is note- worthy. The unique occurrence of a mosasaur at Site 4 is to be further dealt with by 0. A. Russell in another publication.

As stratigraphic distances at Scabby Butte are small, horizons will not be indicated in the