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Journal of Paleontology

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MORPHOLOGY AND ONTOGENY OF THE CORNUAL SINUSES IN CHASMOSAURINE DINOSAURS (ORNITHISCHIA: CERATOPSIDAE)

¹ Department of Anatomical Sciences, Stony Brook University, Stony Brook, New York 11794, <afarke@ic.sunysb.edu>

The first 20% of the full text of this article appears below.

	INTRODUCTION

 
CERATOPSIDS, HORNED herbivorous ornithischians from the Cretaceous of North America, are unique among dinosaurs in the form and expression of their cranial ornamentation. All ceratopsid genera possess a bony parieto-squamosal frill that projects over the neck region and some degree of development of nasal and orbital horns. These horns vary in form and location, from low bosses (e.g., Pachyrhinosaurus Sternberg, 1950) to long, conical horns (e.g., Triceratops Marsh, 1889 postorbital horns). Internal structural changes occurred along with these extreme external modifications of the skull (Forster, 1996).

A frontal sinus complex occupies space variably involving the postorbital, frontal, parietal, supraoccipital, and exoccipital bones of the skull roof in ceratopsid dinosaurs (Fig. 1.1; Forster, 1996). These sinuses are relatively small, simple chambers in most members of the two ceratopsid clades Chasmosaurinae and Centrosaurinae (Lehman, 1990). However, the frontal sinuses reach large proportions in some species, with a portion of the sinuses extending into the base of the postorbital horncores (Forster, 1996; Sampson et al., 1997; Lehman, 1998). Forster (1996) termed this part of the sinus complex the "cornual" sinus, analogous to the cornual diverticulum of the frontal sinuses in bovid mammals (e.g., domesticated goats; Nickel et al., 1973).

View larger version (10K): [in this window] [in a new window]   FIGURE 1—1, Schematic of the major internal cranial cavities in Triceratops Marsh, 1889, primarily based upon USNM 5740 (not to scale). 2–4, Diagrams of cornual sinus position within the postorbital horncore in right lateral view for selected chasmosaurine taxa. 2, Cf. Anchiceratops sp., TMP 84.12.16. 3, 4, Pentaceratops sternbergi Osborn, 1923. 3, NMMNH P.21098. 4, OMNH 10165 (reversed, modified from Lehman, 1998). 5– 8, Chasmosaurine postorbitals in right lateral view, showing an inferred ontogenetic series for the development of the cornual sinus in . . . [Full Text of this Article]