Styracosaurus Research Articles

A subadult individual of Styracosaurus albertensis (Ornithischia: Ceratopsidae) with comments on ontogeny and intraspecific variation in Styracosaurus and Centrosaurus.

Styracosaurus albertensis is an iconic centrosaurine horned dinosaur from the Campanian of Alberta, Canada, known for its large spike-like parietal processes. Although described over 100 years ago, subsequent discoveries were rare the last few decades, during which time several new skulls, skeletons, and bonebeds were found. Here we described an immature individual, the smallest known for the species, represented by a complete skull and fragmentary skeleton. Although ~80% maximum size, it possesses a suite of characters associated with immaturity, and is regarded as a subadult. The ornamentation is characterized by a small, recurved, but fused nasal horncore; low, rounded postorbital horncores; and short, triangular, and flat parietal processes. Using this specimen, and additional skulls and bonebed material, the cranial ontogeny of Styracosaurus is described, and compared to Centrosaurus. Styracosaurus shows a similar early ontogeny of the nasal horncore, starting thin, recurved, and unfused, but retains the recurved morphology into large adult size, and never develops the procurved morphology common in Centrosaurus. The postorbital horncores of Styracosaurus are lower and more rounded than those of Centrosaurus throughout ontogeny, and show greater resorption later in ontogeney. The length and thickness of the parietal processes increase drastically through ontogeny, but their position and orientation are static across the size series. Several diagnostic Styracosaurus albertensis specimens now preserve medially orientated P3 spikes, causing issues for the diagnosis of S. ovatus. Variability in parietal ornamentation, either expression of P1 and P2 parietal processes, or other cranial ornamentations, does not appear to correlate with stratigraphy.

Morphological variation and asymmetrical development in the skull of Styracosaurus albertensis

The ceratopsid Styracosaurus albertensis is an important component of the herbivorous dinosaur fauna preserved in the Campanian-aged Dinosaur Park Formation in Alberta, Canada. A new skull (UALVP55900) exhibits previously unobserved variability and asymmetry in this species. As in the type, the right lateral parietal bar bears seven epiossifications, but the left parietal bar has eight. Epiossifications p3‒p6 are asymmetrical with respect to size, orientation, and position relative to the midline. A re-evaluation of variation in Styracosaurus that includes this skull expands the morphological range of the taxon to incorporate Rubeosaurus ovatus, requiring the synonymy of the latter with the former. Unlike the type, both p1 and p2 epiossifications of UALVP 55900 are large. Epiossification p1 is procurved, and p2 is medially curved. These features converge on the morphology considered diagnostic for Centrosaurus. This observation, in combination with their sequential stratigraphic relationship and geographic overlap might suggest that Centrosaurus and Styracosaurus form an anagenic series, but the stratigraphic placement of skulls exhibiting putative transitional morphologies does not support this hypothesis.

Megaherbivorous dinosaur turnover in the Dinosaur Park Formation (upper Campanian) of Alberta, Canada

Ongoing research into the biostratigraphy of the upper Campanian Dinosaur Park Formation (DPF) of Alberta has demonstrated that megaherbivorous dinosaur taxa (ankylosaurs, ceratopsids, hadrosaurids) are not homogeneously distributed throughout the unit. This has compelled proposals of different, informal assemblage zone schemes, and the hypothesis that faunal turnover was driven by environmental change associated with marine transgression. The current study tests previous zonation schemes in addition to the hypothesis of turnover pulses in the DPF. Clustering and ordination methods are used to demonstrate the existence of two broad assemblage zones within the DPF, each of which lasted ~600Ka: a lower zone characterized by the presence of the ceratopsid Centrosaurus apertus and the hadrosaurids Corythosaurus, and an upper zone characterized by the presence of the ceratopsid Styracosaurus albertensis and the hadrosaurid Prosaurolophus maximus. These zones can be further sub-divided, based on the distributions of rarer or shorter-lived ankylosaur, ceratopsid, and hadrosaurid species, into ~300Ka sub-zones. Canonical correspondence analysis is used to explore the association between the turnover of the megaherbivorous dinosaurs and various palaeoevironmental proxies. Megaherbivorous dinosaur turnover most closely corresponds to that of fossil palynomorphs. However, none of the palaeoenvironmental proxies explains dinosaur distribution better than a simple time gradient, suggesting that dinosaur turnover was not inextricably linked to environmental change as predicted by the turnover pulse hypothesis.

A New Centrosaurine from the Late Cretaceous of Alberta, Canada, and the Evolution of Parietal Ornamentation in Horned Dinosaurs

In 1916, a centrosaurine dinosaur bonebed was excavated within the Campanian-aged deposits of what is now Dinosaur Provincial Park, Alberta, Canada. Specimens from this now-lost quarry, including two parietals, a squamosal, a skull missing the frill, and an incomplete dentary, were purchased by The Natural History Museum, London. The material was recently reprepared and identified herein as a previously unknown taxon, Spinops sternbergorum gen. et sp. nov. Based upon the available locality data and paleopalynology, the quarry lies in either the upper part of the Oldman Formation or the lower part of the Dinosaur Park Formation. The facial region of the partial skull is similar to putative mature specimens of Centrosaurus spp. and Styracosaurus albertensis, with short, rounded postorbital horncores and a large, erect nasal horncore. Parietal ornamentation is consistent on both known parietals and is unique among ceratopsids. Bilateral, procurved parietal hooks occupy the P1 (medial-most) position on the do...

Contributions to Vertebrate Palætology

THE skull of a remarkable new generic type of horned dinosaur (Styracosaurus albertensis), from the Cretaceous of the Red Deer River, Alberta, is described and figured by Mr. L. M. Lambe in the Ottawa Naturalist for December, 1913 (vol. xxvii., pp. 109–16, plates x.–xii.). o It was found by the well-known collectoi Mr. C. H. Sternberg, last summer. The skull is long, depressed, and wedge-shaped, with a single nasal horn of somewhat unusual shape; but its chief peculiarities are the large size of the supra-temporal fossæ, and the production of the hind border of the great occipital flange into four pairs of spines, of which the three innermost on each side are very long. Although the Alberta horned dinosaur may be generically identical with an imperfectly known species from the Cretaceous of Montana, referred by Cope to the genus Monoclonius, under the name of M. sphenocerus, it is considered that the two are specifically distinct.