Description and Classification

Spiclypeus shipporum is the only known species within this genus. It was a medium-sized horned dinosaur, estimated to be about 4.5 to 5 meters (15 to 16 feet) long and weighing around 2 to 3 tons. Like other ceratopsids, Spiclypeus was a four-legged herbivore with a large head, a beak-like mouth, and a prominent bony frill at the back of its skull. Its skull featured a pair of large brow horns that projected upwards and outwards above its eyes, and a smaller, rough-textured nose horn.

The frill of Spiclypeus was particularly notable for its unique ornamentation. This frill likely served multiple purposes, possibly including display to attract mates, species recognition, or defense against predators. Spiclypeus belongs to the Ceratopsidae family, and more specifically to the Chasmosaurinae subfamily. Chasmosaurines, like Triceratops and Chasmosaurus, are generally characterized by their long frills and well-developed brow horns. Spiclypeus provides important information about the diversity and evolution of these horned dinosaurs in North America during the Late Cretaceous.

Distinguishing Features

Spiclypeus can be distinguished from other ceratopsian dinosaurs by several unique characteristics, particularly concerning its frill and horns:

• A unique arrangement of epiossifications (bony growths on the frill edge): the first two pairs of epiparietals (on the central, rear edge of the frill) were triangular and curled forward over the top surface of the frill.
• The third pair of epiparietals pointed outwards and backwards.
• The episquamosals (along the side edges of the frill) were robust, triangular, and projected outwards and downwards.
• A wrinkled bone texture on the top surface of the nasal horncore and the area in front of the brow horns.
• The type specimen, nicknamed “Judith,” shows evidence of significant bone disease and injury. This includes a severe bone infection (osteomyelitis) and arthritis in its left upper arm bone (humerus), and an infection or injury on the left side of its frill, which may have caused some of its unusual asymmetry.

Paleoenvironment and Diet

Spiclypeus lived in what is now Montana, USA, during the Campanian stage of the Late Cretaceous. At that time, the region was part of a vast coastal plain known as the Western Interior Seaway. The environment was characterized by rivers, swamps, and lush forests, supporting a rich diversity of plant and animal life. Spiclypeus shared this ecosystem with many other dinosaurs, including other ceratopsians like Judiceratops and Mercuriceratops, hadrosaurs (duck-billed dinosaurs) such as Brachylophosaurus, armored ankylosaurs, and predatory theropods like tyrannosaurids (such as Gorgosaurus or Daspletosaurus) and smaller “raptor” dinosaurs.

As an herbivore, Spiclypeus used its powerful beak and batteries of shearing teeth to chop and grind tough plant material. Its diet likely consisted of low-growing vegetation such as ferns, cycads, and early flowering plants abundant in its habitat.

Significance and Ongoing Research

The discovery of Spiclypeus is significant because it adds to our understanding of ceratopsian diversity and evolution, particularly within the Chasmosaurinae. It helps fill a gap in the fossil record for these types of horned dinosaurs from the Judith River Formation. The unique features of its frill provide more data for studying how these elaborate structures evolved and what functions they might have served, such as display or species identification.

Furthermore, the type specimen of Spiclypeus offers remarkable insights into the diseases and injuries that dinosaurs could suffer. The evidence of severe bone infections and arthritis in “Judith” indicates a hard life and suggests that this individual lived for some time with its ailments. Ongoing research continues to focus on the detailed anatomy of Spiclypeus, its relationships to other ceratopsians like Kosmoceratops and Vagaceratops, and the implications of its pathologies. Future fossil discoveries may provide even more information about this “spiked shield” dinosaur and the ancient world it inhabited.