Description and Classification

Parksosaurus was a bipedal dinosaur, meaning it walked on two legs. It measured about 2 to 2.5 meters (6.5 to 8 feet) in length and weighed an estimated 60 to 75 kilograms (130 to 165 pounds), making it about the size of a large dog or a small deer. It had a slender build with long hind legs, suggesting it was a fast runner. Its arms were shorter than its legs, and it had a long tail that helped it balance.

The skull of Parksosaurus was relatively small, with a beak-like mouth suited for nipping off plants. Its teeth were leaf-shaped and designed for grinding tough plant material. Parksosaurus belongs to the Ornithischia order of dinosaurs, known as “bird-hipped” dinosaurs. More specifically, it is classified as an ornithopod. It is often placed within the family Thescelosauridae, a group of small, agile herbivorous dinosaurs that were more primitive than the large “duck-billed” dinosaurs, or hadrosaurs, like Edmontosaurus, which lived at the same time. Other relatives might include Hypsilophodon and its closer cousin Thescelosaurus.

Distinguishing Features

Parksosaurus had several features that help identify it:

• Its hind limbs were notably long and slender for its body size, indicating it was capable of running quickly to evade predators.
• It possessed ossified (bony) tendons along its backbone and tail. These rod-like structures would have made its tail stiff, acting as a counterbalance when running.
• Unusually for an ornithopod, Parksosaurus had intercostal plates, which are thin, flat bones found between its ribs. The exact purpose of these plates is still debated by scientists, but they might have helped with breathing or offered some protection.
• Certain bones in its ankle were fused, which is a characteristic seen in some small, running ornithopods.

Paleoenvironment and Diet

Fossils of Parksosaurus have been found in the Horseshoe Canyon Formation in Alberta, Canada. During the Late Cretaceous, this area was a coastal plain with rivers, forests, and swamps. The climate was likely warm and humid. Parksosaurus shared this environment with many other dinosaurs. These included large predators like Albertosaurus (a relative of Tyrannosaurus rex), giant plant-eaters like the hadrosaur Edmontosaurus and the horned dinosaur Pachyrhinosaurus, and armored dinosaurs such as Ankylosaurus and Euoplocephalus.

As a herbivore, Parksosaurus would have eaten plants. Its beak was good for snipping off vegetation, and its cheek teeth ground up the food. It likely ate low-growing plants such as ferns, cycads, and possibly early flowering plants. Being relatively small, it probably browsed selectively on specific plants rather than eating everything in its path.

Significance and Ongoing Research

Parksosaurus is important because it helps scientists understand the diversity of smaller plant-eating dinosaurs that lived in North America towards the end of the age of dinosaurs. While large dinosaurs often get more attention, smaller animals like Parksosaurus played a key role in their ecosystems. Its unique features, such as the intercostal plates and ossified tendons, provide valuable clues about how these small ornithopods moved, breathed, and survived.

Ongoing research continues to explore various aspects of Parksosaurus. Scientists are interested in learning more about its running speed and agility by studying its limb bones and comparing them to modern animals. The exact function of its intercostal plates is still a topic of investigation. Further research also focuses on its relationships with other ornithopod dinosaurs, like Thescelosaurus, to better understand the evolution of this group. Discoveries of new fossils could provide more information about its appearance, behavior, and the environment it inhabited alongside giants like Tyrannosaurus rex during the final stages of the Cretaceous period.