Description and Classification

Rativates was a type of “ostrich-mimic” dinosaur, belonging to the family Ornithomimidae. Like its relatives, it was a lightly built, two-legged dinosaur designed for speed. It had a long neck, a small head with a toothless beak, large eyes, and long, slender legs. Scientists estimate that Rativates was about 3.3 meters (11 feet) long and weighed around 90 kilograms (200 pounds). Although no direct evidence of feathers has been found for Rativates itself, other ornithomimids like Ornithomimus are known to have been feathered, so it is very likely that Rativates was also covered in feathers.

In the classification of dinosaurs, Rativates is placed within Theropoda, the group of primarily carnivorous dinosaurs that also includes giants like Tyrannosaurus rex and birds. More specifically, it is part of Coelurosauria, a subgroup of theropods that includes tyrannosaurs, “raptors,” and ornithomimosaurs. Within Ornithomimosauria, it belongs to the family Ornithomimidae, which includes other well-known genera such as Struthiomimus, Gallimimus, and Ornithomimus. The recognition of Rativates as a distinct genus was based on a detailed re-examination of fossils that highlighted subtle but important differences from other ornithomimids.

Distinguishing Features

Rativates can be distinguished from other ornithomimids, particularly Struthiomimus, by a unique combination of anatomical features. Some of these key differences include:

• Specific details in how its hip bones (the ilium and pubis) connected, featuring a V-shaped gap between them when viewed from the side.
• The precise shape of the joining surfaces at the lower end of one of its main foot bones (the second metatarsal).
• Fusion of certain ankle bones to the shin bones (forming a tibiotarsus) and to the upper foot bones (forming a tarsometatarsus). This feature, also seen in modern birds, suggests it was a more advanced type of ornithomimid.
• Relatively straight toe claws, unlike the more curved claws of some other theropods.

These features, while subtle, were enough for paleontologists to determine that the fossil specimen (ROM 1790) represented a new genus and species, Rativates evadens.

Paleoenvironment and Diet

Rativates lived in the coastal plain environment of what is now the Dinosaur Park Formation in Alberta, Canada, during the late Campanian stage of the Late Cretaceous. This region was a lush landscape with rivers, swamps, and forests, supporting a rich diversity of life. The climate was warm and humid.

It shared this ecosystem with many other dinosaurs. These included large hadrosaurs (duck-billed dinosaurs) like Corythosaurus and Parasaurolophus, horned dinosaurs such as Centrosaurus and Styracosaurus, armored ankylosaurs like Euoplocephalus, and other theropods, including the fearsome tyrannosaurid Gorgosaurus, as well as smaller dromaeosaurids (“raptors”) and troodontids.

The diet of Rativates, like other ornithomimids, is thought to have been omnivorous. Its toothless beak would have been suitable for a variety of food items. It likely ate plants, seeds, fruits, insects, and occasionally small animals like lizards or mammals. The “swimmer” part of its name refers to a general hypothesis about ornithomimids being capable swimmers, possibly foraging near water, rather than a specific dietary adaptation unique to Rativates.

Significance and Ongoing Research

The discovery of Rativates is significant because it adds to our understanding of ornithomimid diversity in North America during the Late Cretaceous. It demonstrates that multiple species of these ostrich-mimic dinosaurs coexisted in the same ecosystems, likely specializing in slightly different food sources or habitats to avoid direct competition. For example, Rativates lived alongside other, yet-to-be-fully-described ornithomimids in the Dinosaur Park Formation.

This find also emphasizes the importance of re-examining fossil specimens already held in museum collections, as they can often yield new scientific information and even new species. Ongoing research on ornithomimids continues to uncover details about their anatomy, evolution, and behavior. Future discoveries of more complete Rativates fossils could provide further insights into its specific adaptations and its precise relationships to other members of the Ornithomimidae family, helping to paint a clearer picture of these swift and elegant dinosaurs.