An international team of paleontologists, led by Carleton University researcher Bradley McFeeters, has added another ornithomimid dinosaur to the prehistoric catalog, and this one was found in the Canadian province of Alberta.
An artistic life reconstruction of Rativates evadens in the paleoenvironment of the Late Cretaceous of Alberta. Image credit: Andrey-Atuchin.
The new dinosaur, named Rativates evadens, is thought to have lived about 76 million years ago (Late Cretaceous period).
It was about 11 feet (3.3 m) long and 5 feet (1.5 m) tall. It weighed about 200 pounds (90 kg) and resembled a modern ostrich, but had long, fingered arms and a long tail.
A partial skeleton of Rativates evadens was collected in 1934 from the lower Dinosaur Park Formation near Dinosaur Provincial Park, Alberta, Canada.
“Rativates evadens was previously identified as another specimen of the more common ostrich-mimic dinosaur Struthiomimus altus, but lacks the key diagnostic characters of that species,” McFeeters explained.
“We can tell that it is a new species based on features of its skull, tail, pelvis and feet, including the shape of the long bones of the feet.”
Partial skull and skeletal reconstruction of Rativates evadens (right). Image credit: Bradley McFeeters et al.
“The referral of fossils to the named species of ostrich-mimic dinosaurs like Struthiomimus is complicated because many specimens are incomplete,” said team member Dr. Michael Ryan, from the Cleveland Museum of Natural History.
“The recognition of Rativates evadens helps clear up these problems, and at the same time strengthens a connection between Canadian ornithomimids and their Asian cousins.”
“We histologically thin-sectioned the femur of Rativates evadens to analyze its growth and determined it was at least eight years old and nearly adult-sized at the time of death,” said Thomas Cullen, from the University of Toronto.
“This is only 80% as long, and half as massive as, the adult size of the closely related species Struthiomimus altus, that is estimated to have weighed 385 pounds (175 kg).”
“This suggests that there are at least two differently-sized, but closely-related dinosaur species that lived together on the ancient landscape, similar to what we see today in the closely related predators like foxes, coyotes and wolves,” said Dr. Claudia Schröder-Adams, of Carleton University.
Although it is a member of Theropoda (carnivorous dinosaurs), Rativates evadens lacked teeth and, similar to birds, had beaked mouths.
The new species and other ornithomimid dinosaurs are believed to have been omnivorous, meaning they ate plants, insects and other small animals.
Their long, powerful legs would have made them fast runners (like Gallimimus in the original Jurassic Park movie), whether they were hunting prey or escaping from larger predators, like Gorgosaurus.
Although no skin impressions were found with the fossil, the closely related ornithomimid, Ornithomimus, also from Alberta, is known to have had a downy covering over most of its body. It may have had true feathers as well.
The research describing Rativates evadens was published on September 20, 2016 in the Journal of Vertebrate Paleontology.
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Bradley McFeeters et al. A new ornithomimid theropod from the Dinosaur Park Formation of Alberta, Canada. Journal of Vertebrate Paleontology, published online September 20, 2016; doi: 10.1080/02724634.2016.1221415
