A fossilized femur bone hidden away in a drawer at The G. Gemmellaro Geological Museum, in Palermo, Italy, has helped researchers discover just how large a feathered, carnivorous dinosaur with diminutive forelimbs grew.
Abelisaurs were a predatory group of dinosaurs that traversed the Earth around 95 million years ago, during the late Cretaceous Period. According to researchers Alessandro Chiarenza and Andrea Cau, the specimen observed in their study, which was published in PeerJ today, would have called North Africa home. During the late Cretaceous, North Africa was a luscious savannah environment, which boasted rivers and mangrove swamps. There, abelisaur would have fed on other dinosaurs and aquatic animals, such as turtles, crocodiles, and fish.
Based on the femur specimen, the researchers estimated that abelisaur grew up to nine m in length, and had a body mass size around two metric tons.
“This find confirms that abelisaurids had reached their largest body size in the ‘middle Cretaceous,’” the researchers wrote in their study.
Femora can help scientists determine the overall size of a dinosaur because they’re attached to the thigh and tail muscles. These areas are subject to scarring and bumps, which can help the researchers determine where muscles and ligaments attached to the bone, and how large the muscles and ligaments were.
Donated to The G. Gemmellaro Geological Museum in 2005, the studied fossilized femur was collected from a sedimentary outcrop in Morocco known as the Kem Kem Beds. The area is host to a variety of giant predatory fossil assemblages. But the sheer number of predatory dinosaur groups discovered has led scientists to question why the dinosaurs wouldn’t have hunted each other to extinction.
Chiarenza, of the Imperial College London, and Cau, of the Univ. of Bologna, postulated that the heavy geological activity in the region caused the fossil fragment records to mix together. During an excavation, this can give the illusion that these dinosaurs coexisted.
“Rather than sharing the same environment, which the jumbled up fossil records may be leading us to believe, we think these creatures lived far away from one another in different types of environments,” said Chiarenza in a prepared statement.
According to the researchers, abelisaurs were likely inland hunters.