(CN) — A newly discovered, 110-million-year-old theropod’s elaborate appearance, including pairs of blades protruding backwards from its shoulders, suggest the bright plumage and courtship displays seen in today’s birds may date further back than scientists previously believed.
“We’ve been perhaps too conservative in our reconstruction of other dinosaurs. I think we have to be a bit more imaginative,” said Robert Smyth, a paleobiologist at the University of Portsmouth in England and the lead author of a study published Monday in Cretaceous Research about the new dinosaur.
Ubirajara jubatis — “lord of the spear” in an indigenous Brazilian Tupi language — was a carnivorous theropod, a member of that clade of dinosaurs sporting hollow bones and three-toed limbs. The most popularly known theropod is likely the Tyrannosaurus rex, a giant compared to Ubirajara, which was about the size of a chicken.
Well-preserved remains allowed Smyth and his colleagues to find that Ubirajara sported a long fur mane along its back and featured unique long, flat, stiff “ribbons” that jutted outward and backward from its shoulders.
“It’s really unusual in that it preserves really elaborate display plumage,” Smyth said in an interview. “This includes a mane of really elongated monofilaments along the animal’s back, and something we’ve never seen before in any kind of dinosaur or bird: these weird, broad ribbon-slash-bladelike structures that appear to come out from the animal’s shoulder blade.”
A sharp ridge ran down the middle of each ribbon, each of which jutted out and away from the dinosaur’s limbs so they wouldn’t interfere with its movement.
“They could perhaps have been used for other types of social interactions, maybe threat displays, or — whenever you see elaborate displays like that, in modern birds, it’s been normally evolved for the purposes of intra-specific communication: communicating with members of the same species,” Smyth said.
Ubirajara could have been an early step toward the development of the extravagant, showy inclinations seen in peacocks and other contemporary birds — the world’s only still-living dinosaurs, descended from theropods themselves — and their bright plumage and elaborate courtship rituals.
“All the really elaborate and extravagant display behaviors that we see in birds — for a long time we thought those were uniquely avian characteristics, we believed they were restricted to those dinosaurs that were really closely related to birds,” Smyth said. “This new dinosaur shows us the link, that capacity for integumentary [skin-protruding] structures to become really elaborate goes really deep in the evolution of feathers, almost to the beginning.”
The Ubirajara specimen was preserved between two slabs of limestone in an ancient lagoon located in northeastern Brazil’s Crato Crato Formation. An X-ray scan revealed skeletal remains and soft tissue, providing the researchers rare insight into the individual’s ancient anatomy.
“The conditions in this lagoon are really beneficial to the fossilization process because they inhibit decomposition and this allows structures like soft tissues … to be preserved,” Smyth said.
If it weren’t for the high-quality fossils, Smyth and his colleagues would never have guessed Ubirajara had its showy blades or mane. Nor could they have known that these features were composed of keratin, the same fibrous protein that makes up anatomical parts such as claws, feathers, fur, hair and nails.
Smyth said keratin is less resource-intensive for bodies to produce, and can be more easily replaced or repaired if damaged. The bony crests of other dinosaurs, by comparison, were heavier and more dangerous if broken.
“Really the most, I think, exciting part is that this is the earliest example, from the theropod family tree, of these really elaborate structures,” he said. “Elaborate feathery displays go way further back into the dinosaur lineage than we had previously supposed.”