Fancy dinosaur with bizarre shoulder decorations was the peacock of the Cretaceous

Artist's impression of Ubirajara jubatus.

Artist’s impression of Ubirajara jubatus.
Illustration: Bob Nicholls / 2020

The reanalysis of an ancient fossil has revealed features never seen in a dinosaur before, including a long, fur-like mane along its back and a pair of stiff structures protruding from its shoulders. Scientists say these elaborate decorations were likely used for display, in what is a very early version of peacocks.

Introduction Ubirajara jubatus, a theropod dinosaur that lived 110 million years ago in the supercontinent of Gondwana. In addition to waving an impressive mane on his back, Ubirajara had two pairs of straw-like structures that probably protruded from his shoulders. This feature has never been seen in a non-avian dinosaur, and it is reminiscent of the elongated feathers seen in the extant male standardwing bird of paradise.

Which Ubirajara Using these expanded structures for display is a clear possibility, according to the authors of the new study, published today in the journal Cretaceous Research. The size of a chicken Ubirajara may have flashed the adornment to attract a mate, intimidate male rivals, or deter potential predators.

Ubirajara jubatus

Ubirajara jubatus
Illustration: © Bob Nicholls / 2020

The sex of the specimen could not be determined, but this flamboyant display would suggest a male, given the differences seen in modern male and female birds. Modern birds and ancient theropods share a common ancestor, and this discovery suggests that the whole peacock thing is something the two groups inherited from earlier dinosaur relatives. Or they independently acquired the same strategy – difficult to know.

The partial skeleton was found decades ago in the Crato Formation in northeastern Brazil and was preserved on two slabs of limestone that, when combined, “fit together perfectly,” the authors wrote. The specimen eventually found its way to Germany, where it is stored in the State Museum of Natural History in Karlsruhe. Recently, a team of paleontologists decided to re-examine the fossil with a high-resolution digital X-ray machine, revealing its previously invisible features.

Despite the fossil’s incompleteness, the researchers were able to discover well-preserved thread-like structures in the limestone. The long, flat, and stiff filaments turned out to be composed of keratin – the same stuff that makes up hair, feathers, and fingernails. These four filamentous structures would normally be hidden away Ubirajarabody so as not to interfere with its dexterity, and according to the study, they would likely only be deployed when needed.

“The ribbon-like structures are unlike anything we’ve seen before. They are elongated and flat with a ridge running their length that probably strengthens the structures, ”said Paleontologist Robert Smyth of the University of Portsmouth, lead author of the article, in an email. “Similar-Filaments formed are known in other dinosaurs, but none that are so large compared to the size of the animal. “

Smyth said Ubirajara is the earliest branch of the evolutionary theropod tree known to have such characteristics.

“Until now, expanded view Feathers were thought to be limited to those dinosaurs that were already complex developed, bird-like feathers, ”he added.

The paleontologists also documented the long, thick mane from fur-like filaments. As the authors speculate, Ubirajara controlled his mane with muscles along his back, similar to a dog’s raised hackles.

“The ‘mane’ is made up of densely packed elongated monofilaments, similar in thickness to coarse hair, that increase in length from the nape of the neck down the back,” Smyth wrote in his email. “We believe these monofilaments come from follicles that would have given the dinosaur the ability to raise and lower them.”

Smyth said Ubirajara lived in a semi-arid environment bordering an ancient sea, and it probably fed on small reptiles and amphibians.

Ubirajara is also important because it is the first non-avian dinosaur discovered in the Brazilian Crato Formation. As for the name, “Ubirajara” means “lord of the spear” in the native Tupi language, and “jubatus” means “mane” or “crest” in Latin.

Finds like this one, which allow paleontologists to study an animal’s outer structures, radically change our views on dinosaurs and what they looked like. At the same time, this type of research can also provide new insights into their possible behaviors. As regards Ubirajara, I picture this little guy walking around with his four thread-like structures held up while doing a seductive dance for the dinosaur ladies.


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