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AnimalsScience

Feathered Dinosaurs May Have Been The Norm, Fossil Discovery Suggests

 
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The fossil of a previously unknown species of dinosaur has been discovered in the chalk beds of the Franconian Jura, and it shows very clear traces of fluffy plumage. The discovery brings up an interesting question — were all dinosaurs feathered?

The new discovery is helping to change our perception of how predatory dinosaurs looked. Sciurumimus albersdoerferi is the first evidence that we have that theropod dinosaurs, which are not closely related to birds, were feathered.

“This is a surprising find from the cradle of feathered dinosaur work, the very formation where the first feathered dinosaur Archaeopteryx was collected over 150 years ago,” said Mark Norell, chair of the Division of Palaeontology at the American Museum of Natural History and an author on the new paper along with researchers from Bayerische Staatssammlung für Paläontologie und Geologie and the Ludwig Maximilians University.

Theropod dinosaurs were bipedal, mostly carnivorous dinosaurs. There have been many recent discoveries showing that many species of theropods were feathered.

Previously, before this new discovery, though, feathering had only been found in fossils of the theropods known as coelurosaurs, a very diverse group that included animals as different as the T. rex and primitive birds.

Sciurumimus albersdoerferi, though, is a megalosaur, not a coelurosaur; the first example of a feathered megalosaur. Interestingly, the new species is “deep within the evolutionary tree of theropods, much more so than coelurosaurs, meaning that the species that stem from Sciurumimus are likely to have similar characteristics.”

“All of the feathered predatory dinosaurs known so far represent close relatives of birds,” said palaeontologist Oliver Rauhut, of the Bayerische Staatssammlung für Paläontologie und Geologie. “Sciurumimus is much more basal within the dinosaur family tree and thus indicates that all predatory dinosaurs had feathers.”

“Sciurumimus belongs to a much older branch of the family tree of predatory dinosaurs.Its plumage may be telling us that all predatory dinosaurs had feathers.”

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The researchers also bring up the fact that fossils of the flying reptiles that lived alongside dinosaurs, pterosaurs, have been found that also show similar plumage.

“If that is the case, we must abandon all our notions about giant reptiles encased in tough scales,” Rauhut says.

The fossil is of a baby Sciurumimus, and was found “in the limestones of northern Bavaria and preserves remains of a filamentous plumage, indicating that the whole body was covered with feathers. The genus name of Sciurumimus albersdoerferi refers to the scientific name of the tree squirrels, Scurius, and means ‘squirrel-mimic’-referring to the especially bushy tail of the animal. The species name honours the private collector who made the specimen available for scientific study.”

“Under ultraviolet light, remains of the skin and feathers show up as luminous patches around the skeleton,” said co-author Helmut Tischlinger, from the Jura Museum Eichstatt.

“When the skeleton was irradiated we were able to discern fragments of the skin and the plumage as fluorescent spots and filaments.”

The fossil stands out for more than just its feathers though — the skeleton is the most complete predatory dinosaur yet found in Europe, and is a rare glimpse at what a young dinosaur looked like. In addition to well known juvenile characteristics, like large eyes, the new fossil helped confirm other hypotheses about juvenile theropods.

“It has been suggested for some time that the lifestyle of predatory dinosaurs changed considerably during their growth,” Rauhut said. “Sciurumimus shows a remarkable difference to adult megalosaurs in the dentition, which clearly indicates that it had a different diet.”

“Adult megalosaurs reached about 20 feet in length and often weighed more than a ton. They were active predators, which probably also hunted other large dinosaurs. The juvenile specimen of Sciurumimus, which was only about 28 inches in length, probably hunted insects and other small prey, as evidenced by the slender, pointed teeth in the tip of the jaws.”

“We know that dinosaurs were able to grow at terrific rates; diminutive hatchlings could reach adult lengths of several meters,” Rauhut points out. “And even if they might have looked fluffy, they were certainly among the top predators in the food chain.”

“Everything we find these days shows just how deep in the family tree many characteristics of modern birds go, and just how bird-like these animals were,” Norell said. “At this point it will surprise no one if feather like structures were present in the ancestors of all dinosaurs.

The study was financed primarily by the Volkswagen Foundation and the American Museum of Natural History.

The newly discovered fossil is scientifically described in a paper published in the Proceedings of the National Academy of Sciences on July 2.

Source: LMU MunichImage Credits: H. TischlingerJura Museum Eichstatt, Ludwig-Maximilians-Universität München




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