Feathered Dinosaurs

[Oresai]

(I could have sworn we had a Paleantology forum! :confused:)


Feathered Dinosaur Most Likely Flightless
Posted on: Tuesday, 13 January 2009, 14:13 CST

Early dinosaurs were likely to have used their feathers for looks rather than for flight or staying warm, researchers reported on Monday.

Researchers formed their hypothesis after studying two 125-million-year-old dinosaur fossils discovered in China.

The Beipiaosaurus fossils depicted individual feathers as represented by a single broad filament, Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and colleagues wrote in the Proceedings of the National Academy of Science.

The first type of feather is a short, slender filament that resembles those found on other flightless theropods.

The second type, called Elongated Broad Filamentous Feathers (EBFFs), was previously unknown to science: it is a single, unbranched filament which is much longer than those seen before on theropod dinosaurs.

Researchers are still unsure about what role the feathers played, although they are fairly certain they were not used for flight or insulation.

Instead, they estimate that dinosaurs used the feathers for visual display, based on the length and stiffness of the feathers.

Researchers said the structures must have been stiff because none of them were preserved in a curved position. What’s more, the feathers are only found on the creature’s head, neck and tail, which implies that they are too spread out for flight.

The “congruence between the full range of paleontological and developmental data strongly supports the hypothesis that feathers evolved and initially diversified in nonavian theropods before the origin of birds and the evolution of flight,” researchers wrote.


http://www.paleontologynews.com/story.asp?ID=376960&Title=Feathered%20Dinosaur%20Most%20Likely%20Fligh tless

[Aodhan]

:0

[Rugevit]

The origin of birds refers to the initial stages in the evolution of birds. The scientific consensus is that birds are a group of theropod dinosaurs that evolved during the Mesozoic Era.
A close relationship between birds and dinosaurs was first proposed in the nineteenth century after the discovery of the primitive bird Archaeopteryx in Germany. Birds share many unique skeletal features with dinosaurs.[1] Moreover, fossils of more than twenty species of dinosaur have been collected with preserved feathers. There are even very small dinosaurs, such as Microraptor and Anchiornis, which have long, vaned, arm and leg feathers forming wings. The Jurassic basal avialan Pedopenna also shows these long foot feathers. Witmer (2009) has concluded that this evidence is sufficient to demonstrate that avian evolution went through a four-winged stage.[2]
Fossil evidence also demonstrates that birds and dinosaurs shared features such as hollow, pneumatized bones, gastroliths in the digestive system, nest-building and brooding behaviors. The ground-breaking discovery of fossilized Tyrannosaurus rex soft tissue allowed a molecular comparison of cellular anatomy and protein sequencing of collagen tissue, both of which demonstrated that T. rex and birds are more closely related to each other than either is to Alligator.[3] A second molecular study robustly supported the relationship of birds to dinosaurs, though it did not place birds within Theropoda, as expected. This study utilized eight additional collagen sequences extracted from a femur of Brachylophosaurus canadensis, a hadrosaur.[4] A study comparing embryonic, juvenile and adult archosaur skulls concluded that bird skulls are derived from those of theropod dinosaurs by progenesis, a type of paedomorphic heterochrony, which resulted in retention of juvenile characteristics of their ancestors.[5]
The origin of birds has historically been a contentious topic within evolutionary biology. However, only a few scientists still debate the dinosaurian origin of birds, suggesting descent from other types of archosaurian reptiles. Among the consensus that supports dinosaurian ancestry, the exact sequence of evolutionary events that gave rise to the early birds within maniraptoran theropods is hotly disputed. The origin of bird flight is a separate but related question for which there are also several proposed answers.