Archaeopteryx, the iconic early bird that lived around 150 million years ago, sported feathered “trousers” on its hind limbs as well as other decorative feathers, and researchers now believe at least some non-avian dinosaur and bird feathers evolved for flashy display before they were later recruited for flight.
That's the conclusion of a new study, published in the journal Nature, which describes a remarkable new specimen of Archaeopteryx that includes extensive feather preservation.
“The excellent preservation of the feathers in the new specimen helps to clarify many contentious issues,” senior author Oliver Rauhut of Ludwig-Maximilians University Munich told Discovery News. “The specimen not only shows the wing and tail feathers in great detail, but also body plumage and feathers along the hind limbs…(which are) similar to the feather ‘trousers’ found in many modern birds of prey.”
The researchers determined that quill-like feathers covered Archaeopteryx’s entire body up to its head. Its hind limb feathers were symmetrical, indicating they didn't help with flight.
Its tail feathers were extremely long -- more than 60 percent of the length of its bony tail -- with some being asymmetrical and therefore useful in flight. Its wing feathers were also suitable for flight, and appear to have been just as strong as those seen in modern flying birds.
“There are a number of indications that Archaeopteryx was capable of aerial locomotion, but just how well it could fly remains debated,” Rauhut said, adding that the jury is still out as to whether Archaeopteryx was a non-avian dinosaur or a bird. That’s because the transition from one to the other happened gradually.
Current evidence does, however, suggest that Archaeopteryx was a representative of the main evolutionary lineage going toward birds. The evidence also suggests that Archaeopteryx and its dinosaur predecessors were colorful and flashy.
Rauhut shared that “it is very likely that dinosaurs could see colors, and many animals that have this capability tend to be colorful.” Prior studies support this theory.
He and his team suspect that, like modern birds, the colorful feathers likely were used in displays, such as for mating.
It appears that proto-feathers originally evolved for regulating body temperature. The quill-like contour feathers, on the other hand, could have first evolved for show.
“Once present, these feathers could then be adapted for many other functions, such as balance during fast running, protecting and shading the eggs during breeding, and flight,” Rauhut said.
“This is a fine and important piece of work on a great new specimen,” said Mark Norell, division chair and curator-in-charge of the American Museum of Natural History’s Division of Paleontology. “It clearly shows that the evolution of hind limb feathers is very complex and the evolution of feathers as a whole is de-coupled from flight.”
Lawrence Witmer, a professor of anatomy and paleontology at Ohio University, also believes that the new specimen “is a really important find.”
Witmer added, “When you combine the new information from Archaeopteryx with what we see in other bird-like dinosaurs and dinosaur-like birds, the picture that emerges is that maybe (quilled) feathers evolved more as ornaments for display and were later co-opted by evolution for flight … maybe multiple times. I think the authors make a good case. The display argument is very compelling.”