Anchiornis huxleyi, Chinese Fossil Discovery Adds to the Understanding of the Relationship Between Form and Function in Dinosaurs and the Evolution of Flight

 The lithe creature, Anchiornis huxleyi which stood about 28 centimeters tall at the hip, is the oldest known to have sported feathers.-artist's representation

Recent fossil analysis of dinosaurs with feathers, often speculated to have been capable of flight , indicates an important discovery for the scientific "understanding of bird and flight evolution.that speculates that feathered dinosaurs were tree dwellers and consequently has "bolstering the notion that flight developed from the trees down, not from the ground up." Such is the opinion of Larry D. Martin, a paleontologist at the University of Kansas in Lawrence, who provided his opinion on Anchiornis huxleyi and said: : “No dinosaur could walk well with feathers on its feet like that.”

Anchiornis huxleyi -artist's representation

Anchiornis huxleyi was discovered in a region of northeastern China and has been estimated to be between 151 to 161 million years old or approximately "between 1 million and 11 million years older than Archaeopteryx, which scientists regularly refer to as the original bird of antiquity.

Archaeopteryx (meaning "ancient wing") is a very early prehistoric bird, dating from about 150 million years ago during the Jurassic period, when many dinosaurs lived. It is one of the oldest-known birds.-artist's representation

"Archaeopteryx seemed to be part bird and part dinosaur. Unlike modern-day birds, it had teeth, three claws on each wing, a flat sternum (breastbone), belly ribs (gastralia), and a long, bony tail. Like modern-day birds, it had feathers, a lightly-built body with hollow bones, a wishbone (furcula) and reduced fingers. This crow-sized animal may have been able to fly, but not very far and not very well. Although it had feathers and could fly, it had similarities to dinosaurs, including its teeth, skull, lack of a horny bill, and certain bone structures. Archaeopteryx had a wingspan of about 1.5 feet (0.5 m) and was about 1 foot ( 30 cm) long from beak to tail. It probably weighed from 11 to 18 ounces (300 to 500 grams).

Archaeopteryx were highly non symmetrical; and their tail feathers were rather broad. "This implies that the wings and tail were used for lift generation. In 1868, Thomas Henry Huxley interpreted the Archaeopteryx fossil to be a transitional bird having many reptilian features. Using the fossils of Archaeopteryx , Huxley argued that birds and reptiles were descended from common ancestors. Decades later, Huxley's ideas fell out of favor, only to be reconsidered over a century later (after much research and ado) in the 1970's.

Researchers have also determined that feathers have had non-flight purposes and according to an article that appeared in Nature and reported on by Alexis Madrigal of WIRED SCIENCE have elaborated that: "Form can precede function, at least when it comes to mate-attracting feathers."

Madrigal explained: "A part-bird, part-dinosaur described in the journal Nature this week didn’t have feathers for flying, but did possess ostentatious ornamental plumage, including four tailfeathers three times longer than its pigeon-sized body.

"Epidexipteryx ("display" + "wing, feather") lived during the middle-to-late Jurassic, predating the famed Archaeoptryx, and represents an alternative evolutionary pathway from dinosaurs to birds," Madrigal continued.

"The discovery by the Chinese Academy of Sciences adds complexity to the presumed road from T-rex to turkey vulture because the creature looks like a mythological chimera." Madrigal discusses. "And that, in the words of the authors of the paper,  is "bizarre".

"In 1986, J. A. Gauthier looked at over 100 characteristics of birds and dinosaurs and showed that birds belonged to the clade of coelurosaurian dinosaurs. [Gauthier, J.A., 1986. Saurischian monophyly and the origin of birds, in: The Origin of Birds and the Evolution of Flight, California Academy of Sciences Memoir No. 8]"

"Paleontologists think that Archaeopteryx was a dead-end in evolution and that coelurosaurian theropods (a group of dinosaurs that included the Dromaeosaurs Deinonychus, Utahraptor, and Velociraptor) led to the birds," Sid Perkins of ScienceNews has written.

Dromaeosaurs Deinonychus-artist's representation

Dromaeosaurs Utahraptor-artist's representation

 

Dromaeosaurs Velociraptor-artist's representation

The Anchiornis huxleyi has been described as being covered abundantly with two types of feather materials; “dino-fuzz,” resembles a frayed bundle of filaments. The other type, similar in overall structure to the feathers of modern-day birds, consists of small filaments that branch from a larger shaft-like filament."

Sid Perkins writes: "The "dino-fuzz" decorates the creature’s head and neck" an occurrence that was quite common among dinosaurs and suggests "that feathers evolved for purposes unrelated to flight." About two dozen of the shafted feathers adorn each forelimb, and a similar number embellish each lower leg and foot, the researchers report. Unlike most feathered dinosaurs described previously, which have the longest forelimb feathers near the tip of the limb.

"Anchiornis’ longest forelimb feathers are on the wrist, Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing said. Feathers on the legs and feet appear to have overlapped each other, creating aerodynamic surfaces that would have, in essence, given Anchiornis a wing on each of its four limbs. A similar configuration has been seen in other feathered dinosaurs, including Microraptor (SN: 1/27/07, p. 53) and Archaeopteryx (SN: 9/23/06, p. 197)."

Perkins, summarized remarks made by vertebrate paleontologist James M. Clark of George Washington University in Washington, D.C.:"With so many species with this arrangement, the four-winged configuration must have been an important phase in the evolutionary transition from dinosaurs to birds."

Writer, Perkins provided a summary of the prevalent view among many researchers who "scoff at the suggestion that the filamentary structures found on some dinosaurs, especially those unearthed in China in recent years, represent nascent feathers. But those creatures lived many millions of years after Archaeopteryx, which had feathers indistinguishable from those on modern-day birds." 

Vertebrate paleontologist at the University of Bristol in England, Mike Benton is paraphrased by Perkins: "The new find is important because it undoubtedly includes the oldest known feathers on any creature."

“These exceptional fossils provide us with evidence that has been missing until now,” Xu said. “Now it all fits neatly into place, and we have tied up some of the loose ends.”