In the late Jurassic period, about 150 million years ago, the Altmühl valley in Bavaria was part of the northern tropics and covered by a shallow sea. It is from this region, that all known specimens of Archaeopteryx have come.
Archaeopteryx is of particular interest to paleontologists because it is considered an early bird and a late dinosaur. The animal, which was at most the size of a raven, represents a transition and may yield important clues about how dinosaurs took to the air.
New research, published in the journal Nature by paleontologists of Ludwig-Maximilians-Universitaet (LMU) in Munich takes a closer look at a new specimen with the best preserved plumage found to date. This preservation, primarily as impressions in the rock matrix, allows for comparison with other feathered dinosaurs.
A team led by Dr. Oliver Rauhut, a paleontologist in the Department of Earth and Environmental Sciences at LMU Munich, is conducting a highly detailed analysis of the specimen.
“For the first time, it has become possible to examine the detailed structure of the feathers on the body, the tail and, above all, on the legs,” said Rauhut in a statement.
One of the most striking discoveries the team has made to date is that feathers appear to have evolved independently, prior to flight.
“Comparisons with other feathered predatory dinosaurs indicate that the plumage in the different regions of the body varied widely between these species. That suggests that primordial feathers did not evolve in connection with flight-related roles, but originated in other functional contexts,” noted Dr. Christian Foth of LMU and the Bavarian State Collection for Paleontology and Geology in Munich.
Predatory theropods with body plumage are known to predate the Archaeopteryx. It is believed that their feathers probably evolved to provide insulation. Feathered forearms may have also been used to aid in balance while running, similar to modern ostriches. Brooding, camouflage and display are also possible reasons for the evolution of feathers.
“If feathers had evolved originally for flight, functional constraints should have restricted their range of variation. And in primitive birds we do see less variation in wing feathers than in those on the hind-limbs or the tail,” explained Foth.
Once feathers were present, they could have been easily co-opted for flight and aerial navigation. It is also possible that flight, in early birds, was an on again – off again proposition.
“It is even possible that the ability to fly evolved more than once within the theropods. Since the feathers were already present, different groups of predatory dinosaurs and their descendants, the birds, could have exploited these structures in different ways,” said Rauhut.
The researchers’ work with the 11th known archaeopteryx specimen is ongoing and will likely yield more interesting results.