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Zeiss SEM Used to Uncover New Evidence of Feather Color in Winged Dinosaur

Carl Zeiss Microscopy, LLC, announces that it participated in a major research study that uncovered new evidence of feather color in the winged dinosaur Archaeopteryx

The research team used the ZEISS SUPRA 55VP scanning electron microscope to study a feather from an Archaeopteryx fossil found in 1861 and determined the wing feathers had traits that would have helped the dinosaur to fly. The study, which appears in Nature Communications, was funded by the National Geographic Society and the U.S. Air Force Office of Scientific Research.

The team of researchers was led by Ryan Carney of Brown University and included researchers from Yale University, the University of Akron and the Carl Zeiss Nanotechnology Center in Oberkochen, Germany. Paleontologists have long been excited about the Archaeopteryx fossil, believing it placed the dinosaur at the base of the bird evolutionary tree. Much of the debate on the bird-dinosaur connection focused on the iconic creature’s wings and the mystery of whether – and how well – it could fly.

After two unsuccessful attempts to image the feather’s melanosomes (pigment-producing cell parts), the team switched to examining the feather specimen without coating using the ZEISS SUPRA 55VP, a field emission, scanning electron microscope (FE-SEM), at the Carl Zeiss laboratory in Germany. The system was equipped with an Oxford INCA Energy 300 SEM-energy dispersive X-ray spectroscopy system. In addition to the FE-SEM used to image the melanosomes for the color reconstruction, the electronic data system (EDS) allowed the team to determine that the feather was preserved as an organosulfur residue.

Through this novel analytic approach, the researchers were able to determine that the well-preserved feather on the raven-sized dinosaur’s wing was black. The color and parts of cells that would have supplied pigment are evidence that the wing feathers were rigid and durable. These traits would have helped the Archaeopteryx to fly.

The team also learned from its examination that an Archaeopteryx’s feather structure is identical to that of living birds, a discovery that shows modern wing feathers had evolved as early as 150 million years ago in the Jurassic period. Scientists posit that if Archaeopteryx was flapping or gliding, the presence of melanosomes would have given the feathers additional structural support, which would have been advantageous during this early evolutionary stage of dinosaur flight.

The team measured the length and width of the sausage-shaped melanosomes to be roughly 1 micron long and 250 nanometers wide. To determine the melanosomes’ color, researchers statistically compared Archaeopteryx’s melanosomes with those found in 87 species of living birds, representing four classes: black, gray, brown, and a type found in penguins. They discovered that the feather was predicted to be black with 95 percent certainty.

Next, the team sought to better define the melanosomes’ structure. For that, they examined the fossilized barbules, tiny, rib-like appendages that overlap and interlock like zippers to give a feather rigidity and strength. The barbules and the alignment of melanosomes within them are identical to those found in modern birds.

The importance of the pigment is less clear. The black color of the Archaeopteryx wing feather may have served to regulate body temperature, act as camouflage or be employed for display. It could have been for flight as well. While the study does not conclusively prove that Archaeopteryx was a flier, melanosomes in modern bird feathers provide additional strength and resistance to abrasion from flight, which is why wing feathers and their tips are the most likely areas to be pigmented. This leads researchers to hypothesize that the melanosomes in Archaeopteryx would have provided similar structural advantages, regardless of whether the pigmentation initially evolved for another purpose.

Article citation: Carney, R. M. et al. New evidence on the colour and nature of the isolated Archaeopteryx feather.Nature Communications 3:637 doi: 10.1038/ncomms1642 (2012)

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