Fossils rarely retain evidence of an organism’s original color, but these 99 million-year-old amber fossils found in Myanmar are revealing the vibrant hues of another world.
New Research published today in Proceedings of the Royal Society B highlights dozens of amber fossils from the Cretaceous period that still contain evidence of the original colors of their occupants. Bursting in metallic blue, purple and green, these ancient insects are both alien and strangely familiar.
Nature, of course, is very colorful. Unfortunately, however, fossils usually provide an opaque and monochromatic view of the past. That said, paleontologists are finding ways to make fun of colors from well-preserved fossils, whether they are dinosaurs is flying reptiles or ancient snakes is mammals.
Determining the color of extinct species is important because it can tell paleontologists one or two things about the animal’s behavior, for example if it used extravagant colors to attract mates or warn potential predators, blend in to hide or hide, or colors that they helped with the temperature regulation. Color can also shed light on ancient environments and ecosystems, especially when it comes to camouflaging.
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For the new study, a research team from the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (NIGPAS) studied 35 individual amber samples with fantastically preserved insects trapped inside. The fossils were found in an amber mine in northern Myanmar.
“Amber is in the mid-Cretaceous period, approximately 99 million years old, dating back to the golden age of dinosaurs,” explained Cai Chenyan, associate professor of NIGPAS and lead author of the new study, in a press release. “It is essentially resin produced from ancient conifers that grew in a tropical rainforest environment. Animals and plants trapped in the dense resin have been preserved, some with realistic fidelity. “
Colors in nature tend to fall into three main categories: bioluminescence, pigments and structural colors. These amber fossils retain the structural colors, which tend to be intense and rather captivating (including metallic colors) and are produced by microscopic light diffusion structures located on the heads, bodies and limbs of animals.
“The type of color preserved in amber fossils is called structural color,” explained Pan Yanhong, co-author of the study and professor at NIGPAS. “The surface nanostructure scatters light of specific wavelengths” which “produces very intense colors,” said Pan, adding that this “mechanism is responsible for many of the colors we know from our daily lives.”
These amber fossils retained evidence of their structural colors, but not before careful preparation, as the authors explain in their article:
For standard observation, the fossils were polished using different grades of sandpaper and diatomite powder, to get closer to the [fossils] as much as possible without damaging them. Where it helped observation, some pieces were smoothed into very thin slices, making the insect [fossils] clearly observable and the surrounding amber matrix almost transparent in full light.
For you photographers out there:
The photographs on various backgrounds were taken using a Canon EOS 5D Mark III digital camera, equipped with a Canon 65mm MP-E macro lens (F2.8, 1–5X) and a mounted Canon MT-24EX dual flash. Focus Stacking software (Zerene Stacker, v. 1.04) was used to increase the depth of field.
The images were edited in Photoshop, but only to adjust the brightness and contrast.
The cuckoo wasps were particularly stunning, with the head, chest, abdomen and legs in shades of metallic blue-green, yellow-red, purple and green. Fascinatingly, these color patterns were a close correspondence with the cuckoo wasps alive today, according to research. Other overtime features include the soldier’s blue and purple beetles and dark green metallic flies. The blue-greenish dyes were attributed to mimicry, but other functions, such as thermoregulation, could not be excluded.
To test whether the observed colors were caused by the nanostructures, the scientists made some theoretical models. They studied a sample of wasp selected using an electron microscope, which allowed them to match the models with specific colors. In particular, the reflectance wavelengths at 514 nanometers corresponded to the bluish-green color seen under the white light, which perfectly matched what they saw with their eyes.
The colors seen in these amber samples, therefore, are indicative of how these insects actually appeared during the Cretaceous, according to the research.
“[Our] observations strongly suggest that the color preserved in some amber [fossils] it could be the same shown by insects when they were alive about 99 million years ago, “wrote the authors in the study. “This is further corroborated by the fact that metallic blue-green coloring is often found in place [living] cuckoo wasps. “
The authors also analyzed amber fossils in which the color was not preserved. In these cases, the nanostructures were severely damaged, resulting in brownish and blackish coloring.
This is an exciting result, because it means that other amber fossils could also produce structural colors. Time for scientists to revisit some old specimens.