Looking for the “skin color” lost by dinosaurs

  Open an atlas of extinct animals, and you can see many strange-looking animals: red prawns with giant tongs, blue spiral tooth sharks with spiral teeth, two pairs of bright black raptors, etc. . While lamenting their magical appearance, have you ever wondered whether they really look like this? How do scientists know?
  Looking color from fossil
  Anomalocaris large pliers, rotating helical teeth and tooth shark Microraptor of two pairs of wings, although very weird, but it really is based on the facts, after all these structures are preserved in the fossil life. However, the fossils are all gray. How can scientists see the red of the prawns, the blue of the spiral tooth shark, and the “colorful black” of Microraptor?
  For these ancient extinct animals, we naturally can’t find paintings and video materials, so we can only directly refer to modern animals. For example, modern sharks are mostly gray-blue, which is their protective color in the ocean, so scientists speculate that spiral tooth sharks are blue. Odd shrimp is the ancestor of shrimp and crabs. In the picture, it is often painted as the color of king crab-red. Of course, this method is not so accurate. It was not until the beginning of this century that scientists found a reliable method to predict the skin color of ancient creatures.
  If you ask you, why are the leaves of plants green? You might tell me right away because they have chloroplasts. Although animals do not have chloroplasts, they do have another kind of pigment-melanosomes. In 2006, the biologist Jacob Venter of the University of Bristol in the United Kingdom discovered this chromosome for the first time. While studying a 200 million-year-old squid ink sac fossil, Venter saw that there were vacuoles containing many black particles in the squid cells, which he named melanosomes. These melanosomes are filled with squid ink. Because of the melanosomes, the entire ink sac is black. Venter observed the feathers of many birds and found similar vacuoles in the cells. After careful observation, Venter divided the melanosomes into two types: one is oval, which produces black pigment; one The species is spherical and produces rust red pigment. In Toba, these different melanins are mixed with each other, and finally blended into gray, brown, white and other colors.
  Since the structure of melanosomes can be clearly seen in cuttlefish fossils 200 million years ago, can melanosomes be seen in fossils of other animals? The answer is yes. In 2010, many paleontologists, including Venter, first discovered melanosomes on the feather fossils of Chinese dragon bird (a small carnivorous dinosaur). In order to restore the color of Chinese dragon bird, scientists need to sample the head, back, abdomen, limbs and other parts of animal fossils, analyze the shape of melanosomes and the distribution density of various places, and then compare them with the blackness of existing birds. The element structure is compared, and if there are more matches, the colors are mostly consistent. For example, the melanosomes in the black feathers of modern birds are long-axis melanosomes. If a feather somewhere in the fossil also has such melanosomes, it means that the color of the feathers in that part is similar to the black feathers of modern birds. . In this way, the scientists finally restored the appearance of the Chinese dragon bird. Its hair is millet or reddish brown, and its tail is orange and white. The overall “skin color” is similar to that of a squirrel.
  In addition to melanosomes, there are some other pigments in the animal body, such as heme and carotene, but these pigments are not stored in a special cell structure. They are easily degraded during the formation of fossils, and once they are degraded, they are almost irrecoverable. These colored pigments are almost invisible in fossils. However, scientists have discovered that many pigments are related to certain metal atoms. For example, the central element of heme is iron, and the enzyme that synthesizes eumelanin requires copper. Therefore, if relevant elements are found in the fossils, the body color of the part can also be inferred.
  ”Colorful black” What is black
  Actually, if you observe carefully, you will find the biological body color is not a single color. Under light exposure, the body color of organisms often varies in shades. This is because body color is not entirely determined by pigments, but is also related to body structure. The microstructure of different body parts will affect the penetration path and the degree of reflection of light, filtering or reflecting specific wavelengths of light, so that we will see different colors. Scientists call this color produced by different body structures as structural colors, which are much brighter and richer than pigment colors.
  Beetles are a typical representative of structural colors. With dozens of beetles placed in one place, it is almost impossible to find two of the same color. It is unbelievable that these “skin colors” are also produced by the same pigments. Maria McNamara, a paleontologist at Cork University in Ireland, and her team studied the fossils of about 600 different insects and found that the exoskeleton of these insects (a kind of hard external structure that covers the whole body unique to insects) is It is made up of many thin layers only 100 nanometers thick. These thin layers reflect different degrees of light. The more layers, the brighter the colors displayed. Therefore, despite the same pigment composition, the beetle’s skin color will not be exactly the same.
  Microraptor is another representative of colorful structural colors. Among the fossils of Microraptor, researchers from Peking University and the University of Texas in the United States have only found melanosomes, but they believe that Microraptor’s “black skin” is not simply black. It is a kind of “colorful black” that can reflect multi-colors, thanks to the nanostructure of melanosomes.
  The researchers took 26 samples from various parts of Microraptor, scanned the structure and distribution of the melanosomes in these parts, and then compared them with the melanosomes of modern birds’ rainbow-colored feathers. Data analysis shows that the melanosomes of the rainbow-colored feathers are more slender and arranged more regularly than the melanosomes of the black-gray feathers. Among the 26 samples of Microraptor, 7 were not detected. Samples, 13 of the remaining 19 samples have the same shape and arrangement as the melanosomes of rainbow-colored feathers. Based on this, the researchers concluded that the black feathers of Microraptor would reflect blue, green, red, yellow and other colors under different light angles.
  Different colors, different habitats
  to see here, surely you could not see out, presumably paleontology complexion is indeed a difficult task, and probably because of incomplete structure and get the wrong answer, then is there any way to verify what result?
  In the study of modern organisms, we found that the skin color of organisms has a great relationship with the habitat, such as the white polar bears in the polar regions and the brown African lions on the savanna. Therefore, it can be considered that the habitat of paleontology and skin color are also related, and the two can be mutually verified.
  In September 2016, researchers at the University of Bristol in the United Kingdom reproduced the skin color of Psittacosaurus. Its face is darker, the back is dark brown, the abdomen is gradually lighter in color, the forelegs have black spots, and the back skin has stripes of different shades. Biologists call this body color distribution “anti-shadow”. Many modern animals have this kind of body color distribution. For example, fish often have the characteristics of dark back and light abdomen, so that when viewed from the top, the dark back is integrated with the sea. The color of the belly is similar to the color of the sky, so it is not easy to be found. Similarly, creatures living in an environment where light reflects in all directions also have this body color, such as various birds in the forest. Based on this, the researchers speculated that Psittacosaurus also lived in the forest, and the anti-shadow skin color helped them to “stealth” in the forest and avoid the ferocious carnivorous dinosaurs, which is also related to their “small” and herbivorous characteristics. Match.
  In contrast to Psittacosaurus, the brighter Chinese dragon bird may live near rivers with low trees and sparse vegetation. A research team from the University of Bristol in the UK conducted a lighting experiment after reconstructing the skin color model of the Chinese dragon bird. The results showed that in the comparison of the three illumination states of oblique light, direct light and diffused light at 30°, the skin color change of Chinese dragon bird under oblique light is the least obvious, the concealment effect is the best, and diffused light is the least conducive The Chinese dragon bird “stealth”. Therefore, the researchers speculate that the Chinese dragon bird should live near the water with less dense trees. The undigested lizard found in the stomach of the Chinese dragon bird can also prove this point. This lizard has a morphological structure similar to that of modern lizards living near the water.
  No one of us has seen ancient creatures that went extinct hundreds of millions of years ago, and it’s hard to tell exactly what they looked like. However, with the advancement and synergistic application of multiple technical methods, our understanding of them will become more and more accurate