Producer: Popular Science China
Producer: Liao Junqi DinosaurX
Producer: Computer Network Information Center, Chinese Academy of Sciences
The transformation of the dinosaur image
△ The image of dinosaurs is constantly changing with the discovery of fossils (source: https://www.researchgate.net/publication/281344854_Taking_up_the_legacy_of_Waterhouse_Hawkins_and_Owen_art_and_science_for_a_new_Italian_project_to_bring_back_dinosaurs_to_life/figures?lo=1 )
1. Giant lizards coming out of mythology
Concepts related to paleontology had already sprouted in ancient Greek times, but due to the medieval concept of "God is the greatest", the entire discipline stagnated until the 17th century, and the term "dinosaur" did not appear until the 19th century.
Since the 17th century, dinosaur fossils have been used as giant fish, elephant leg bones, and even giant scrotums, and the first correct description as a "giant reptile" was until 1824, when the megalodon named after the Oxford missionary William Buckland and the iguanodon published by the British physician Mantel in 1825, but at this time only these bones were used as overdeveloped ancient lizards.
Megalodon leg bone described as giant scrotum (source: https://imgur.com/DLyP6fj)
With the discovery of more and more fossils, some people began to notice that these fossils were different from living lizards and crocodiles, so in 1841 Richard Owen proposed the classification concept of "dinosaurs", officially opening the research prelude to this taxon.
2. Dinosaurs that "stand" on top of the world!
Although dinosaurs were self-reliant, stereotypes of reptiles continued to poison people's perceptions, such as the restoration of iguanodon and megalodons lying on the ground with four stout legs at the First World's Fair in 1851.
△ 1851 version of the Iguanodon restoration (Source: https://www.pinterest.com/pin/436567757616280534/)
This image was modified until 1878, when a complete Iguanodon skeleton was found in a mine pit 300 meters underground in Belgium, and due to the obvious difference in the proportion of the front and back limbs, the dinosaur stood up straight like a kangaroo.
△ Upright Iguanodon restoration diagram (source: http://dinosaurpictures.org/Iguanodon-pictures)
Although this image is still wrong, it has a profound impact on many monsters in classic film and television images, such as the domineering posture of the king of the monsters "Godzilla" and the dinosaur doll in George's hand in Peppa Pig, which belongs to the restoration of this era.
Subsequently, the research boom of dinosaur fossils also shifted from Europe to the rest of the world, for example, the famous "fossil war" in the western United States was caused by two paleontologists Marsh and Kopp in order to compete for fossils, and dinosaur superstars such as Stegosaurus, Diplodocus, and Allosaurus were also found in the local area.
In addition, Africa and Asia also have many Western expeditions and expeditions to carry out fossil excavations, such as large carnivorous dinosaurs such as Spinosaurus, Sharktooth and Five-story Brachiosaurus in East Africa, while the first nest of dinosaur eggs was found in Asia, and the Gobi Desert also found Protocerapidosaurus, Oviraptorosaurus and Velociraptor.
Until modern times, more and more dinosaur fossils have been found around the world, and even dug up to Australia, Antarctica have found dinosaur fossils (of course, the dinosaur era is hotter than now, the Antarctic is not so "south", so although it is also cold, but the Antarctic of the dinosaur era may not have ice and snow), so the dinosaurs at that time were in the essence of dominating the whole earth. Many early dinosaurs are found in the Triassic strata of South America and Africa, giving people the opportunity to glimpse the mystery of the origin of dinosaurs.
3. The intimacy of dragons and birds
The first to suspect that dinosaurs and birds were adulterous were darwin and Huxley, who advocated "evolution", who believed that the Discovery of Archaeopteryx in Germany in 1860 was a transitional species from reptiles to birds. Owen, who invented the term "dinosaur", agreed on this matter, believing that Archaeopteryx was just a bird that retained embryonic characteristics. Due to the lack of materials, the controversy was shelved for a long time.
△ Archaeopteryx fossil specimen (source: https://www.livescience.com/18085-winged-dinosaur-archaeopteryx-black-feathers.html) The turning point of the event appeared in 1930, and many small carnivorous dinosaurs found in the United States and Mongolia, such as dinosaurs, velociraptors, oviraptors, etc., have many similarities in skeletal structure to birds.
This change had a significant impact on the image of dinosaurs, such as in the late 1960s, when scholars began to suggest that dinosaurs should not be large, dull reptiles, but closer to birds with high metabolic rates and agile and intelligent mobility. On the skeleton, the dinosaur stood from the kangaroo and bent down, its spine parallel to the ground, like a bird.
The most classic case is the Jurassic Park released in 1993, where Spielberg created a tyrannosaurus rex bent down and running wild, velociraptor clever and cunning horror disaster movie based on the most cutting-edge restoration of the time.
△ Dinosaur spines resemble birds parallel to the ground (Source: https://www.google.com/search?tbm=isch&q=jurassic+park&chips=q:jurassic+park,g_1:t+rex:WKjkX_bKzUs%3D&usg=AI4_-kQSGoxjwSA0qsjGuELNvV7WfAQ8zQ&sa=X&ved=0ahUKEwi4nOKMjf_fAhUDjLwKHZSGAfEQ4lYIKCgB&biw=1536&bih=706&dpr=1.25#imgrc=21AG5pu5k5LUnM:)
But the image of the dinosaur has not yet drawn a rest here, and more follow-up studies have shown that the age of dinosaurs should be more than we think... Fluffy and hairy.
4. The fluffy dinosaur appears
Feathers have long been patented as birds, but at the end of the 20th century, China began to discover a large number of exquisite dinosaur fossils, and most surprisingly, they all carried feathers. This wave of fossil discoveries has led to epoch-making progress, allowing China to leap to the center of ancient biological research in an instant.
These feathered dinosaurs not only support the evolutionary path of dinosaurs to birds, but also witness the development of feathers. For example, in a series of fossils, we can see that the feathers go from villi to symmetrical feathers containing a central axis, and then from symmetrical to asymmetrical feathers to adapt to flight.
The position of the feathers also bears witness to attempts at flight. Now look at birds such as chickens, ducks, sparrows, pigeons, etc., and you can see that their feet are bare, and they have no feathers and no wings. But in the famous little raptors, feathers can be seen on the legs, indicating that the birds also experienced the stage of four-winged gliding before fully adapting to flying (look at bats and flying squirrels, their legs are still connected to the wing membrane to help glide).
△四翼飞行的小盗龙(來源: Li, Q. , Gao, K. Q. , Meng, Q. , Clarke, J. A. , Shawkey, M. D. , & D"Alba, L. , et al. (2012). Reconstruction of microraptor and the evolution of iridescent plumage. Science, 335(6073), 1215-1219.)
In the follow-up more fossil studies, the distribution range of feathers has also been expanding, such as sickle-shaped dinosaurs, tyrannosaurs, oviraptorosaurs and other theropod dinosaurs have also found feather distribution, not only that, but also in the ornithischian dinosaurs of the parrot-billed dragon, Tianyu dragon and Kulinda ben dragon also found feathers, so the feathers may have been worn since the time of the dinosaur ancestors.
△ Gorgeous Feather King Dragon Restoration Diagram (Source: https://www.smithsonianmag.com/science-nature/scientists-discover-a-gigantic-feathered-tyrannosaur-172633563/)
The 2018 study found that the hairs on pterosaurs had similar bird feather structures, and if the two hairy structures were homologous, the distribution of feathers should be earlier and more widely distributed among reptiles such as dinosaurs and pterosaurs in the Mesozoic Era than we expected.
△疑似带有羽毛结构的翼龙化石(Z. Yang, B. Jiang, M. McNamara, S. Kearns, M. Pittman, T. Kaye, P. Orr, X. Xu and M. Benton, 2018. Pterosaur integumentary structures with complex feather-like branching. Nature Ecology and Evolution. https://doi.org/10.1038/s41559-018-0728-7)
Modern methods of studying the development of dinosaurs
In the 21st century, in addition to new locations, new materials, and new discoveries, we are also using more new methods to study dinosaurs.
1. See in the bones!
△ Studying the growth of dinosaurs from bone tissue (Erickson, & Gregory, M. Thompson, (2014). On dinosaur growth. Annual Review of Earth and Planetary Sciences, 42(1), 675-697.)
Dinosaurs will continue to grow throughout their lives, and will have different growth rates in different seasons as the temperature and food resources change, so they will form a structure similar to the "annual rings" of plants on the bones.
By counting these "annual rings", we can know how old the dinosaurs were when they died, and the width and narrowness of the interval between each "annual ring" also witnessed the speed of the annual growth rate, which can be used to infer whether a dinosaur belongs to the rapid growth of the young stage or has not grown much, dying of old stage.
This method of cutting dinosaur bones to determine the growth process and age has been practiced for many years, and in modern times, with the deepening of research and the advancement of imaging technology, people have continuously improved this research method, such as discussing the growth process with the growth curve, and judging the growth structure and subtle differences between different species through more subtle bone cells and fiber levels.
2. How to measure the body temperature of dinosaurs?
The question of whether dinosaurs were cold-blooded animals used to be indirectly inferred by anatomical structures, but with the application of stable isotopes, the body temperature of dinosaurs can now be directly detected.
Atoms with the same number of protons and different neutron numbers will constitute "isotopes", and those with stable properties that will not decay are called "stable isotopes", and the weight of stable isotopes is different, and at different temperatures, the activity of these different weight atoms is also different, so the temperature at the time of formation can be judged by the proportion of isotopes in the constituent fossil elements.
According to the latest research, the body temperature of small theropod dinosaurs such as oviraptorosaurs is about 32 degrees Celsius, and the body temperature of large sauropods is 35 to 38 degrees Celsius. These body temperatures are low relative to mammals or birds of the same size, that is, although dinosaurs have a certain body temperature, their metabolism and function of producing temperature are not as efficient as mammals or birds, so they are classified as "mesothermal animals".
3. Dinosaur color
In the past, most of the colors of dinosaurs were filled by scholars, but now if you use electron microscopy to scan feathers, you can observe the structure of the pigment body in them.
Scholars have found that in the different colors of feathers of living birds, there will be different pigment body compositions. For example, rod-shaped melanoid bodies represent black, round brown melanin represents ochre red, white lacks pigment bodies, and pigment bodies with different arrangement patterns also reflect optical color, such as neatly arranged melanoids that emit metallic luster in light.
△ The color of the feathers can be distinguished from the arrangement and shape of the pigment body (Li, Q. , Gao, K. Q. , Meng, Q. Clarke, J. A. , Shawkey, M. D. , & D"Alba, L. , et al. (2012). Reconstruction of microraptor and the evolution of iridescent plumage. Science, 335(6073), 1215-1219.)
Applying this data to dinosaur feather fossils can reflect the color and luster of the feathers on dinosaurs.
In addition to the above fields, with the development of science and technology and the combination of interdisciplinarity, more and more rich research methods have been applied to dinosaur research.
Resurrect dinosaurs
Since the craze sparked by the movie Jurassic Park, the resurrection of dinosaurs has been a dream or nightmare for many.
Stills from the movie Jurassic Park (Source: http://jurassicpark.wikia.com/wiki/File:Drilling_amber.png)
In the movie, the extraction of dinosaur blood DNA through mosquitoes in amber seems to be very scientific, but in reality this method does not work. Because DNA degrades continuously at the beginning of the death of an organism, the more optimistic data suggests that there is a chance to preserve for about 1 million years, but the extinction of dinosaurs is already 66 million years ago, so the chances of DNA being preserved are very slim.
If it didn't work in the past, some scholars moved the idea to the existing dinosaurs - birds. Birds are the only descendants of the dinosaur family to survive the mass extinction, and for scholars who want to resurrect dinosaurs, the DNA in birds may be a key turnaround in the event.
In the process of embryonic development, there will be many ancestral features, such as human embryos at a specific stage of development will also appear webbing, gill fissures of these ancestral characteristics, so the evolutionary memory will actually be partially left in the blueprint of genes, and appear in the embryonic development stage, such related research belongs to the category of "evolutionary developmental biology".
Some results have been achieved in this type of research, for example, in the chicken experiment, some ancestral genes have been successfully opened to allow chickens to have teeth structure, and the next step is to study a process from wings to claws, tail feathers to tails, and realize a half-chicken and half-dragon "chicken dragon".
△ Will there be a chance to see chickens turn into dinosaurs in the future? (Source: http://jurassicpark.wikia.com/wiki/File:Chickenosaurus-horner-chicken-111222c-02.jpg)
(The pictures reproduced in this article have indicated the source)