With the help of newly discovered fossils and new technologies, scientists are gradually understanding how dinosaurs lived and died. 77 million years ago (it was near the end of the dinosaur era, but it was12 million years before the extinction of dinosaurs), a dying young hadrosaur fell near the vast inland sea, which covered most parts of central North America.
Usually dinosaurs can't rest in peace after death: they are either torn and eaten by scavengers or washed downstream by floods; Their bones are scattered all over the floor, and I don't know where to throw them-until they are dug up. Many dinosaur bones stored in museums now are pieced together with dinosaur bones unearthed in different places. But the situation of this hadrosaur is different. It lay on its side in a shallow river and was quickly buried under the sediment, so it not only preserved the shape of bones, but also preserved the impressions of skin, muscles and internal organs. When Buck, a famous dinosaur researcher, first saw this hadrosaur in a small museum in north-central Montana, he took off his hat with excitement and knelt down with tears in his eyes. He said: "At that time, I felt like I saw the statue of the Virgin Reiko Kobayakawa."
Even if you don't love dinosaurs like Buck, you will appreciate this unique animal. This fossil, half embedded in the rock, lies with its head bent back, and its shape seems to be trapped by the current rushing to the shore. It is far more impressive than any patchwork skeleton: it used to be a living real animal. Four years ago, independent paleontologist Murphy excavated this hadrosaur on a hillside in Montana. Until now, he is still considering how to study without destroying the internal organs of animal fossils. He said, "I don't know what I will find. Will there be crops in it to help digest plants? We can see the heart. Is it three cavities like the heart of modern reptiles or four cavities like birds? Isn't it good to know this? "
Even if you imagine a complete dinosaur to study, it is almost equivalent to a revolution in paleontology, because in the field of paleontology, most of the biological history is inferred from one tooth. Another revolution is already under way: scientists are using CT scanners, supercomputers and their intelligence to study dinosaur bones that have been silent for many years and reveal their secrets. A biologist discovered traces of blood vessels and even blood cells by decomposing the mineral structure in dinosaur bones. There is another question that people have been speculating with interest for a long time: How fast can Tyrannosaurus Rex run? Now you can use biomechanical algorithm to calculate. Engineers completely changed people's previous understanding of the way this long-necked behemoth stood and walked. At present, some dinosaur models in museums will have feathers (which people never thought of ten years ago), because more and more evidence shows that dinosaurs are closely related to birds. All these discoveries are the contents of the first large-scale dinosaur exhibition in the American Museum of Natural History in new york in five years. Norell, director of paleontology in the museum, said that in the past 20 years, paleontology has not been limited to taxonomy, but has developed into a study of dinosaur physiology, ecology and even behavior habits. He also said that this industry has become a discipline driven by research and experiment, not just discovery.
However, the discovery of dinosaur bones has not decreased. The secrets of the past are still buried underground. As the land is eroded, some dinosaur bones are exposed every season. New dinosaur species are discovered every month. Malkovich, curator of dinosaurs at the Chicago Field Museum, estimates that as many as 900 species have been found that meet the principle of biological classification, at least double that of 20 years ago. Of course, many of them only have skulls, even broken skulls. Barker found that even the five-ton Hydreigon, "the trunk is generally not found much, because it has been eaten by other animals." Farmers in Liaoning Province, China have discovered a series of well-preserved fossils, showing a complete ecosystem, including plants, insects, fish, turtles, small mammals and birds-like dinosaurs that have never been seen before. Among the bird-like dinosaurs, the 1.5-meter-long Odontosaurus was an early relative of Tyrannosaurus rex with underdeveloped feathers. The function of these feathers is obviously to keep warm, not to fly. There is also Microraptor Gu, whose hind legs are feathered and look like a bird with four wings. The poor and arid areas in Patagonia, South Africa and the western United States have experienced a complete cycle of soil deposition, uplift and erosion since the late Cretaceous, exposing the sediments 70 million years ago. The dinosaur bones in these places are exposed on the ground, waiting for someone who can distinguish them from the rocks to pick them up (one way to distinguish them is licking; Bones stick to the tongue). Two years ago, the Salisbury brothers in Sioux City, Iowa, USA (doctors and veterinarians respectively) and their lawyer friend Buckmel went to the rugged mountains in western South Dakota to look for fossils. They found a spherical bone (about 2 cm in diameter) the size of a quarter coin at the foot of the mountain, and several blackened teeth at a height of 9. 15 meters. These bones belong to the skull of a pachiosaurus. The pachycephalosaurus was about the size of a horse. It is usually characterized by a raised forehead, surrounded by volleyball-shaped protrusions, spikes and crests. But unlike all other known pachycephalosaurus in North America, this dinosaur's forehead was flat, not protruding. Barker said, "We know that Pachycephalosaurus appeared in China and Mongolia earlier, and their foreheads evolved into bulges about 80 million years ago. That's all we found in North America. It was not until this dinosaur was discovered that there was also a flat-headed dinosaur in North America. This dinosaur lived in an era when dinosaurs were about to die out. I once wrote that the evolution of dinosaurs will slow down and will not differentiate into new species. This view is wrong. "
It is unthinkable for lawyers like Crick and Watson to immerse themselves in the discovery of molecular genetics in their spare time. But from the spiritual level, it is equivalent to Crick and Watson's scientific world, and dinosaur paleontology is closer to Darwin's scientific world, or more concerned about new discoveries in the wild. Large universities are competing with state research institutions, such as the Montenegro Museum of Natural History in South Dakota and the Rocky Mountain Museum in Montana. The Salisbury brothers donated the thick-toothed faucet bone they found to the Indianapolis Children's Museum. Education is not a prerequisite. Murphy studied dinosaurs with his grandmother and famous paleontologist Wright, but he didn't even have a college degree. He established a research center in the former site of a tire shop in Malta, a remote town in Montana, to raise research funds. Most of the staff of the center are volunteers, and the operating expenses mainly come from sporadic visitors and explorers. They paid Murphy to give priority to searching for dinosaur fossils in the countryside. Burke, a wealthy dinosaur fan in new york, paid Murphy last year to collect fossils in Argentine Patagonia Plateau. Dinosaur research lacks strong corporate sponsorship, with Universal Studios and director Spielberg as the only exceptions. They set up the Jurassic Park Research Institute, and used part of the profits from making dinosaur movies to support the excavation work. On the other hand, creationists who think dinosaurs died in floods are also dissatisfied with paleontology. A rabbi in Brooklyn, new york, wrote to Norell of the American Museum of Natural History, complaining that if there was news that birds were actually dinosaurs, people would think that chickens were not kosher clean food.
In the summer of 2000, a volunteer working for Murphy found a bone on a low cliff facing west in a cattle farm in the north of Malta town. Murphy's main assistant is his teenage son Matt. At that time, Matt dug down and found four coccygeal vertebrae, so he called his father Murphy. Murphy is an easygoing and calm scientist who has been wearing khaki shorts and a wide-brimmed fedora for many years. He is talented in visualizing how bones are put together to form animals, which makes up for the lack of orthodox training. He stood under the low cliff and looked up. He saw something and thought it was undoubtedly the outline of pelvis and ankle. The next day, he told the owner of the cattle farm what he had found.
Cattle owner Hammond recalled: "I tried to be very excited." When I got home, my daughter asked me how I was. I replied,' It's like a big stain on a rock.' "
The first thing to do is to name it. Not a scientific name; It is already a very famous species, called brachiosaurus, which belongs to a duckbill herbivorous dinosaur in the late Cretaceous, and its length can reach 10.7 meters. However, some discovered dinosaurs are generally given a cute nickname by the discoverer. Psychologists may think that this is a kind of psychological compensation, because human beings are insignificant in the face of such a formidable behemoth. The spectacular Tyrannosaurus Rex exhibited at the Chicago Museum of Natural History is called Su (discovered by sue hendrickson). Murphy also found three almost intact hadrosaurs, named Elvis, Pinat and Roberta. The newly discovered Leonardo was named after a sentence engraved on a nearby rock: "Leona Dobb loved Geneva Jordan deeply, 19 16".
The following summer, Murphy returned to the place where Da Vinci was discovered and began to dig. They carefully blasted the half-meter-thick rock covered on it, then used bulldozers to remove the broken sand more than two meters high, and then volunteers manually removed the last 1.2-meter-thick sand. While they were dealing with a front leg, a volunteer found something unusual and called Murphy.
"I looked at it and said,' Oh, my God! This is skin. "
Murphy suddenly realized that this time, he not only found the bone, but also had to change his plan. Instead of digging out the bones piece by piece, they dug around the seven-meter-long specimen so that the whole piece (weighing six tons) could be transported back to the research laboratory. He originally arranged to borrow an air force helicopter to fly the specimens out of this remote valley, but the 9- 1 1 incident happened that day, and the air force had more important tasks to perform. So they carefully hoisted the specimen to the flatbed truck and transported it back to the laboratory. Then there are countless hours of cleaning work; Leonardo was half buried in sedimentary rocks, and researchers cleaned the sand one by one. After cleaning, you can see the spiny ridges on Leonardo's back, the tendons swinging his tail, the delicate scales on his back and flank, and the rough scales on his calves, which are often scratched by tough twigs and bushes. Due to carelessness, there are two cracks on the surface of Leonardo da Vinci's trunk, so you can see what's inside. Murphy thinks this is a fossil of intestinal contents. Karen Chin, an expert on dinosaur dung fossils at the University of Colorado, believes that those are undrained dung balls, and she has been studying these substances to determine what food Leonardo ate. A paleobotanist found that there are 36 different kinds of pollen in this material. Murphy's next goal is to transport Leonardo to Hill Air Force Base in Utah, which has one of the largest CT scanners in the world. If Leonardo's heart, lungs, kidneys and other organs are really preserved in fossils, then they can be displayed there through images or even made into three-dimensional models. He estimated that it would cost nearly 1 ten thousand dollars this time. There is already a Las Vegas casino willing to pay more than this amount in exchange for the opportunity to exhibit Leonardo da Vinci in the casino, but Murphy and Hammond disagree; Because in sparsely populated Malta, dinosaur tourism has the potential to become an important economic sector.
It would be an amazing achievement to scan the whole dinosaur mummy with CT, but what Schwaerzel, a biologist at North Carolina State University, did with only one Tyrannosaurus Rex bone was equally amazing. This broken bone came from a specimen excavated by Horner in the Rocky Mountain Museum in 2003. Schwartzel recalled: "Horner had to take it back to the camp. It's too big to fit into a helicopter. " Schwaerzel put fossils into weak acids used by biologists to study fresh bones; Weak acid dissolves mineral structure, leaving organic tissue. No one has applied this method to fossils before, because no one thought that organic matter could be preserved after tens of millions of years. To Schwaerzel's surprise, she found a soft substance similar to collagen (the main organic component of bones), as well as traces of blood vessels and red blood cells. Moreover, blood cells seem to have nuclei, and perhaps some genetic material can be found. If DNA can still be found after 68 million years (even if it is incomplete), it will really surprise people, but some researchers think it is possible. Apart from the unlikely event of cloning a complete dinosaur, this discovery is also a great gain for researchers trying to rebuild the relationship between dinosaurs, birds and reptiles. Schwartzel said: "If we really have a chance to find dinosaur DNA, we will also find it from such samples."
Schwaerzel made another amazing discovery. "I took the broken bones out of the box and exclaimed,' Oh, my God, this is a pregnant little female dragon.' "She found a known substance called medullary bone, which is unique to birds that are ovulating. The calcium that makes up the eggshell depends on this bone, which forms a new tissue with a unique structure. " It can be seen from this organization that the relationship between dinosaurs and birds is not only morphological, but also physiological. In terms of reproductive physiology, dinosaurs are birds. "(morphology refers to the pelvis. Feather structure )
Other researchers have done equally well in bone research. Stevens, a computer scientist at the University of Oregon, became interested in large sauropods in the late Jurassic 65.438+0.5 billion years ago. It is taken for granted that sauropods, including Lei Long and Liang Long, feed on the young leaves in the treetops. They are generally described as standing steady and holding their heads high, just like bloated short-legged giraffes. In fact, Murphy can see this dinosaur pattern from the Sinclair Oil Company logo opposite the research station every morning. But when Stevens drew the skeleton model on the computer, he found that the vertebrae looked like dinosaurs born together. The natural posture of their long necks seems to be almost parallel to the ground or even downward, so they can look for low shrubs or aquatic plants. Stevens found that this situation made many laymen feel unhappy. He said: "This is not in line with people's childhood expectations; We have replaced it with something that looks less dignified, and many people find it difficult to accept. " The person in charge of the museum is not very happy about this, because the museum is going to redo the dinosaur model. For Sinclair Oil Company, which started to use the Lei Long logo from 1932, Stevens' research has no influence. A spokesman for the company told Newsweek: "We have no plans to change the company logo."
Stevens' next project is to study the biomechanics of Tyrannosaurus Rex. Tyrannosaurus rex is a more powerful and attractive animal. Stevens is interested in how this five-ton biped squats down (for example, when eating a corpse) and how to stand up again. Hutchinson of the University of London is also studying a similar topic-how fast Tyrannosaurus Rex can walk; This question has always been what people who have been chased by Tyrannosaurus Rex in nightmares want to know most. Fifty years ago, science fiction writer bradbury imagined that Tyrannosaurus Rex could run 100 yards (about 9 1.4 meters) in six seconds, which was equivalent to 54.7 kilometers per hour. Jurassic Park Tyrannosaurus Rex can almost catch up with a jeep driving at the fourth speed. But the filmmakers revealed to Hutchinson that they could not realistically make such a high-speed Tyrannosaurus Rex. With Tyrannosaurus rex's size and assumed speed, it would run off a cliff like a cartoon character, with its legs spinning rapidly. Looking at it one by one, the speed of Tyrannosaurus rex in the movie is a little over 24 kilometers per hour, which Hutchinson thinks is similar. He calculated that the maximum speed should be in the range of 16 to 40 kilometers per hour, and the speed of 16 kilometers per hour is much more likely than 40 kilometers per hour. The speed of terrestrial animals is limited by the muscle mass of their legs, but to a certain extent, the principle of diminishing returns will come into play: the increase of muscle mass means that their weight will increase and their burden will exceed the strength they supply. Hutchinson wrote that if you want to run at a speed of 72 kilometers per hour, the weight of the leg muscles of Tyrannosaurus Rex needs to account for 86% of its weight, which is obviously absurd. Recently, he reduced the proportion to 465,438+0%, which is less than half of the original estimate, but he still thinks that "according to his body structure, it is still very impossible."
Hutchinson's research also has some implications for another major debate about Tyrannosaurus Rex: Is it a predator at the top of the food chain or is it basically a scavenger? Hutchinson himself has no intention of questioning the fierce temperament of Tyrannosaurus Rex (this is a topic that is easy to cause controversy among paleontologists). He pointed out that large prey animals are not very fast at the same time. He added: "There is no need to chase animals that run 24 kilometers at a speed of 72 kilometers per hour." On the other hand, Horner pointed out that if the eaten animal is dead, it is useless for the predator to walk slowly. Most researchers have concluded that Tyrannosaurus Rex will eat anything it can catch, just like carnivores today. Erickson of Florida State University calculated the growth rate of Tyrannosaurus Rex. By analyzing their skeleton rings (similar to those of trees), he thought that Tyrannosaurus Rex gained about 2.3 kilograms a day on average during its rapid puberty. Norell of the American Museum thought for a moment and said, "It is hard to imagine that there were so many carrion around at that time."
This question was the theme of a Tyrannosaurus Rex conference held in Heigang Museum in June this year. At the meeting, Harper of the University of Shenandoah showed a three-headed keel collected near Jordan, Montana. Its left corner is missing about a third, which is obviously bitten off. Judging from the distance of tooth marks on the wrinkles of its neck shell, it should be done by Tyrannosaurus Rex. It is understood that Tyrannosaurus Rex was the only large carnivore in the area at that time. This in itself cannot refute the hypothesis of scavengers. However, judging from the fact that the wound on the leading bone has begun to heal, it shows that the dragon was still alive and healthy enough to cope with the attack of Tyrannosaurus Rex. Judging from the bite position, the two dinosaurs fought face to face. Harper said: "We don't know what happened later, but three dragons are still alive and two big horns are still there. Maybe Tyrannosaurus Rex weighed the pros and cons and gave up fighting. It can survive for millions of years, indicating that this creature has always been reckless. "
After the dinosaurs survived for millions of years, the disaster came unexpectedly; It may be that the climate has changed (the reason for the change is still controversial); The Cretaceous meteorite, which ended in a crashing blow, is traveling through space and will hit the earth fatally. Everything is waiting for an incredible biological evolution. One day, they will calculate the trajectory of the comet, dig out the long-buried bones to explore the mystery, and marvel at all the intricacies and beauty.