When the Earth’s temperature rose and the amount of oxygen in the oceans decreased about 252 million years ago, most life on our planet suffered the same tragic fate. It is estimated that this extinction event, also known as the “Great Dying”, killed 70% of species on land and about 96% of species in the oceans. Illustration: Getty However, there are no sharks among them. “They’re the last surviving species,” said Elizabeth Sibert, a paleontologist and identifier of fossils and an oceanographer at Yale University. The next extinction event at the end of the Triassic period or even the meteorite event that wiped out the dinosaurs 66 million years ago could not have caused the shark to become extinct. The shark’s survival or longevity is extraordinary, but the animal was also close to the brink of extinction, a study in the journal Science revealed June 3. The study, led by scientist Sibert, shows that a previously unknown extinction event pushed sharks to the brink of extinction 19 million years ago, leaving just one in ten of the sharks. Sharks in the oceans survive. “Something happened and wiped out 90% of the shark population overnight,” said scientist Sibert. The so-called something is still uncertain but it has caused immense destruction. The meteorite that wiped out the dinosaurs on Earth only caused 30-35% of the shark species to be wiped out while the above event was 2-3 times worse. To find this discovery, oceanographer Sibert and his collaborator Leah Rubin went through a remarkable process. Discover the mystery When a marine species dies, its body will fall to the bottom of the sea and decompose into discrete parts. Small parts, such as their teeth, will gradually accumulate in the sediments under the sea. “The seabed is essentially a grave for all aquatic species,” Sibert said. The sediment samples used in this study were collected from two locations in the Pacific Ocean, one in the north and one in the south, covering a period of 40 million years. However, it was not easy to analyze the small teeth inside each of these specimens. These parts are so small, even smaller than the width of a human hair. Oceanographer Sibert filtered dried sediment samples under a microscope and isolated the tiny bits of shark teeth. After separating them, scientist Rubin will identify and describe the features, as well as classify them. These little bits of teeth can reveal a lot to us. There were about 1,300 small tooth pieces identified in the above study with 85 samples with different shapes. Most of them are from the period before 19 million years and only a few samples belong to the later period. So, the question arises, what happened to the sharks? The tip of the iceberg The small tooth fragments suggest a decline in shark numbers and diversity about 19 million years ago, but the cause behind this event is unknown. “This is really a mystery. Right now we don’t know what happened,” Ms. Sibert said. The key to solving this mystery is to learn about the time when the sharks almost disappeared. This period is called the “Miocene” and is described by the scientist Sibert as the “transition phase” of the Earth. 15 million years before the mysterious shark event occurred, the Earth gradually became an “ice house” as permafrost increased in Antarctica. The oceans at that time were no different from the oceans of today, although we cannot find such species as tuna, swordfish and seabirds. Dolphins and whales had not yet evolved. However, there is not much evidence to find out the cause of the shark eradication. Even the discovery, which took place during a rather unusual time in Earth’s history, is just the tip of the iceberg. “There are many questions that need to be answered,” said researcher Rubin. Did some change in the environment lead to the decline in shark populations? This is difficult to confirm because the oxygen and carbon levels show no anomalies, but scientists can use more data around this time stamp. Did the event happen across the oceans and affect other marine species as well? Ms. Sibert said this is a global event but we still need more data. Also, what about other bodies of water? Can sedimentation in lakes and coastal areas occur other phenomena? How were terrestrial species affected during this time? Are there any chemicals that can tell us about the environment then? Ms. Sibert even thought that an epidemic, such as a virus, could be responsible for the decline in shark populations. Still, for this oceanographer, the extinction event was a remarkable phenomenon. The fact that sharks have existed for more than 400 million years, surviving multiple extinction events leads her to believe that something truly intense happened and that the sharks may be the gateway to understanding major changes. collided with Earth during the early Miocene. “There is a lot of data waiting to be discovered,” said researcher Rubin. The discovery not only shows the unpredictable change of the marine environment, but also shows how difficult it is for species to recover when they are pushed to the brink of extinction. “Biology is trying to tell us something and I think we need to listen,” Sibert said.

But recently, paleontologists have had to change this view and push the herbivorous history of dinosaurs to the early Cretaceous period, 125 million years ago, grasses began to appear. This was discovered during the study of fossils of the dinosaur Equijubus found in China. Mount Mazong is located at the northern end of the Hexi Corridor, in present-day Gansu Province, China. The mountain is named because it looks like a horse’s mane blowing in the wind. Mazong Mountain is a desolate place, but beneath that gravel are the remains of creatures that died hundreds of millions of years ago. In 2000, paleontologists from China and the United States formed a joint expedition to unearth paleontological fossils in the Mazong mountain area. During this excavation, paleontologists discovered a large number of fossils. Chinese paleontologist You – Hailu studied the fossils of a new dinosaur species and he named this dinosaur Equijubus. The genus name is derived from the Latin words “equus” meaning “horse” and “juba” meaning “mane”, the genus name meaning “horse mane” because the fossil was found in Mount Mazong. The new species was given the full name Equijubus normani, with “Normani” being named in honor of the famous British paleontologist David B. Norman. Illustration. Equijubus can be considered an intermediate dinosaur between Iguanodon and Hasrosauridae. Equijubus has a fairly large body when compared to a “basic” Hasrosauridae, but they can still run on two legs after being chased by predators. Fossil specimens of this dinosaur include skulls, lower jaw bones, cervical vertebrae, dorsal vertebrae and other parts. Through fossil analysis, it can be seen that Equijubus belongs to the primitive Hadrosauridae, it already possesses some features of Hadrosauridae, but its skull also has obvious features of Iguanodon. Paleontologists surmise that the dinosaur Equijubus could be up to 7 m long, 2 m high and weigh 2.5 tons, almost the size of a small truck. Equijubus would have had a long head, a horn beak on the front of its mouth and flat teeth on the inside of its cheeks, allowing it to chew on hard plants. Equijubus also have a robust body, they often walk on all fours and run on two legs when fleeing predators. Although there are not many fossils of this species, the discovery of Equijubus has great significance for paleontology. As a very primitive Hadrosauridae, Equijubus has shown that the Hasrosauridae may have originated in Asia and that they evolved directly from Iguanodon. 14 years after the Equijubus species was named, paleontologists are once again studying their fossils using the latest technology. They found evidence of herbivorous dinosaurs actually eating grass in fossils! On December 21, 2017, You Hailu and other paleontologists published a research paper titled “Dinosaur-related cuticles and crystals from the Chinese Gramineae family of the Cretaceous Period” on National Science Journal of China. The paper mentioned that the microstructure of primitive herbaceous plants (herbs, rice) was silicified between the teeth of the dinosaur Equijubus. This suggests that herbaceous plants were originally the food of this dinosaur. In fact, to answer the question of whether or not herbivorous dinosaurs ate grass, we need to know that the grass family is a large family of plants with more than 650 genera. Rice, wheat, corn, millet, sorghum, etc… the plants that we cannot live without are all grasses, and many other plants that we can eat are also grasses. People have always doubted the existence of the grass family, and the time period of its appearance is also quite unclear. And in the past, scientists always thought that they appeared after dinosaurs. But through the discovery of secrets from the fossils of the dinosaur Equijubus, we have learned that grass appeared on Earth 125 million years ago. This means that on Earth, dinosaurs of that time also had herbivorous habits (literally eating grass). The earliest known seed-bearing plants can be traced back to the Middle Jurassic or earlier, 164 million years ago. It was discovered during the Boda Jurassic period in Inner Mongolia. Although this plant is only a few centimeters tall, it already has roots, stems, leaves, and fruits.

Billions of T. rex have been wandering North America, a group of experts say. Although not a simple task, paleontologists from the University of California (USA) gave the T. rex dinosaur numbers in the Cretaceous period 65 – 98 million years ago. Challenging work Fossils have long been used to improve our understanding of extinct creatures like dinosaurs, but experts suggest that these skeletons are used to calculate densities and levels. Their abundance is a challenge. Director Charles Marshall of the University of California’s Museum of Paleontology is part of the research team. “There is no information available to make an estimate,” he said. If you find an Easter egg in your garden, how do you estimate how many Easter eggs ever existed? It simply cannot be done. You need information from somewhere else, for example, the density of the Easter eggs, how many years they can be found and how many Easter eggs have been placed in the garden. Paleontologist Nizar Ibrahim at the University of Portsmouth (UK) is not involved in the study. “Previously researchers tried to estimate things like the size of the Tyrannosaurus’ habitable area and their basic energy needs, so this is an extension of the work,” he said. before that, including many updates about Tyrannosaurus ”. There are 20,000 T.rex dinosaurs in North America T.rex is predicted to have a lifespan of 28 years. Using fossil records, densities and data from climate models, the University of California team calculated that about 20,000 adult T. rex, living across North America, could exist at the same time. . In a study published in the Journal of Science, researchers say this means that about 2.5 billion T. rex have lived and died over a period of nearly 2.5 million years – a process The dinosaurs live. For the first time, the team also calculated the lifespan of dinosaurs. Using scientific literature and expert opinion, they estimated T.rex’s adult age to be 15.5 years and its lifespan could reach around 28 years. The average adult body weight of this dinosaur is about 5,200 kg and a growth after maturity can make them weigh up to 7,000 kg. From the above estimates, the team concluded that each generation of T.rex lasted for about 19 years and there was a dinosaur for every 100 square kilometers. They determined that, with 20,000 permanent dinosaurs and about 127,000 generations of this species, there would be about 2.5 billion T.rex overall. “The researchers’ approach seems informative, while also pointing to current limits on what can be done,” said Jason C.Poole of the Bighorn Institute of Paleontology (USA). learned from the known “. “I’m sure it opens the door to better focus on questions about population density and what it means over time. So this can really help us understand how animals change over time as it is related to evolution and changing ecosystems, ”said Mr. Poole. The researchers estimated that the population density of T. rex was equivalent to 3,800 carnivorous dinosaurs in an area the size of California, but only 2 in an area the size of Washington DC. . Open up the possibility to find out more information A T.rex dinosaur could have an average weight of 5.2 tons. Meanwhile, the results also allow the authors to determine that only about 1 in 80 million T. rex is preserved as fossil remains. “The big impact of this study may be how rare the fossils are, they represent only a fraction of the individual organisms that ever existed, not to mention the depth of time and the rate. it happened in a few thousand to a million years, ”Mr. Poole said. Study co-author Professor Marshall of the University of California said, “In a way, this is a paleontological exercise of what we can know and how we can know what. there… It’s amazing what we know about this dinosaur so we can calculate more information.Our understanding of T. rex has expanded greatly over the decades. Through more fossils, more analytical methods and better ways of integrating information through known fossils ”. Mr Ibrahim sees other possibilities stemming from this study. There is a lot we don’t know about T.rex’s physiology, behavior, and food environment, he said, but this study offers an interesting approach to estimating abundance and prevalence. conservation of dinosaurs. “I would love to see it apply to the other dinosaurs we know from fossils. Looking at a wide range of dinosaurs, predators and prey, we can better compare dinosaur animal communities to modern ones, ”he said. What we see is superficial, according to Ibrahim, and even with this fascinating research, there is still a long way to go for us to confidently apply these approaches widely in research. save dinosaurs.