Dinosaurs are not completely gone. Look up if you don't believe me.

Dinosaurs are known to almost everyone. These prehistoric giants that ruled the earth for 160 million years have almost become synonymous with "paleontology" in the minds of the public. At present, humans have discovered more than 900 genera and more than 1,000 species of dinosaurs, and new dinosaur species are discovered around the world every year. From fossils displayed in natural history museums, various models in store windows, to movies, books, cartoons and games, the image of dinosaurs can be seen everywhere. Almost every child's childhood is inseparable from the company of these big "monsters".

Xixia Dinosaur Park, China | Gary Todd / Wikimedia Commons

However, no matter how much we like dinosaurs and how much we yearn for the world they lived in, dinosaurs have long been extinct on Earth. Paleontologists can only imagine and restore their forms and habits before they died based on fossils excavated from the strata. People can't help but ask, how did the dinosaurs, the overlords of the Mesozoic Era, disappear from the Earth? Are all dinosaurs really extinct?

The Age of Reptiles

Let's go back 66 million years, which is the last stage of the Late Cretaceous: the Maastrichtian Stage. At this time, groups of Triceratops and Edmontosaurs roamed the plains of the North American continent, and the tall Alamosaurus strolled on the edge of the forest to find food. The most famous dinosaur star, Tyrannosaurus, was at the top of the food chain at that time; in the southern part of the Asian continent, there lived many abelisaurs such as Indusaurus, Indosuchus and King Long, and even "old people from the past" such as Isisaurus and Stegosaurus survived. In the Mongolian Bayin Manduhu, there were small, short and fat primitive ceratopsians with no horns, such as Weak Ceratops and Dwarf Ceratops, as well as strange-looking, feathered Alvarazsaurus and Oviraptorosaurs; on the isolated island of Madagascar in Africa, there lived the Rapedosaurus, the buck-toothed Nophlebotosaurus, and the local "local emperor" - the fierce Majungasaurus.

Tyrannosaurus Rex skeleton | Wikimedia Commons

Stegosaurus skeleton | Thomas Quine / Wikimedia Commons

In the ocean, giant lamellae roamed in the warm shallow seas, using their small heads and extremely long necks to prey on schools of fish and squids. The polar swimmers living in the cold waters of Antarctica may even use their fine teeth to filter tiny invertebrates in the seabed sediments like the gray whales that exist today. Mosasaurs were the most prosperous marine reptiles at this time. Among them, there were super predators like Saturacodon and Hoffmann's Mosasaurus, which were more than ten meters long, deep-diving species like Meixi Phosphasaurus that "sucked squids", and shallow-sea predators like Long-snouted Alligator Dragon that fed on small fish. Some species even began to enter fresh water. In the sky, huge pterosaurs soared. Some species, such as Quetzalcoatlus and Hatzegopteryx, had a wingspan of more than 10 meters, like a small airplane, and were the largest flying animals that had ever appeared on Earth.

Reconstruction of the Dinosaurus | Nobu Tamura / Wikimedia Commons

Of course, there were some familiar members living on Earth at that time, such as snakes, lizards and frogs crawling and jumping in the ground vegetation, turtles, salamanders and crocodiles swimming in freshwater, as well as birds and mammals; compared with ancient reptiles such as dinosaurs, pterosaurs, plesiosaurs and mosasaurs that occupied the mainstream ecological niche, they could only be regarded as "second-class citizens". However, this world full of vitality and prosperity was about to undergo a radical change.

Disaster strikes from the sky

In the 1980s, Spanish-American physicist Luis Alvarez and his son Walter Alvarez discovered that the iridium content was particularly high in the strata between the Late Cretaceous and Paleogene periods, which coincided with the Cretaceous mass extinction that ended the dinosaur era. The content of iridium in the earth's crust is relatively low, but it is relatively common in meteorites from the universe. Therefore, they believe that the "culprit" in this extinction event that overturned the earth's biosphere was an "alien visitor."

Barringer Crater, USA | Mike Beauregard / Wikimedia Commonséopold Boilly / Wikimedia Commons

In the early 1990s, a huge meteorite crater with a diameter of 180 kilometers was discovered on the seabed of the Gulf of Mexico. It was named Sucsilup Crater. Its discovery confirmed the theory of Alvarez and his son: 66 million years ago, a huge meteorite with a diameter of 10-15 kilometers hit the Gulf of Mexico near the Yucatan Peninsula today. The energy generated by the impact was equivalent to 100 megatons of TNT explosives; the impact triggered earthquakes, tsunamis, violent volcanic activities and fire storms around the world. At the same time, a large amount of dust full of toxic sulfides (about 300 billion tons) was thrown into the atmosphere, which not only caused severe acid rain, but also suspended in the atmosphere, blocking the sun for years.

Drawing of the Succulent Lube meteorite impact | Donald E. Davis / Wikimedia Commons

Because sunlight could not reach the surface, global temperatures dropped sharply, and vegetation on land and phytoplankton in the ocean could no longer photosynthesize, so they died in large numbers. The disappearance of producers led to the collapse of the entire food chain, and herbivores lost their food source, and with their demise and disappearance, the carnivores that fed on them would also not be able to survive. 75% of the world's animal and plant species disappeared in this extinction event, and almost all quadrupeds weighing more than 25 kilograms were wiped out, including dinosaurs, all pterosaurs, plesiosaurs, and mosasaurs. The era of giant reptiles ruling the earth has come to an end.

Descendants of the dinosaurs

The huge ancient reptiles disappeared, but some animals that seemed "insignificant" compared to the giant dinosaurs miraculously survived the mass extinction at the end of the Cretaceous period, including the vast majority of amphibians, more than 80% of turtles, and most snakes and lizards (except the mosasauroids). They survived by relying on their smaller size and lower metabolism, and quickly occupied the ecological gap left by the extinction of dinosaurs and giant marine reptiles in the Cenozoic Era, evolving into large members such as the 14-meter-long Titanoboa, the 1.72-meter-long Carbon Turtle, and the 10-meter-long Colossus Ancient Cup Snake.

Titanoboa was 14 meters long and weighed more than 1,100 kilograms. | Nobu Tamura / Wikimedia Commons

About 50% of crocodiles survived the extinction event, and they continued to occupy the ecological niche of top freshwater predators in the Cenozoic Era and launched a charge towards land. Most bony fish and the vast majority of cartilaginous fish also survived the Cenozoic Era, and the freshwater and oceans of the Cenozoic Era soon became vibrant again.

The main mammal groups of the Late Cretaceous, such as Gondwanatheria, Multituberculates, and the Monotremes (existing members include the platypus and three echidnas), Metatheria (including various existing marsupials), and Eutheria, all survived the extinction event with their smaller sizes. Among them, Eutheria evolved into the most mainstream large animal group on Earth in the long years that followed, becoming the ancestors of the vast majority of existing mammals, including humans.

The familiar platypus | Brisbane City Council / Wikimedia Commons

As descendants of theropod dinosaurs, birds suffered a heavy blow in the Cretaceous mass extinction, and the most prosperous and diverse enantiornithines of the Cretaceous period all became extinct; however, a few smaller, terrestrial or semi-aquatic modern birds managed to survive into the Cenozoic Era and evolved into the approximately 8,600 existing bird species. Dinosaurs did not completely disappear, and those feathered elves flying in the blue sky that we are familiar with are their descendants who have survived to this day.

Look up, they're flying by | Mike Baird / Wikimedia Commons

This article comes from the Species Calendar, welcome to forward