Black dragon, tumor dragon, phenol dragon, sea dragon, plesiosaur,

About 250 million years ago, life on earth just experienced a large-scale extinction, many species disappeared, and reptiles also set foot on this land at this time and spent the rest of their lives. Millions of years later, when the earliest dinosaurs began to rule the land, some of them slipped into the rough sea. Later, these animals became masters of the ocean, and their roles were very similar to those of whales, dolphins and seals that are still active in the ocean today.

199 1 year, in a river in British Columbia, western Canada, paleontologist Elizabeth Nichols and her colleagues discovered the fossil of this marine animal. After sorting out the fossils, they found that the monster was 23 meters long, with a skull close to 6 meters and a fin length of 5.3 meters. Scientists speculate that this animal may be the largest carnivore that has ever lived on earth.

Ichthyosaurs swam in prehistoric oceans for 65.438+0.5 billion years, and their close relatives, the dinosaur family, ruled the landing site. During this time, some ichthyosaurs kept the characteristics of their ancestors' lizards, while others changed obviously. Their bodies have evolved into streamlined dolphins and their living habits are similar to those of these mammals.

Through the study of ichthyosaur fins, scientists know how this animal migrated from land to sea. Their original legs became short and flat, and their toes joined together and became soft and smooth fins. Their skin is smooth and they have a crescent tail. When these changes are completed, they can swim freely in the water, but on land, their fins can't support their heavy bodies at all.

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Scientists believe that at least some ichthyosaurs have different lives from reptiles today. For example, today's sea iguanas are still inseparable from land. They must climb ashore to bask in the sun to keep their body temperature and maintain normal biochemical activities in their bodies. But many ichthyosaurs no longer need this. Their bodies can generate some heat, and their huge bodies are also conducive to maintaining body temperature. Therefore, this part of ichthyosaurs will bid farewell to land forever, and they can't live without water like fish. Roske Motani, a paleontologist at the Royal Ontario Museum, believes that some ichthyosaurs have very aerodynamic streamlined shapes, and their crescent-shaped tails are very powerful and can swing flexibly from side to side. In the spring of 2002, in the journal Paleontology, Motani published his research results on a ichthyosaur named Stenopterygius. He said that this ichthyosaur can swim at a speed of 1 meter per second, which is equivalent to bluefin tuna and yellowfin tuna in the ocean today.

However, other ichthyosaurs, especially the early species, still partially retained the shape of lizards, with long tails, soft ridges and not as fast as the former. Biologist Richard Cowen even thinks that the wave swimming of this ichthyosaur will affect their breathing, because it is very difficult to swim at high speed and breathe at the same time in that way. So scientists speculate that these ichthyosaurs may jump out of the water from time to time when swimming, just like dolphins today, so that ichthyosaurs absorb enough oxygen in the process of chasing prey and can swim a long distance.

The secret of big eyes

The food of ichthyosaurs is the most interesting issue for scientists. In the study, a large number of arrow stones were found in the abdomen of ichthyosaurs, which were paleontological fossils formed by the extinct cephalopod inner shell related to squid. In another ichthyosaur fossil, people found the remains of some undigested fish and turtles. These turtles were 6 cm in size, completely swallowed into the stomach of ichthyosaur, and some of them were bitten by its teeth. 200 teeth were found in the mouth of an immature ichthyosaur. They are conical, each tooth is 4 cm long and protrudes from the gum by 65438 0 cm ~ 2 cm. Ichthyosaurs used these teeth to crush food and then swallowed it.

What surprised scientists most was the eyes of ichthyosaurs. Generally speaking, if fish dragons swim fast, they can dive deep, because only by swimming fast can they swim deeper in the limited time of holding their breath, which is an important skill for them to get rich food. Some biologists believe that ichthyosaurs can dive deep, and one of the important evidences is that they have a pair of huge eyes.

Found a ichthyosaur with a length of only 9 meters and a pair of big eyes with a diameter of more than 26 cm. They look like a pair of big plates for food. This is the largest eye in the world that people have found. Another ichthyosaur is very small, only 4 meters, but their eyes are more than 22 centimeters. Compared with their bodies, these are also a pair of surprisingly big eyes. Scientists have not found any animal's eyes in such an extraordinary proportion to its body. However, in today's ocean, there are also some guys with amazing eyes, such as a giant squid, whose eyes can reach 25 cm in diameter, and the eyes of blue whales can also reach 15 cm.

Imaginary ichthyosaur

What are big eyes for? Two Scottish scholars at Glasgow University, Stilt Han Fils and Germ D Blackstone, published an article saying that in the dark ocean, big eyes can collect more light, which is beneficial to find small animals hidden in deep water, and sharp vision also enables ichthyosaurs to cooperate in chasing prey in dark deep water.

Some people question this view. In modern mammals, such as seals, they don't have such big eyes, but they can also hunt flexibly in deep water. However, Blackstone retorted that although seals don't have big eyes, they have other sensitive sensors, such as tentacles, which can detect the changes of water flow caused by animal activities, while some whales rely on sonar to chase food.

So does ichthyosaur have a similar detection system? Benjamin P. Kyle, an Australian paleontologist, and George Collis, another radiologist, hope to reveal this secret through CD scanning technology. They scanned the fossil of an underage ichthyosaur.

Kyle, they found that there was indeed an internal nose structure between the top of the skull and the upper jaw of ichthyosaur, much like the organ responsible for smell. There are also some strange marks on the skull. In the brains of modern animals, there are areas that control vision and smell. They also found some deep grooves in the skull. They believe that those grooves are channels for nerves and blood vessels, those neural networks can transmit information from the front of ichthyosaurs, and those grooves may even hide some complex sensory systems, such as electric field receptors. In modern marine animals, such as some fish and sharks have such organs, and their sensory neurons can detect the electric field from prey. Scientists say that it is likely that some species of ichthyosaurs have similar detection systems, because although they have big eyes, there is a big blind spot in front of them, and ichthyosaurs may have to rely on some kind of sensor to detect places that their eyes can't see.

Scientists have found that the number of ichthyosaur species is closely related to the climate change on the earth. From the discovery of fossils, when the climate was warm and suitable, they were quite prosperous and varied, but in the geological era with cold and harsh climate, their species decreased. Studies have shown that although ichthyosaurs and dinosaurs appeared on the earth almost at the same time, they died out at different times. 90 million years ago, ichthyosaurs gradually disappeared, and 25 million years later, ichthyosaurs became extinct, and dinosaurs suddenly disappeared from the earth.