Study: Ancient Sharks Might Have Competed Against Each Other
2022-06-06
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1Researchers are learning more about the disappearance of the largest-known shark.
2Sharks are large and often dangerous sea fish known for their sharp teeth.
3The international researchers studied the mineral zinc found in the teeth of both living and extinct sharks.
4The study involved teeth from 20 living kinds of sharks and 13 extinct kinds.
5The research on the teeth suggested the position of these sharks in the food chain.
6The largest shark that ever lived is called the megalodon.
7Researchers compared its teeth to those of sharks living today including the great white shark.
8Their research suggests the megalodon might have been out-competed by the great white shark in ancient seas.
9Researchers compared the amounts of two forms of zinc in the outer covering of the sharks' teeth.
10The researchers learned something about the shark's diet and their position in the food chain from the comparison.
11The researchers found the megalodon was on top of the food chain for millions of years.
12But they found that the great white shark's arrival about 5.3 million years ago added a hunter in the same position competing for similar food.
13The megalodon's scientific name is Otodus megalodon and it appeared about 15 million years ago.
14The animal went extinct about 3.6 million years ago.
15It was one of the largest hunters, or predators, in Earth's history.
16The shark reached at least 15 meters to possibly 20 meters in length.
17It fed on sea mammals, a group of animals that includes whales.
18The great white shark, which scientists call Carcharodon carcharias, is smaller, reaching a length of about six meters.
19It may have been better at swimming and hunting than Megalodon.
20Kenshu Shimada is a scientist who studies extinct animals at DePaul University in Chicago, Illinois.
21He helped write the study which was published recently in Nature Communications.
22Shimada said the two sharks lived together during a period of time called the early Pliocene.
23He added that the zinc data suggests they seemed to have been in the same position in the food chain.
24Shimada said there are many ideas about why the megalodon went extinct.
25They include climate change and a decrease in food.
26He said a recent scientific theory is that the megalodon "lost the competition with the newly evolved great white shark."
27Shimada said their study appears to support that idea.
28But he added that it could have been a combination of reasons.
29The researchers said it is not thought that the great white actually hunted the larger shark.
30Much still remains unknown about the megalodon.
31Sharks do not have bones but a material called cartilage.
32Cartilage does not fossilize well.
33That makes it difficult to know what megalodon looked like.
34However, many megalodon tooth fossils have been found around the world.
35Shimada said, "the reality is that we still know very little about this extinct shark."
36I'm Jill Robbins.
1Researchers are learning more about the disappearance of the largest-known shark. 2Sharks are large and often dangerous sea fish known for their sharp teeth. 3The international researchers studied the mineral zinc found in the teeth of both living and extinct sharks. 4The study involved teeth from 20 living kinds of sharks and 13 extinct kinds. The research on the teeth suggested the position of these sharks in the food chain. 5The largest shark that ever lived is called the megalodon. Researchers compared its teeth to those of sharks living today including the great white shark. Their research suggests the megalodon might have been out-competed by the great white shark in ancient seas. 6Researchers compared the amounts of two forms of zinc in the outer covering of the sharks' teeth. The researchers learned something about the shark's diet and their position in the food chain from the comparison. 7The researchers found the megalodon was on top of the food chain for millions of years. But they found that the great white shark's arrival about 5.3 million years ago added a hunter in the same position competing for similar food. 8The megalodon's scientific name is Otodus megalodon and it appeared about 15 million years ago. The animal went extinct about 3.6 million years ago. It was one of the largest hunters, or predators, in Earth's history. 9The shark reached at least 15 meters to possibly 20 meters in length. It fed on sea mammals, a group of animals that includes whales. 10The great white shark, which scientists call Carcharodon carcharias, is smaller, reaching a length of about six meters. It may have been better at swimming and hunting than Megalodon. 11Kenshu Shimada is a scientist who studies extinct animals at DePaul University in Chicago, Illinois. He helped write the study which was published recently in Nature Communications. 12Shimada said the two sharks lived together during a period of time called the early Pliocene. He added that the zinc data suggests they seemed to have been in the same position in the food chain. 13Shimada said there are many ideas about why the megalodon went extinct. They include climate change and a decrease in food. He said a recent scientific theory is that the megalodon "lost the competition with the newly evolved great white shark." 14Shimada said their study appears to support that idea. But he added that it could have been a combination of reasons. 15The researchers said it is not thought that the great white actually hunted the larger shark. 16Much still remains unknown about the megalodon. Sharks do not have bones but a material called cartilage. Cartilage does not fossilize well. That makes it difficult to know what megalodon looked like. However, many megalodon tooth fossils have been found around the world. 17Shimada said, "the reality is that we still know very little about this extinct shark." 18I'm Jill Robbins. 19Will Dunham reported this story for Reuters. Gregory Stachel adapted it for VOA Learning English. 20___________________________________________________________________ 21Words in This Story 22extinct - adj. no longer existing 23food chain - n. a series of types of living things in which each one uses the next lower member of the series as a source of food 24evolve -v. to develop into something more complex or better over a long period of time 25fossil - n. something (such as a leaf, skeleton, or footprint) that is from a plant or animal which lived in ancient times and that you can see in some rocks 26reality - n. the real situation 27We want to hear