托福阅读真题第294篇Polar Dinosaurs

托福真题网 2022-10-16 发布于山东

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托福阅读真题第294篇Polar Dinosaurs

Polar Dinosaurs

Once there was an idea that dinosaurs were cold-blooded and only thrived in the swamps and wetlands of tropical climes. But the more we look, the more we realize dinosaurs were found in as many different kinds of habitats as birds and mammals are today. Polar dinosaurs, probably warm-blooded and feathery, were thriving roughly 70- -100 million years ago in great polar forests, of which there is no modem equivalent. Fossils of such dinosaurs have been discovered in Siberia, specifically at the Kakanaut River on the Kamchatka Peninsula. The dinosaur remains found here over the years are mostly teeth, but also include some bones, and they reveal the presence of a variety of species. All of these remains are from the very end of the Cretaceous, 66- 68 million years ago, just before the mass extinction event that saw the extinction of the non-bird dinosaurs. "The material was fragmentary but showed that the Arctic dinosaurs were very diverse," says Pascal Godefroit, an expert on early birds and birdlike dinosaurs who has been involved in the work at the Kakanaut River.

The Kakanaut finds have been important in understanding the end-Cretaceous extinction event. This is in part because Kakanaut was within the Arctic Circle and just 1 ,600 kilometers from the North Pole at that time. Conditions then were warmer than today, but mean annual temperatures were still around 10 degrees Celsius, and there would have been frequent spells below freezing and many months of darkness. Dinosaur fossils found farther east across the Bering Sea in Alaska were left by creatures that endured similar climatic conditions, but some experts have argued that they migrated south in the winter, en masse, to avoid the coldest months. At Kakanaut, researchers found fragments of eggshell from hadrosaur and theropod dinosaurs, which suggested that these animals were breeding in polar regions and living there year-round.

Many scientists argue that the dinosaurs went extinct as a result of Earth's collision with a massive asteroid or comet about 66 million years ago that created the Chicxulub Crater on Mexico's Yucatan Peninsula. Other scientists have claimed that falling global temperatures had led to a decline in dinosaurs around the world in the period before the impact (collision). However, the rich fauna (animal life) found by Godefroit and his colleagues suggests that not only had a diverse ecosystem of dinosaurs persisted in the Arctic in the L ate Cretaceous, but also that they were thriving in very cold conditions. The herbivores here must have fed on plants, such as conifers, that remained green year-round and also taken advantage during summer months of a profusion of nutritious fresh growth thrown out by plants bathing in light 24 hours a day.

"For the first time we have firm evidence that these polar dinosaurs were able to reproduce and live in these relatively cold regions. There is no way of knowing for sure, but dinosaurs were probably warm- blooded just like modem birds, which are the direct descendants of dinosaurs," Godefroit told reporters when his findings were published in the German journal Naturwissenschaften in 2009. "The dinosaurs were incredibly diverse in polar regions- as diverse as they were in tropical regions. It was a big surprise for us."

Rather than dinosaurs slowly dying out due to climate change in the period before the impact, Godefroit believes that the discovery backs up the idea that dinosaurs were killed off in a rapid and brutal fashion by cataclysmic conditions that swept the world following the Chicxulub impact. Debris in the atmosphere may have blackened the skies for several years, killing off plants and destroying the food supply- -particularly as large herbivores (plant eaters), such as sauropod dinosaurs, required vast quantities of plant matter to fuel their massive bulk. Starved for meat, the flesh eaters would eventually have succumbed too, as herbivores disappeared.

It is likely that a combination of factors led to the demise of the non-bird dinosaurs, but the precise explanation remains a fascinating and enduring mystery. It had been thought that Siberia had a paucity of fossils in comparison to its southern neighbors Mongolia and China, but the recent discoveries suggest this may not be true.

1.Once there was an idea that dinosaurs were cold-blooded and only thrived in the swamps and wetlands of tropical climes. But the more we look, the more we realize dinosaurs were found in as many different kinds of habitats as birds and mammals are today. Polar dinosaurs, probably warm-blooded and feathery, were thriving roughly 70- -100 million years ago in great polar forests, of which there is no modem equivalent. Fossils of such dinosaurs have been discovered in Siberia, specifically at the Kakanaut River on the Kamchatka Peninsula. The dinosaur remains found here over the years are mostly teeth, but also include some bones, and they reveal the presence of a variety of species. All of these remains are from the very end of the Cretaceous, 66- 68 million years ago, just before the mass extinction event that saw the extinction of the non-bird dinosaurs. "The material was fragmentary but showed that the Arctic dinosaurs were very diverse," says Pascal Godefroit, an expert on early birds and birdlike dinosaurs who has been involved in the work at the Kakanaut River.

2.Once there was an idea that dinosaurs were cold-blooded and only thrived in the swamps and wetlands of tropical climes. But the more we look, the more we realize dinosaurs were found in as many different kinds of habitats as birds and mammals are today. Polar dinosaurs, probably warm-blooded and feathery, were thriving roughly 70- -100 million years ago in great polar forests, of which there is no modem equivalent. Fossils of such dinosaurs have been discovered in Siberia, specifically at the Kakanaut River on the Kamchatka Peninsula. The dinosaur remains found here over the years are mostly teeth, but also include some bones, and they reveal the presence of a variety of species. All of these remains are from the very end of the Cretaceous, 66- 68 million years ago, just before the mass extinction event that saw the extinction of the non-bird dinosaurs. "The material was fragmentary but showed that the Arctic dinosaurs were very diverse," says Pascal Godefroit, an expert on early birds and birdlike dinosaurs who has been involved in the work at the Kakanaut River.

3.Once there was an idea that dinosaurs were cold-blooded and only thrived in the swamps and wetlands of tropical climes. But the more we look, the more we realize dinosaurs were found in as many different kinds of habitats as birds and mammals are today. Polar dinosaurs, probably warm-blooded and feathery, were thriving roughly 70- -100 million years ago in great polar forests, of which there is no modem equivalent. Fossils of such dinosaurs have been discovered in Siberia, specifically at the Kakanaut River on the Kamchatka Peninsula. The dinosaur remains found here over the years are mostly teeth, but also include some bones, and they reveal the presence of a variety of species. All of these remains are from the very end of the Cretaceous, 66- 68 million years ago, just before the mass extinction event that saw the extinction of the non-bird dinosaurs. "The material was fragmentary but showed that the Arctic dinosaurs were very diverse," says Pascal Godefroit, an expert on early birds and birdlike dinosaurs who has been involved in the work at the Kakanaut River.

4.The Kakanaut finds have been important in understanding the end-Cretaceous extinction event. This is in part because Kakanaut was within the Arctic Circle and just 1 ,600 kilometers from the North Pole at that time. Conditions then were warmer than today, but mean annual temperatures were still around 10 degrees Celsius, and there would have been frequent spells below freezing and many months of darkness. Dinosaur fossils found farther east across the Bering Sea in Alaska were left by creatures that endured similar climatic conditions, but some experts have argued that they migrated south in the winter, en masse, to avoid the coldest months. At Kakanaut, researchers found fragments of eggshell from hadrosaur and theropod dinosaurs, which suggested that these animals were breeding in polar regions and living there year-round.

5.The Kakanaut finds have been important in understanding the end-Cretaceous extinction event. This is in part because Kakanaut was within the Arctic Circle and just 1 ,600 kilometers from the North Pole at that time. Conditions then were warmer than today, but mean annual temperatures were still around 10 degrees Celsius, and there would have been frequent spells below freezing and many months of darkness. Dinosaur fossils found farther east across the Bering Sea in Alaska were left by creatures that endured similar climatic conditions, but some experts have argued that they migrated south in the winter, en masse, to avoid the coldest months. At Kakanaut, researchers found fragments of eggshell from hadrosaur and theropod dinosaurs, which suggested that these animals were breeding in polar regions and living there year-round.

6.Many scientists argue that the dinosaurs went extinct as a result of Earth's collision with a massive asteroid or comet about 66 million years ago that created the Chicxulub Crater on Mexico's Yucatan Peninsula. Other scientists have claimed that falling global temperatures had led to a decline in dinosaurs around the world in the period before the impact (collision). However, the rich fauna (animal life) found by Godefroit and his colleagues suggests that not only had a diverse ecosystem of dinosaurs persisted in the Arctic in the L ate Cretaceous, but also that they were thriving in very cold conditions. The herbivores here must have fed on plants, such as conifers, that remained green year-round and also taken advantage during summer months of a profusion of nutritious fresh growth thrown out by plants bathing in light 24 hours a day.

7."For the first time we have firm evidence that these polar dinosaurs were able to reproduce and live in these relatively cold regions. There is no way of knowing for sure, but dinosaurs were probably warm- blooded just like modem birds, which are the direct descendants of dinosaurs," Godefroit told reporters when his findings were published in the German journal Naturwissenschaften in 2009. "The dinosaurs were incredibly diverse in polar regions- as diverse as they were in tropical regions. It was a big surprise for us."

8.It is likely that a combination of factors led to the demise of the non-bird dinosaurs, but the precise explanation remains a fascinating and enduring mystery. It had been thought that Siberia had a paucity of fossils in comparison to its southern neighbors Mongolia and China, but the recent discoveries suggest this may not be true.

Rather than dinosaurs slowly dying out due to climate change in the period before the impact, Godefroit believes that the discovery backs up the idea that dinosaurs were killed off in a rapid and brutal fashion by cataclysmic conditions that swept the world following the Chicxulub impact. ⬛ Debris in the atmosphere may have blackened the skies for several years, killing off plants and destroying the food supply- -particularly as large herbivores (plant eaters), such as sauropod dinosaurs, required vast quantities of plant matter to fuel their massive bulk. ⬛ Starved for meat, the flesh eaters would eventually have succumbed too, as herbivores disappeared.

⬛ It is likely that a combination of factors led to the demise of the non-bird dinosaurs, but the precise explanation remains a fascinating and enduring mystery. ⬛ It had been thought that Siberia had a paucity of fossils in comparison to its southern neighbors Mongolia and China, but the recent discoveries suggest this may not be true.