托福听力背景知识：蜥脚类恐龙

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　　Introduction：

　　Sauropod

　　如果时光倒流 1.5 亿年,那时陆地上的统治者就是巨大恐龙群,其中的主角则是有 100 多个种类的蜥脚类恐龙(属于蜥臀目)。蜥脚类恐龙中身长最大的超过 30 米,有很长的颈和尾,粗壮的四肢支撑着如大酒桶般的身躯。当时,虽然陆地上的生命已出现了 4 亿年,但是除了蜥脚类恐龙之外,陆生动物中没有身长超过 20 米的。

　　Background information：

　　Sauropoda,or the sauropods, are an infraorder of saurischian ("lizard-hipped") dinosaurs.They had very long necks, long tails, small heads (relative to the rest oftheir body), and thick, pillar-like legs. They are notable for the enormoussizes attained by some species, and the group includes the largest animals tohave ever lived on land.

　　Well-knowngenera include Brachiosaurus, Diplodocus, and Apatosaurus . Sauropods firstappeared in the late Triassic Period, where they somewhat resembled the closelyrelated (and possibly ancestral) group Prosauropoda. By the Late Jurassic (150million years ago), sauropods had become widespread (especially the diplodocidsand brachiosaurids). By the Late Cretaceous, those groups had mainly beenreplaced by the titanosaurs, which had a near-global distribution. However, aswith all other non-avian dinosaurs, the titanosaurs died out in theCretaceous–Paleogene extinction event. Fossilised remains of sauropods havebeen found on every continent, including Antarctica.

　　The nameSauropoda was coined by O.C. Marsh in 1878, and is derived from Greek, meaning"lizard foot". Sauropods are one of the most recognizable groups ofdinosaurs, and have become a fixture in popular culture due to their largesizes.

　　Completesauropod fossil finds are rare. Many species, especially the largest, are knownonly from isolated and disarticulated bones. Many near-complete specimens lackheads, tail tips and limbs.

　　Knowledge points：

　　1. Sauropod 是恐龙的一种。它们有长脖子,长尾巴,头很小和粗壮的腿部。

　　2. 后侏罗纪时期,Sauropod 大量出现。

　　3. Sauropod 恐龙的化石出现在各个大陆,包括南极洲。

　　4. Sauropod 一词来源于希腊语,意思是蜥蜴的脚。

　　Vocabulary prediction：

　　Anatomy 解剖,分解

　　Chew 咀嚼

　　Reptile 爬行动物

　　grind...up 把...磨成粉末

　　Test Point – TPO27L3

　　Your reading for today touched on dinosaurfossils from the Mesozoic era, which ended about 65 million years ago. Today wewill be discussing the sauropods. I think our discussion of sauropods willillustrate what we can learn by comparing the fossil record to modern animals.By fossils, we mean traces of prehistoric animals such as bones, which becomemineralized, or impressions of bones or organs that are left in stone.

　　Now sauropods were among the largestanimals to exist ever! They were larger than blue whales, which are the largestanimals alive today. They weigh up to one hundred tons, twenty times as much aselephants. Also, they were an extremely successful kind of dinosaur. There’sevidence of sauropods in the fossil record for an unusually long time, over onehundred million years.

　　So, why were sauropods so successful?

　　Biologically speaking, sauropods shouldn’thave been successful. Large animals like elephants, say, they require much morefood and energy and have fewer offspring than smaller animals. This makesmaintaining a population harder. The largest animals today don’t live on land.But in the ocean where food is easier to find, a blue whale, for instance, caneat up to 8,000 pounds of food a day. And they give birth only once every fewyears. We also know that body heat that... well, large animals can’t easily getrid of excess body heat. But for an oceangoing whale, that’s not a problem. Fora 100-ton land animal, it can be.

　　For years, we have assumed it was theabundant plant life of the Mesozoic that allowed these giants to thrive.However, we now know that since oxygen levels were much lower in the Mesozoicthan we assumed, there was much less plant life for sauropods to eat than wethought.

　　Knowledge points

　　1.蜥脚类恐龙是出现过的最大的动物。它们比现存的最大的动物蓝鲸都要大。

　　2.蜥脚类恐龙需要大量的食物供给和能量消耗,比起体型较小的动物来说它们后代也少。这使得它们维持数量有难度。

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