雅思阅读练习：Missing link in tyrannosaur family tree discovered

　　新东方在线雅思网为大家带来了雅思阅读练习：Missing link in tyrannosaur family tree discovered。正文都做了贴心的注解，文章包含雅思词汇、例句讲解。希望以下内容能够为同学们的雅思备考提供帮助。新东方在线雅思网将第一时间为大家发布最新、最全、最专业的雅思报名官网消息和雅思考试真题及解析，供大家参考。

　　1.7亿年-1亿年前的暴龙(tyrannosaur)体型很小，奔跑在天地之缘。然而，到8000万年前，暴龙却成了体积最大、最恐怖的捕食者。那么，在这2000万年间，到底发生了什么?新发现试图填补暴龙家族史中这缺失的一环。

　　A new species(物种) of tyrannosaur(暴龙)adds to the fearsome group of dinosaurs(恐龙)to which Tyrannosaurus rex belonged. Scientists found its 90-million-year-old bones in the harsh deserts of Uzbekistan.

　　The newly described species, Timurlengia euotica, is an oddball(古怪的人或物). The horse-sized dinosaur resembles(与……相似)earlier,smaller tyrannosaurs. Yet its large brain and advanced ears—their outlines preserved(保存)in a skull fragment(碎片)—mirror those of later tyrannosaurs like T. rex.

　　“Timurlengia is truly a curveball(曲线球;难以把握的事物),”says Thomas Carr of Carthage College, who wasn’t involved with the study. “I had to readjust the way I thought about tyrannosaurs. It’s a weirdo(古怪的人或物).”

　　A Growing Mystery

　　The new species, described Monday in the Proceedings of the National Academy of Sciences, could also help untangle(解开谜团)one of the most frustrating questions in dinosaur evolution: How and why did tyrannosaurs get so big?

　　Tyrannosaurs first appear in the fossil record about 170 million years ago, and until about 100 million years ago, they scampered(惊慌地奔跑)about on the ecological margins(边缘), some no bigger than dogs.

　　But by the late Cretaceous(白垩的，白垩纪的)—about 80 million years ago—tyrannosaurs such as T. rex had ballooned into some of the biggest, most intimidating(令人害怕的) land predators(捕食者) ever to walk the planet. Head to tail, they could get as long as a bus, and their enormous heads and powerful jaws could generate bites with nearly 13,000 pounds of force.

　　“The funny thing is that T. rex is such a pop star,” says Lawrence Witmer of Ohio University, who wasn’t involved with the study. “None of us can even remember a time when we didn’t know about Tyrannosaurus. But the reality is that how [it] evolved is a bit of a mystery.”

　　What’s more, T. rex wasn’t just big. It was gifted.

　　“Contrary to what people learned in the first Jurassic Park movie, T.rex had acute senses,” says study co-author Hans-Dieter Sues of the Smithsonian National Museum of Natural History. “It clearly had very keen eyesight, a spectacularly keen sense of smell, [and] keen hearing.”

　　Its killer senses stemmed from(来源于……)its impressive brain: T. rex’s two olfactory(嗅觉的)lobes—the brain regions devoted to smell—were each the size of a grapefruit. And its long, looped ear canals helped it hear the low-frequency sounds emitted(发出)by distant prey’s footsteps.

　　“It was sort of a superpredator,” says Sues.

　　But paleontologists have struggled to pin down how tyrannosaurs got brainier and brawnier, largely because the fossil record between 100 and 80 million years ago, when small tyrannosaurs would have evolved into giants, is so sparse(稀缺的).

　　“At that particular point in time, sea levels were very high,” says Sues. “We just didn’t have the record from the land animals.”

　　Digging for Answers

　　The fall of the Soviet Union, however, presented researchers with a new opportunity: the Bissekty Formation, a site in what’s now Uzbekistan with fossils between 92 and 90 million years old. Soviet paleontologist Lev Nesov had investigated the site since the mid-1970s, but as the old regime dissolved(溶解), Nesov,his Ph.D. student Alexander Averianov, and colleague J. David Archibald of SanDiego State University planned a major excavation(挖掘;出土)of the site—one that the National Geographic Society eventually would help fund in 1997 and 1998.

　　Bigger Than T. rex: Spinosaurus Fossils discovered in 2014 revealed that Spinosaurus, bigger than T. rex, was an excellent swimmer, unlike any other dinosaur. Found in the sands of Morocco,the bones suggest that, unlike its land-dwelling cousins, this meat-eating creature likely fed on sharks and other fish.

　　The team worked in difficult conditions.“The highest temperature I remember was 43 degrees Celsius (109 degrees Fahrenheit) in the shadow,” wrote Averianov, a co-author of the study. Sues recalls that it once got so hot inside his tent, his tooth paste’s fluoride stripes separated out, liquified by the intense heat.

　　In 2004 the team found an intriguing bone lump the size of a grapefruit. It was part of a braincase, which would have anchored the dinosaur’s neck muscles and protected its brain and ear canals.

　　The braincase remained with Averianov for ten years, stored in a cardboard box in the Zoological Institute of the Russian Academy of Sciences, until tyrannosaur expert Steve Brusatte saw it in 2014.

　　“When I looked at it, it struck me really quickly that this looked like a tyrannosaur braincase,” says Brusatte, of the University of Edinburgh.“Not exactly T. rex, much smaller; the same bones in a T. rex would be bigger than a basketball.”

　　Detailed CT scans proved Brusatte right. For instance, they revealed that Timurlengia, like later tyrannosaurs, had remarkably long inner ear canals, which would have endowed(赋予)it with superb low-frequency hearing, hence its species name euotica, Greek for “well-eared.”

　　However, the braincase was short—more in keeping with Xiongguanlong, an early tyrannosaur—and lacked some of the deep recesses and knobs in later tyrannosaurs like T. rex.

　　“The braincase was really the Rosetta stone,” says Sues, “because it showed that this animal had the same basic brain structure of the later T. rex but had primitive brain structure, as well.”

　　Other bone fragments all pointed the same direction: to a new tyrannosaur about the size of a horse, seemingly caught between the early and late tyrannosaurs in terms of age, size, and sensory ability.

　　Brains, Then Brawn?

　　The finding suggests that tyrannosaurs first evolved their distinct senses and brain structure, and then grew in size much later. In fact, tyrannosaurs' smarts may have made it easier for them to take over for the allosauroids, an earlier group of big-bodied, carnivorous(肉食的)dinosaurs that went extinct(灭绝的)some 94 million years ago. “It’s the head-first mode of evolution,” says Sues. “The brains[are] for the operation, and then you develop the bulk.”

　　But the team’s work is far from over, given that they have only one surefire(确定的)Timurlengia specimen(标本): the braincase. “It’s like trying to solve a murder with one clue,”says Brusatte. “More than any other experiment or analysis, we just need morefossils.”

　　In the meantime, all paleontologists know for sure is that Timurlengia was no sensory slouch(笨拙的).

　　“I think all we can say is that they weren’t as dumb as their predecessors(前任，前辈),” says Carr.

　　Vocabulary

　　species 物种

　　dinosaur 恐龙

　　oddball 奇怪的人或物

　　resemble 与......相似

　　preserve 保存

　　fragment 碎片

　　curveball 曲线球;难以把握的人或物

　　weirdo 奇怪的人或物

　　untangle 揭开谜团

　　scamper 惊慌地奔跑

　　margin 边缘

　　intimidating 令人害怕的

　　predator 捕食者

　　stem from 来源于......

　　olfactory 嗅觉的

　　emit 散发出

　　sparse 稀少的

　　dissolve 溶解

　　excavation 挖掘;出土

　　endow 赋予

　　carnivorous 食肉的

　　extinct 灭绝的

　　surefire 确信的

　　specimen 标本

　　slouch 笨拙的

　　predecessor 前任;前辈

　　Comprehension Questions

　　1. What is the name of the newly discovered species of tyrannosaur? why is it described as an "oddball" by some scientists?

　　2. In what sense is Timurlengia the "missing link" in tyannosaur family?

　　读真题，记词汇

　　1. Baleen species, on the other hand, appear to have some related brain structures but it is not known whether these are functional. (剑4T1P2)

　　参考译文：另一方面，鲸须类动物似乎有一些相关的脑结构，但其脑结构是否会有任何功用还是个未知数。

　　2. They have developed a hit-list of our main fears: that natural resources are running out; that the population is ever growing, leaving less and less to eat; that species are becoming extinct in vast numbers, and that the planet's air and water are becoming ever more polluted.(剑5T1P3)

　　参考译文：他们列出了一系列我们担忧的问题：自然资源正在枯竭，人口不断增长，粮食越来越少，物种大批灭绝，地球的空气污染和水污染越来越严重。

　　3. For example,vision is obviously more useful to inhabiting clear open waters than to those living in turbid rivers and flooded plains.(剑4T1P2)

　　参考译文：例如，与那些生活在浑浊的河里以及河漫滩上的生物相比，视觉对生活在开阔水域的物种会更有用。

　　4. Trace amounts of nickel and sulphur are usually present in the raw materials used to make glass, and nickel can also be introduced by fragments of nickel alloys falling into the molten glass.(剑5P4T2)

　　参考译文：微量的镍和硫通常出现在制作玻璃的原材料中，熔化过程中镍合金碎片也会增加玻璃的镍含量。

　　5.However, the major problems of the travel and tourism industry that have hidden, orobscured, its economic impact are the diversity and fragmentation of the industry itself.(剑10T3P1)

　　参考译文：然而，旅行以及旅游产业隐藏在经济效益后的主要问题，是这个产业本身的多样性和脆弱性。

　　6. A violent eruption can blow the top few kilometers off a mountain, scatter fine ash practically all over the globe and hurl rock fragments into the stratosphere to darken the skies a continent away.(剑4T3P2)

　　参考译文：一次激烈的火山喷发会将山顶掀到几千米开外，让火山灰弥漫到全球，并且能将岩屑抛掷到平流层从而覆盖一片大陆之外的天空。