单选题 Conventional wisdom has long held that mammals stayed millions of years on earth. As long as dinosaurs roamed the lands, our distant ancestors never got to be much more than chicken-hearted creatures that sneaked out at night to grab bits of plants when the terrible lizards were asleep. Only when they were wiped out did mammals begin to earn a little evolutionary respect.
But that picture changed dramatically with the announcement in Nature of two impressive fossils. One, of a brand-new species named R. giganticus , broke apart the notion that most dinosaur-age mammals were never larger than squirrels. The animal had the dimensions of a midsize dog-by far the biggest dinosaur-age mammal ever found. And the second, a new specimen of a previously discovered species called R. robustus , refuted the notion that it was always the mammals that got eaten. Inside the skeleton where the animal"s stomach would have been are the fossilized remains of a baby dinosaur. "This discovery was the chance of a lifetime," says Jin Meng, scientist and coauthor of the paper.
Indeed, Meng didn"t expect to find things like this at all. The smaller skeleton was discovered about two years ago by villagers in China"s Liaoning province, site of some of the richest fossil beds in the world. They brought it to the attention of scientists, who took it to an institute for examination. "We didn"t see the stomach contents at first," says Meng.
After they did, however, it didn"t take them long to realize they had struck scientific gold. On closer examination, the scientists determined that the remains were those of a juvenile dinosaur. Some of the arm and leg bones were still attached to each other, suggesting that R. robustus didn"t chew its food thoroughly but wolfed it down in large chunks.
Taken together, the finds overturn the already eroded idea that early mammals were tiny and timid. Now paleontologists can stop cooking up theories to explain why mammals were so little—that they had to be small to avoid being found, for example, or they couldn"t grow larger because dinosaurs already occupied those ecological spaces.
But it"s now clear that mammals did fill some of the spaces reserved for larger animals. "It"s quite possible," says paleontologist Anne Weil, "that they competed with dinosaurs for the same prey." And because they ate dinosaurs, they may even have had an influence on dinosaur evolution. What sort of influence? "We don"t know," she says. "That"s how it is with the best finds. They leave you with more questions than answers."

单选题 Mammals in the dinosaur age used to be described as

【正确答案】 D

【答案解析】[解析] 句意：恐龙时代的哺乳动物曾经被描述为什么?根据第一段第二句“As long as dinosaurs roamed the lands, our distant ancestors never got to be much more than chicken-hearted creatures that sneaked out at night to grab bits of plants when the terrible lizards were asleep”可知，传统观点认为我们远古的祖先只会等到可怕的恐龙在夜晚入睡的时候，才胆小如鼠地从藏身之地偷偷出来采集植物充饥。根据第二段第二句“One, of a brand-new species named R. giganticus, broke apart the notion that most dinosaur-age mammals were never larger than squirrels.”可知，全新的物种R. giganticus化石的发现，推翻了大多数恐龙时期的哺乳动物都不比松鼠大的观点。由此可知，恐龙时代的哺乳动物曾被描述为瘦小而懦弱，故选D。

单选题 The fossil of a baby dinosaur in the skeleton of R. robustus indicates that

【正确答案】 C

【答案解析】[解析] 句意：R. robustus骨骼当中的小恐龙化石说明了什么?根据第二段第4-5句“And the second, a new specimen...refuted the notion that it was always the mammals that got eaten. Inside the skeleton where the animal"s stomach would have been are the fossilized remains of a baby dinosaur.”可知，新发现的R. robustus标本推翻了哺乳动物总是被捕食这一观点。在这个标本的胃部发现了一个变成化石的小恐龙的遗骸。因此，R. robustus腹中的小恐龙是被它吞下的食物，故选C。

单选题 By saying "they had struck scientific gold" (Lines 1—2, Paragraph 4), the author means that

单选题 The expression "cooking up" (Line 2, Paragraph 5) indicates that the author

【正确答案】 A

【答案解析】[解析] 句意：“cooking up”(第五段第二行)这一短语表明作者持有何种观点?第五段第二句“Now paleontologists can stop cooking up theories to explain why mammals were so little—that they had to be small to avoid being found, for example, or they couldn"t grow larger because dinosaurs already occupied those ecological spaces.”意为“现在，古生物学家不必再编造理论来解释哺乳动物为什么那么瘦小了，例如，有的理论认为，它们之所以长得瘦小是为了避免被发现，或者，它们没法长大是因为恐龙已经占领了它们的生存空间。”根据第二段第一句“But that picture changed dramatically with the announcement in Nature of two impressive fossils.”和第五段第一句“Taken together, the finds overturn the already eroded idea that early mammals were tiny and timid.”可知，《自然》杂志上发表的关于两块化石的文章彻底改变了传统的观念。因此可知，作者基于最新的发现，对传统观点的真实性产生了质疑，故选A。