托福阅读带你认识恐龙.pdfVIP

智 课 网 托 福 备 考 资 料 托福阅读带你认识恐龙 如今托福阅读的背景知识要求越来越多，托福阅读题材也越来越广 泛，如果大家不能在新托福阅读的复习时对各种资料有一个了解的话考 试的时候会很困难，下面的材料是关于恐龙的背景知识，希望对大家有 帮助。 新托福阅读准备之托福阅读题材：关于恐龙 托福阅读原文：Reproductive biology Three eggs, bluish with black speckling, sit atop a layer of white mollusk shells pieces, surrounded by sandy ground and small bits of bluish stone. Nest of a plover (Charadrius). All dinosaurs lay amniotic eggs with hard shells made mostly of calcium carbonate. Eggs are usually laid in a nest. Most species create somewhat elaborate nests, which can be cups, domes, plates, beds scrapes, mounds, or burrows. Some species of modern bird have no nests; the cliff-nesting Common Guillemot lays its eggs on bare rock, and male Emperor Penguins keep eggs between their body and feet. Primitive birds and many non-avialan dinosaurs often lay eggs in communal nests, with males primarily incubating the eggs. While modern birds have only one functional oviduct and lay one egg at a time, more primitive birds and dinosaurs had two oviducts, like crocodiles. Some non-avialan dinosaurs, such as Troodon, exhibited iterative laying, where the adult might lay a pair of eggs every one or two days, and then ensured simultaneous hatching by delaying brooding until all eggs were laid. When laying eggs, females grow a special type of bone between the hard outer bone and the marrow of their limbs. This medullary bone, which is rich in calcium, is used to make eggshells. A discovery of features in a Tyrannosaurus rex skeleton provided evidence of medullary bone in extinct dinosaurs and, for the first time, allowed paleontologists to establish the sex of a fossil dinosaur specimen. Further research has found medullary bone in the carnosaur Allosaurus and the ornithopod Tenontosaurus. Because the line of dinosaurs that includes Allosaurus and Tyrannosaurus d