VOA科学技术2014--Dinosaurs Displayed Fast Growth Rate Early

Dinosaurs² existed for 165 million years. The animals' evolutionary³ success was partly due to their fast growth rate.

A new study finds that this pattern of fast growth appeared in the earliest dinosaurs. The researchers examined microscopic⁴ details in dinosaur¹ bone fossils from Argentina.

The details showed that the earliest dinosaurs had growth rates similar to animals found today like mammals and birds.

Scientist Kristi Curry⁵ Rogers of Macalester College in Minnesota studies fossils. She is the lead writer of the research recently released in the publication PLOS ONE.

She said, "Growing quickly allows organisms to escape the risky⁶ business of being small for a long part of their life history." And she added that it also allows them to reproduce more throughout their life. That means each following generation will be more successful.

The researchers examined patterns fossilized within the bones of dinosaurs and some of their relatives. The dinosaurs they looked at lived in northwestern Argentina between 231 and 229 million years ago.

Curry Rogers said cellular⁷ and chemical details in the fossils all show relative speed of growth. She added that the soft parts of the animal are no longer present, but the hard parts like the bones left a record of spaces where the soft parts once were.

She said, "This allows us to reconstruct and compare growth patterns among animals."

The researchers studied five early dinosaurs. They all walked on two feet, were quick on their feet, had clawed hands that could hold objects and had sharp teeth.

Three were meat-eaters and the ancestors of large meat-eaters like T. rex and Giganotosaurus. The dinosaurs included Herrerasaurus and Sanjuansaurus which were around 3-4.5 meters long. The last meat-eater Eodromaeus was the size of a large bird.

The two others, Eoraptor and Chromogisaurus, were also around the size of a large bird. They were the ancestors of long-necked, four-legged large dinosaurs like Argentinosaurus and Dreadnoughtus.

All five showed signs of fast growth.

But the researchers also surprisingly found that some non-dinosaur reptiles⁹ in the same area and time had their own fast growth rates.

Quick growth was also found in four-legged Saurosuchus. It was a top-level meat-eater on land that was 7 meters long and similar to a reptile⁸ found today, the crocodile. Additionally, quick growth was found in crocodile relatives like Proterochampsa and Trialestes.

Other animals like the planting-eating reptile Hyperodapedon and mammal-like reptile Exaeretodon also grew quickly. But they regularly paused their growth throughout their life. That is different than the continuous fast growth of dinosaurs.

The first dinosaurs and these other animals evolved during a time on earth called the Triassic Period. It followed after Earth's worst mass extinction¹⁰ 252 million years ago at the end of the Permian Period.

About 95 percent of different kinds of animals were lost after severe climate change. The climate change may have been caused by massive volcanic¹¹ activity in an area found in today's Russia.

Curry Rogers said that fast growth was good for them in a changing world. And she said that fast growth combined with dinosaur biology and behavior allowed dinosaurs to succeed early.

Another mass extinction at the end of the Triassic about 201 million years ago killed off many early competitors to the dinosaurs.

Curry Rogers said that as time continued, dinosaurs held onto these high growth rates. She said that lead to many different kinds of dinosaurs. But she said their competitors, like crocodile-cousins, had less differences in growth patterns and behavior.

Words in This Story

evolve - v. to change or develop slowly often into a better, more complex, or more advanced state

pattern - n. something that happens in a regular and repeated way

fossil - n. something (such as a leaf, skeleton, or footprint) that is from a plant or animal which lived in ancient times and that you can see in some rocks

allow - v. to permit (something)

claw - n. a sharp curved part on the toe of an animal (such as a cat or bird)

neck - n. the part of the body between the head and the shoulders

extinction - n. the state or situation that results when something (such as a plant or animal species) has died out completely

1 dinosaur   

n.恐龙

参考例句：

• Are you trying to tell me that David was attacked by a dinosaur?你是想要告诉我大卫被一支恐龙所攻击？
• He stared at the faithful miniature of the dinosaur.他凝视著精确的恐龙缩小模型。

2 dinosaurs   

n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西

参考例句：

• The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
• Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》

3 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。

4 microscopic   

adj.微小的，细微的，极小的，显微的

参考例句：

• It's impossible to read his microscopic handwriting.不可能看清他那极小的书写字迹。
• A plant's lungs are the microscopic pores in its leaves.植物的肺就是其叶片上微细的气孔。

5 curry   

n.咖哩粉，咖哩饭菜；v.用咖哩粉调味，用马栉梳，制革

参考例句：

• Rice makes an excellent complement to a curry dish.有咖喱的菜配米饭最棒。
• Add a teaspoonful of curry powder.加一茶匙咖喱粉。

6 risky   

adj.有风险的，冒险的

参考例句：

• It may be risky but we will chance it anyhow.这可能有危险，但我们无论如何要冒一冒险。
• He is well aware how risky this investment is.他心里对这项投资的风险十分清楚。

7 cellular   

adj.移动的；细胞的，由细胞组成的

参考例句：

• She has a cellular telephone in her car.她的汽车里有一部无线通讯电话机。
• Many people use cellular materials as sensitive elements in hygrometers.很多人用蜂窝状的材料作为测量温度的传感元件。

8 reptile   

n.爬行动物；两栖动物

参考例句：

• The frog is not a true reptile.青蛙并非真正的爬行动物。
• So you should not be surprised to see someone keep a reptile as a pet.所以，你不必惊奇有人养了一只爬行动物作为宠物。

9 reptiles   

n.爬行动物，爬虫( reptile的名词复数 )

参考例句：

• Snakes and crocodiles are both reptiles. 蛇和鳄鱼都是爬行动物。 来自《简明英汉词典》
• Birds, reptiles and insects come from eggs. 鸟类、爬虫及昆虫是卵生的。 来自《现代汉英综合大词典》

10 extinction   

n.熄灭，消亡，消灭，灭绝，绝种

参考例句：

• The plant is now in danger of extinction.这种植物现在有绝种的危险。
• The island's way of life is doomed to extinction.这个岛上的生活方式注定要消失。

11 volcanic   

adj.火山的；象火山的；由火山引起的

参考例句：

• There have been several volcanic eruptions this year.今年火山爆发了好几次。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。