Source: CCTV.com
10-17-2008 13:48
Zhang Chun'guang, a professor at the Institute of Zoology, Chinese Academy of Sciences, has been conducting ichthyological research since the 1980s. In April 2001, he was invited to the natural pits in Le Ye, Guangxi province.
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Dashiwei is the biggest natural pit in China with a depth of 613 meters. It's 600 meters from east to west and 420 meters from south to north. Nearly 28 natural pits of varying sizes surround Dashiwei. Geological experts said that it has almost every type of karst cave pits and landscapes.
There are ranges of successive mountains in the Yunnan-Guizhou Plateau, which are called karst landforms by geologists. They look tall and straight on the outside, but they look quite the opposite on the inside. Rain erosion and underground rivers have caused the roof of the caves to collapse, gradually forming natural pits. The shape of these pits is like a funnel. It is very steep around the four sides. To carry out research and exploration is quite difficult. In April 2001, a team of 15 researchers started from Le Ye and came to a place 1 kilometer away from Dashiwei. They found many red cliffs covered with spiral-shaped fossils along the roadside.
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About 250 million years ago, there was a vast sea in Guangxi province. The sea was very shallow. The organisms that lived there were mostly coelenterates. 220 million years later, the land emerged from the bottom of the sea and formed the karst landform. The fossils on the cliff were left by those ancient sea animals.
After several hours of walking on mountain paths, the researchers arrived at the top of the pits. Some of them went down to the bottom with the help of local guides.
After several days' investigation, the researchers were making progress. It was a pity that no large animals had yet to be found. However, there was a new discovery at the Huangjing Cave.
The fossil in sight is wrapped by thick limestone. It's a skull as seen from the outline. Zhang Chun'guang thought it was a mammal fossil.
About 65 million years ago, dinosaurs disappeared from the earth for unknown reasons. Small animals that looked similar to rodents were able to survive. They were the oldest mammals on earth.
There are three types of mammals with three different modes of reproduction. One type is monotremes and the mode of their reproduction is oviparity similar to reptiles such as platypus. The second type is marsupial. They are also viviparous, but the baby animals they bear are not well developed. The babies have to live in their mothers' pouches for some time like the kangaroos in Australia. The third type is placental mammals such as the tigers. After millions of years' of evolution, the population of these mammals continued to increase. Some of them competed for the top spot on the food chain. They have developed different shape of body and skull from others.
The predators have a special feature - their iliac crest is very sharp and tall on the top of their skeleton. Also, they have two carnassials teeth, which act like a pair of scissors. Once they close their teeth, they can tear the muscles of other animals, and even crush their bones.
But the researchers wondered why the fossils of these land animals appeared halfway up the cliff. After several days' exploration, they found no more clues other than some teeth of small animals. Which animal did this skeleton belong to? From the size and shape of this skeleton, Zhang Chuan'guang thought that it wasn't a tiger or wolf.
Eight kinds of bears have been found so far. And four of them live in china, including brown bears, pandas, sun bears and black bears. The black bears are the most widespread. Sometimes they're found in Guangxi.
Because of its size, the black bear is considered a large mammal. But they can't move as quickly as tigers. However, if they're on a tall mountain, even a tigers couldn't win a fight with them. That's because they're good at running on the cliffs and climbing trees. They're also not picky about their food, so they've been nicknamed “opportunists.”