zt 袋兽 from 中恐

格子布鞋

http://www.oursci.org/bbs/sinodino/viewthread.php?tid=1350&extra=page%3D17


中国发现有袋动物

不知道大家看过没有，贴出来

Fossil bridges gap in mammal evolution
Thursday, December 11, 2003 Posted: 3:48 PM EST (2048 GMT)


WASHINGTON (AP) -- The fossil of a tiny creature found in Northeast China is helping scientists determine when mammals split into different groups: those with babies that develop inside their mothers and those that raise their offspring in pouches.

The two groups make up more than 99 percent of all mammals today, and the new fossil evidence indicates the separation began in Asia about 125 million years ago.

The newly found ancient animal, named Sinodelphys szalayi, is the earliest known marsupial, meaning an animal with a pouch. It was chipmunk-sized, about 6 inches long and weighed about an ounce, according to Zhe-Xi Luo of the Carnegie Museum of Natural History in Pittsburgh.

Its skeleton was found in 2000 in a region where researchers had previously found Eomaia, a fossil believed to be among the earliest known placental mammals, of about the same age. The discovery is reported in Friday's issue of the journal Science.

The finding of the two fossils indicates an approximate date for the split between the placental and pouch mammals, Luo said in a telephone interview.

"All this was happening while dinosaurs dominated the world. Mammals were able to explore a different niche and able to hang on," Luo said. "Otherwise there wouldn't be any cute koala bears to look at."

Luo noted that Sinodelphys had hands and feet with fingers and strong wrists well adapted to climbing, indicating it could retreat to the trees to avoid hunting dinosaurs.

The discovery also adds support for the 19th century theory of Thomas Henry Huxley that the first marsupials lived in trees.

Luo said evidence indicates that marsupials developed in Asia, spread to North America and then moved southward to South America and Australia. Today marsupials are most common in Australia and South America, with only fossil remains in the northern hemisphere. Opossums, the only marsupial in the north, are a recent immigrant.

"It's an interesting paradox," Luo said. "If you look across the world, South America and Australia, you find the present-day marsupials in great abundance and diversity. But those are not the original points where they evolved."

The find provides unprecedented information on the biology of early marsupials, supporting the theory they lived in trees, Richard L. Cifelli and Brian M. Davis of the Oklahoma Museum of Natural History comment in an accompanying article.

Further evidence is needed, however, to indicate whether that was important in their diverging from placental mammals, they added.

The discovery is important because it helps support evidence for the dates of early mammals developed in other research, said Davis and Cifelli.

Today more than 99 percent of mammals -- animals that provide milk for their young -- are either marsupials like kangaroos and bandicoots, or placental mammals like humans, cats, dogs and others. The remaining small group of mammals, which lay eggs, are called monotremes -- the platypus and echidna.




Fossil bridges gap in mammal evolution

在中国东北发现了一种小型生物的化石，它帮助科学家确定哺乳动物从什么时候开始分成截然不同的两个类群：那些胚胎在母体内发育的和那些在育儿袋内发育的。这两个类群构成了今天99%的哺乳动物，新的化石证据显示，分离开始于1亿2500万年前。

新发现的动物叫做Sinodelphys szalayi，是已知最早的有袋类。据匹兹堡自然历史博物馆的罗哲喜（音）介绍，它有花栗鼠那么大，约6英寸长，1盎司重。它的骨架发现于2000年，其出土地区还曾经找到过大约同一时期的Eomaia，据信是已知最早的胎盘动物。

罗哲喜认为，这两具化石的发现显示了胎盘动物和有袋动物分道扬镳的大致时间。“所有这些事都发生在恐龙占统治地位的世界。哺乳动物能够找到各不相同的生态位并繁衍下去。”他说，“否则今天就看不到可爱的树袋熊了。”

罗哲喜注意到Sinodelphys的前后脚有手指和脚趾，并且有十分适合攀爬的腕关节，这暗示的它能够为躲避猎食的恐龙而爬到树上。这个发现也支持了19世纪脱马斯·亨利贺·胥黎的理论，即最早的有袋类动物是生活在树上的。

罗哲喜说，这个证据表明有袋动物起源于亚洲，之后传播到北美，再向南迁徙到南美和澳洲。今天有袋类主要分布再澳洲和南美洲，北半球只留有它们的化石。北半球唯一的有袋动物是负鼠，也是新近迁入的。“这是一个有趣的矛盾，”罗哲喜说，“如果你纵览全世界，你会发现今天澳洲和南美洲的有袋类十分丰富且具多样性，但是那里却不是有袋类进化的发源地。”

俄克拉荷马州自然历史博物馆的Richard L. Cifelli和Brian M. Davis在一篇附随的论文里指出，这个发现为早期有袋类动物提供了空前的生物学信息，支持了它们为树栖的理论。但是他们补充说，还需要更多的证据才能知道这种动物在有袋类脱离有胎盘类的过程中是否为重要的环节。

Davis和Cifelli认为，这次发现的重要性还在于，它为早期哺乳动物进化的其它研究提供了时间上的证据。


Sinodelphys szalayi到底叫什么好呢？有啊，袋兽嘛，前几天，我还给三思发热，登在首页

Eomaia是什么？始祖攀缘兽吗？


Eomaia应该是攀援始祖兽，可是google上的“Eomaia”怎么就没有中恐的网页呢


英寸和盎司怎么换算成公制？

这两句翻得不是很确定：
Further evidence is needed, however, to indicate whether that was important in their diverging from placental mammals
(还需要更多的证据才能知道这种动物在有袋类脱离有胎盘类的过程中是否为重要的环节。)

The discovery is important because it helps support evidence for the dates of early mammals developed in other research
(这次发现的重要性还在于，它为早期哺乳动物进化的其它研究提供了时间上的证据。)

一些太简单的东西没翻。


在我国和澳洲都发现了早期的贫齿类化石，不过我国（比如钟健兽）的似乎不太肯定。生物的起源地和发展中心可以完全不同，最有趣的我看还是北美洲的马，既是已知的发源地，又是演化中心，可是后来偏偏就没有了


vimb兄这一句可能没翻对：

Further evidence is needed, however, to indicate whether that was important in their diverging from placental mammals
(还需要更多的证据才能知道这种动物在有袋类脱离有胎盘类的过程中是否为重要的环节。)

考虑上文，我觉得这里的that是指“树栖”这个发现，因此我想是不是应该翻译为：

但是，还需要更多的证据才能知道，树栖这种行为是否在有袋类与胎盘类分道扬镳的过程中起了重要作用。