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海龟那题实在有点烦人，就google了一下 Triassic + shell + fossil +turtle 结果在nature上面发现了这么一段文字 还是咱们中国人写的。。。
http://www.nature.com/nature/journal/v456/n7221/full/nature07533.html
An ancestral turtle from the Late Triassic of southwestern China
Chun Li1, Xiao-Chun Wu2, Olivier Rieppel3, Li-Ting Wang4 & Li-Jun Zhao5
The origin of the turtle body plan remains one of the great mysteries of reptile evolution. The anatomy of turtles is highly derived, which renders it difficult to establish the relationships of turtles with other groups of reptiles. The oldest known turtle, Proganochelys from the Late Triassic period of Germany1, has a fully formed shell and offers no clue as to its origin. Here we describe a new 220-million-year-old turtle from China, somewhat older than Proganochelys, that documents an intermediate step in the evolution of the shell and associated structures. A ventral plastron is fully developed, but the dorsal carapace consists of neural plates only. The dorsal ribs are expanded, and osteoderms are absent. The new species shows that the plastron evolved before the carapace and that the first step of carapace formation is the ossification of the neural plates coupled with a broadening of the ribs. This corresponds to early embryonic stages of carapace formation in extant turtles, and shows that the turtle shell is not derived from a fusion of osteoderms. Phylogenetic analysis places the new species basal to all known turtles, fossil and extant. The marine deposits that yielded the fossils indicate that this primitive turtle inhabited marginal areas of the sea or river deltas.
除去关于学术的一大段(用google translater用到吐，建议大家不用读了，和jj描述事实基本吻合，除了科学家的推断没有出现)，最后一句让我眼前一亮， 说有证据indicate 这种史前海龟是生活在海或者三角洲里的。
既然jj里科学家的推理是基于这段事实的，那么没有出现的最后一句就是科学家没有考虑到的了。
至此基本可以确定选“忽略了有的龟不是生活在海里” |
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发表于 2011-9-6 23:32:58
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