早期白时期的类动物和胎盘-类动物二分法
Shundong Bi1,2,3, Xiaoting Zheng4,5, Xiaoli Wang6,7
1Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming, China. shundong.bi@iup.edu.
Nature
|June 15, 2018
概括
新的化石证据显示,早期的胎盘哺乳动物 (Eutheria) 和有袋动物 (Metatheria) 比以前认为的更早地共存. 这重新分类了早期的哺乳动物化石,改变了我们对哺乳动物进化的理解.
科学领域:
- 古生物学
- 哺乳动物进化
- 比较解剖学
背景情况:
- 分子时钟的估计表明胎盘和袋鼠哺乳动物在罗纪的分歧.
- 早期的化石如来自中国的Juramaia (eutherian) 和Sinodelphys (metatherian) 支持这些时间线.
- 之前对化石差异的解释表明,eutherians和metatherians的生态入侵是不同的.
研究的目的:
- 重新评估早期哺乳动物化石的遗传位置.
- 了解早期胎盘哺乳动物 (Eutheria) 和有袋动物 (Metatheria) 之间的进化关系.
- 澄清早期哺乳动物的解剖学差异的重要性.
主要方法:
- 描述和分析一个新的Jehol eutherian化石,Amblestes zhoui.
- 对安博莱斯特斯 (Ambolestes zhoui),西诺德尔菲斯 (Sinodelphys) 和欧玛亚 (Eomaia) 的比较解剖学研究.
- 根据新的化石证据重新解释头骨后骨差异.
主要成果:
- 这种新型的Jehol eutherian具有独特的解剖细节,
- 化石证据表明Sinodelphys是一个eutherian,而不是一个metatherian.
- 在Sinodelphys和Eomaia之间的后差异代表了早期eutherians中的变异,而不是单独的利基入侵.
结论:
- 已知最古老的甲类动物现在被确定为来自北美西部的1. 1亿年前的化石,而不是东亚.
- 这一发现为Metatheria创造了5000万年的"幽灵血统",表明其起源早得多.
- 这项研究修订了对早期的类和类多样性和分布的理解.
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