THE ORIGIN OF EGG-LAYING MAMMALS
THE ORIGIN OF EGG-LAYING MAMMALS
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DOI：
10.1038/326871a0
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发表时间：
1987-04-30
期刊：
影响因子：
64.8
通讯作者：
JENKINS, FA
中科院分区：
文献类型：
--
作者：
KIELANJAWOROWSKA, Z;CROMPTON, AW;JENKINS, FA
单孔动物--澳大利亚地区的产卵哺乳动物--的起源以及它们与兽类(有袋类和胎盘动物)的关系一直是个有趣的动物学问题。最近，Archer等人。描述了来自澳大利亚的早白垩世单孔动物(Steropodon Galmani)的下颌骨碎片，并将其牙齿解释为摩擦性牙齿，因此被认为来自于人类进化的相对高级阶段。这一发现具有重大意义，并从根本上改变了目前的观点，即单孔动物和兽类在哺乳动物进化的最早阶段就出现了分歧。我们同意立体齿象是一种兽类动物，但我们会争辩说，它的牙齿并不具有摩擦性。在侏罗纪时期，在有摩擦的牙齿发育之前，立体齿象似乎就是从人类进化而来的。
The origin of monotremes-egg-laying mammals from the Australian region-and their relationship to therians (marsupials and placentals) have been intriguing zoological problems. Recently Archer et al. described a fragment of a lower jaw of an early Cretaceous monotreme from Australia (Steropodon galmani) and interpreted its teeth as tribosphenic and thus supposedly derived from a relatively advanced stage in therian evolution. This discovery is of major importance, and radically alters currently held opinion that monotremes and therians diverged at the earliest stage of mammalian evolution. We agree that Steropodon is a therian but would argue that its teeth are not tribosphenic. Steropodon appears to have been derived from therians before the development of tribosphenic teeth, possibly during the Jurassic period.