Theria includes Eutheria and its sister taxon Metatheria. Placentalia includes extant eutherians plus their most recent common ancestor. The oldest eutherian is from 125mya (million years ago). Molecular studies place this origin at about 130-185mya. Older dates cannot be refuted based on fossil evidence as earliest eutherian remains are scarce. Earliest superordinal clades (hence Placentalia) range from 64-104mya (median 84mya) based on molecules, similar to 85-90mya based on fossils. Superordinal clades Archonta, Ferungulata, Glires, and Paenungulata based on fossils are similar to molecularly based clades, except Afrotheria was not predicted by fossils. Both fossils and molecules recognize 16 of 18 extant placental orders. Fossils place the origins of orders around 65mya as do some molecular studies, but others suggest ordinal diversification as old as 100mya. Fossil evidence supports a Laurasian origin for Eutheria (and Metatheria) and Placentalia, although some molecular studies suggest a Gondwanan origin for both taxa.

译文

:Theria包括Eutheria及其姊妹分类单元Metatheria。胎盘素包括现存的古希腊人及其最近的共同祖先。最古老的以太坊来自125mya(百万年前)。分子研究将此起源定在约130-185mya。由于化石的最早遗存稀少,因此无法根据化石证据推翻较旧的日期。最早的上等进化枝(因此称为胎盘虫)基于分子的范围为64-104mya(中位数为84mya),类似于基于化石的85-90mya。基于化石的上等进化枝Archonta,Ferungulata,Glires和Paenungulata与基于分子的进化枝相似,不同的是化石不能预测非洲菊。化石和分子都识别18个现存胎盘中的16个。化石像一些分子研究一样,将点状起源定在65mya左右,但另一些人则认为序数多样化的历史可以追溯到100mya。化石的证据支持Eutheria(和Metatheria)和Placentalia的Laurasian起源,尽管一些分子研究表明,这两个分类群都来自冈瓦纳人。

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