Dual origin of tribosphenic mammals
Dual origin of tribosphenic mammals
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DOI：
10.1038/35051023
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发表时间：
2001-01-04
期刊：
影响因子：
64.8
通讯作者：
Kielan-Jaworowska, Z
中科院分区：
文献类型：
--
作者：
Luo, ZX;Cifelli, RL;Kielan-Jaworowska, Z
有袋动物、胎盘动物和它们的近亲兽类拥有复杂的磨牙，能够具有多种咬合功能。这种功能复合体被广泛认为是现存兽类及其近亲（tribosphenidans）早期多样化和进化成功的关键。长期以来，人们一直认为这些哺乳动物起源于北方大陆，但最近有报道称，它们来自南方大陆。这些新哺乳动物的巨大年龄和先进形态导致了另一种说法，即该群体起源于冈瓦纳人。这两种生物地理学假说都隐含着这样的假设：在哺乳动物的进化史上，磨牙只进化了一次。包括这些新发现的分类群在内的系统发育和形态计量学分析提出了一种不同的解释：具有摩擦磨牙的哺乳动物不是单系的。在侏罗纪/白垩纪早期，在两个地理分布不同的古代哺乳动物群体中，摩擦齿独立进化：冈瓦南大陆特有的australosphenidan分支，由现存的单孔目动物存活；以及Laurasian大陆的一个boreosphenidan分支，包括现存的有袋动物、胎盘动物及其亲属。
Marsupials, placentals and their close therian relatives possess complex (tribosphenic) molars that are capable of versatile occlusal functions. This functional complex is widely thought to be a key to the early diversification and evolutionary success of extant therians and their close relatives (tribosphenidans). Long thought to have arisen on northern continents, tribosphenic mammals have recently been reported from southern landmasses. The great age and advanced morphology of these new mammals has led to the alternative suggestion of a Gondwanan origin for the group. Implicit in both biogeographic hypotheses is the assumption that tribosphenic molars evolved only once in mammalian evolutionary history. Phylogenetic and morphometric analyses including these newly discovered taxa suggest a different interpretation: that mammals with tribosphenic molars are not monophyletic. Tribosphenic molars evolved independently in two ancient (holotherian) mammalian groups with different geographic distributions during the Jurassic/Early Cretaceous: an australosphenidan clade endemic to Gondwanan landmasses, survived by extant monotremes; and a boreosphenidan clade of Laurasian continents, including extant marsupials, placentals and their relatives.