Early tetrapod relationships revisited
Early tetrapod relationships revisited
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重温早期四足动物关系
DOI：
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发表时间：
2003
影响因子：
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通讯作者：
D. Quicke
中科院分区：
文献类型：
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作者：
M. Ruta;M. Coates;D. Quicke
在试图调查最广泛讨论的早期四足动物关系的假设之间的差异，我们组装了一个新的数据矩阵，包括90个分类群编码的319颅和颅后字符。我们已经纳入，在可能的情况下，原始观察的许多类群分布在整个主要的四足动物分支。四足类的基于茎（总群）的定义优于基于无定形和节点（冠群）的定义。这个定义是可操作的，因为它是基于一个正式的性格分析。PAUP* 搜索使用最近实现的版本的简约棘轮方法产生64个最短的树。这些树之间的区别在于：（1）异足类的内部关系，其中三个选择的物种形成一个分支;（2）栓节的内部关系，与Archeria crassidisca和Pingerpeton scutigerum在一个分支中与Anthracosaurus russelli和Pingerpeton attheyi形成一个分支;（3）衍生类间的内在联系，与四个两栖类物种形成一个未解决的节点，一个分支由micromelerpetontids和branchiosaurids组成，一个分支由albanerpetontids加上基底冠群组成lissampibians;（4）白尾蜥和小足始盲蜥的位置，它们形成一个未解决的节点，一个对着Karaurus sharovi，Valdotriton gracilis和Triadobatrachus massinoti的分支;（5）衍生的双尾蜥的分支模式，与Batrachiderpeton reticulatum和Diceratosaurus brevirostris在一个由Diplocaulus magnicornis和Diploceraspis burkei形成的分支中崩溃。原始简约运行的结果-以及从数据集的其他几种处理中检索到的结果（例如，排除颅后和下颌数据;字符重新加权;反向加权）-表明早期四足动物在lissampibian-和brachote-相关类群之间存在深刻的分裂。Colosteids，Crassigalus，Whatcheeria和bapphetids是越来越多的冠向茎四足动物。Caerorhachis，bolomeres，gephyrostegids，Solenodonsaurus和seymouriamorphs是越来越多的冠状茎-茎。Eucritta是temnospondyls的基部，冠-lissampibians嵌套在dissorophoids内。Westlothiana是Lepospondyli的基础，但后者的单系地位的证据是薄弱的。Westlothiana和Lepospondyli形成姐妹群，以diadectomorphs和冠群Aromotes。小型类和小型类依次与一个分支更密切相关，包括近端：（1）溶脊类;（2）Acherontiscus作为adelospondyls的姐妹分类单元;（3）双尾龙科;（4）尾心龙科加上Aïstopods。一个使用颅骨特征的数据集只将微龙类放在四足动物的茎上，但在几棵树中，其余的鳞椎类作为四足动物茎上的Colosteids的姐妹群出现。这种安排并不比从完整数据集的分析中获得的树形拓扑结构差。temnospondyl-lissamphibian树冠部的姐妹群关系模式再次强调了dissorophoids在lissamphibian起源争论中的重要作用。然而，没有特定的dissorophoid可以被鉴定为冠群lissampibians的直接姐妹分类单元。各种茎群的分支序列揭示了一组连贯的internested特征状态变化，这些变化与在几种石炭-二叠纪形式中逐渐获得更多的陆地习性有关。
In an attempt to investigate differences between the most widely discussed hypotheses of early tetrapod relationships, we assembled a new data matrix including 90 taxa coded for 319 cranial and postcranial characters. We have incorporated, where possible, original observations of numerous taxa spread throughout the major tetrapod clades. A stem‐based (total‐group) definition of Tetrapoda is preferred over apomorphy‐ and node‐based (crown‐group) definitions. This definition is operational, since it is based on a formal character analysis. A PAUP* search using a recently implemented version of the parsimony ratchet method yields 64 shortest trees. Differences between these trees concern: (1) the internal relationships of aistopods, the three selected species of which form a trichotomy; (2) the internal relationships of embolomeres, with Archeria crassidisca and Pholiderpeton scutigerum collapsed in a trichotomy with a clade formed by Anthracosaurus russelli and Pholiderpeton attheyi; (3) the internal relationships of derived dissorophoids, with four amphibamid species forming an unresolved node with a clade consisting of micromelerpetontids and branchiosaurids and a clade consisting of albanerpetontids plus basal crown‐group lissamphibians; (4) the position of albenerpetontids and Eocaecilia micropoda, which form an unresolved node with a trichotomy subtending Karaurus sharovi, Valdotriton gracilis and Triadobatrachus massinoti;(5) the branching pattern of derived diplocaulid nectrideans, with Batrachiderpeton reticulatum and Diceratosaurus brevirostris collapsed in a trichotomy with a clade formed by Diplocaulus magnicornis and Diploceraspis burkei. The results of the original parsimony run ‐ as well as those retrieved from several other treatments of the data set (e.g. exclusion of postcranial and lower jaw data;character reweighting; reverse weighting) ‐ indicate a deep split of early tetrapods between lissamphibian‐ and amniote‐related taxa. Colosteids, Crassigyrinus, Whatcheeria and baphetids are progressively more crownward stemtetrapods. Caerorhachis, embolomeres, gephyrostegids, Solenodonsaurus and seymouriamorphs are progressively more crownward stem‐amniotes. Eucritta is basal to temnospondyls, with crown‐lissamphibians nested within dissorophoids. Westlothiana is basal to Lepospondyli, but evidence for the monophyletic status of the latter is weak. Westlothiana and Lepospondyli form the sister group to diadectomorphs and crown‐group amniotes. Tuditanomorph and microbrachomorph microsaurs are successively more closely related to a clade including proximodistally: (1) lysorophids; (2) Acherontiscus as sister taxon to adelospondyls; (3) scincosaurids plus diplocaulids; (4) urocordylids plus aïstopods. A data set employing cranial characters only places microsaurs on the amniote stem, but forces remaining lepospondyls to appear as sister group to colosteids on the tetrapod stem in several trees. This arrangement is not significantly worse than the tree topology obtained from the analysis of the complete data set. The pattern of sister group relationships in the crownward part of the temnospondyl‐lissamphibian tree re‐emphasizes the important role of dissorophoids in the lissamphibian origin debate. However, no specific dissorophoid can be identiffed as the immediate sister taxon to crown‐group lissamphibians. The branching sequence of various stem‐group amniotes reveals a coherent set of internested character‐state changes related to the acquisition of progressively more terrestrial habits in several Permo‐Carboniferous forms.