In quest for a phylogeny of Mesozoic mammals
In quest for a phylogeny of Mesozoic mammals
复制标题
DOI：
--
复制
发表时间：
2002
影响因子：
1.8
通讯作者：
Zhe‐Xi Luo;Z. Kielan-Jaworowska;R. Cifelli
中科院分区：
文献类型：
--
作者：
Zhe‐Xi Luo;Z. Kielan-Jaworowska;R. Cifelli
基于对46个类群的系统发育分析和275个骨骼和牙齿特征的系统发育分析，我们提出了中生代哺乳动物所有主要类群的系统发育（Swofford 2000）。哺乳动物（有些作者称之为哺乳动物）是单系的。在哺乳动物中，刺齿兽是最原始的分类群。Sinoconodon、morganu - codontids、docodonts和Hadrocodium位于哺乳动物冠类（crown therians + Monotremata）之外，与冠类的亲缘关系依次较近。在哺乳动物冠群中，我们认为有一个基本的划分为australosphenidan （Gondwana）和boreosphenidan （Laurasia）分支，可能在侏罗纪和早白垩世具有交替的地理分布。我们提供了支持这两个古老分支的额外衍生特征，并提出了关于早期单孔目动物臼齿如何进化的两种进化假设。我们考虑了两种不同的异源类（哈拉米类+多瘤类）。第一种观点得到了大多数节俭树严格共识的支持，它表明多瘤树（但不是其他所有龙属）与包括空间龙属+冠龙属（此处重新定义）在内的进化分支密切相关。另一种选择是，异种动物可以被排除在哺乳动物冠类之外，这反映了传统上对多瘤牙齿独特性的强调。给定我们的数据集，这些替代拓扑在树长度上的差异仅为总树长度的0.6%；统计检验表明，这些立场彼此之间没有显著差异。同样，在中生代哺乳动物中存在两种不同的正齿状突位置，这取决于其他主要哺乳动物分支的位置。其中，我们暂时倾向于识别一种单系的真齿兽，嵌套在哺乳动物冠群中。我们认为“钝角对称齿”是副形的，它们缺乏可靠和明确的突触形态。
We propose a phylogeny of all major groups of Mesozoic mammals based on phylogenetic analyses of 46 taxa and 275 osteological and dental characters, using parsimony methods (Swofford 2000). Mammalia sensu lato (Mammaliaformes of some authors) are monophyletic. Within mammals, Sinoconodon is the most primitive taxon. Sinoconodon, morganu− codontids, docodonts, and Hadrocodium lie outside the mammalian crown group (crown therians + Monotremata) and are, successively, more closely related to the crown group. Within the mammalian crown group, we recognize a funda− mental division into australosphenidan (Gondwana) and boreosphenidan (Laurasia) clades, possibly with vicariant geo− graphic distributions during the Jurassic and Early Cretaceous. We provide additional derived characters supporting these two ancient clades, and we present two evolutionary hypotheses as to how the molars of early monotremes could have evolved. We consider two alternative placements of allotherians (haramiyids + multituberculates). The first, supported by strict consensus of most parsimonious trees, suggests that multituberculates (but not other alllotherians) are closely re− lated to a clade including spalacotheriids + crown therians (Trechnotheria as redefined herein). Alternatively, allotherians can be placed outside the mammalian crown group by a constrained search that reflects the traditional emphasis on the uniqueness of the multituberculate dentition. Given our dataset, these alternative topologies differ in tree−length by only ~0.6% of the total tree length; statistical tests show that these positions do not differ significantly from one another. Simi− larly, there exist two alternative positions of eutriconodonts among Mesozoic mammals, contingent on the placement of other major mammalian clades. Of these, we tentatively favor recognition of a monophyletic Eutriconodonta, nested within the mammalian crown group. We suggest that the “obtuse−angle symmetrodonts” are paraphyletic, and that they lack reliable and unambiguous synapomorphies.