The systematic relationships and biogeographic history of ornithischian dinosaurs.
The systematic relationships and biogeographic history of ornithischian dinosaurs.
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鸟臀目恐龙的系统关系和生物地理学历史。
作者：
Boyd CA
传统上被称为“基础鸟脚类”或“hypsilophodontids”的分类群的系统关系仍然没有得到很好的解决，因为它被发现，这些分类群不是一个单系群，而是一个并系的新鸟臀目分类群。因此，即使这些类群的已知多样性在过去的二十年里急剧增加，我们对它们之间的相对位置以及主要的鸟臀目亚支的了解仍然不完整。本研究采用了迄今为止最大的系统发育数据集，以评估基础鸟臀目的关系（255个字符的65个物种水平的终端类群）。由此产生的严格的共识树是最好的解决，地层一致的假设基础鸟臀类的关系尚未假设。在这次分析中发现的唯一非禽龙类鸟脚亚目（=基鸟脚亚目）是Hypsilophodon foxii。大多数前'hypsilophodontid'类群恢复在一个单一的分支（Parksosauridae），位于姐妹分类单元的Cerapoda。帕克索龙科分为两个亚支，Orodrominae和Thescelosaurinae。这项研究没有恢复一个分支组成的亚洲分类群长春龙，哈亚，和热河龙（=热河龙科）。相反，前两个分类群是作为Thescelosaurinae的基部成员被发现的，而后者则是在新鸟臀目基部附近与岳龙属在一个分支中被发现的。这项研究支持恐龙的起源和鸟臀目在冈瓦纳的早期多样化。新鸟臀目最早在早侏罗世出现在非洲，然后在中侏罗世晚期之前分散到亚洲，在那里出现了许多非角足动物的新鸟臀目。在最简单的情况下，帕克索斯龙科起源于北美洲，后来至少有两次扩散到亚洲，一次扩散到南美洲。然而，当幽灵谱系被考虑时，另一种分散假说认为，在早白垩世期间，这些塞隆龙从亚洲分散到南美洲（通过北美洲），然后在白垩纪晚期回到北美洲。后一种假说可能解释了在马斯特里赫特阶之前，orodromine类群在北美的优势地位，以及从马斯特里赫特阶早期开始，thescelosaurines在北美的突然出现和广泛分布。在过去的15年里，帕克索斯龙科的多样性大大增加，但在帕克索斯龙科和Cerapoda之间存在着超过4000万年的幽灵谱系，这表明这个分支的早期历史和多样性尚未被发现。这一新的系统发育假说提供了一个全面的框架，进一步测试假设有关的进化模式和过程中鸟臀目。
The systematic relationships of taxa traditionally referred to as ‘basal ornithopods’ or ‘hypsilophodontids’ remain poorly resolved since it was discovered that these taxa are not a monophyletic group, but rather a paraphyletic set of neornithischian taxa. Thus, even as the known diversity of these taxa has dramatically increased over the past two decades, our knowledge of their placement relative to each other and the major ornithischian subclades remained incomplete. This study employs the largest phylogenetic dataset yet compiled to assess basal ornithischian relationships (255 characters for 65 species level terminal taxa). The resulting strict consensus tree is the most well-resolved, stratigraphically consistent hypothesis of basal ornithischian relationships yet hypothesized. The only non-iguanodontian ornithopod (=basal ornithopod) recovered in this analysis is Hypsilophodon foxii. The majority of former ‘hypsilophodontid’ taxa are recovered within a single clade (Parksosauridae) that is situated as the sister-taxon to Cerapoda. The Parksosauridae is divided between two subclades, the Orodrominae and the Thescelosaurinae. This study does not recover a clade consisting of the Asian taxa Changchunsaurus, Haya, and Jeholosaurus (=Jeholosauridae). Rather, the former two taxa are recovered as basal members of Thescelosaurinae, while the latter taxon is recovered in a clade with Yueosaurus near the base of Neornithischia.The endemic South American clade Elasmaria is recovered within the Thescelosaurinae as the sister taxon to Thescelosaurus. This study supports the origination of Dinosauria and the early diversification of Ornithischia within Gondwana. Neornithischia first arose in Africa by the Early Jurassic before dispersing to Asia before the late Middle Jurassic, where much of the diversification among non-cerapodan neornithischians occurred. Under the simplest scenario the Parksosauridae originated in North America, with at least two later dispersals to Asia and one to South America. However, when ghost lineages are considered, an alternate dispersal hypothesis has thescelosaurines dispersing from Asia into South America (via North America) during the Early Cretaceous, then back into North America in the latest Cretaceous. The latter hypothesis may explain the dominance of orodromine taxa prior to the Maastrichtian in North America and the sudden appearance and wide distribution of thescelosaurines in North America beginning in the early Maastrichtian. While the diversity of parksosaurids has greatly increased over the last fifteen years, a ghost lineage of over 40 myr is present between the base of Parksosauridae and Cerapoda, indicating that much of the early history and diversity of this clade is yet to be discovered. This new phylogenetic hypothesis provides a comprehensive framework for testing further hypotheses regarding evolutionary patterns and processes within Ornithischia.