Department of Palaeontology, Natural History Museum, London, UK.
Biol Rev Camb Philos Soc. 2010 May;85(2):361-92. doi: 10.1111/j.1469-185X.2009.00107.x. Epub 2009 Dec 9.
Previous attempts to resolve plesiosaurian phylogeny are reviewed and a new phylogenetic data set of 66 taxa (67% of ingroup taxa examined directly) and 178 characters (eight new) is presented. We recover two key novel results: a monophyletic Plesiosauridae comprising Plesiosaurus dolichodeirus, Hydrorion brachypterygius, Microcleidus homalospondylus, Occitanosaurus tournemirensis and Seeleyosaurus guilelmiimperatoris; and five plesiosaurian taxa recovered outside the split between Plesiosauroidea and Pliosauroidea. These taxa are Attenborosaurus conybeari, 'Plesiosaurus'macrocephalus and a clade comprising Archaeonectrus rostratus, Macroplata tenuiceps and BMNH 49202. Based on this result, a new name, Neoplesiosauria, is erected for the clade comprising Plesiosauroidea and Pliosauroidea. Taxon subsamples of the new dataset are used to simulate previous investigations of global plesiosaurian relationships. Based on these simulations, most major differences between previous global phylogenetic hypotheses can be attributed to differences in taxon sampling. These include the position of Leptocleididae and Polycotylidae and the monophyly or paraphyly of Rhomaleosauridae. On this basis we favour the results recovered by our, larger analysis. Leptocleididae and Polycotylidae are sister taxa, forming a monophyletic clade within Plesiosauroidea, indicating that the large-headed, short-necked 'pliosauromorph' body plan evolved twice within Plesiosauria. Rhomaleosauridae forms the monophyletic sister taxon of Pliosauridae within Pliosauroidea. Problems are identified with previous phylogenetic definitions of plesiosaurian clades and new, stem-based definitions are presented that should maintain their integrity over a range of phylogenetic hypotheses. New, rank-free clade names Cryptoclidia and Leptocleidia are erected to replace the superfamilies Cryptoclidoidea and Leptocleidoidea. These were problematic as they were nested within the superfamily Plesiosauroidea. The incongruence length difference test indicates no significant difference in levels of homoplasy between cranial and postcranial characters.
先前解决蛇颈龙系统发育的尝试进行了回顾，并提出了一个新的系统发育数据集，其中包含 66 个分类群（直接检查的内类群分类群的 67%）和 178 个特征（8 个新特征）。我们得出了两个关键的新结果：一个单系的蛇颈龙科，包括长颈部的蛇颈龙、短翅的Hydrobates brachypterygius、小肢的 Microcleidus homalospondylus、Occitanosaurus tournemirensis 和 Seeleyosaurus guilelmiimperatoris；以及五个在蛇颈龙超目和上龙超目之间分裂之外发现的蛇颈龙类分类群。这些分类群包括 Attenborosaurus conybeari、“蛇颈龙”macrocephalus 和一个由 Archaeonectrus rostratus、Macroplata tenuiceps 和 BMNH 49202 组成的分支。基于这个结果，为包括蛇颈龙超目和上龙超目在内的分支建立了一个新名称，即 Neoplesiosauria。新数据集的分类群子样本用于模拟先前对全球蛇颈龙关系的研究。基于这些模拟，先前全球系统发育假说之间的大多数主要差异都可以归因于分类群采样的差异。这些差异包括 Leptocleididae 和 Polycotylidae 的位置以及 Rhomaleosauridae 的单系或并系。基于此，我们赞成我们更大规模分析得出的结果。Leptocleididae 和 Polycotylidae 是姐妹分类群，在蛇颈龙超目中形成一个单系分支，表明大型、短颈的“上龙形”身体计划在蛇颈龙目中进化了两次。Rhomaleosauridae 在 Pliosauroidea 中形成了上龙科的单系姐妹分类群。先前蛇颈龙类分类群的系统发育定义存在问题，提出了新的基于茎的定义，这些定义应在一系列系统发育假设中保持其完整性。新的、无等级的分类群名称 Cryptoclidia 和 Leptocleidia 被建立来取代 Cryptoclidoidea 和 Leptocleidoidea 超科。这些分类群存在问题，因为它们嵌套在超科 Plesiosauroidea 中。不一致长度差异检验表明，颅后特征和颅特征的同形性水平没有显著差异。
