New Anatomical Information on Rhoetosaurus brownei Longman, 1926, a Gravisaurian Sauropodomorph Dinosaur from the Middle Jurassic of Queensland, Australia
New Anatomical Information on Rhoetosaurus brownei Longman, 1926, a Gravisaurian Sauropodomorph Dinosaur from the Middle Jurassic of Queensland, Australia
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DOI：
10.1080/02724634.2012.622324
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发表时间：
2012-02
期刊：
影响因子：
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通讯作者：
Jay P. Nair;S. Salisbury
中科院分区：
文献类型：
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作者：
Jay P. Nair;S. Salisbury
褐褐红齿龙是澳大利亚唯一已知的白垩纪前蜥脚类恐龙。因此，它是了解早期蜥脚类动物的全球古生物地理和系统发育模式的潜在重要分类群。尽管它的重要性显而易见，但人们对它的了解太少，以至于无法将其纳入最近的早期蜥脚类动物进化分析中。考虑到这一点，我们评估了未描述的红喙龙材料的骨学和系统发育，以试图弥合这种理解的差距。红顶龙的下后肢突出了与其他蜥脚类动物的大量不同，即使在没有其他材料的情况下，也支持了红顶龙的独特性。一些独特的特征包括胫骨内侧突出的嵴和沟，狭窄的跖关节桥，脚爪有附属沟或窝。巨爪龙在外形上保留了四个爪子，而大多数蜥脚类动物都有三个爪子，表面上与恐龙相似。初步的分支分析证实了红齿龙是一种非新蜥脚类重症龙，尽管对最简约的拓扑结构的微弱支持表明需要进一步的发现来改进特征数据的不完整性。对不同系统发育假说的检验排除了Rhoetosaurus与东亚侏罗纪蜥脚类恐龙之间的密切关系，并表明有必要更深入地研究Rhoetosaurus与其他同时期中侏罗世Gondwanan蜥脚类恐龙之间的潜在关系。
ABSTRACT Rhoetosaurus brownei is the only known named pre-Cretaceous sauropod from Australia. It is therefore a potentially important taxon for understanding global paleobiogeographic and phylogenetic patterns among early sauropods. Despite its obvious significance, Rhoetosaurus has been too poorly understood to be included in most recent analyses of early sauropod evolution. With this in mind, we evaluated the osteology and phylogeny of undescribed materials of Rhoetosaurus, in order to attempt to close the gap in this understanding. The lower hind limb of Rhoetosaurus highlights a plethora of differences from other sauropods, supporting the distinctiveness of Rhoetosaurus even in the absence of other materials. Some unique traits include prominent crests and sulci on the tibia medially, a narrow metatarsal articular bridge, and pedal claws with an accessory groove or fossa. The pes plesiomorphically retains four claws where most sauropods have three, and bears superficial similarity to that of Shunosaurus. Preliminary cladistic analysis confirms that Rhoetosaurus is a non-neosauropod gravisaurian, although weak support for the most parsimonious topology suggests further findings are required to improve upon incompleteness in the character data. Examination of alternative phylogenetic hypotheses rules out a close relationship between Rhoetosaurus and East Asian Jurassic sauropods, and indicates a closer examination of the potential relationships between Rhoetosaurus and other contemporaneous Middle Jurassic Gondwanan sauropods is necessary.