Abstract

The titanosaurian sauropod dinosaur Diamantinasaurus matildae is represented by two individuals from the Cenomanian–lower Turonian ‘upper’ Winton Formation of central Queensland, north-eastern Australia. The type specimen has been described in detail, whereas the referred specimen, which includes several elements not present in the type series (partial skull, atlas, axis and postaxial cervical vertebrae), has only been described briefly. Herein, we provide a comprehensive description of this referred specimen, including a thorough assessment of the external and internal anatomy of the braincase, and identify several new autapomorphies of D. matildae. Via an expanded data matrix consisting of 125 taxa scored for 552 characters, we recover a close, well-supported relationship between Diamantinasaurus and its contemporary, Savannasaurus elliottorum. Unlike previous iterations of this data matrix, under a parsimony framework we consistently recover Diamantinasaurus and Savannasaurus as early-diverging members of Titanosauria using both equal weighting and extended implied weighting, with the overall topology largely consistent between analyses. We erect a new clade, named Diamantinasauria herein, that also includes the contemporaneous Sarmientosaurus musacchioi from southern Argentina, which shares several cranial features with the referred Diamantinasaurus specimen. Thus, Diamantinasauria is represented in the mid-Cretaceous of both South America and Australia, supporting the hypothesis that some titanosaurians, in addition to megaraptoran theropods and possibly some ornithopods, were able to disperse between these two continents via Antarctica. Conversely, there is no evidence for rebbachisaurids in Australia, which might indicate that they were unable to expand into high latitudes before their extinction in the Cenomanian–Turonian. Likewise, there is no evidence for titanosaurs with procoelous caudal vertebrae in the mid-Cretaceous Australian record, despite scarce but compelling evidence for their presence in both Antarctica and New Zealand during the Campanian–Maastrichtian. These later titanosaurs presumably dispersed into these landmasses from South America before the Campanian (~85 Mya), when seafloor spreading between Zealandia and Australia commenced. Although Australian mid-Cretaceous dinosaur faunas appear to be cosmopolitan at higher taxonomic levels, closer affinities with South America at finer scales are becoming better supported for sauropods, theropods and ornithopods.

中文翻译：

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晚白垩世澳大利亚蜥脚类恐龙 Diamantinasaurus matildae 的第二个标本为早期泰坦龙的头骨和颈部提供了新的解剖学信息

摘要

泰坦龙类蜥脚类恐龙Diamantinasaurus matildae由来自澳大利亚东北部昆士兰中部的森诺曼阶 - 下图伦阶“上”温顿组的两个个体代表。对典型标本进行了详细描述，而所提及的标本，其中包括在类型系列中不存在的几个元素（部分颅骨、寰椎、中轴和轴后颈椎），只进行了简要描述。在这里，我们提供了这个参考标本的全面描述，包括对脑壳的外部和内部解剖结构的彻底评估，并确定了D. matildae 的几个新的自体形态。通过由 125 个分类群组成的扩展数据矩阵，对 552 个字符进行评分，我们恢复了Diamantinasaurus及其同时代的Savannasaurus elliottorum。与此不同的数据矩阵的先前迭代，下一个简约框架我们一致地恢复迪亚曼蒂纳龙属和Savannasaurus作为同时使用相同的权重Titanosauria的早期-发散构件和扩展隐含加权，具有整体的拓扑分析之间基本一致。我们建立了一个新的分支，在此命名为 Diamantinasauria，其中还包括来自阿根廷南部的同时代的Sarmientosaurus musacchioi，它与提到的Diamantinasaurus有几个颅骨特征标本。因此，南美洲和澳大利亚的白垩纪中期都出现了钻石龙，这支持了这样的假设，即除了巨型盗龙类兽脚类恐龙和可能的一些鸟脚类恐龙之外，一些泰坦龙类能够通过南极洲在这两个大陆之间分散。相反，没有证据表明澳大利亚有 rebbachisauruds，这可能表明它们在 Cenomanian-Turonian 灭绝之前无法扩展到高纬度地区。同样，在白垩纪中期的澳大利亚记录中，没有证据表明泰坦龙具有前体尾椎骨，尽管在坎帕尼亚-马斯特里赫特纪期间，它们在南极洲和新西兰都存在的证据稀少但令人信服。这些后来的泰坦龙可能在坎帕尼亚（~85 Mya）之前从南美洲分散到这些陆地中，当西兰西亚和澳大利亚之间的海底开始扩张时。尽管澳大利亚白垩纪中期恐龙动物群在更高的分类学水平上似乎是世界性的，但在更精细的尺度上与南美洲的亲缘关系更密切，蜥脚类恐龙、兽脚类恐龙和鸟脚类动物得到了更好的支持。