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首页> 美国卫生研究院文献>Proceedings of the Royal Society B: Biological Sciences >A new Palaeocene crocodylian from southern Argentina sheds light on the early history of caimanines
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A new Palaeocene crocodylian from southern Argentina sheds light on the early history of caimanines

机译：来自阿根廷南部的新古新世鳄鱼为人们揭示了凯门鳄的早期历史

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摘要

Caimanines are crocodylians currently restricted to South and Central America and the oldest members are from lower Palaeocene localities of the Salamanca Formation (Chubut Province, Argentina). We report here a new caimanine from this same unit represented by a skull roof and partial braincase. Its phylogenetic relationships were explored in a cladistic analysis using standard characters and a morphogeometric two-dimensional configuration of the skull roof. The phylogenetic results were used for an event-based supermodel quantitative palaeobiogeographic analysis. The new species is recovered as the most basal member of the South American caimanines, and the Cretaceous North American lineage ‘Brachychampsa and related forms' as the most basal Caimaninae. The biogeographic results estimated north-central North America as the ancestral area of Caimaninae, showing that the Cretaceous and Palaeocene species of the group were more widespread than thought and became regionally extinct in North America around the Cretaceous–Palaeocene boundary. A dispersal event from north-central North America during the middle Late Cretaceous explains the arrival of the group to South America. The Palaeogene assemblage of Patagonian crocodylians is composed of three lineages of caimanines as a consequence of independent dispersal events that occurred between North and South America and within South America around the Cretaceous–Palaeogene boundary.
机译：Caimanines是目前仅局限于南美和中美洲的鳄鱼，而最古老的成员来自萨拉曼卡组（阿根廷丘布特省）的古新世下部。我们在这里报告了一个由头骨顶和部分脑箱代表的同一单元的新凯门鳄。在系统分析中使用标准字符和颅骨顶的形态几何二维配置对它的系统关系进行了探索。系统发育结果用于基于事件的超模型定量古生物地理分析。这些新物种被发现为南美凯门鳄的最基础成员，而白垩纪北美血统“ Brachychampsa及其相关形式”被认为是最基础的凯门鳄。生物地理结果估计北美洲中北部是凯马涅纳的祖先地区，表明该组的白垩纪和古新世物种比想象中的分布更广泛，并在北美白垩纪-古新世边界附近灭绝。白垩纪中后期，北美洲中北部的一次分散事件解释了该小组到达南美的原因。巴塔哥尼亚鳄的古近纪组合由凯门鳄的三个谱系组成，这是北美和南美之间以及南美洲白垩纪-古近纪边界附近发生的独立扩散事件的结果。

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