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The oldest lamprophiid (Serpentes, Caenophidia) fossil from the late Oligocene Rukwa Rift Basin, Tanzania and the origins of African snake diversity
Geobios ( IF 1.6 ) Pub Date : 2020-12-02 , DOI: 10.1016/j.geobios.2020.07.005
Jacob A. McCartney , Sierra N. Bouchard , Josephine A. Reinhardt , Eric M. Roberts , Patrick M. O'Connor , Cassy Mtelela , Nancy J. Stevens

Extant snake faunas have their origins in the mid-Cenozoic, when colubroids replaced booid-grade snakes as the dominant species. The timing of this faunal changeover in North America and Europe based on fossils is thought to have occurred in the early Neogene, after a period of global cooling opened environments and made them suitable for more active predators. However, new fossils from the late Oligocene of Tanzania have revealed an early colubroid-dominated fauna in Africa suggesting a different pattern of faunal turnover there. Additionally, molecular divergence times suggest colubroid diversification began sometime in the Paleogene, although the exact timing and driving forces behind the diversification are not clear. Here we present the first fossil snake referred to the African clade Lamprophiinae, and the oldest fossil known of Lamprophiidae. As such, this specimen provides the only potential fossil calibration point for the African snake radiation represented by Lamprophiidae, and is the oldest snake referred to Elapoidea. A molecular clock analysis using this and other previously reported fossils as calibration points reveals colubroid diversification minimally occurred in the earliest Paleogene, although a Cretaceous origin cannot be excluded. The elapoid and colubrid lineages diverged during the period of global warming near the Paleocene-Eocene boundary, with both clades diversifying beginning in the early Eocene (proximate to the Early Eocene Climate Optimum) and continuing into the cooler Miocene. The majority of subclades diverge well before the appearance of colubroid dominance in the fossil record. These results suggest an earlier diversification of colubroids than generally previously thought, with hypothesized origins of these clades in Asia and Africa where the fossil record is relatively poorly known. Further work in these regions may provide new insights into the timing of, and environmental influences contributing to, the rise of colubroid snakes.



中文翻译:

来自坦桑尼亚渐新世晚期鲁夸裂谷盆地的最古老的萤火虫(Serpentes,Caenophidia)化石和非洲蛇类多样性的起源

现存的蛇类动物群起源于中新生代,当时蛇类蛇类取代了类蛇类成为优势物种。这种基于化石的北美和欧洲动物群转变的时间被认为发生在新近纪早期,经过一段时间的全球冷却开放环境并使其适合更活跃的捕食者。然而,来自坦桑尼亚渐新世晚期的新化石揭示了非洲早期以毛状体为主的动物群,表明那里的动物群更新模式不同。此外,分子分化时间表明,在古近纪的某个时候开始了柱状体多样化,尽管多样化背后的确切时间和驱动力尚不清楚。在这里,我们展示了第一条被称为非洲进化枝 Lamprophiinae 的化石蛇,以及已知最古老的灯蛾科化石。因此,该标本为以 Lamprophiidae 为代表的非洲蛇辐射提供了唯一潜在的化石校准点,并且是被称为 Elapoidea 的最古老的蛇。使用该化石和其他先前报道的化石作为校准点进行的分子钟分析显示,尽管不能排除白垩纪起源,但在最早的古近纪中发生的柱状体多样化最少。在古新世 - 始新世边界附近的全球变暖期间,elapoid 和 colubrid 谱系发生分化,两个进化枝从始新世早期(接近早期始新世气候最佳)开始多样化,并继续进入较冷的中新世。大多数子分支在化石记录中出现colubroid优势之前就已经分化了。这些结果表明,colubroids 的多样化比以前普遍认为的要早,这些进化枝的假设起源于亚洲和非洲,那里的化石记录相对鲜为人知。在这些地区开展的进一步工作可能会为了解蛇类蛇的兴起的时间和环境影响提供新的见解。

更新日期:2020-12-02
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