Conodont diversity and evolution through the latest Permian and Early Triassic upheavals
Conodont diversity and evolution through the latest Permian and Early Triassic upheavals
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DOI：
10.1016/j.palaeo.2006.11.037
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发表时间：
2007-08
期刊：
影响因子：
--
通讯作者：
M. Orchard
中科院分区：
文献类型：
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作者：
M. Orchard
对二叠纪末和三叠纪初多元素牙形刺的研究表明，在地球生物圈高度紧张的时期，它们的进化史经历了八个阶段。这些步骤是：（1）长兴期科属逐渐衰落（1）古生物学特征：古生物学特征5）早-中期Smithian的爆发性辐射; 6）晚期Smithian的大灭绝; 7）早期Spathian的大辐射; 8）晚期Spathian到早期Anisian的逐渐更替和衰退。牙形刺类由长兴纪初期的五科减少到PTB的三科，到格里斯巴赫纪晚期又减少到两科。从长兴纪到格里斯巴赫纪晚期，刚多螺科只有一个多元素的器官，而奥伦尼克纪至少有12个。考虑到绝对的年龄限制，牙形石在PTB之后的恢复是非凡的。牙形石的演化在Dienerian仍然是模糊的，但在多元素装置的变化方面是非常重要的。尽管印度河的灭绝，属的多样性普遍增加，从PTB到晚期史密斯。从种、属和多元素组成来看，三叠纪牙形刺的最高峰在史密斯世中期，最大灭绝发生在史密斯世晚期。在这次灭绝之后，属和器的多样性迅速恢复到高水平，标志着一个显着的Spathian复苏。逐渐衰落的特点是晚期Spathian和持续到早期Anisian。对下三叠统牙形刺的时间分布和相互关系的综合总结为生物地层学和生物年代学研究提供了更好的基础。灭绝和辐射趋势与海平面变化和层序边界相关：动物区系更替对应于格里斯巴赫阶晚期、史密斯阶晚期和斯帕斯阶晚期的低位，辐射对应于格里斯巴赫阶早期、史密斯阶早期和斯帕斯阶早期的海侵。这些趋势也与碳循环的扰动相关，下三叠世δ 13 C最小值对应于灭绝和动物群更替，正值通常出现在辐射期间。然而，中三叠世海洋底栖生物的恢复遵循一个积极的最大值和牙形石多样性的整体下降。新分类群Borinella chowadensis，B. megacuspa、Neogondolella griesbachensis和N. Mongeri描述。
A study of latest Permian and Early Triassic multielement conodonts identifies eight steps in their evolutionary history during an interval when Earth's biosphere was highly stressed. These steps are: 1) gradual decline of families and genera through the Changhsingian (up to the late Griesbachian); 2) conodont biofacies change and extinction of Tethyan endemic species close to the Permian–Triassic Boundary (PTB); 3) faunal turnover with extinction and origination in the late Griesbachian; 4) initial radiation in gondolellids and diversification in apparatuses during the Dienerian; 5) explosive radiation in the early–middle Smithian; 6) major extinction in the late Smithian; 7) major radiation early in the Spathian; 8) gradual turnover and decline in the late Spathian through early Anisian. Conodontophorids were reduced from five families at the beginning of the Changhsingian to three by the PTB, and to two late in the Griesbachian. From the Changhsingian to the late Griesbachian, there was a single multielement apparatus represented in the Gondolellidae, whereas by the Olenekian there were at least twelve. Given absolute age constraints, the conodont recovery in the aftermath of the PTB was extraordinary. Conodont evolution during the Dienerian remains obscure but was very significant in terms of changes in multielement apparatuses. In spite of Induan extinctions, generic diversity generally increased from the PTB up to the late Smithian. In terms of species, genera, and multielement apparatuses, the acme of Triassic conodonts was in the middle Smithian, and the biggest extinction was in the late Smithian. After this extinction, generic and apparatus diversity quickly returned to high levels, marking a significant Spathian recovery. Gradual decline characterized the late Spathian and persisted into the early Anisian. A synthetic summary of the temporal distribution and proposed relationships amongst all known Lower Triassic conodonts provide an improved foundation for biostratigraphic and biochronologic studies. Extinction and radiation trends correlate well with sea-level changes and sequence boundaries: faunal turnovers correspond to lowstands in the late Griesbachian, late Smithian, and late Spathian, and radiations correspond to transgressions in the early Griesbachian, early Smithian, and early Spathian. The trends also correlate with perturbations in the carbon cycle, with Lower Triassic δ13C minima corresponding to extinction and faunal turnover, and positive values generally occurring during radiations. However, Middle Triassic recovery of marine benthos follows a positive maxima and an overall decline in conodont diversity. New taxa Borinella chowadensis, B. megacuspa, Neogondolella griesbachensis, and N. mongeri are described.