Data from: Evolutionary rates of mid-Permian tetrapods from South Africa and the role of temporal resolution in turnover reconstruction

The Main Karoo Basin of South Africa contains a near-continuous sequence of continental deposition spanning 45 million years from the middle Permian to the Early Jurassic. The terrestrial vertebrates of this sequence provide a high-resolution stratigraphic record of regional origination and extinction, especially for the middle–late Permian. Until now, data have only been surveyed at coarse stratigraphic resolution using methods that are biased by non-uniform sampling rates, limiting our understanding of the dynamics of diversification through this important time period. High-resolution data now cross the mid-to-late Permian transition; to these we apply robust methods (gap-filler and modified gap-filler rates) for the inference of patterns of species richness, origination rates and extinction rates to a subset of 1321 securely-identified fossil occurrences resolved to approximately 50 metre stratigraphic intervals. This dataset provides an approximate time resolution of 0.3-0.6 million years and shows that extinction rates increased considerably in the upper 100 metres of the middle Permian Abrahamskraal Formation, corresponding to the latest part of the Tapinocephalus Assemblage Zone (AZ). Origination rates were weakly elevated in the same interval, and were not sufficient to compensate for these extinctions. Subsampled species richness estimates for the lower part of the overlying Teekloof Formation (corresponding to the Pristerognathus and Tropidostoma AZs) are low, and show that species richness remained low for at least 1.5–3 million years after the main extinction pulse. A high unevenness of the taxon abundance-frequency distribution, which is classically associated with trophically unstable post-extinction faunas, in fact developed shortly before the acme of elevated extinction rates due to the appearance and proliferation of the dicynodont Diictodon. Our findings provide strong support for a Capitanian (‘end-Guadalupian’) extinction event among terrestrial vertebrates and suggest that further high-resolution quantitative studies may help resolve the lack of consensus among palaeobiologists regarding this event.南非卡鲁主盆地（Main Karoo Basin）保存了一套近乎连续的陆相沉积序列，时限覆盖中二叠世至早侏罗世，跨度达4500万年。该序列产出的陆生脊椎动物化石，为区域类群起源与灭绝事件（尤以中二叠世晚期为甚）提供了高分辨率的地层记录。此前，相关数据仅通过粗分辨率地层采样方法获取，且受非均匀采样率的偏差影响，极大限制了学界对这一重要地质时段内类群演化分化动态的认知。目前，我们已获取跨越中二叠世至晚二叠世过渡阶段的高分辨率数据；针对其中经约50米地层间隔厘定、经严格鉴定的1321个化石产出点子集，我们采用稳健的分析方法——间隙填补法（gap-filler）与改进型间隙填补速率法，对物种丰富度、起源速率与灭绝速率的变化模式进行推断。本数据集的时间分辨率约为0.3至0.6百万年，分析结果显示：在中二叠世亚伯拉罕斯克拉尔组（Abrahamskraal Formation）上部100米地层（对应塔皮诺兽组合带（Tapinocephalus Assemblage Zone, AZ）的最新段），灭绝速率显著升高；同期起源速率仅小幅提升，未能抵消该时段的灭绝规模。覆于亚伯拉罕斯克拉尔组之上的蒂克洛夫组（Teekloof Formation）下部（对应普里斯特罗格纳图斯组合带（Pristerognathus Assemblage Zone）与特罗皮多斯托玛组合带（Tropidostoma Assemblage Zone））的物种丰富度抽样估计值偏低，且表明主灭绝脉冲发生后，物种丰富度至少持续150至300万年处于低位。值得关注的是，经典认知中与营养级不稳定的灭绝后动物群相关的类群丰度-频率分布高度不均一性，实际上早在灭绝速率升高的顶峰期之前就已出现，其驱动因素为二齿兽类狄克逊兽（Diictodon）的出现与种群扩散。本研究结果为陆生脊椎动物的卡皮坦期（瓜德鲁普世末期）灭绝事件提供了有力支撑，同时表明进一步开展高分辨率定量研究，或可解决古生物学家对该事件尚存的学术分歧。