Data from: Effects of the early Toarcian Oceanic Anoxic Event on ichthyosaur body size and faunal composition in the Southwest German Basin

The Early Jurassic Toarcian Oceanic Anoxic Event is considered one of the most dramatic environmental perturbations of the Mesozoic. An elevated extinction rate among marine invertebrates accompanied rapid environmental changes, but effects on large vertebrates are less understood. We examined changes in ichthyosaur body size in the Posidonia Shale of the Southwest German Basin spanning the extinction interval to assess how environmental changes and biotic crisis among prey species affected large reptiles. We report no species-level extinction among the ichthyosaurs coinciding with peak invertebrate extinction. Large ichthyosaurs were absent from the fauna during the extinction interval, but became more abundant in the immediate aftermath. Stenopterygius quadriscissus, the most abundant species during the extinction interval, increased in body size after the biotic event. Rapid invasion by large taxa occurred immediately following the extinction event at the end of the first ammonite zone of the early Toarcian. Greater mobility permitting exploitation of ephemeral resources and opportunistic feeding behavior may minimize the impacts of environmental change on large vertebrates.

早侏罗世托阿尔阶海洋缺氧事件（Early Jurassic Toarcian Oceanic Anoxic Event）被认为是中生代最剧烈的环境扰动事件之一。海洋无脊椎动物的灭绝率升高伴随着快速的环境变化，但该事件对大型脊椎动物的影响尚不明晰。我们针对覆盖该灭绝间隔期的德国西南部盆地波西多尼亚页岩（Posidonia Shale）中的鱼龙（ichthyosaur）体型变化开展研究，以此评估环境变化与猎物类群的生物危机如何影响这类大型爬行动物。研究结果显示，与无脊椎动物灭绝峰值同期的鱼龙并未发生物种级灭绝事件。在该灭绝间隔期内，该动物群中并无大型鱼龙的记录，但在灭绝事件结束后随即变得更为繁盛。灭绝间隔期内最为丰富的物种——四棘狭翼鱼龙（Stenopterygius quadriscissus），在此次生物危机事件后体型有所增大。早托阿尔阶首个菊石带（ammonite zone）结束时的灭绝事件发生后，大型类群随即快速迁入该区域。具备更强运动能力以利用短暂性资源并采取机会主义摄食策略，或可最大程度降低环境变化对大型脊椎动物的负面影响。