Laboury Antoine, Stubbs Thomas L, Wolniewicz Andrzej S, Liu Jun, Scheyer Torsten M, Jones Marc E H, Fischer Valentin
Evolution & Diversity Dynamics Lab, University of Liège, Liège, Belgium.
School of Life, Health & Chemical Sciences, Open University, Milton Keynes, United Kingdom.
Evolution. 2024 Dec 22;79(1):38-50. doi: 10.1093/evolut/qpae138.
The iconic marine raptorial predators Ichthyosauria and Eosauropterygia co-existed in the same ecosystems throughout most of the Mesozoic Era, facing similar evolutionary pressures and environmental perturbations. Both groups seemingly went through a massive macroevolutionary bottleneck across the Triassic-Jurassic (T/J) transition that greatly reduced their morphological diversity, leaving pelagic lineages as the only survivors. However, analyses of marine reptile disparity across the T/J transition have usually employed coarse morphological and temporal data. We comprehensively compare the evolution of ichthyosaurian and eosauropterygian morphology and body size across the Middle Triassic to Early Jurassic interval and find contrasting macroevolutionary patterns. The ecomorphospace of eosauropterygians predominantly reflects a strong phylogenetic signal, resulting in the clustering of three clades with clearly distinct craniodental phenotypes, suggesting "leaps" toward novel feeding ecologies. Ichthyosaurian diversification lacks a discernible evolutionary trend, as we find evidence for a wide overlap of craniodental morphologies between Triassic and Early Jurassic forms. The temporal evolution of ecomorphological disparity, fin shape and body size of eosauropterygians and ichthyosaurians during the Late Triassic does not support the hypothesis of an abrupt macroevolutionary bottleneck near the T/J transition. Rather, an important turnover event should be sought earlier, during times of rapid sea level falls.
标志性的海洋肉食性掠食者鱼龙目和始蜥鳍龙目在中生代的大部分时间里共存于相同的生态系统中，面临着相似的进化压力和环境扰动。这两个类群似乎都在三叠纪 - 侏罗纪（T/J）过渡期间经历了一次大规模的宏观进化瓶颈，这极大地减少了它们的形态多样性，使得远洋类群成为唯一的幸存者。然而，对T/J过渡期间海洋爬行动物差异的分析通常采用粗略的形态学和时间数据。我们全面比较了中三叠世至早侏罗世期间鱼龙目和始蜥鳍龙目形态及体型的演化，发现了截然不同的宏观进化模式。始蜥鳍龙目的生态形态空间主要反映了强烈的系统发育信号，导致三个具有明显不同颅齿表型的类群聚集在一起，这表明向新的摄食生态的“飞跃”。鱼龙目的多样化缺乏明显的进化趋势，因为我们发现三叠纪和早侏罗世形态之间的颅齿形态有广泛重叠的证据。晚三叠世期间始蜥鳍龙目和鱼龙目的生态形态差异、鳍的形状和体型的时间演化并不支持在T/J过渡附近存在突然的宏观进化瓶颈这一假设。相反，应该在海平面快速下降时期更早的时候寻找一个重要的更替事件。
