Data from: Faunal turnover of marine tetrapods during the Jurassic–Cretaceous transition

Marine and terrestrial animals show a mosaic of lineage extinctions and diversifications during the Jurassic–Cretaceous transition. However, despite its potential importance in shaping animal evolution, few palaeontological studies have focussed on this interval and the possible climate and biotic drivers of its faunal turnover. In consequence evolutionary patterns in most groups are poorly understood. We use a new, large morphological dataset to examine patterns of lineage diversity and disparity (variety of form) in the marine tetrapod clade Plesiosauria, and compare these patterns with those of other organisms. Although seven plesiosaurian lineages have been hypothesised as crossing the Jurassic–Cretaceous boundary, our most parsimonious topology suggests the number was only three. The robust recovery of a novel group including most Cretaceous plesiosauroids (Xenopsaria, new clade) is instrumental in this result. Substantial plesiosaurian turnover occurred during the Jurassic–Cretaceous boundary interval, including the loss of substantial pliosaurid, and cryptoclidid diversity and disparity, followed by the radiation of Xenopsaria during the Early Cretaceous. Possible physical drivers of this turnover include climatic fluctuations that influenced oceanic productivity and diversity: Late Jurassic climates were characterised by widespread global monsoonal conditions and increased nutrient flux into the opening Atlantic-Tethys, resulting in eutrophication and a highly productive, but taxonomically depauperate, plankton. Latest Jurassic and Early Cretaceous climates were more arid, resulting in oligotrophic ocean conditions and high taxonomic diversity of radiolarians, calcareous nannoplankton and possibly ammonoids. However, the observation of discordant extinction patterns in other marine tetrapod groups such as ichthyosaurs and marine crocodylomorphs suggests that clade-specific, factors may be more important than overarching extrinsic factors in driving faunal turnover during the Jurassic–Cretaceous boundary interval.海洋与陆生动物在侏罗纪-白垩纪过渡时期呈现出谱系灭绝与物种分化交织的镶嵌式演化格局。尽管该时段对动物演化的塑造具有潜在重要意义，但目前古生物学研究极少关注这一时期，以及驱动该时期动物群更替的潜在气候与生物因素。因此，多数类群的演化模式至今仍不甚明晰。我们依托全新的大型形态学数据集，对海洋四足类群蛇颈龙目（Plesiosauria）的谱系多样性与形态差异度（形态多样程度）展开分析，并将该类群的演化模式与其他生物类群进行对比。尽管此前假说认为有7个蛇颈龙谱系跨越了侏罗纪-白垩纪界线，但我们基于最简约拓扑结构的分析结果显示，这一数目仅为3个。包含绝大多数白垩纪蛇颈龙超科类群的全新支系——异孔亚目（Xenopsaria，新演化支）的稳健支持，是得出该结论的关键依据。侏罗纪-白垩纪界线时段内发生了显著的蛇颈龙类群更替：包括上龙科（Pliosauridae）与隐锁龙科（Cryptoclididae）类群的多样性与形态差异度大幅丧失，随后异孔亚目在早白垩世发生辐射演化。此次更替的潜在物理驱动因素包括影响海洋生产力与多样性的气候波动：晚侏罗世气候以全球广泛分布的季风条件为特征，且营养物质向正在张开的大西洋-特提斯洋输入量增加，引发水体富营养化，形成了生产力极高但分类群极度贫乏的浮游生物群落。晚侏罗世末期至早白垩世气候更为干旱，导致海洋处于贫营养状态，同时放射虫、钙质超微浮游生物以及可能的菊石类的分类群多样性显著升高。然而，对鱼龙类（Ichthyosauria）与海洋鳄形类（Crocodylomorpha）等其他海洋四足类群灭绝模式不一致的观测结果表明，在侏罗纪-白垩纪界线时段的动物群更替驱动因素中，类群特异性因素可能比全局性外在因素更为关键。