Data from: How many dinosaur species were there? Fossil bias and true richness estimated using a Poisson sampling model

The fossil record is a rich source of information about biological diversity in the past. However, the fossil record is not only incomplete but has also inherent biases due to geological, physical, chemical and biological factors. Our knowledge of past life is also biased because of differences in academic and amateur interests and sampling efforts. As a result, not all individuals or species that lived in the past are equally likely to be discovered at any point in time or space. To reconstruct temporal dynamics of diversity using the fossil record, biased sampling must be explicitly taken into account. Here, we introduce an approach that uses the variation in the number of times each species is observed in the fossil record to estimate both sampling bias and true richness. We term our technique TRiPS (True Richness estimated using a Poisson Sampling model) and explore its robustness to violation of its assumptions via simulations. We then venture to estimate sampling bias and absolute species richness of dinosaurs in the geological stages of the Mesozoic. Using TRiPS, we estimate that 1936 (1543–2468) species of dinosaurs roamed the Earth during the Mesozoic. We also present improved estimates of species richness trajectories of the three major dinosaur clades: the sauropodomorphs, ornithischians and theropods, casting doubt on the Jurassic–Cretaceous extinction event and demonstrating that all dinosaur groups are subject to considerable sampling bias throughout the Mesozoic.化石记录是揭示过去生物多样性的宝贵信息来源。然而，化石记录不仅存在记录缺失，还因地质、物理、化学及生物因素存在固有偏差。我们对古生物的认知同样存在偏差，这源于学术与业余研究兴趣的差异以及采样投入的不均衡。因此，历史上存在过的所有个体或物种，在任意时空节点被发现的概率并不均等。若要借助化石记录重建生物多样性的时间动态，必须明确将有偏采样纳入考量范畴。本文提出一种方法，通过各物种在化石记录中的观测次数差异，同时估算采样偏差与真实物种丰富度。我们将该技术命名为TRiPS（True Richness estimated using a Poisson Sampling model），并通过模拟实验检验其在假设条件被违反时的稳健性。随后，我们尝试估算中生代各地质阶段的恐龙采样偏差与绝对物种丰富度。利用TRiPS方法，我们估算得出中生代时期地球曾栖息着1936（1543~2468）种恐龙。我们还对三大主要恐龙演化支——蜥脚形亚目（sauropodomorphs）、鸟臀目（ornithischians）和兽脚亚目（theropods）的物种丰富度变化轨迹进行了优化估算，结果对侏罗纪-白垩纪灭绝事件（Jurassic–Cretaceous extinction event）提出了质疑，并证实所有恐龙类群在整个中生代均受到显著的采样偏差影响。