Data from: The mosasaur fossil record through the lens of fossil completeness

The quality of the fossil record affects our understanding of macroevolutionary patterns. Palaeodiversity is filtered through geological and human processes; efforts to correct for these biases are part of a debate concerning the role of sampling proxies and standardization in biodiversity models. We analyse the fossil record of mosasaurs in terms of fossil completeness as a measure of fossil quality, using three novel, correlating metrics of fossil completeness and 4083 specimens. A new qualitative measure of character completeness (QCM) correlates with the phylogenetic character completeness metric. Mean completeness by species decreases with specimen count; average completeness by substage varies significantly. Mean specimen completeness is higher for species‐named fossils than those identified to genus and family. We consider the effect of tooth‐only specimens. Importantly, we find that completeness of species does not correlate with completeness of specimens. Completeness varies by palaeogeography: North American specimens show higher completeness than those from Eurasia and Gondwana. These metrics can be used to identify exceptional preservation; specimen completeness varies significantly by both formation and lithology. The Belgian Ciply Formation displays the highest completeness; clay lithologies show higher completeness values. Neither species diversity nor sea level correlates significantly with fossil completeness. A generalized least squares (GLS) analysis using multiple variables agrees with this result, but reveals two variables with significant predictive value for modelling averaged diversity: sea level, and mosasaur and plesiosaur‐bearing formations (the latter is redundant with diversity). Mosasaur completeness is not driven by sea level, nor does completeness limit the mosasaur diversity signal.化石记录的质量会影响我们对宏观进化模式的认知。古生物多样性会受到地质过程与人类活动的筛选；针对这些偏差进行校正的相关努力，属于生物多样性模型中采样替代指标作用与标准化规范之争的一部分。本研究以化石完整度作为化石质量的衡量指标，结合三项全新且相互关联的化石完整度量化指标与4083件标本，对沧龙类（mosasaurs）的化石记录展开分析。一种全新的性状完整度定性量化指标（QCM）与系统发育性状完整度度量指标存在相关性。按物种统计的平均完整度随标本数量增多而降低；按亚阶划分的平均完整度则存在显著差异。以物种层级定名的化石，其标本平均完整度高于仅鉴定至属或科的化石。本研究亦探讨了仅含牙齿标本的影响。尤为重要的是，本研究发现物种层面的完整度与标本层面的完整度并无相关性。完整度存在显著的古地理差异：北美地区的标本完整度高于欧亚大陆与冈瓦纳大陆（Gondwana）的标本。上述量化指标可用于识别特异埋藏化石；标本完整度同时受地层组（formation）与岩性（lithology）的显著影响。比利时西普利（Ciply）地层组的完整度最高；黏土岩性的标本完整度整体更高。物种多样性与海平面均与化石完整度无显著相关性。基于多变量的广义最小二乘（generalized least squares, GLS）分析验证了上述结论，但同时识别出两个对平均多样性建模具有显著预测价值的变量：海平面，以及产出沧龙与蛇颈龙类的地层组（后者与多样性指标存在冗余性）。沧龙类化石的完整度并非由海平面决定，同时完整度也不会限制沧龙类多样性信号的提取。