Data from: Assessing the completeness of the fossil record: comparison of different methods applied to parareptilian tetrapods (Vertebrata: Sauropsida)

As paleontological studies are generally distorted by gaps and biases in the fossil record, it is important to assess its completeness. Here we address the fossil record of Parareptilia, a Permian–Triassic amniote clade, applying two measures of specimen completeness: the skeletal completeness metric (SCM) and the character completeness metric (CCM). The SCM quantifies how much of the skeletal material of a taxon is preserved, whereas the CCM measures the amount of phylogenetic information available. The latter was implemented using two different approaches. In this study, we compare three completeness metrics. Two CCM implementations show a strong correlation with each other, but only the second implementation of the CCM correlates significantly with the SCM, possibly due to character selection in phylogenetic data sets. There is no correlation between diversity of parareptiles and their completeness, implying that the observed fluctuations in diversity are not driven by the completeness of the fossils. The mean completeness of parareptiles through time is consistently high compared with previously studied tetrapod clades, suggesting that most parareptile taxa are based on reasonably complete specimens. Clade-specific differences reveal no link between body size and completeness. However, the analyses confirm the impact of ecology, with aquatic mesosaurids being better preserved than terrestrial taxa.

古生物学研究通常会因化石记录存在空白与偏差而出现结果失真，因此评估化石记录的完整性显得尤为关键。本研究针对副爬行动物（Parareptilia）——一个二叠纪至三叠纪的羊膜类演化支——的化石记录展开分析，采用两项标本完整性评价指标：骨骼完整性指数（Skeletal Completeness Metric, SCM）与特征完整性指数（Character Completeness Metric, CCM）。其中，SCM用于量化某一分类群的骨骼化石保存比例，而CCM则衡量可供研究的系统发育信息量。后者采用两种不同的实现路径。本研究共对比了三项完整性评价指标。两种CCM实现方案之间呈现极强的相关性，但仅第二种CCM实现方案与SCM存在显著相关性，这一现象可能源于系统发育数据集的特征筛选效应。副爬行动物的物种多样性与其化石完整性之间不存在相关性，这表明观测到的多样性波动并非由化石保存完整性所主导。与此前已被研究的四足类演化支相比，副爬行动物在地质历史中的平均完整性始终处于较高水平，这意味着绝大多数副爬行动物分类群的标本保存程度较为可观。针对特定演化支的差异分析显示，体型大小与化石完整性之间并无关联。但分析结果证实了生态学因素的影响：水生的中龙科（Mesosauridae）类群较陆生分类群的保存状况更为优良。