The ability of palaeontologists to correctly diagnose and classify new fossil species from incomplete morphological data is fundamental to our understanding of evolution. Different parts of the vertebrate skeleton have different likelihoods of fossil preservation and varying amounts of taxonomic information, which could bias our interpretations of fossil material. Substantial previous research has focused on the diversity and macroevolution of non-avian theropod dinosaurs. Theropods provide a rich dataset for analysis of the interactions between taxonomic diagnosability and fossil preservation. We use specimen data and formal taxonomic diagnoses to create a new metric, the Likelihood of Diagnosis, which quantifies the diagnostic likelihood of fossil species in relation to bone preservation potential. We use this to assess whether a taxonomic identification bias impacts the non-avian theropod fossil record. We find that the patterns of differential species abundance and clade diversity are not a consequence of their relative diagnosability. Although there are other factors that bias the theropod fossil record that are not investigated here, our results suggest that patterns of relative abundance and diversity for theropods might be more representative of Mesozoic ecology than often considered.

古生物学家从不完整的形态学数据中正确诊断和分类新化石物种的能力是我们理解进化的基础。脊椎动物骨骼的不同部分具有不同的化石保存可能性和不同数量的分类信息，这可能会影响我们对化石材料的解释。以前的大量研究集中在非鸟类兽脚亚目恐龙的多样性和宏观进化上。兽脚类恐龙为分析分类可诊断性和化石保存之间的相互作用提供了丰富的数据集。我们使用标本数据和正式的分类学诊断来创建一个新的指标，即诊断的可能性，它量化了与骨骼保存潜力相关的化石物种的诊断可能性。我们用它来评估分类识别偏差是否影响非鸟类兽脚亚目化石记录。我们发现差异物种丰度和进化枝多样性的模式不是它们相对可诊断性的结果。虽然这里没有研究其他影响兽脚类恐龙化石记录的因素，但我们的结果表明，兽脚类动物的相对丰度和多样性模式可能比通常考虑的更能代表中生代生态学。