Role of Taxa Age and Geologic Range: Survival Analysis of Marine Biota over the Last 538 Million Years

Abstract

Understanding past extinction processes is an important and current matter, and regression methods in the domain of survival analysis can be applied to fossil data. The chief goal of this study is to relate genus-level lifetimes to ancient environmental conditions (e.g., sea level and surface temperatures or carbon dioxide concentration). The Cox proportional hazards model was used to characterize the extinction risks of marine genera, enabling quantitative and graphical comparisons between selected taxonomic groups over geologic time. The environment was confirmed to be a significant factor, and both age-dependent coefficients and time-dependent covariates were required to accommodate the data. The Cox model analyzed in this study provides new insights into the extinction patterns of marine biota over the past 538.8 million years (Ma). Previous works focusing on specific groups at certain geologic times suggest that the extinction risk is related to taxa age, taxonomic group, and, in some particular cases, geologic time. Here, this idea is confirmed for a larger taxonomic group, during a larger time span (ca. 530 Ma), providing a more complete and complex scenario than previous works. After applying survival analyses, conjoint effects were observed between taxa and their age, their time of existence, and the prevailing environmental conditions found at any particular moment.