CONGRUENCE OF DIVERSITY TRAJECTORIES BETWEEN BODY FOSSILS AND TRACE FOSSILS

The diversity trajectories of trace fossils and body fossils through the Phanerozoic are compared for the first time. Ichnologic analysis of the Cambrian Explosion (CE), the Great Ordovician Biodiversification Event (GOBE) and the Mesozoic Marine Revolution (MMR) indicates that evolutionary radiations are also expressed in the trace fossil record. A 433 % increase in ichnodiversity took place in marine environments during the Terraneuvian (12 and 64 ichnogenera in the Ediacaran and Terraneuvian, respectively) and a 77 % occurred as a result of the GOBE (82 ichnogenera in the Furongian and 145 ichnogenera by the Late Ordovician). A more protracted and modest increase in ichnodiversity occurred during the MMR with increases in the Early Jurassic (9%; 164 and 179 ichnogenera in the Late Triassic and Early Jurassic, respectively) and Late Cretaceous (19%; 188 and 223 ichnogenera in the Early and Late Cretaceous, respectively). Analysis of ichnodiversity trajectories supports Sepkoski’s three-phase kinetic model, which was originally based on analysis of marine body fossils. In contrast, increases in ichnodisparity are not necessarily linked to evolutionary radiations, but to the colonization of empty ecospace, as revealed by the CE for softground colonization and the GOBE for colonization of hard substrates. This pattern supports analysis based on body fossils that indicates a “first disparity, then diversity” scenario. Our study indicates that ichnologic information represents an independent line of evidence that yield valuable insights to evaluate paleobiologic megatrends.