THE RISE OF THE MESOZOIC MARINE REVOLUTION

The Triassic records the return of diverse marine communities after the severe end-Permian mass extinction. This rediversification is reported as the origin of a remarkable reorganizations of marine ecosystems where various predators cause adaptation among their prey. However, some researchers argue that these major evolutionary changes began in the Jurassic continuing through the Cretaceous. To aid in resolving the inception point of this ecological reorganization, stratigraphic range data were examined to determine which taxa actually extend into the later Mesozoic and ecologies were tracked to assess adaptive radiations. Using the Paleobiology database stratigraphic ranges for all invertebrate taxa present within the Late Permian through the Late Triassic were analyzed. In total, 2718 taxa within 20 different classes were present. Out of these taxa 31% taxa died at the Permian-Triassic boundary, 13% taxa died out before the Middle Triassic, 42% taxa died out before the Late Triassic, and 14% recovered and continued into the Jurassic and beyond. Out of the recovery taxa, 40% make through the Cretaceous and reach the Cenozoic. Overall, the data indicate that the Middle Triassic and Late Triassic record a remarkable radiation of taxa with more modern adaptation; however, the majority of the taxa go extinct before their respective epoch ends. This research suggest two overall conclusions: 1) possession of a modern adaptations does not necessarily predict longevity within a group and 2) the Middle and Late Triassic record the origination of more modern adaptations, albeit a small fraction of the overall taxa, that extend into the middle and late Mesozoic as well as the Cenozoic.