End-Triassic Extinction Reset Evolution of Marine Apex Predators

Thorne, P. M., Ruta, M., and M. J. Benton. 2011. Resetting the evolution of marine reptiles at the Triassic-Jurassic boundary. PNAS Early Online, DOI: 10.1073/pnas.1018959108. [suppl. info]

Abstract - Ichthyosaurs were important marine predators in the Early Jurassic, and an abundant and diverse component of Mesozoic marine ecosystems. Despite their ecological importance, however, the Early Jurassic species represent a reduced remnant of their former significance in the Triassic. Ichthyosaurs passed through an evolutionary bottleneck at, or close to, the Triassic-Jurassic boundary, which reduced their diversity to as few as three or four lineages. Diversity bounced back to some extent in the aftermath of the end-Triassic mass extinction, but disparity remained at less than one-tenth of pre-extinction levels, and never recovered. The group remained at low diversity and disparity for its final 100 Myr. The end-Triassic mass extinction had a previously unsuspected profound effect in resetting the evolution of apex marine predators of the Mesozoic.