Resetting the evolution of marine reptiles at the Triassic-Jurassic boundary

Ichthyosaurs were important marine predators in the Early Jurassic,and an abundant and diverse component of Mesozoic marineecosystems. Despite their ecological importance, however, theEarly Jurassic species represent a reduced remnant of their formersignificance in the Triassic. Ichthyosaurs passed through an evolutionarybottleneck 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 theend-Triassic mass extinction, but disparity remained at less thanone-tenth of pre-extinction levels, and never recovered. The groupremained at low diversity and disparity for its final 100 Myr. Theend-Triassic mass extinction had a previously unsuspected profoundeffect in resetting the evolution of apex marine predatorsof the Mesozoic.