The Triassic Revolution on land

The evolution of terrestrial life was as profoundly affected by the end-Permian mass extinction as life in the sea. The recovery of life in the Triassic represented much more than simply a return to pre-extinction conditions, but in fact an entirely new world was ushered in. The generalized replacement of synapsids by archosauromorph reptiles had long been recognized, together with the rise of the dinosaurs to ecological dominance and origins of many modern groups including lissamphibians, turtles, lizards, crocodilomorphs, and mammals. In addition, all the new larger tetrapods had switched from a sprawling posture before the crisis to an erect posture and parasagittal gait afterwards, and this hints at higher activity levels. This is confirmed by the more recent discovery that many of the Triassic archosauromorphs had indicators of endothermy (warm-bloodedness) in their bone histology, and that these Triassic tetrapods also had insulating dermal structures: hair in synapsids and feathers in dinosaurs, pterosaurs and their ancestors. All these indications of endothermy are debated and yet to be confirmed by further study, but they suggest an overall increase of energy in ecosystems, a general speeding up of life as competition and predation increased. Also, it means that these tetrapods were consuming more energy than their Permian forebears. In many ways, these discoveries suggest a macroevolutionary model equivalent to the Mesozoic Marine Revolution, in which Mesozoic marine life was more active and more meaty than much if Palaeozoic marine life.