Biota - Lifeforms

Very small true mammals first appeared in the Late Triassic. Fossils have been collected from Late Triassic Rhaetian bone layers, but evolution from reptiles to mammals in the Late Triassic is not clearly demonstrated by well-preserved fossils.

First encountered in the Early Triassic, the thecodonts became common during the Middle Triassic but disappeared before the beginning of the Jurassic. Typical of this group of archosaurs in the Triassic were small bipedal forms belonging to the pseudosuchians. Forms such as Lagosuchus were swift-running predators that had erect limbs directly under the body, which made them more mobile and agile. This group presumably gave rise to primitive dinosaurs belonging to the saurischian and ornithischian orders during the Late Triassic to Early Jurassic.

Some of the earliest lizards may have been the first vertebrates to fly. Small lizards from the Late Triassic, such as Icarosaurus, are thought to have used skin stretched between their ribs to form wings, allowing them to glide for short periods of time, like the flying squirrels of today.

Land plants were also affected by the Permian-Triassic crisis, but not as much as animals, as the collapse of the flora began much earlier, at the end of the Paleozoic. The Triassic lower flora is dominated by ferns, while most of the middle flora is open-seeded. The upper part of the Triassic forest consisted of conifers, the most famous fossils of which are preserved in the Upper Triassic Chinle Formation.