The end-Permian mass extinction nearly wiped out all life on the planet. Those animals that stumbled into the Triassic Period and the era of "middle life" required 10 million years to return to previous levels of diversity. Marine animals and coral reefs took even longer to recover. Many families of plants survived the end-Permian extinction in relatively good numbers, but gradual changes in climate and habitats saw the once-dominant broadleaf seed ferns and cordaites replaced by conifers, cycads, ginkgoes, and spore-bearing plants such as club mosses, ferns, and horsetails. The dominant land animals of the Early to Middle Triassic were the rhyncho-saurs, dicynodonts, and cynodonts, many of which had successfully migrated to the farthest corners of Pangaea prior to its gradual breakup into small landmasses.
The newfound stability of the Early to Middle Triassic did not last. Between 228 million and 199.6 million years ago, in the Late Triassic Epoch, two more mass-extinction events laid waste large numbers of animals and plants. Among those devastated were the fiercest predators and largest herbivores of the time, including the rhynchosaurs, most dicynodonts and cynodonts, and even some archosaurs. Plants also suffered greatly: The newly dominant seed ferns—including conifers, cycads, and ginkgoes—and the spore-bearing club mosses were nearly wiped out and supplanted by other conifers, larger cycads, and surviving mosses. These extinctions have been blamed on climate shifts, the first of which may have been caused by a likely asteroid impact, as evidenced by the 43-mile (70 km) diameter Manicouagan Crater in Quebec, Canada.
Curiously, the Late Triassic extinctions coincided with the appearance of the first dinosaurs—an association that is the subject of much scientific debate that will be explored in Chapter 3. Chapter 2 explores the rise of the archosaurs, or "ruling reptiles," and the likely reasons for their early success.
Was this article helpful?