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Disaster taxa, such as fungi and lichens, are the first to colonize disaster areas. Lystrosaurus, a distant ancestor of modern animals, was the dominant land vertebrate for millions of years after the Permian-Triassic extinction event. Small mammals were the primary calamity taxa after the Cretaceous-Tertiary extinction event. Coconut plants, fungi, lichens, mosses, and small arthropods are common disaster taxa today.
Disaster taxa are groups of organisms that rehabilitate areas destroyed by a natural disaster, such as a volcanic eruption, or survive a major mass extinction. Classic examples are fungi and lichens, which are among the first to colonize disaster areas, and microscopic animals accustomed to living in almost any ecosystem imaginable, such as nematodes. In the case of disaster taxa that survive mass extinctions, they may serve as the basis for a new adaptive radiation, and their ancestors will possess characteristics derived from them.
As for the largest disaster taxa, a famous example is Lystrosaurus, a distant ancestor of modern animals that was the dominant land vertebrate for millions of years when it was one of the only survivors of the Permian-Triassic extinction event (the most grave of history, which occurred 251 million years ago), which constitute 95% of all terrestrial vertebrate fossils. This is thought to have been the only time in planetary history that an organism dominated the earth to such an extent. Named Lystrosaurus, meaning “shovel lizard,” for its shovel-shaped head, the animal had a barrel-shaped chest and was about the size of a pig. While some paleontologists attribute its survival to being able to breathe in the noxious gases in the atmosphere at the time, others call it dumb luck.
More recently, soon after the Cretaceous-Tertiary extinction event wiped out the non-avian dinosaurs, small mammals were fortunate enough to be the primary calamity taxa among terrestrial vertebrates. Since nearly all dinosaurs were wiped out, this left numerous empty niches for mammals to exploit, which continue to thrive today. Before, most mammals were small and uniform, resembling small shrews, but they quickly diversified and today range in size from a couple of inches (mice) to 110 feet (blue whale).
As for the disaster taxa inhabiting areas destroyed by natural disasters, the most common today are coconut plants, the aforementioned fungi and lichens, mosses and small arthropods. Most animals require a complex, leafy ecosystem already in place to thrive.
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