The Temnospondyli (meaning cut vertebrae) are a diverse order of small to giant tetrapods that flourished worldwide during the Carboniferous, Permian, and Triassic periods. A few species continued into the Cretaceous. Their Fossils have been found on every continent. During about 210 million years of evolutionary history, they adapted to a wide range of habitats. Their life history is well understood, with fossils known from the larval stage, metamorphosis, and maturity. Most temnospondyls were semiaquatic, although some were almost terrestrial. These temnospondyls were some of the first vertebrates fully adapted to life on land. Although temnospondyls are considered amphibians, many had characteristics, such as scales, claws, and armor-like bony plates, that distinguish them from modern amphibians. Temnospondyls have been known since the early 19th century, and were initially thought to be reptiles. They were described at various times as batrachians and labyrinthodonts, although these names are now rarely used. Animals now grouped in Temnospondyli were spread out among several amphibian groups until the early 20th century, when they were found to belong to a distinct taxon based on the structure of their vertebrae. Temnospondyli means "cut vertebrae", as each vertebra is divided into several parts. Authorities disagree over whether temnospondyls were ancestral to modern amphibians, or whether the whole group died out without leaving any descendants. Different hypotheses have placed modern amphibians as the descendants of temnospondyls, another group of early tetrapods called lepospondyls, or even as descendants of both groups. Recent studies place a family of temnosondyls called the amphibamids as the closest relatives of modern amphibians. Similarities in teeth, skulls, and hearing structures link the two groups.
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