page_title: Tetrapod
section_title: Carboniferous
hierarchical_section_title: Tetrapod / Devonian fossils / Palaeozoic / Carboniferous
caption_attribution_description: Edops craigi
context_page_description: Tetrapods are four-limbed animals constituting the superclass Tetrapoda. It includes extant and extinct amphibians, reptiles, and mammals. Tetrapods evolved from a group of animals known as the Tetrapodomorpha which, in turn, evolved from ancient sarcopterygians around 390 million years ago in the middle Devonian period; their forms were transitional between lobe-finned fishes and the four-limbed tetrapods. The first tetrapods appeared by the late Devonian, 367.5 million years ago. The specific aquatic ancestors of the tetrapods and the process by which they colonized Earth's land after emerging from water remains unclear. The change from a body plan for breathing and navigating in water to a body plan enabling the animal to move on land is one of the most profound evolutionary changes known. The first tetrapods were primarily aquatic. Modern amphibians, which evolved from earlier groups, are generally semiaquatic; the first stage of their lives is as fish-like tadpoles, and later stages are partly terrestrial and partly aquatic.
context_section_description: During the early Carboniferous, the number of digits on hands and feet of stem-tetropods became standardized at no more than five, as lineages with more digits died out. By mid-Carboniferous times, the stem-tetrapods had radiated into two branches of true ("crown group") tetrapods. Modern amphibians are derived from either the temnospondyls or the lepospondyls (or possibly both), whereas the anthracosaurs were the relatives and ancestors of the amniotes (reptiles, mammals, and kin). The first amniotes are known from the early part of the Late Carboniferous. All basal amniotes, like basal batrachomorphs and reptiliomorphs, had a small body size.  Amphibians must return to water to lay eggs; in contrast, amniote eggs have a membrane ensuring gas exchange out of water and can therefore be laid on land.
  Amphibians and amniotes were affected by the Carboniferous Rainforest Collapse (CRC), an extinction event that occurred ≈300 million years ago. The sudden collapse of a vital ecosystem shifted the diversity and abundance of major groups. Amniotes were more suited to the new conditions. They invaded new ecological niches and began diversifying their diets to include plants and other tetrapods, previously having been limited to insects and fish.
caption: Edops, 323-299 Ma
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