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CARBONIFEROUS PERIOD

359-299 million years ago

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skullskull


The common ancestor of Casineria and amniotes had modified its vertebrae so that the pleurocentra were increasingly dominant over intercentra, the ribs were long and thin, the arm bones slender. The number of digits on the hands and feet was limited to five and the curved last phalanx improved its grasp.Like most early amphibians, the skull contained many bones which modern amphibians lack but which are components of the skulls of rhipidistian fish.