Dating gas pumps
The aortic arches then merge above the gills to form a dorsal aorta supplying the body with oxygenated blood.
Tetrapods are categorized as a biological superclass, Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals.The third mechanism for a breath is the actual motion of the breath.This mechanism predates the LCA of Osteichthyes, as it can be observed in Lampetra camtshatica, the sister clade to Osteichthyes.This allowed for a movable joint at the base of the fins in the early bony fishes, and would later function in a weight bearing structure in tetrapods.As part of the overall armour of rhomboid cosmin scales, the skull had a full cover of dermal bone, constituting a skull roof over the otherwise shark-like cartilaginous inner cranium.
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The specific aquatic ancestors of the tetrapods, and the process by which land colonization occurred, remain unclear, and are areas of active research and debate among palaeontologists at present.