The Australian Lungfish, Neoceratodus forsteri (family Ceratodontidae), is the oldest known living vertebrate, and is the only surviving member of the Order Ceratodontiformes. This species is one of only three native Australian fishes that evolved in freshwater, rather than evolving from a marine ancestor.
Australian Lungfish have highly vascularised swim bladders that are similar to the primitive lungs found in the lower tetrapods or four legged vertebrate animals (amphibians). Although Australian Lungfish usually breathe with their gills, they often gulp air in poorly-oxygenated water or during times of increased activity.
Australian Lungfish have long, heavily scaled bodies, wide flat heads, small eyes, fleshy, paddle-like paired fins and a pointed tail.
Although fossil lungfish are well-known from the Cretaceous Period (165-94 Mya), the fossil record for the order extends back into the Triassic Period (251-200 Mya). Australian Lungfish fossils are known from the Early Cretaceous Period, about 100 million years ago.
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