The Sarcopterygii was the first fish to ever breathe air, the original video I watched to learn about this fish no longer exists. But, the one below also does a fairly good job on explaining. The fish originally came to be around 418 million years ago and was apart of a family of fish known as the lobe finned fish. Essentially meaning it had short strong fins and mostly crawled on the ocean floor to get around. However, when trees and plant life fell into the water the oxygen levels in the water began to quickly deplete. So, as the fish needed air it began to come up for air. The more the fish did this, the more its body evolved to breath air outside of water by making the following changes:
- The fishes swim bladder (the pocket of air within the fish to keep it buoyant) became a lung of sorts to store air for when the fish went back under water. Getting air through its nare (small hole on fishes head, resembling a nostril).
- Gravity outside of the water was considerably heavier and so the light weight bones within the fish became more study and strong to withstand the force from above the water
- With its bones becoming stronger they also evolved into a more rigid land animal design and the fish was able to use its short stout fins like legs to move around the environment.
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