The first organisms that could be described as primitive fish, appeared in the fossil record about 530 million years ago. These were not anything we would recognize today. They were without jaws, had primitive spinal columns called notochords and rudimentary gills. One of the primitive fish is Haikouichthys. In addition to having an early spinal column it had other revolutionary features. Its head was distinct from its tail, and its body was bilaterally symmetric, meaning the left side was a mirror image of the right. In the head it had two eyes and a mouth.
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