At around 530 million years old, the Pikaia may have been the oldest known ancestor of modern vertebrates. It had a head distinct from the tail, bilateral symmetry, v-shaped muscles and a nerve cord running down the length of its body. The Haikouichthys, with eyes and a defined skull, may have been the earliest jawless fish. Along with the Myllokunmingia, these could be the first animals to have skulls. The Myllokunmingia was also the first known animal to have gill pouches.
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