Oldest chordate spawned everything with backbones

This strange eel-like creature from half a billion years ago is a forerunner of all modern animals with backbones, from fish to reptiles and humans. Some 505 million years old, it is the oldest known chordate.

An analysis of 114 fossils of Pikaia gracilens discovered since 1911 shows that it was an evolutionary staging post on the way from worms to vertebrates.

Although Pikaia didn’t have a skull, it did have mouthparts, two small tentacles, and small openings nearby that probably served as gills.

The 5-centimetre-long animal also had zig-zag-shaped muscle segments, called myomeres, all along its length. These enabled it to swim, by swerving from side to side.

Running down the back of the animal was an elastic rod of tissue: the notochord. This was the evolutionary forerunner of the backbone in all vertebrates. Learn more here.

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