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These creatures have been existing for millions of years. They lack a brain and nervous system.
This weird creature has no brain, head, gills or skeleton.
This animal has a nerve running down in each arm but no central brain.
This cucumber-like creature has a single nerve to respond to the environment and no brain.
They have a nerve ring around their mouth and radial nerves in spines but no brain.
They have a nervous system but no brain.
These animals are older than dinosaurs and have a complex appearance with no brain.
They have a nervous system , internal organs and a heart but no brain.