Which ancient creatures may be the ancestors of modern animals?

 

                 Animals such as fish, amphibians, reptiles, birds and mammals have a backbone. It supports their body and serves as an anchorage for the muscles. These animals are called vertebrates. Some of the ancestors of vertebrates are found in old fossils. They have traces of a stiffening rod to support their back, which is thought to have later evolved into a proper spine.

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