Chordata
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Chordata is a phylum of animals, named after their common feature - possession of a spinal cord.
The phylum includes several classes:
- Mammalia - the mammals
- Aves - the birds
- Reptilia - The reptiles
- Amphibia - the amphibians (such as frogs, newts and salamanders)
- Pisces - the fish
There are also several obscure animals including the acorn worm, lancelet and hagfish.
Apart from the spinal cord, other common features include a single brain and a zig-zag muscle structure in the torso.
Scientists believe that the chordata are closest to the arthropoda (shelled, joint-legged animals such as insects and crustaceans) and annelida (earthworms) in biology, due to common features such as segmentation, which are not seen in other phyla such as the mollusca (molluscs) or coelenterata jellyfish and sea anemones.