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Protostome (前口動物, zenkōdōbutsu) is one of the major divisions of animals. It is also called protostomia or archaeostomia. It includes 24 of the 34 phyla of the animal kingdom, including a wide variety of arthropods and mollusks.
The body structure is characterized by the order of the nervous system, digestive organs, and circulatory organs from the ventral side, with the digestive organs of the head penetrating the nervous system.
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