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Temporal range: Ediacaran – Recent
Caribbean reef squid.jpg
The caribbean reef squid, an example of a protostome
Scientific classification

Grobben, 1908

Protostomes are a nephrozoan taxon of animals above the level of phylum. It is not part of the normal system of classification.

They are a subtaxon of the Bilateria, and are contrasted with the deuterostomes. Protosomes are distingued by their embryo: in deuterostomes, the first opening (the blastopore) becomes the anus, while in protostomes it becomes the mouth.

DNA sequence analysis suggests that protostome animals can be divided into three major groups:

as well as a number of minor taxa, like the Chaetognatha.