Ambulacrarians and chordates are united into the clade Deuterostomia.In addition to sharing deuterostome characters like radial cleavage and an anus that forms in the region of the embryonic blastopore,the validity of the clade is supported by a wealth of molecular evidence.Another synapomorphy was once considered to be uniquely chordate,but now it is thought to have evolved very early in the deuterostome lineage and then lost in the echinoderm branch.This character is

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Pharyngeal slits are a synapomorphy once considered unique to chordates, but it is now believed to have evolved early in the deuterostome lineage and later lost in the echinoderm branch.

Ambulacrarians and Chordates Are United into the Clade Deuterostomia