The Subphylum Urochorda is a group of invertebrate animals that includes sea squirts, tunicates, and salps. These organisms are chordates, meaning they possess a hollow nerve cord that runs along their dorsal side. They are characterized by their unique filtering system, which helps them filter nutrients from the surrounding water. There are several synonyms for the Subphylum Urochorda, including Tunicata, Ascidiacea, and Thaliacea. These names reflect the diverse groups of animals that make up this subphylum and their shared characteristics, such as their tough, protective tunic and their ability to reproduce both sexually and asexually. Despite their small size, Urochordates play an important role in marine ecosystems and provide valuable insight into the evolution of vertebrates.