Urochordata
| Urochordates | ||||||||
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| Scientific classification | ||||||||
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| Classes | ||||||||
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Ascidiacea Thaliacea Larvacea |
Urochordata (Tunicate worms, "Sea Squirts") are saclike filter feeders with input and output siphons.
Some larval forms appear very much like primitive chordates or hemichordates with a notochord (primitive spinal cord). Some forms have a calcereous spicule that may be preserved as a fossil. Jurassic to Present with one proposed Neoproterozoic form - Yarnemia. Some workers class the Urochordates as a subphylum of the chordata.