Why aren鈥檛 sea cucumbers placed into Subphylum Urochordata?

There pretty much nothing like tunicates. Sea cucumbers are in the phylum echinodermata and urochardates are part of the phylum chordata.|||Urochordata is a subphylum of Chordata; being placed in chordata a species must show at some point in their life stage the 5 hallmark traits, postanal tail, notochord, nerve chord, endosytle, and pharyngeal slits/pouches. Sea cucumbers lack these hallmarks, they can't be placed within chordata

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|||Adult sea cucumbers have five fold symmetry and an ambulacral vascular system, modified from the coelem. The ambulacral system runs in 5 longitudinal strips that power tube feet in some species. Even in species that lack tube feet there are oral tentacles as part of the vascular system powered by hydraullic fluid displacements the same way tube feet operate.


These are some critical characteristic that define echinoderms and distinguish their species from other phyla.


http://books.google.com/books?id=BUOOUD5鈥?/a>|||Sea ccucumber is not an animal. Thats why.