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Blastozoa

Blastozoa (phylum Echinodermata) Subphylum of extinct, stalked echinoderms, ranging from the Silurian to the Permian. The stem (rarely preserved) was surmounted by a bud-like theca with five prominent petaloid ambulacra showing a well-developed pentameral symmetry. The theca had 13 major plates arranged in three circlets. The ambulacra each had a central food groove, with delicate food gathering appendages called brachioles to either side. Underlying the ambulacra were the characteristic hydrospires, thought to have functioned in respiration. These were thin-walled, calcareous infoldings (more rarely simple tubes), forming water conduits, that communicated with the outer environment via marginal pores in the ambulacra and five apertures around the mouth (the spiracles). Blastozoa are not common as fossils, except locally in shallow-water calcareous rocks, often associated with reef limestones.

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"Blastozoa." A Dictionary of Earth Sciences. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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"Blastozoa." A Dictionary of Earth Sciences. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/blastozoa

Blastozoa

Blastozoa (phylum Echinodermata) A subphylum, whose validity is not universally accepted, that includes the extinct classes Eocrinoidea, Rhomoifera, Blastoidea, and Parablastoidea.

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"Blastozoa." A Dictionary of Zoology. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

"Blastozoa." A Dictionary of Zoology. . Encyclopedia.com. (August 19, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/blastozoa-0

"Blastozoa." A Dictionary of Zoology. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/blastozoa-0