A newly discovered organism exhibits radial symmetry in its adult stage, but its larval stage is bilaterally symmetrical. It possesses a water vascular system and its body surface is covered by calcareous ossicles. Which of the following taxonomic placements would be most appropriate for this organism?
Correct: B
The key features described are radial symmetry in adults with bilateral larvae, a water vascular system, and calcareous ossicles. These are hallmark characteristics of the Phylum Echinodermata. Echinoderms uniquely exhibit secondary radial symmetry, meaning their ancestors were bilaterally symmetrical, and this is reflected in their larval forms. The water vascular system is characteristic for locomotion, feeding, and respiration, while their endoskeleton consists of calcareous ossicles. Class Asteroidea includes starfish, which fit this description perfectly. Mollusca, Annelida, and Coelenterata (Cnidaria) do not possess this unique combination of features.