Phylum Coelenterata or Cnidaria: Cnidarians are the first true metazoans that have attained tissue grade of construction. Cnidaria is a phylum of diploblastic, acoelomatic animals that possess stinging cells and a blind sac gastrovascular cavity. The phylum evolved in the Proterozoic era, more than 600 million years ago. The term Coelenterata was coined by Leuckart (1847). Characteristics of Phylum Coelenterata or Cnidaria: Coelenterates are mostly marine except for Hydra which is a freshwater form. These may be solitary (Hydra) or colonial and sedentary (corals) or free-swimming (sea anemones and jellyfishes). They are multicellular, diploblastic, radially or biradially symmetrical with tissue … Continue reading Phylum Coelenterata or Cnidaria