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Pacific sea nettles, Chrysaora fuscescens. Cnidaria (/ n ɪ ˈ d ɛər i ə, n aɪ-/ nih-DAIR-ee-ə, NY-) [4] is a phylum under kingdom Animalia containing over 11,000 species [5] of aquatic invertebrates found both in fresh water and marine environments (predominantly the latter), including jellyfish, hydroids, sea anemones, corals and some of the smallest marine parasites.
The evolution of the molluscs is the way in which the Mollusca, one of the largest groups of invertebrate animals, evolved. This phylum includes gastropods, bivalves, scaphopods, cephalopods, and several other groups. The fossil record of mollusks is relatively complete, and they are well represented in most fossil-bearing marine strata.
The Scyphozoa are an exclusively marine class of the phylum Cnidaria, [2] referred to as the true jellyfish (or "true jellies"). The class name Scyphozoa comes from the Greek word skyphos (σκύφος), denoting a kind of drinking cup and alluding to the cup shape of the organism. [3] Scyphozoans have existed from the earliest Cambrian to the ...
Planulozoa is a clade of animals that includes the superphyla Cnidaria (jellyfish, hydrozoans, sea anemones, corals, etc.) and the Bilateria (all complex animals with bilateral symmetry, including arthropods, molluscs, vertebrates, etc.). [2] [3] The designation Planulozoa may be considered a synonym to ParaHoxozoa, which also contains Placozoa ...
The phylum Cnidaria is widely accepted as being monophyletic and consisting of two clades, Anthozoa and Medusozoa. Anthozoa includes the classes Hexacorallia, the hard corals, and Octocorallia, the soft corals, as well as Ceriantharia, the tube-dwelling anemones. There is strong support for this group having been the first to branch off from ...
Cnidarians include corals, sea anemones, jellyfish and hydrozoans. They form a phylum containing over 10,000 [ 32 ] species of animals found exclusively in aquatic (mainly marine) environments. Their bodies consist of mesoglea , a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick .
Now, this is generally considered convergent evolution, owing to many morphological and genetic differences between the two phyla. [54] Among lesser phyla of invertebrates are the Hemichordata, or acorn worms, [55] and the Chaetognatha, or arrow worms. Other phyla include Acoelomorpha, Brachiopoda, Bryozoa, Entoprocta, Phoronida, and ...
Cephalization is a characteristic feature of any animal that habitually moves in one direction, thereby gaining a front end. In practice, this primarily means the bilaterians, a large group containing the majority of animal phyla. [3]