do tunicates have a cranium?
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The Kingdom Animalia phylum Chordata includes three classes: lancelets, tunicates, and vertebrates. Lancelets and tunicates have no backbone or well-developed head, but all chordates have at some a notochord, a hollow nerve cord, pharyngeal pouches, and a tail. ... They also have a well-developed head protected by a skull.
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They are thought to be descended from the placoderms, which had skeletons made of bone; thus, the cartilaginous skeleton of Chondrichthyes is a later development. Parts of shark skeleton are strengthened by granules of calcium carbonate, but this is not the same as bone.
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Chordates include vertebrates and invertebrates that have a notochord. Invertebrate chordates do not have a backbone.
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Echinoderms evolved from animals with bilateral symmetry. Although adult echinoderms possess pentaradial, or five-sided, symmetry, echinoderm larvae are ciliated, free-swimming organisms that organize in bilateral symmetry which makes them look like embryonic chordates.
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Like all sharks and rays, a manta's skeleton is made of cartilage (instead of bone). ... Their food consists of tiny particles such as plankton and they lack the stinging barb that some of their ray cousins have, rendering them harmless to humans. Both the reef and giant manta species are filter feeders.
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Two distinct species of chordates are tunicates and lancelets. Tunicates belong to the phylum Chordata and the subphylum Urochordata. They are sessile marine chordates that lack a backbone. They are very closely related to craniates (hagfish, lampreys, and jawed vertebrates).
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The skull consists of three parts, of different embryological origin—the neurocranium, the sutures, and the facial skeleton (also called the membraneous viscerocranium). The neurocranium (or braincase) forms the protective cranial cavity that surrounds and houses the brain and brainstem.
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Echinoderms are also characterized by a unique water-based vascular system possessed by no other animal. This highly specialized system not only allows them to transport food and water along the outside of their bodies, but it also allows for other nutrients and gases to be transported as well.
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['They are bilaterally symmetrical and triploblastic.', 'Chordates are coelomate and show an organ system level of organisation.', 'They have the characteristic notochord, dorsal nerve cord, pharyngeal slits.', 'Also, they have a post-anal.']
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All annelids are segmented. ... Annelids have a well-developed, closed circulatory system (one in which blood is limited to vessels) that is segmentally arranged. They also have a complete, one-way digestive tract with a mouth and anus. The digestive tract is not segmented.
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Sharks do not have bones. Their cartilaginous skeletons are much lighter than true bone and their large livers are full of low-density oils, both helping them to be buoyant. Even though sharks don't have bones, they still can fossilize.
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The main difference between lancelets and tunicates is that lancelets belong to the subphylum Cephalochordata, which contains a notochord extending from the head region whereas tunicates belong to the subphylum Urochordata, whose adult forms do not possess a hollow, dorsal notochord.
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Echinoderms are cold-blooded, ocean dwelling spiny-skinned invertebrates covered with a skeleton of plates and spines made of calcium carbonate. Echinoderms use water pressure in a unique circulatory system for movement, feeding and obtaining oxygen.
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All complex animals have a true coelom, including the mollusks, annelids, arthropods, echinoderms and chordates. They have a true coelom that is completely lined by the mesoderm layer. The internal organs in a true coelom are more complex, and they are held in place by mesentaries.
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Skeleton. Birds have a lightweight skeleton made of mostly thin and hollow bones. The keel-shaped sternum (breastbone) is where the powerful flight muscles attach to the body. Birds have a smaller total number of bones than mammals or reptiles.
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['A hard exoskeleton made of calcium - no internal skeleton.', 'The head has two compound eyes, two pairs of antennae, and three pairs of mouthparts.', 'A pair of green glands excrete wastes near the base of antennae.', 'The abdominal segments have swimmerets (swimming legs)']
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It was recognised that echinoderms, hemichordates and chordates – including vertebrates – were members of one evolutionary line, the deuterostomes, when all three groups were found to share the following four, basic developmental features: All are triploblastic: their three-layered bodies derive from three germ layers.