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A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics ( synapomorphies ) that distinguish them from other taxa .
A tunicate is an exclusively marine invertebrate animal, a member of the subphylum Tunicata (/ ˌ tj uː n ɪ ˈ k eɪ t ə / TEW-nih-KAY-tə).This grouping is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates).
Branchiostoma belcheri exhibit all basic characteristics of the Chordata phylum including the notochord, dorsal nerve cord, pharynx, buccal cavity, cirri, tail, dorsal fin, nerve cord, segmented muscle, and ocelli. Starting with the internal structure, said organisms have true coeloms where the critical organs develop.
The following details the development of two popularly studied species of the hemichordata phylum Saccoglossus kowalevskii and Ptychodera flava. Saccoglossus kowalevskii is a direct developer and Ptychodera flava is an indirect developer. Most of what has been detailed in Hemichordate development has come from hemichordates that develop directly.
The evolution of the notochord within the phylum Chordata is considered in detail by Holland and Somorjai (2020). Vertebrates now have spines so they do not need a notochord. [26] The following organisms retain a post-embryonic notochord: Acipenseriformes (paddlefish and sturgeon) [27] Lancelet (Amphioxus) Tunicate (larval stage only) Hagfish ...
This article contains a list of all of the classes and orders that are located in the Phylum Chordata. The subphyla Tunicata and Vertebrata are in the unranked Olfactores clade, while the subphylum Cephalochordata is not. Animals in Olfactores are characterized as having a more advanced olfactory system than animals not in it.
The pineal gland, a photosensitive organ regulating melatonin production by capturing light signals through the photoreceptor cell converting them into intercellular signals of the lamprey is located in the midline of its body, for lamprey, the pineal eye is accompanied by the parapineal organ.
Regions of a Chondrichthyes brain colored and labeled on dissected skate. The rostral end of the skate is to the right. In chondrichthyans, the nervous system is composed of a small brain, 8–10 pairs of cranial nerves, and a spinal cord with spinal nerves. [11] They have several sensory organs which provide information to be processed.