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A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal 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.
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 ...
Olfactores represent the overwhelming majority of the phylum Chordata, as the Cephalochordata are the only chordates not included in the clade. This clade is defined by a more advanced olfactory system which, in the immediate vertebrate generation, gave rise to nostrils .
Segmentation in biology is the division of some animal and plant body plans into a linear series of repetitive segments that may or may not be interconnected to each other. This article focuses on the segmentation of animal body plans, specifically using the examples of the taxa Arthropoda, Chordata, and Annelida. These three groups form ...
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).
The notochord was reinterpreted to run underneath the dorsal organ a thin rod-like filament. The body segments are anatomically blocks of skeletal muscles, called the myomeres, which are found in vertebrates only. No eyes can be observed. [24] The muscle orientation and flat shaped body indicate that Pikaia was an active and free swimmer. [8]
Lancelets have four known kinds of light-sensing structures: Joseph cells, Hesse organs, an unpaired anterior eye and lamellar body, all of which utilize opsins as light receptors. All of these organs and structures are located in the neural tube, with the frontal eye at the front, followed by the lamellar body, the Joseph cells, and the Hesse ...
Anatomical diagram of Branchiostoma lanceolatum. Branchiostoma lanceolatum has an elongated body, flattened laterally and pointed at both ends. A stiffening rod of tightly packed cells, the notochord, extends the whole length of the body. Unlike vertebrates, the notochord persists in the adult, in the form of a simple dorsal neural tube ...