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The name "chordate" comes from the first of these synapomorphies, the notochord, which plays a significant role in chordate body plan structuring and movements. Chordates are also bilaterally symmetric, have a coelom, possess a closed circulatory system, and exhibit metameric segmentation.
Hemichordate. Acorn worm, a hemichordate. Hemichordata (/ ˌhɛmɪkɔːrˈdeɪtə / HEM-ih-kor-DAY-tə) is a phylum which consists of triploblastic, eucoelomate, and bilaterally symmetrical marine deuterostome animals, generally considered the sister group of the echinoderms.
Deuterostomes (from Greek: lit. 'mouth second') are bilaterian animals of the superphylum Deuterostomia (/ ˌdjuːtərəˈstoʊmi.ə /), [3][4] typically characterized by their anus forming before the mouth during embryonic development. Deuterostomia is further divided into four phyla: Chordata, Echinodermata, Hemichordata, and the extinct ...
Bilateria (/ ˌ b aɪ l ə ˈ t ɪər i ə / BY-lə-TEER-ee-ə) [2] is a large clade or infrakingdom of animals called bilaterians (/ ˌ b aɪ l ə ˈ t ɪər i ə n / BY-lə-TEER-ee-ən), [3] characterized by bilateral symmetry (i.e. having a left and a right side that are mirror images of each other) during embryonic development.
Feeding and digestive system. Lancelets are passive filter feeders, [14] spending most of the time half-buried in sand with only their frontal part protruding. [66] They eat a wide variety of small planktonic organisms, such as bacteria, fungi, diatoms, and zooplankton, and they will also take detritus. [67]
Cephalization is an evolutionary trend in animals that, over many generations, the special sense organs and nerve ganglia become concentrated towards the rostral end of the body where the mouth is located, often producing an enlarged head. This is associated with the animal's movement direction and bilateral symmetry, and cephalization of the ...
Echinoderm larvae, like chordates, are bilaterally symmetric. Especially notable are their similarities to larvae of hemichordates, which are a step closer to chordates as they share two of the five most commonly noted chordate characteristics, namely a hollow neural tube and pharyngeal slits. [13] [2] is his definitive statement of the hypothesis.
A tunicate is an exclusively marine invertebrate animal, a member of the subphylum Tunicata (/ ˌtjuːnɪˈkeɪtə / 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 subphylum was at one time called Urochordata, and the term ...