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  2. Chordate - Wikipedia

    en.wikipedia.org/wiki/Chordate

    Hemichordates ("half chordates") have some features similar to those of chordates: branchial openings that open into the pharynx and look rather like gill slits; stomochords, similar in composition to notochords, but running in a circle round the "collar", which is ahead of the mouth; and a dorsal nerve cord—but also a smaller ventral nerve cord.

  3. List of chordate orders - Wikipedia

    en.wikipedia.org/wiki/List_of_chordate_orders

    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 only extinct classes shown are Placodermi and Acanthodii. Note that there are many other extinct chordate groups ...

  4. Lancelet - Wikipedia

    en.wikipedia.org/wiki/Lancelet

    Also like vertebrates, the muscles are arranged in blocks called myomeres. [50] Unlike vertebrates, the dorsal nerve cord is not protected by bone but by a simpler notochord made up of a cylinder of cells that are closely packed in collagen fibers to form a toughened rod. The lancelet notochord, unlike the vertebrate spine, extends

  5. Acorn worm - Wikipedia

    en.wikipedia.org/wiki/Acorn_worm

    An interesting trait is that its three-section body plan is no longer present in the vertebrates, except for the anatomy of the frontal neural tube, later developed into a brain which is divided into three main parts. This means some of the original anatomy of the early chordate ancestors is still present even if it is not always visible.

  6. Craniate - Wikipedia

    en.wikipedia.org/wiki/Craniate

    This, combined with an apparent lack of vertebral elements within the Myxini, suggested that the Myxini were descended from a more ancient lineage than the vertebrates, and that the skull developed before the vertebral column. The clade was thus composed of the Myxini and the vertebrates, and any extinct chordates with skulls.

  7. Marine invertebrates - Wikipedia

    en.wikipedia.org/wiki/Marine_invertebrates

    Non-craniate chordates are close relatives of vertebrates The lancelet , a small translucent fish-like Cephalochordate , is the closest living invertebrate relative of the vertebrates. [ 73 ] [ 74 ]

  8. Invertebrate - Wikipedia

    en.wikipedia.org/wiki/Invertebrate

    The term invertebrates does not describe a taxon in the same way that Arthropoda, Vertebrata or Manidae do. Each of those terms describes a valid taxon, phylum, subphylum or family. "Invertebrata" is a term of convenience, not a taxon; it has very little circumscriptional significance except within the Chordata.

  9. Haikouichthys - Wikipedia

    en.wikipedia.org/wiki/Haikouichthys

    3D restoration. Haikouichthys is about 2.5 cm (1 in) long and is narrower than Myllokunmingia, another putative chordate that comes from the same beds. [2] The holotype of Haikouichthys ercaicunensis was found in the Yuanshan member of the Qiongzhusi Formation in the 'Eoredlichia' Zone near Ercai Village in the Haikou Subdistrict (not to be confused with the city of Haikou in Hainan) of Xishan ...