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anatomical features, including notochord, of a primitive chordate
Notochord and other anatomical features of a primitive chordate
The notochord, a characteristic of chordates, is a stiff rod of tissue along the back of the body which is the first stage in the development of a flexible internal skeleton.

All chordates possess a notochord at some time during their lives. Though replaced by cartilage or bone in the adult vertebrate and absent in the adults of other chordate groups, e.g., tunicates, it is well developed in the embryos and larvae of all these groups, confirming evolutionary relationships within the class.

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