Chordate anatomy

thumb|400px|Position of notochordes and axochords in bilaterians. (A) Zebrafish notochord. (B) Ascidian notochord. (C) Lancelet notochord. Notochord is positioned just ventral to the neural tube and dorsal to the gut, flanked by myotome. (D) Notochord homolog in annelid. Cross-section showing the position of the proposed axochord to the ventral mesentery, blood vessel, and nerve chord. Axochord is found to be dorsal to the nerve chord and ventral to gut of the animal. Red: notochord; Magenta: axochord; Green: nerve chord; Blue: epidermis; Yellow: mesoderm.

Embyronic group of cells giving rise to diverse cell lineages

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thumb|right|upright|Fish fillet|Filet of [[salmon showing the zig-zagging pattern of its myomeres. The white fascia divides each myomere from its neighbors]] Myomeres are blocks of skeletal muscle tissue arranged in sequence, commonly found in aquatic chordates. Myomeres are separated from adjacent myomeres by fascia consisting of connective tissue, known as myosepta. Myomere counts are sometimes used for identifying specimens using meristics, since their number corresponds to the number of vertebrae in the adults. Myomere location varies, with some species containing these only near the tails

in chordates

repeated openings that appear along the pharynx of chordates