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CAMBRIAN PERIOD

542-488 million years ago

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CHORDATE FOSSIL

MODEL OF CHORDATE

 

CEPHALOCHORDATES

From Early Cambrian urochordates evolved Early Cambrian cephalochordates. These chordates evolved a number of features which they shared with their descendants, the first fish.

Several primitive chordates are known from the Cambrian Period. Haikouella lanceolata (3 cm in length) is known from a 530 million year old fossil bed of Yunnan, China. It was similar to the hemichordate fossil Yunnanozoon (in such features as its large dorsal muscular fin with about 2 dozen straight segments and its large pharynx with 6-7 branchial arches) but had additional features such as a heart, notochord, ventral and dorsal aortae, a post-anal tail, gill filaments, a relatively large brain, and possibly lateral eyes.