(Fish from Haikou).
Named By: Luo, et al 1999.
Classification: Chordata, Craniata, Agnatha.
Species: C. ercaicunensis (Type).
Type: Exact feeding behaviour unkown.
Size: 2.5 centimeters.
Known locations: China, Qiongzhusi Formation.
Time period: Tommotian of the Cambrian.
Fossil representation: One preserved specimen.
Haikouichthys is one of the earliest fish discovered and by extension, earliest vertebrates. At the time of the discovery the first fish were thought to have evolved 50 million years later. Haikouichthys had between six to nine girls, and what appears to be a notochord. A dorsal fin runs almost the entire length of the body from the back of the head, curving all the way around to the rear underside. There are 13 circular structures along the base but their function to date is only speculative.
- Head and backbone of the Early Cambrian vertebrate Haikouichthys - D. G. Shu, S. C. Morris, J. Han, Z. F. Zhang, K. Yasui, P. Janvier, L. Chen, X. L. Zhang et al. - 2003.
- A paleontological perspective of vertebrate origin. - Chinese Science Bulletin 2003 Vol. 48 No. 8. - D. G. Shu - 2003. - Evidence for a single median fin-fold and tail in the Lower Cambrian vertebrate, Haikouichthys ercaicunensis - X. G. Zhang & X.G.Hou - 2004.