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Haikouichthys Fossil range: Early Cambrian
Artists concept of Haikouichthys ercaicunensis
Scientific classification
Kingdom: Animalia Phylum: Chordata Superclass: Agnatha Genus: Haikouichthys Species: H. ercaicunensis
Binomial name
Haikouichthys ercaicunensis

Haikouichthys ercaicunensis was a primitive fish-like animal from the Early Cambrian Maotianshan shales of China.

Cladistic analysis indicates that the animal is probably a primitive agnathan fish most closely related to the Lampreys. It is about 2.5cm long and is narrower than the Myllokunmingia, another primitive fish that comes from the same beds. The holotype was found in the Yuansshan member of the Qiongzhusi Formation in the 'Eoredlichia' Zone near Haikou at Ercaicun, Kunming City, Yunnan, China. The animal has a distinct head and trunk. The head has at least six and perhaps nine probable gills. There are a number of segments (myomeres) with rear directed Vs in the trunk. There is probably a notochord although only a short segment is preserved in the single known specimen. The tail end of the animal is apparently missing. There is a prominent dorsal fin with fin radials. The fin radials seem to angle "forward" toward the end thought on the basis of internal structures to be the head. This happens with a few modern fish but is an uncommon arrangement. There is a ventral fin fold. There are 13 circular structures along the bottom that may be gonads, slime organs, or something else entirely. There is no sign of mineralization of the skeletal elements.

A similar creature from these shales is known as Myllokunmingia.

There is one species Haikouichthys ercaicunensis Luo, Hu & Shu.

As being an early vertebrate, Haikouichthys was distantly related to all other vertebrates, including its closest living relative, the lamprey.

• Ostracoderm
• Walking with Monsters. A school of Haikouichthys was shown attacking an injured Anomalocaris. This type of behavior is speculative.

• See the following web sites for more information and pictures:
  • http://www.sciencenews.org/sn_arc99/11_6_99/fob1.htm
  • http://news.bbc.co.uk/1/hi/sci/tech/504776.stm