Haikouichthys is about 2.5 cm (1 inch) long and is narrower than Myllokunmingia, another putative chordate that comes from the same beds. The holotype of Haikouichthys ercaicunensis was found in the Yuansshan member of the Qiongzhusi Formation in the 'Eoredlichia' Zone near Haikou at Ercaicun, Kunming City, Yunnan, China,[3] hence its name "Haikou fish from Ercaicun". The fossil was recovered among the Chengjiang fauna, in one of a series of Lagerstätten sites where thousands of exquisitely preserved soft-bodied fossils have already been found.[4] Following the discovery of the holotype, additional Lower Cambrian fossils of Haikouichthys ercaicunensis have been discovered.[3]