The Myllokunmingiidae are the only family of the order Myllokunmingiida forming a monophyletic group. They are important in several ways. First they are the first vertebrates with the beginnings of a defined skull though they were not mineralized to any extent so were not the best. Second, they predated a huge split between the lineage that led to modern jawless fish like lampreys and the lineage that includes gnathostomata i.e. the jawed fish.
First and perhaps most famous of the three genera is Haikouichthys which in life would have been very small reaching only 1 in long. It was discovered in 1999. It gets it's name from the capital of the region it's from Haikou and Icthys which means fish, therefore Haikou's fish.
Second of the genera and the one from which the Family and Order's name comes from Myllokunmingia. This animal was slightly larger reaching 1.1 inches long and it had a comparatively more robust body with fewer gill arches. Other differences include myomeres , which are blocks of skeletal muscle that are segmented and used for swimming, that were more acute, It's name is similar to the last one but inverted.
Third and most obscure is the Zhongjianichthys which on the surface looks alot less primitive than the other two, with it's more back positioned eyes, large nose like structure on the head and thickened skin. However this superficial similarity to later more derived jawless fish groups is due to convergent evolution stemming from it's believed ecology as that of a fossorial animal.
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