Mayomyzon pieckoensis is an extinct species of lamprey that lived during the Late Carboniferous period, about 300 million years ago.

[1] The fossil of M. pieckoensis is preserved as a carbon film in a concretion, which shows the outline of its body and some internal structures.

The specimen is about 10 cm long and has a circular mouth with teeth, a single nostril, seven pairs of gill openings, and a dorsal fin that extends to the tail.

[1][2] M. pieckoensis is considered to be one of the most basal lampreys, as it shares some features with the jawed vertebrates, such as the presence of a notochord and a cartilaginous skeleton.

It also differs from modern lampreys in having fewer gill openings, larger eyes, and more teeth.