First fossil lamprey: a record from the Pennsylvanian of Illinois.

A fossil record of lampreys has previously been unknown. A new genus demonstrates the presence of this group in the Pennsylvanian. The body outline, parts of the head skeleton, rasping tongue mechanism, gill basket, and other internal organs are preserved. The fossils are very similar in structure to modern forms. The absence of hagfish characters in the fossil supports the view that the common ancestor of lampreys and hagfishes lived prior to the Pennsylvanian.