The University of Witwatersrand's Bruce Rubidge and graduate student and lead author Rob Gess in Johannesburg, South Africa, were joined by the University of Chicago's Michael Coates in describing the new find in the current issue of the journal Nature.
"Apart from being the oldest fossil lamprey yet discovered, this fossil shows that lampreys have been parasitic for at least 360 million years," said Rubidge, director of the Bernard Price Institute for Paleontological Research.
"This fossil changes how we look at lampreys today," said Coates, noting the find reveals the anatomical evolution of lampreys is more conservative than scientists thought.
Gess found the specimen from the Devonian period in an ancient estuary in Grahamstown, South Africa. The fossil measures less than 2 inches long and reveals a set of 14 teeth surrounding the mouth that is proportionately larger than its descendents today.
The scientists said the find places the origin of modern lamprey morphology deep within the Palaeozoic period and adds essential detail to the emerging and changing picture of early vertebrate evolution.