Priscomyzon riniensis

Priscomyzon is a genus of extinct lamprey that lived around 360 million years ago during the Famennian (Late Devonian) in a marine or estuarine environment in South Africa. This small agnathan is anatomically similar to the Mazon Creek lampreys, but is some 35 million years older. Its key developments included the first known large oral disc, circumoral teeth and a branchial basket.

thumb|Life reconstruction of Priscomyzon riniensis ==Discovery and naming== The lamprey fossil was discovered on Waterloo Farm in rocks of the Witteberg Group near Grahamstown in South Africa. The species was described by Robert W. Gess & Bruce S. Rubidge of the Bernard Price Institute (Palaeontology) Wits University, and Michael I. Coates of the Department of Organismal Biology University of Chicago in the journal Nature of 26 October 2006. The shale containing the fossil was discovered as far back as 1985 during construction of the N2 bypass outside Grahamstown. The site consists of black carbonaceous shale formed from anaerobic mud deposited in a marine estuary on the Agulhas Sea. A variety of organic remains are found in this setting, including algae, terrestrial plants and fish. Invertebrate remains are of small bivalves, ostracods, clam shrimp, and a eurypterid. Fossil material has been greatly compressed and original tissue replaced by metamorphic mica altered to chlorite during uplift. To prevent rockfalls onto the road from the unstable formation, the steep slopes were cut back again in 1999 and once more in 2007/8. During these upgrades Gess managed to obtain a large sample of rock blocks with the help of the road construction company, and worked intermittently on exposing their contents.