Lampreys

upright=1.2|thumb|Sea lamprey, Petromyzon marinusthumb|Mouth of a sea lamprey, [[Petromyzon marinus]] thumb|318x318px|Median plane|Median section of lamprey demonstrating internal anatomy thumb|Microscopic cross section through the pharynx of a larva from an unknown lamprey species

species of chordates

Geotria is the only genus in the lamprey family Geotriidae. It has 2 known species: Geotria australis (pouched lamprey) and Geotria macrostoma (Argentinian lamprey). Both species were considered conspecific until G. macrostoma was revived in a 2020 study.

chemical compound

left|thumb|250x250px|The lamprey Hardistiella montanensis from the Carboniferous of Bear Gulch, Montana. Coll. Oilshale. Hardistiella montanensis is an extinct species of lamprey, found, dating from the Carboniferous period, at the Bear Gulch Limestone site in the U.S. state of Montana.

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.

Mesomyzon is an extinct lamprey genus from freshwater strata of the Early Cretaceous (Barremian–Aptian age) Yixian Formation of China. It contains a single species, M. mengae.