''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. The family Geotriidae is most closely related to the lamprey family

Mordaciidae ''Mordacia'' is a genus of lamprey, the sole genus of the family Mordaciidae, also known as the southern topeyed lampreys. The family Mordaciidae is most closely related to the lamprey family Geotriidae, which has a similar Gondwanan distributi ...

, which has a similar

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

n distribution, and both families diverged during the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

. Together, their common ancestor diverged from the

Petromyzontidae Petromyzontidae are a family of lampreys native to the Northern Hemisphere, comprising the vast majority of living lampreys. Petromyzontids have the highest number of chromosomes (164–174) among vertebrates. Genera * '' Caspiomyzon'' * '' En ...

during the

Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...

. ''G. australis'' spawns in

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

-draining river basins in on either side of the southern Pacific (both

Australasia Australasia is a subregion of Oceania, comprising Australia, New Zealand (overlapping with Polynesia), and sometimes including New Guinea and surrounding islands (overlapping with Melanesia). The term is used in a number of different context ...

and

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

), while ''G. macrostoma'' spawns in

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

-draining basins in southern

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

and nearby subantarctic islands. Despite the occurrence of both species in South America and both formerly being considered conspecific, phylogenetic studies suggest that the lineages of both species diverged during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

, indicating very ancient origins for both.

References

Lampreys Taxa named by John Edward Gray Jawless fish genera {{Jawless-fish-stub