Rarest jawless fish
- Who
- Greek brook lamprey Eudontomyzon hellenicus
- What
- 10 square kilometre(s)
- Where
- Greece
- When
- 04 November 2013
The rarest jawless fish or agnathan is the Greek brook lamprey Eudontomyzon hellenicus. Categorized as "Critically Endangered" by the IUCN and threatened by habitat loss, it is now restricted entirely to Greece's Louros and Strymon river basins, in which it is estimated to occupy less than 10 square kilometres.