The northern lampreys (Petromyzontidae) are a family of lampreys. Northern lampreys have the highest number of chromosomes (164–174) among vertebrates. Genera Caspiomyzon Entosphenus Eudontomyzon Ichthyomyzon Lampetra Lethenteron Petromyzon Tetrapleurodon References External links FishBase.org: Details for family Petromyzontidae – the Northern lampreys Fish described in 1827 Fish families Fish of Asia Fish of Europe Fish of North America Fish of the Atlantic Ocean Fish of the Pacific Ocean . Taxa named by Antoine Risso