After Nelson, 1994, with Recent species from Froese & Pauly, 2001 [“The Fishbase”]

<==o Petromyzontidae [Petromyxontiformes sensu stricto] (modern lampreys; nykynahkiaiset)
   |-- Geotria australis Gray, 1851 [Exomegas] [Geotriinae] (australiannahkiainen; Pouched lamprey)
   |--o Mordacia [Mordaciinae] (etelätyynenmerennahkiaiset)
   |  |-- M. lapicida (Gray, 1851) (Chilean lamprey)
   |  |-- M. mordax (Richardson, 1846) (Australian lamprey)
   |  `-- M. praecox Potter, 1968 (Non-parasitic lamprey)
   `--o Petromyzoninae
      |--o Petromyzontini
      |  |-- Petromyzon marinus Linnaeus, 1758 (merinahkiainen; Sea lamprey)
      |  |-- Caspiomyzon wagneri (Kessler, 1870) (kaspianmerennahkiainen; Caspian lamprey)
      |  `--o Ichthyomyzon [6]
      |     |-- I. bdellium (Jordan, 1885) (Ohio lamprey)
      |     |-- I. castaneus Girard, 1858 (Chestnut lamprey)
      |     |-- I. fossor Reighard & Cummins, 1916 (Northern brook lamprey)
      |     |-- I. gagei Hubbs & Trautman, 1937 (Southern brook lamprey)
      |     |-- I. greeleyi Hubbs & Trautman, 1937 (Mountain brook lamprey)
      |     `-- I. unicuspis Hubbs & Trautman, 1937 (Silver lamprey)
      `--o Lampetrini [Lampetra sensu lato]
         |--o Eudontomyzon (mustanmerennahkiaiset)
         |  |-- E. sp.1
         |  |-- E. sp.2
         |  |-- E. danfordi Regan, 1911 (Carpathian lamprey)
         |  |-- E. hellenicus Vladykov, Renaud, Kott & Economidis, 1982 (Greek brook lamprey)
         |  |-- E. mariae (Berg, 1931) (Ukrainian brook lamprey)
         |  `-- E. vladykovi Oliva & Zanandrea, 1959 (Vladykov's lamprey)
         |--o Lethenteron (jäämerennahkiaiset)
         |  |-- L. appendix (DeKay, 1842) (American brook lamprey)
         |  |-- L. camtschaticum (Tilesius, 1811) (Arctic lamprey)
         |  |-- L. kessleri (Anikin, 1905) (Siberian brook lamprey)
         |  `-- L. zanandreai (Vladykov, 1955) (Po brook lamprey)
         |?- Okkelbergia (pohjoisamerikannahkiainen) [ssp. => Lampetra?]
         |?- Tetrapleurodon (meksikonnahkiaiset) [ssp. => Lampetra?]
         |?- Entosphenus (tyynenmerennahkiaiset) [†1,7] [ssp. => Lampetra?]
         `--o Lampetra [incl. Okkelbergia; Tetrapleurodon & Entosphenus]
            |-- L. aepyptera (Abbott, 1860) (Least brook lamprey)
            |-- L. ayresi (Günther, 1870) (River lamprey)
            |-- L. fluviatilis (Linnaeus, 1758) (tavallinen nahkiainen, nahkiainen; European river lamprey)
            |-- L. folletti (Vladykov & Kott, 1976) (Modoc Brook lamprey)
            |-- L. geminis (Alvarez, 1964) (Mexican brook lamprey)
            |-- L. hubbsi (Vladykov & Kott, 1976) (Kern brook lamprey)
            |-- L. lanceolata Kux & Steiner, 1972 (Turkish brook lamprey)
            |-- L. macrostoma Beamish, 1982 (Vancouver lamprey)
            |-- L. morii Berg, 1931 (Korean lamprey)
            |-- L. pacifica Vladykov, 1973 (Pacific brook lamprey)
            |-- L. planeri (Bloch, 1784) (pikkunahkiainen; European brook lamprey)
            |-- L. reissneri (Dybowski, 1869) (Far Eastern brook lamprey)
            |-- L. richardsoni Vladykov & Follett, 1965 (Western brook lamprey)
            |-- L. spadicea Bean, 1887 (Mexican lamprey)
            |--+-- L. lethophaga Hubbs, 1971 (Pit-Klamath brook lamprey)
            |  `-- L. minima Bond & Kan, 1973 (Miller Lake lamprey)
            `--+-- L. tridentata (Richardson, 1836) (Pacific lamprey)
               `-- L. similis (Vladykov & Kott, 1979) (Klamath river lamprey)

Reference(s):