1. With three or four pairs of branchiae...................................................................... 2
- With more than four pairs of branchiae..................................................................... 6
2. Branchiae present from chaetiger 3..................................... Prionospio (Minuspio) pilkena Wilson, 1990
- Branchiae present from chaetiger 2........................................................................ 3
3. With dorsal flaps on chaetigers 5–13............................................ P. (M.) laciniosa Maciolek, 1985
- Without a dorsal flap................................................................................... 4
4. Some branchia distinctly wrinkled.............................................. P. (M.) fauchaldi Maciolek, 1985
- All branchiae smooth, not wrinkled...................................................................... 5
5. With dorsal crests........................................................... P. (M.) elegantula Imajima, 1990
- Without dorsal crests............................................................ P. (M.) japonica Okuda, 1935
6. 39 pairs of branchiae....................................................... P. (M.) polybranchiata Fauvel, 1929
- Fewer than 39 pairs of branchiae......................................................................... 7
7. Interparapodial pouches present.................................................... P. (M.) aluta Maciolek, 1985
- Interparapodial pouches absent........................................................................... 8
8. Ventral sabre chaeta absent.................................................... P. (M.) perkinsi Maciolek, 1985
– Ventral sabre chaeta present............................................................................. 9
9. Some branchia distinctly longer than (minimally 4–5 times) notopodial lamellae................................... 10
- All branchiae short, nearly as long as notopodial lamellae..................................................... 15
10. Prostomium with peaks............................................................................... 11
- Prostomium without peaks............................................................................. 14
11. Anterior part of prostomium truncated, with a small medial peak.......................... P. (M.) delta Hartman, 1965
- Anterior part of prostomium rounded, with 3–5 peaks....................................................... 12
12. Eyes absent...................................................................... P. (M.) anatolica sp. nov.
- Two pairs of eyes.................................................................................... 13
13. Dorsal crests absent............................................................. P. (M.) lighti Maciolek, 1985
- Dorsal crests present........................................................... P. (M.) pulchra Imajima, 1990
14. Branchiae longest on chaetiger 2, prostomium widest at mid–point......................... P. (M.) tatura Wilson, 1990
- Branchiae longest on chaetigers 4–5, prostomium widest at posterior most region.............. P. (M.) yuriel Wilson, 1990
15. Notopodial lamellae lacking on chaetiger 1................................................................ 16
- Notopodial lamellae more or less well–developed on chaetiger 1............................................... 19
16. Dorsal crests absent......................................................... P. (M.) patagonica Augener, 1923
- Dorsal crests present................................................................................. 17
17. Without prostomial peaks......................................................... P. (M.) maciolekae sp. nov.
- With prostomial peaks................................................................................. 18
18. Anterior margin of prostomium truncated and with only a small peak..................... P. (M.) wireni Maciolek, 1985
- Anterior margin of prostomium rounded and with five small peaks............... P. (M.) multibranchiata Berkeley, 1927
19. More than 10 pairs of branchiae........................................................................ 20
- Fewer than 10 pairs of branchiae....................................................................... 21
20. Dorsal crests absent.............................................................. P. (M.) wambri Wilson, 1990
- Dorsal crests present.......................................................... P. (M.) elongata Imajima, 1990
21. Eyes absent, branchiae wrinkled................................................ P. (M.) sandersi Maciolek, 1981 b
- One or two pairs eyes present, branchiae narrow and cylindrical.......................... P. (M.) cirrifera Wirén, 1883