Key to the Atlantic and Mediterranean species of Apseudopsis

1. Pereopod 1 merus with dorsodistal spine.................................................................... 2

- Pereopod 1 merus without dorsodistal spine................................................................. 4

2. Pereonites 2–6 with apophyses on anterior and posterior corners; antennula inner flagellum of four segments, outer flagellum of 4–8 segments in mature specimens; pereopod 1 propodus with five ventral spines; male with hyposphenia on pereonites 2– 5, female with hyposphenia on pereonites 2–6..................... .. A. elisae (Băcescu, 1961) [Monaco, Mediterranean]

- Pereonites without anterolateral or posterolateral apophyses....................................................3

3. Antennula inner flagellum of 7–9 segments, outer flagellum of 15–16 segments in mature specimens; pereopod 1 propodus with four spines on ventral margin; male with hyposphenia on pereonites 2–5, female with hyposphenia on pereonites 1–6...................................................................... A. robustus (Sars 1882) [Mediterranean]

- Antennula inner flagellum of four segments, outer flagellum of 8–10 segments; pereopod 1 propodus with three spines on ventral margin; only female with hyposphenia, on pereonites 2–6..... A. latreillii (Milne-Edwards, 1828) [European Atlantic]

4. Pereonites without apophyses............................................................................5

- Some pereonites with anterolateral or posterolateral apophyses................................................. 6

5. Rostrum pointed with rounded shoulders; pereopod 1 propodus with four ventral spines; male cheliped merus with spur, chela fixed finger cutting edge with proximal invagination; females with hyposphenium on pereonite 6 only...................................................................................... A. rogi Esquete, sp. nov. [Canary Islands]

- Rostrum pointed, short, subtriangular; pereopod 1 propodus with three ventral spines; male cheliped merus without spur, chela fixed finger with semicircular apophysis; females with hyposphenia on pereonites 3 and 6....................................................................................... A. apocryphus (Guţu, 2002) [Israel, Mediterranean]

6. Pereopod 1 propodus with five or more ventral spines......................................................... 7

- Pereopod 1 propodus with four or fewer ventral spines....................................................... 10

7. Pereopod 1 propodus with five ventral spines.............................................................. 8

- Pereopod 1 propodus with six ventral spines............................................................... 9

8. Rostrum short; all pereonites with posterolateral acute apophyses; female with hyposphenium on pereonite 6 only; male chela fixed finger cutting edge with semicircular apophysis.............. A. annabensis (Guţu, 2002) [Algeria, Mediterranean]

- Rostrum relatively long, acute, with rounded shoulders; all pereonites with posterolateral hook-like apophyses, female with hyposphenia on pereonites 2 and 6 (males unknown)............................ A. cuanzanus Bochert, 2012 [Angola]

9. Rostrum short, pointed; all pereonites with posterolateral apophyses; female with hyposphenia on pereonites 2 and 6; male chela fixed finger with semicircular apophysis.............................. A. arguinensis (Guţu, 2002) [Mauritania]

- Rostrum long, acute; pereonites 2–5 with short posterolateral hooks; females with hyposphenia on pereonites 2–6; cheliped not sexually dimorphic, slender, merus about 3.5 times as long as broad, chela cutting edges not ornamented....................................................................................... A. isochelatus Guţu, 2006 [Mauritania]

10. Rostrum acute, with rounded lobes; pereonites with posterolateral apophyses; pereopod 1 propodus with three ventral spines (sole specimen known is a copulatory female)........................ A. minimus (Guţu, 2002) [Israel, Mediterranean]

- Pereopod 1 propodus with four ventral spines..............................................................11

11. Pereonites 3–6 with anterolateral and posterolateral apophyses.................................................12

- No pereonite with anterolateral apophyses................................................................. 13

12. Rostrum long, acute; anterolateral apophyses on pereonites 3–6 directed forward; females with hyposphenia on pereonites 2, 3, 5 and 6 (male unknown).................................. A. acutifrons (Sars 1882) [Gulf of Naples, Mediterranean]

- Rostrum short, pointed; anterolateral apophyses on pereonites 3–6 not directed forward, but perpendicular to the main axis of the body; females with hyposphenia on pereonites 1–6; male chela fixed finger with triangular apophysis on cutting edge........................................................... A. ostroumovi (Băcescu & Cărăuşu, 1947) [Black Sea]

13. Pereonites 1–6 with posterolateral apophyses; mature specimens’ outer flagellum of antennule of 6–8 segments.......... 14

- Only pereonites 2–6 with posterolateral apophyses; mature specimens’ outer flagellum of antennule of ten segments; females with hyposphenium on pereonite 6 only; male chela fixed finger with semicircular and triangular apophyses on cutting edge.................................................. A. adami Esquete & Bamber, 2012. [Atlantic Iberian Peninsula].

14. Females with hyposphenia on pereonites 2, 3 and 6; male chela with apophysis on fixed finger cutting edge and proximal apophysis on dactylus cutting edge.............................. A. bacescui (Guţu, 2002) [Balearic Sea, Mediterranean].

- Females with hyposphenia on pereonites 2 and 6. Male cheliped fixed finger cutting edge with proximal semicircular apophyses and invagination......................... A. mediterraneus (Guţu, 2002) [Israel, Mediterranean coast of France].