Key to species of Retrozetes

1. Apices of lamellae S-shaped: curved posteriorly, then recurved anteriorly; median sclerotised bands of lamellar cuticle forming Y-shaped structure dorsally (Fig. 15)................................................ R. novaecaledoniae sp. nov.

- Apices of lamellae not S-shaped: only curved posteriorly, not recurved anteriorly; median sclerotised bands of lamellar cuticle sub-parallel or forming V-shaped structure dorsally........................................................... 2

2. Apex of rostrum visible in dorsal orientation, with acute projection; stalk of bothridial seta recurved; apices of lamellae separated by drop-shaped fissure (Fig. 17)................................................. R. fernandezi sp. nov.

- Apex of rostrum covered by lamellae in dorsal orientation, without acute projection; stalk of bothridial seta not recurved; apices of lamellae separated narrow slit or broad U-shaped or rectangular fissure................................... 3

3. Lamellar cuspides divided by broad rectangular or circular fissure; cerotegument thick, reticulate; lenticulus broader than long; notogastral margin scalloped in region of setae of h series; genital and anal plates separated by distance of half length of genital plate................................................................................................ 4

- Lamellar cuspides divided by narrow slit; cerotegument light, reticulate or amorphous; lenticulus longer than broad; notogastral margin smooth; genital and anal plates almost abutting (Fig. 14)....................... R. mirabilis sp. nov.

4. Small species (≤155 μm long), rostral seta long, thick, curved, blunt apically covered in cerotegument; head of bothridial seta broad, club-shaped; setae of ad series spaced equidistantly............................ R. hanswursti (Mahunka, 1999)

- Larger species (≥350 μm long), rostral setae short, thin, straight, without thick cerotegument; head of bothridial seta narrow, elongate, expanding apically; setae ad 2-3 positioned close together lateral of anal plates (Fig. 11)..... R. koghisensis sp. nov.