Hexapodidae, Miers, 1886

Rahayu, Dwi Listyo & Ng, Peter K. L., 2014, New genera and new species of Hexapodidae (Crustacea, Brachyura) from the Indo-West Pacific and east Atlantic, Raffles Bulletin of Zoology 62, pp. 396-483 : 397-399

Key to genera of Hexapodidae (modified from Manning & Holthuis, 1981)

1. Eye hammer-shaped, cornea very large, much broader than peduncle; carpus, propodus, and dactylus of third maxilliped very slender; P2–P4 very long, slender, merus of longest pair longer than carapace [Indo-West Pacific]................................. ........................................................... Hexaplax Doflein, 1904

– Eye relatively small or reduced, cornea scarcely or not broader than peduncle; third maxilliped and P2–P4 various. ............. 2

2. Eyes fixed; P2–P4 long, slender, merus of longest pair much longer than carapace; male thoracic sternal groove long, narrow, transverse, extending laterally from sternoabdominal cavity to beyond base of third maxilliped; carpus, propodus and dactylus of third maxilliped slender [Indian Ocean].............................. ................................................... Lambdophallus Alcock, 1900

– Eyes movable; P2–P4 relatively short, merus of longest pair shorter or subequal in length to carapace; male thoracic sternal groove with or without transverse extension from sternoabdominal cavity to base of third maxilliped; third maxilliped various................................................................... 3

3. Propodus of third maxilliped strongly dilated distally........... 4

– Propodus of third maxilliped not strongly dilated distally, slender; carpus and dactylus relatively slender...................... 6

4. G1 stout, strongly twisted into a tight spiral [ South Africa]... ...................................... Spiroplax Manning & Holthuis, 1981

– G1 variously shaped, not twisted into tight spiral................. 5

5. Male abdominal somite 6 relatively long; male telson with lateral margins concave; G1 slender, sinuous directed anteriorly [West Africa]. .............................. Thaumastoplax Miers, 1881

– Male abdominal somite 6 relatively shorter; male telson with lateral margins convex; G1 recurved posteriorly [Indo-West Pacific].......................................... Hexalaughlia Guinot, 2006

6. Some of female abdominal somites fused.............................. 7

– All female abdominal somites free......................................... 8

7. Female abdominal somite 1 free, somites 2–6 fused, but sutures visible [ Guatemala]. ........... Stevea Manning & Holthus, 1981

– Female abdominal somites 1–6 fused, suture visible only on somites 5 and 6 [ Japan]....................... Rayapinus , new genus

8. Exopod of third maxilliped with flagellum; dactylus of P2–P4 neither enlarged nor distinctly flattened dorsoventrally; male abdominal somite 6 constricted proximally............................ 9

– Exopod of third maxilliped without flagellum; dactylus of P2–P4 enlarged, triangular, strongly flattened dorsoventrally; male abdominal somite 6 not constricted proximally [West Africa]........................................ Pseudohexapus Monod, 1956

9. Male abdominal somite 6 much longer than combined length of somites 3–5 [Galapagos].............. Paeduma Rathbun, 1897

– Male abdominal somite 6 shorter than combined length of somites 3–5............................................................................ 10

10. Male telson distinctly trilobed or trifoil in shape with distinct lateral angular projection, male abdominal somite 6 divided longitudinally [ South Africa].................................................... ....................................... Tritoplax Manning & Holthuis, 1981

– Male telson various, male abdominal somite 6 entire......... 11

11. Carapace regions distinct; thoracic sternites 1 and 2 strongly bent inwards towards buccal cavity [West Pacific].................. ................................. Latohexapus Huang, Hsueh & Ng, 2002

– Carapace regions indistinct; thoracic sternites 1 and 2 gently curved or flat, not bent inwards towards buccal cavity....... 12

12. Third maxilliped slender, ischium width about 2/3 to 3/4 merus length.....................................................................................13

– Third maxilliped broad, ischium width usually subequal to or longer than merus length. .....................................................14