Diogenes, Dana, 1851

Rahayu, Dwi Listyo & Pratiwi, Rianta, 2022, Diogenes matabiru, a new species of hermit crab from Lombok Island, Indonesia (Crustacea, Decapoda, Anomura, Diogenidae), Zootaxa 5093 (4), pp. 493-500 : 498-499

Key to Indonesian species of Diogenes

1. Intercalary rostral process well developed and marginally armed with spinules; antennal acicle weakly or strongly bifurcate. 2

- Intercalary rostral process well developed, reduced, vestigial or absent, marginally unarmed; antennal acicle straight or slightly concave mesially..................................................................................... 5

2. Outer surface of left cheliped palm with tubercles............................................................ 3

- Outer surface of left cheliped palm with strong spines........................................................ 4

3. Antennal acicle with inner branch not reaching midlength of fourth peduncular segment; outer surface of cheliped palm with covering of low, closely-set flattened tubercles..................................... Diogenes custos Fabricius, 1798

- Antennal acicle with inner branch reaching midlength of fourth peduncular segment; outer surface of cheliped palm with covering of small conical tubercles............................................... Diogenes dubius ( Herbst, 1804)

4. Outer surface of left cheliped with irregular unarmed or weakly spinulous area near upper margin..................................................................................... Diogenes alias McLaughlin & Holthuis, 2001

- Outer surface of left cheliped with 2 irregular longitudinal rows of strong spines in midline and 1 shorter row near upper margin.................................................................... Diogenes mixtus Lanchester, 1902

5. Intercalary rostral process absent/vestigial.................................................................. 6

- Intercalary rostral process well developed.................................................................. 7

6. Ocular peduncles long and slender, longer than shield length, anterior lobe of sternite of P3 subrectangular.................................................................................... Diogenes jousseaumei ( Bouvier, 1897)

- Ocular peduncles slender, obviously shorter than shield, anterior lobe of sternite of P3 distinctly subquadrate....................................................................................... Diogenes jubatus ( Nobili, 1903)

7. Antennal acicle short, subquadrate, not reaching beyond midlength of fourth peduncular segment...................... 8

- Antennal acicle elongate, triangular or subtriangular, overreaching distal margin of fourth peduncular segment........... 9

8. Ocular peduncles slightly inflated proximally and on cornea; subtriangular lobe of telson with distinct median cleft; terminal margin of left lobe armed with large spines, smaller spines on right lobe........ Diogenes dorotheae Morgan & Forest, 1991

- Ocular peduncles inflated proximally and tapering to narrow cornea; subquadrangular lobe of telson with shallow median cleft; terminal margin armed with tiny spines, with 3 moderately large spines on left lobes........ Diogenes takedai Rahayu, 2012

9. Antennal peduncle as long as or longer than ocular peduncle; antennal flagella long and with pair long setae on each article 10

- Antennal peduncle shorter than ocular peduncle; antennal flagella short, lacking pair long setae on each article.......... 16

10. Antennal peduncles without small spine on fourth peduncular segment.......................................... 11

- Antennal peduncles with small spine on fourth peduncular segment............................................ 12

11. Antennal acicle not reaching distal margin of fourth peduncular segment; row of spines on dorsal margin of propodus and carpus of P2.................................................................. Diogenes avarus Heller, 1865

- Antennal acicle overreaching distal margin of fourth peduncular segment; row of small, often relatively obscure, spines on dorsal margin of carpus of P2 and P3...................................... Diogenes moosai Rahayu & Forest, 1995

12. Carpus of left cheliped with spinous protuberance medially......................... Diogenes goniochirus Forest, 1956

- Carpus of left cheliped without spinous protuberance........................................................ 13

13. Ventrolateral margin of left cheliped merus with row of strong spines............. Diogenes klaasi Rahayu & Forest, 1995

- Ventrolateral margin of left cheliped merus without row of strong spines........................................ 14

14. Corneas dilated, dactyls of P2 and P3 slender, long, and curved, carpi with distal spine...... Diogenes foresti Rahayu, 2002

- Corneas not dilated; dactyls of P2 and P3 slender, carpi with row of spines....................................... 15

15. Left cheliped palm with continuation of proximal row of tubercles or spines as longitudinal granular ridge in 0.25 of upper outer surface............................................................. Diogenes fasciatus Rahayu & Forest, 1995

- Left cheliped palm with continuation of proximal row of strong, outwardly directed spines on ventral margin as longitudinal spinose ridge in half of outer surface............................................ Diogenes rectimanus Miers, 1884

16. Antennular peduncles longer than ocular peduncle.......................................................... 17

- Antennular peduncle shorter than ocular peduncle.......................................................... 19

17. Dactyl of right cheliped longer than palm, large hiatus between dactyl and fixed finger, palm without any spines on upper margin.............................................................. Diogenes tumidus Rahayu & Forest, 1995

- Dactyl of right cheliped same length or shorter than palm, no hiatus between fingers, palm with row of spines on upper margin............................................................................................. 18

18. Terminal margin of telson obliquely truncate, with row of spinules, without medial cleft... Diogenes leptocerus Forest, 1956

- Terminal margin of telson with large spines on left lobe, small spines on right lobe, medial cleft distinct................................................................................. Diogenes spinicarpus Rahayu & Forest, 1995

19. Intercalary rostral process short, triangular, not reaching tip of mesial spine of ocular acicle......................... 20

- Intercalary rostral process long, reaching or overreaching tip of mesial spine of ocular acicle........................ 21

20. Shield longer than broad, P4 without any spine, telson broader than long................ Diogenes biramus Morgan, 1987

- Shield as long as broad, P4 with distal spine on propodus and/or carpus, telson longer than broad............................................................................................... Diogenes viridis Haig & Ball, 1988

21. Outer surface of fixed finger of left cheliped slightly convex, armed with strong spine; merus of P2 without any spine on ventral margin........................................................................... Diogenes matabiru n. sp.

- Outer surface of fixed finger of left cheliped flattened, with sparse small spines or tubercles; merus of P2 with 1 to 5 spines on ventral margin.......................................................... Diogenes pallescens Whitelegge, 1897