gammaroid

Copilaș-Ciocianu, Denis & Sidorov, Dmitry, 2022, Taxonomic, ecological and morphological diversity of Ponto-Caspian gammaroidean amphipods: a review, Organisms Diversity & Evolution (New York, N. Y.) 22 (2), pp. 285-315 : 307-308

Key to genera (endemic Ponto-Caspian gammaroid radiation)

1. Gnathopods chelate ................................… Caspicola (monotypic: Caspicola knipovitschi ( Derzhavin, 1944)

- Gnathopods subchelate .............................................. 2

2. Head with lateral projections …............................... 3

- Head without lateral projections ................................ 5

3. Strong lateral-pointing spine on pereonite 5 ......................................................................... Axelboeckia (monotypic: Axelboeckia spinosa ( Sars, 1894a, 1894b))

- No spines, only blunt knobs on pereonite 5 ............... 4

4. Body with two dorso-lateral rows of knobs ................ ........................................................................... Kuzmelina (monotypic: Kuzmelina kusnezowi ( Sowinsky, 1894))

- Body with a central dorsal keel on pereonal segments 6–7 and pleosome ........................................... Gmelinopsis

5. Antenna 1 accessory flagellum uniarticulate ............ 6

- Antenna 1 accessory flagellum two- or multiarticulated ......................................................................................... 10

6. Lateral head lobes form a characteristic “hood” ............................................................................ Scytaelina (monotypic: Scytaelina simplex ( Stock et al., 1998))

- Lateral head lobes normal .......................................... 7

7. Bases of pereopods 5–6 lobed, uropod 3 reduced ....................................................................... Behningiella (monotypic: Behningiella brachypus ( Derzhavin, 1948))

- Bases of pereopods 5–6 not lobed, uropod 3 normal ... 8

8. Body with an obvious central dorsal keel, more pronounced on the pleosome ..................................... Gmelina

- Body with a weak or absent central dorsal keel ......... 9

9. Pereopod 7 basis with a large downward pointing postero-distal lobe ..................................... Jugogammarus (monotypic: Jugogammarus kusceri ( Karaman, 1931))

- Pereopod 7 basis with minute/without a downward pointing postero-distal lobe ............................... Yogmelina

10. Gnathopod 1 broader and larger than gnathopod 2 ........................................................................................ 11

- Gnathopod 1 equal or smaller than gnathopod 2 ..... 13

11. Uropod 3 reduced, exopod shorter than twice the peduncle length .......................................................... Baku (monotypic: Baku paradoxus (Derzhavin in Derzhavin & Pjatakova, 1967))

- Uropod 3 normal, exopod at least twice the peduncle length .............................................................................. 12

12. Dactyli of pereopods 3–7 prehensile ...... Iphigenella (monotypic: Iphigenella acanthopoda ( Sars, 1896))

- Dactyli of pereopods 3 – 7 not prehensile ............................................................... Lanceogammarus (monotypic: Lanceogammarus andrussowi ( Sars, 1896))

13. Pereopod 7 basis not lobed ................................... 14

- Pereopod 7 basis lobed ............................................ 18

14. Antenna 1 accessory flagellum bi-articulated ....................................................................... Cardiophilus

- Antenna 1 accessory flagellum tri- or more articulated ........................................................................................ 15

15. Antenna 2 peduncle greatly expanded, article 3 with a downward projection .................................. Derzhavinella

- Antenna 2 peduncle normal, article 3 without a downward projection ............................................................... 16

16. Antenna 1 peduncle article 3 longer or equal with article 1 ............................................................. Sowinskya (monotypic: Sowinskya macrocera ( Derzhavin, 1948))

- Antenna 1 peduncle article 3 shorter than article 1 ... 17

17. Uropod 3 setae curled, longer than spines ................................................................ Trichogammarus (monotypic: Trichogammarus trichiatus ( Martynov, 1932))

- Uropod 3 setae straight, shorter than spines ............................................................... Chaetogammarus

18. Pereopod 6 basis lobed ........................................ 19

- Pereopod 6 basis not lobed ...................................... 20

19. Pereopod 5–7 meral articles with a postero-distal lobe .............................................................................. Zernovia (monotypic: Zernovia volgensis ( Derzhavin, 1948))

- Pereopod 5–7 meral articles without a postero-distal lobe ........................................................ Shablogammarus (monotypic: Shablogammarus shablensis (Cărău Ș u, 1943))

20. Antenna 1 flagellum shorter than peduncle .......... 21

- Antenna 1 flagellum equal/longer than peduncle ..... 25

21. Epimeron 3 with postero-ventral setal fan ............ 22

- Epimeron 3 without postero-ventral setal fan .......... 24

22. Uropod 3 endopod longer than half of exopod ................................................................. Uroniphargoides (monotypic: Uroniphargoides spinicaudatus (Cărău Ș u, 1943))

- Uropod 3 endopod shorter than half of exopod ........ 23

23. Ganthopod 2 propodus palm longer than posterior margin .............................................. Compactogammarus (monotypic: Compactogammarus compactus ( Sars, 1895))

- Ganthopod 2 propodus palm shorter than posterior margin ................................................................ Niphargoides

24. Uropod 3 exopod 2nd article well developed, bearing lateral setae ........................................ Niphargogammarus

- Uropod 3 exopod 2nd article minute/absent, bearing no lateral setae ............................................ Paraniphargoides

25. Eyes round to ovoid, gnathopod 2 propodus large and triangular, armed with a palmar spine as long as 1/3 of dactylus .............................................................. Pandorites (monotypic: Pandorites podoceroides ( Sars, 1896))

- Eyes reniform, gnathopod 2 propodus armed with a palmar spine(s) shorter than 1/3 of dactylus ....................... 26

26. Antenna 1 peduncular article 1 slender, width not exceeding 1/3 of length, pereopods 3–4 with sparse setae shorter than the width of underlying segment ................ 27

- Antenna 1 peduncular article 1 robust, width exceeding 1/3 of length, pereopods 3–4 with dense setae as long as/longer than the width of underlying segment (except O. subnudus ) ....................................................................... 30

27. Body with a central dorsal a keel ......... Amathillina

- Body without a keel ................................................. 28

28. Head swollen and enlarged ....... Cephalogammarus (monotypic: Cephalogammarus macrocephalus ( Sars, 1896))

- Head normal ............................................................ 29

29. Urosomites 1–2 with columnar tubercles ................................................................ Dikerogammarus

- Urosomites 1–2 without columnar tubercles ................................................................. Akerogammarus

30. Uropod 3 exopod 2nd article at least 1/5 the length of 1st article .................................................................... 31

- Uropod 3 exopod 2nd article much shorter than 1/5 the length of 1st article ......................................................... 32

31. Uropod 3 exopod outer margin armed with few simple setae ......................................................... Stenogammarus

- Uropod 3 exopod outer margin armed with many plumose setae ............................................... Wolgagammarus (monotypic: Wolgagammarus dzjubani (Mordukhai-Boltovskoi & Ljakhov, 1972))

32. Setae on posterior margin of carpal articles of pereopods 3–4 arranged in a continuous fan .... Pontogammarus

- Setae on posterior margin of carpal articles of pereopods 3–4 arranged in clusters .................................................. 33

33. Urosomites 1–2 with noticeable dorsal knobs .................................................................. Turcogammarus

- Urosomites 1–2 flat or humped ........ Obesogammarus