1 Head with lenses (figs. 1, 2)2

⊕ Fig.1 Labidocera sinilobata female ☚   Fig.2 Cephalophanes refulgens female ☚  

Head without lenses5

2 (1) Head with two large contiguous lenses, covering all anterior head; lens triangular in dorsal view (fig. 2). Head without hookCephalophanes

Head with two rounded lenses (fig. 1) sometimes difficult to see. Head with or without lateral hooks3

3 (1) Leg 1: endopod 2-segmented (fig. 3)Labidocera

Leg 1: endopod 3-segmented (fig. 4)4

⊕ Fig.3 Labidocera sinilobata ☚   Fig.4 Pontella securifer female ☚  

4 (3) Pedigerous somites 4 & 5 separate or incompletely fusedPontella

Pedigerous somites 4 & 5 completely fusedIvellopsis

5 (1) Legs 3 & 4: endopod 3-segmented (fig. 5)6

Legs 3 & 4: endopod 2-segmented (fig. 6)171

⊕ Fig.5 Pleuromamma xiphias female ☚   Fig.6 Acartiella sinensis ☚  

6 (5) Leg 1: endopod 3-segmented (fig. 4)7

Leg 1: endopod 2-segmented (fig. 3)63

Leg 1: endopod 1-segmented (fig. 7)76

7 (6) Dark brown knob on the right or left anterolateral corner of pedigerous somite 1 (fig. 8) Pleuromamma

⊕ Fig.7 Macandrewella cochinensis female ☚   Fig.8 Pleuromamma robusta female ☚  

No such knob8

8 (7) Leg 2: endopod segment 1 with an inner hook bent upward toward basis of the leg (fig. 9)9

Leg 2: endopod segment 1 without inner hook10

9 (8) Female: urosome expanded; male and female: anal somite with a backward directed process on each side forming an expansion (fig. 10)Gaussia

⊕ Fig.9 Gaussia asymmetrica female ☚   Fig.10 Gaussia asymmetrica female ☚  

Female: urosome narrow; male and female: anal somite without expansionsMetridia

10 (8) Leg 1: basis with a reflexed hook on inner distal corner (fig. 11)Megacalanus

Leg 1: basis without such hook11

11 (10) Legs 3 & 4: exopod segment 3 with two outer spines (fig. 12)12

⊕ Fig.11 Megacalanus princeps female ☚   Fig.12 Pseudodiaptomus serricaudatus ☚  

Legs 3 & 4: exopod segment 3 with three outer spines (fig. 13)20

12 (11) Legs 3 & 4: terminal spine of exopod segment 3 with toothed outer margin (fig. 14)13

⊕ Fig.13 Disseta palumbii ☚   Fig.14 Pseudodiaptomus serricaudatus ☚  

Legs 3 & 4: terminal spine of exopod segment 3 with smooth and blade-like outer margin (fig. 15). Leg 5 of female biramous, 3-segmented; of male biramous, right leg similar to other legs, left leg variously modified (fig. 16) (Calanidae)14

13 (12) Leg 5 of female uniramous, 3- or 4-segmented (fig. 17); of male biramous, endopod rudimentary or uniramous; exopod 2 or 3-segmented (fig. 18)Pseudodiaptomus

⊕ Fig.15 Neocalanus gracilis ☚   Fig.16 Calanus sinicus male ☚   Fig.17 Pseudodiaptomus trihamatus female ☚   Fig.18 Pseudodiaptomus trihamatus male ☚  

Leg 5 of female biramous and 3-segmented; of male biramous and 3-segmented, highly similar to leg 5 of female (fig. 19)Pontoptilus

Leg 5 of female biramous and 3-segmented, exopod segment 2 inner distal corner expanded forming an elongate process (fig. 20); of male biramous, exopod 2-segmented, endopod 3-segmented(fig. 21)Sinocalanus

14 (12) Leg 5: small teeth bordered inner margin of coxa (fig. 22)15

⊕ Fig.19 Pontoptilus mucronatus male ☚   Fig.20 Sinocalanus sinensis female ☚   Fig.21 Sinocalanus doerrii male ☚   Fig.22 Nannocalanus minor female ☚  

Leg 5: inner margin of coxa naked (fig. 23)16

15 (14) Leg 5: inner margin of coxa with less than 16 teeth (fig. 22). In male, left leg 5: exopod segment 2 with inner distal corner expanded, exopod segments 1 & 2 with outer spines greatly elongated; right leg 5: exopod segment 3 with 2 inner setae (fig. 24)Nannocalanus

⊕ Fig.23 Canthocalanus pauper female ☚   Fig.24 Nannocalanus minor male ☚  

Leg 5: inner margin of coxa with more than 16 teeth (fig. 25). In male, left leg 5: exopod segment 2 with inner distal corner not expanded, exopod segments 1 & 2 with very short outer spines; right leg 5: exopod segment 3 without inner setae (fig. 26)Calanus

Leg 5: inner margin of coxa with more than 16 teeth. In male, right leg 5 similar to other legs; left leg 5: endopod rudimentary and 1-segmented; exopod highly modified and large (fig. 27)Cosmocalanus

16 (14) Leg 2: exopod segment 2 with evaginated proximal outer margin (fig. 28). Left leg 5 of male prehensile (fig. 29)Undinula

⊕ Fig.25 Calanus sinicus female ☚   Fig.26 Calanus sinicus male ☚   Fig.27 Cosmocalanus darwinii male ☚   Fig.28 Undinula vulgaris ☚   Fig.29 Undinula vulgaris male ☚  

These features absent17

17 (16) Leg 1: basis with distally directed seta on anterior surface modified into proximal thickened hook (fig. 30). Mouthparts not reduced in male. Left leg 5 of male: endopod with 2 setae (fig. 31)Canthocalanus

⊕ Fig.30 Canthocalanus pauper female ☚   Fig.31 Canthocalanus pauper male ☚  

Leg 1: basis with distally directed seta on anterior surface of ordinary plumose type. Mouthparts greatly reduced in male. Left leg 5 of male: endopod with 4-8 setae18

18 (17) Leg 2: exopod segment 1 without recurved spine. Leg 5 of female and left leg 5 of male: endopod 3-segmened, totally with 7 setaeMesocalanus

Leg 2: exopod segment 1 with (fig. 32) or without recurved spine. Leg 5 of female and left leg 5 of male, totally with 8 or 6 setae 19

⊕ Fig.32 Neocalanus gracilis female ☚  

19 (18) Leg 2: exopod segment 1 with 1 recurved spine at outer distal corner (fig. 32). Leg 5 of female and left leg 5 of male: endopod with 8 setaeNeocalanus

Leg 2: exopod segment 1 without recurved spine. Leg 5 of female and left leg of male: endopod with 6 setaeCalanoides

20 (11) Neither of antennule pair modified as a prehensile organ21

One of antennule pair more or less obviously modified as a prehensile organ (fig. 33)43

⊕Fig.33 Centropages orsinii male ☚  

21 (20) Leg 5 biramous22

Leg 5 uniramous (figs.34-36)39

22 (21) Leg 5: both rami 2-segmented (fig.37)Euaugaptilus hecticus♀

⊕ Fig.34 Nullosetigera auctiseta female ☚   Fig.35 Paraugaptilus buchani female ☚   Fig.36 Arietellus tripartitus female ☚   Fig.37 Euaugaptilus hecticus female ☚  

Leg 5: exopod 3-segmented; endopod 1- to 3-segmented23

23 (22) Leg 5: exopod 3-segmented; endopod 2-segmented. Caudal rami 3 times or more as long as wide (fig. 38)Lucicutia♀

Leg 5: exopod 3-segmented; endopod 1-segmented (fig. 39)Pseudhaloptilus♀

Leg 5: both rami 3-segmented (figs. 40, 41)24

24 (23) Leg 5: inner distal corner of exopod segment 2 extended forming a spinous process (fig. 40)Centropages♀

Leg 5: inner margin of exopod segment 2 with a saber-like spine (fig. 41) or a rudimentary seta25

25 (24) Left caudal ramus: one seta much longer and stronger than any other seta (fig. 42) (Heterorhabdidae)26

⊕ Fig.38 Lucicutia aurita female ☚   Fig.39 Pseudohaloptilus pacificus female ☚   Fig.40 Centropages gracilis female ☚   Fig.41 Heterorhabdus papilliger female ☚   Fig.42 Hemirhabdus grimaldi female ☚  

Caudal setae symmetrical32

26 (25) Right caudal ramus: one seta much longer than others. Maxillule: exopod about reaching distal end of endopod (fig. 43). Maxilla: without strong hooked setae (fig. 44)Disseta♀

⊕ Fig.43 Disseta palumbii female ☚   Fig.44 Disseta palumbii female ☚  

Right caudal ramus: all setae almost equal in length. Maxillule: exopod reaching far beyond distal end of endopod (fig. 45). Maxilla: with strong hooked seta (fig. 46)27

27 (26) Maxillule: 1 seta of praecoxal arthrite transformed into a large spine (fig. 47) Mesorhabdus

⊕ Fig.45 Hemirhabdus grimaldi female ☚   Fig.46 Hemirhabdus grimaldi female ☚   Fig.47 Mesorhabdus gracilis ☚  

Maxillule: none of the setae of praecoxal arthrite transformed into a large spine28

28 (27) Leg 5: exopod segment 2 extremely enlarged in male (fig. 48); exopod segment 2 with serrate distal margin in female (fig. 49)Heterostylites

⊕ Fig.48 Heterostylites longicornis male ☚   Fig.49 Heterostylites longicornis female ☚  

Leg 5: exopod segment 2 not enlarged in male and without serrate distal margin in female29

29 (28) Maxilla: distal praecoxal endite absent (fig. 50)Hemirhabdus

Maxilla: distal praecoxal endite present30

30 (29) Maxilla: one of the setae of each coxal endite strong and curved; setae of proximal coxal endite longer than setae of distal coxal endite (fig. 51)Neorhabdus

⊕ Fig.50 Hemirhabdus grimaldi female ☚   Fig.51 Neorhabdus latus ☚  

Maxilla: no setae of coxal endites curved; setae of proximal coxal endite shorter than setae of distal coxal endite (fig. 52)31

⊕ Fig.52 Paraheterorhabdus compactus ☚  

31 (30) Maxilla: basal endite with a large spine and a small seta (fig. 52)Paraheterorhabdus

Maxilla: basal endite with 2 large spines (fig. 53)Heterorhabdus

⊕Fig.53 Heterorhabdus insukae ☚  

32 (25) Pedigerous somites 4 & 5 separate33

Pedigerous somites 4 & 5 fused34

33 (32) Rostrum stout and sausage-like (fig. 54)Bathycalanus♀

Rostrum undivided and strongly pointed (fig. 55)Pseudocyclops♀

⊕ Fig.54 Bathycalanus richardi female ☚   Fig.55 Pseudocyclops ensiger ☚  

34 (32) Urosome 3-segmented (Augaptilidae, part.)35

Urosome 4-segmented37

35 (34) Maxillule reduced to a 3-segmented rod (fig. 56)Augaptilus♀

Maxillule well-developed36

36 (35) Mandible: gnathobase with many teeth, often cut obliquely (fig. 57). Rostrum most often small or absent, sometimes in the form of two long thin filaments. Setae on maxilliped simpleEuaugaptilus♀

⊕ Fig.56 Augaptilus longicaudatus female ☚   Fig.57 Euaugaptilus magnus ☚  

Mandible: gnathobase very elongated, with two thin curved teeth, and one smaller tooth between them (fig. 58). Rostrum strong, bifurcate, projecting forward (fig. 59). Setae on maxilliped coiled, carrying special shields (fig. 60)Centraugaptilus♀

⊕ Fig.58 Centraugaptilus horridus ☚   Fig.59 Centraugaptilus horridus ☚   Fig.60 Centraugaptilus horridus ☚  

37 (34) Leg 5: exopod segment 2 with a long nude saber-like seta on inner margin; endopod segment 3 with 5 setae (fig. 38)Lucicutia♀

Leg 5: exopod segment 2 without sabre-like seta on inner margin. Leg 5: endopod segment 3 with 4 or 6 setae38

38 (37) Rostrum in the form of two long slender filaments. Mandible: gnathobase a long rod, finely toothed at the tip (fig. 61). Leg 5: endopod segment 3 with 4 setaePseudaugaptilus♀

Mandible: gnathobase with 2-4 (sometimes more) teeth, dorsal tooth largest and far apart from others (fig. 62). Leg 5: endopod segment 3 with 6 setaeHaloptilus♀

⊕ Fig.61 Pseudaugaptilus orientalis ☚   Fig.62 Haloptilus longicornis female ☚  

39 (21) Leg 5: with coxa, basis, and 3-segmented exopod (fig. 34)Nullosetigera♀

Leg 5: with no more than 3 segments (figs. 35, 36)40

40 (39) Leg 5: 1-segmented, with 2 setae (fig. 35)41

Leg 5: with more than one segment (fig.36)42

41 (40) Leg 1: exopod segment 3 with 1 outer spine (fig. 63)Scutogerulus

Leg 1: exopod segment 3 with 2 outer spinesParaugaptilus♀

42 (40) Leg 5: 2-segmented; distal segment with 1 terminal spine, 1 inner plumose seta near distal end, 1 dorsal spine near distal margin (fig. 64)Metacalanus♀

⊕ Fig.63 Scutogerulus boettgerschnackae ☚   Fig.64 Metacalanus acutioperculum female ☚  

Leg 5: 3-segmented, terminal segment (exopod) with 1 distal spine; penultimate segment (basis) with an inner distal knob (endopod) bearing 2-3 setae (fig. 65)Arietellus♀

⊕Fig.65 Arietellus plumifer female ☚  

43 (20) Right antennule prehensile. Leg 5: endopod 3-segmented, with plumose hairs44

Left antennule prehensile48

44 (43) Leg 5: both legs nearly equal, without pincer (fig. 66)45

Left and right leg 5 highly different47

⊕Fig.66 Euaugaptilus hecticus male ☚  

45 (44) Pedigerous somites 4 & 5 fused. Caudal rami length/width ratio about 3Euaugaptilus hecticus♂

Pedigerous somites 4 & 5 separate. Caudal rami length/width ratio about 146

46 (45) Leg 5: biramous, with 3-segmented exopod and endopodBathycalanus♂

Leg 5: both legs uniramous and 3 to 5-segmented (fig. 67)Temorites♂

47 (44) Left leg 5, similar to other legs; right leg 5, exopod modified to form a pincer (fig. 68)Centropages♂

⊕ Fig.67 Temorites elongata male ☚   Fig.68 Centropages tenuiremis male ☚  

Leg 5: highly asymmetrical. Right leg 5 with 1 or 2-segmented exopod, distal segment bearing 2 strong, curved apical claws and 2-3 armature elements; endopod 1-segmented, unarmed, lobate or hook-like. Left leg 5 with 1 or 2-segmented exopod, armed with numerous processes on distal margin; endopod 1-segmented, with up to 5 marginal setae (fig. 69)Pseudocyclops♂

48 (43) Leg 5 symmetrical, uniramous and 4 to 5-segmented (coxa, basis, 2-3 exopod segments) on both legs (fig.70)Metacalanus♂

⊕Fig.69 Pseudocyclops sp. male ☚  

⊕Fig.70 Metacalanus acutioperculum male ☚  

Leg 5 asymmetrical, biramous on both legs, endopod may be rudimentary or lacking on one leg49

49 (48) Leg 5: both rami 3-segmented50

Leg 5: exopod 3-segmented; endopod rudimentary or lacking 61

50 (49) Left caudal ramus longer than right caudal ramus, with one seta much longer and thicker than the rest (fig. 42) (Heterorhabdidae♂)51

Caudal rami and setae symmetrical (Augaptilidae♂)57

51 (50) One seta on right caudal ramus much longer and thicker than the rest. Maxillule: exopod reaching distal end of endopod (fig. 43)Disseta♂

Right caudal setae subequal. Maxillule: exopod reaching beyond distal end of endopod52

52 (51) Right leg 5: basis with a long inner distal conical process, parallel to endopod; exopod segment 2 enlarged; exopod segment 2 with expanded inner margin (fig. 71)Heterostylites♂

These combined features absent53

53 (52) Right leg 5: inner margin of basis expanded, not forming a process; left leg 5: exopod segment 3 with an inner spine and a terminal pointed process (fig. 72)Hemirhabdus♂

⊕ Fig.71 Heterostylites longicornis male ☚   Fig.72 Hemirhabdus grimaldi male ☚  

These combined feature absent54

54 (53) Left leg 5: exopod segment 3 with a terminal spine; right leg 5: exopod segment 2 with a horizontal process, often extending from middle of inner margin (fig. 73)Neorhabdus♂

These combined features absent55

55 (54) Right leg 5: exopod segment 2 with an inner horizontal cylindrical process, often extending from distal end of inner margin; left leg 5: exopod segment 3 with a terminal process (fig. 74)Mesorhabdus♂

⊕ Fig.73 Neorhabdus latus male ☚   Fig.74 Mesorhabdus angustus male ☚  

These combined features absent 56

56 (55) Maxilla: basal endite with a large spine and a small seta (fig. 75)Paraheterorhabdus♂

Maxilla: basal endite with 2 large spines (fig. 76)Heterorhabdus♂

57 (50) Rostrum strong, bifurcate, and projecting downward (fig. 59). Maxilliped: terminal setae coiled, crooked-shaped, with special shields (fig. 77). Body thick-setCentraugaptilus♂

⊕ Fig.75 Paraheterorhabdus robustus female ☚   Fig.76 Heterorhabdus insukae ☚   Fig.77 Centraugaptilus horridus ☚  

These features absent58

58 (57) Leg 5: exopod smooth, without spines or setae, except for a final point; endopod segment 2 with 1 inner seta, segment 3 with 4 setae (fig. 78)Pseudaugaptilus♂

Leg 5: exopod with outer spines; endopod segment 2 with 1 inner seta, segment 3 with 6 setae59

59 (58) Maxillipid without shields on setae. Leg 5: exopod segment 2 without inner point (fig. 79)Haloptilus♂

⊕ Fig.78 Pseudaugaptilus longiremis male ☚   Fig.79 Haloptilus fertilis male ☚  

Maxillipid with numerous shields on setae (fig. 80). Leg 5: exopod segment 2 with at least one inner point, sometimes small (fig. 81)60

⊕ Fig.80 Augaptilus glacialis ☚   Fig.81 Augaptilus anceps male ☚  

60 (59) Maxillule reduced to 3-segmented rod (fig. 56)Augaptilus♂

Maxillule well developedEuaugaptilus♂

61 (49) Leg 5: left endopod large, leaf form; right endopod lacking (fig. 82)Nullosetigera♂

Leg 5: biramous on both legs (figs. 83, 84)62

⊕ Fig.82 Nullosetigera bidentata male ☚   Fig.83 Arietellus setosus male ☚   Fig.84 Paraugaptilus buchani male ☚  

62 (61) Leg 5: left endopod bilobed; last segment of both exopods not enlarged (fig. 83)Arietellus♂

Leg 5: left endopod not bilobed; last segment of both exopods widely enlarged (fig. 84)Paraugaptilus♂

Leg 5: biramous on both legs. Right leg with 2-sgemented exopod and endopod; left leg with 3-segmented exopod and endopod (fig. 85)Lucicutia♂

⊕ Fig.85 Lucicutia curta male ☚  

63 (6) Leg 5: biramous, endopod 2 or 3-segmented, with plumose setae; inner seta of exopod segment 2 modified into a slender spine (fig. 41)Lucicutia

Leg 5: endopod present or absent in one or both legs, if present, without plumose setae64

64 (63)  Legs 3 & 4: posterior surface of endopod naked65

Legs 3 & 4: posterior surface of endopod with rows of spinules (Paracalanidae)71

65 (64) Legs 3 & 4: endopod segment 2 with 2 setae, segment 3 with 7 setae (fig. 86)Temorites

Legs 3 & 4: endopod segment 2 with 1 seta, segment 3 with 5 setae66

66 (65) Leg 5 of female: biramous, endopod sometimes reduced to a spine (fig. 87). Leg 5 of male: left leg uniramous; right leg biramous, endopod reduced to an elongate spine, exopod broad, inner distal corner of distal segment forming a lobular process armed with spinous serration on distal margin (fig. 88)Temoropia

⊕ Fig.86 Temorites brevis female ☚   Fig.87 Temoropia mayumbaensis female ☚   Fig.88 Temoropia mayumbaensis male ☚  

Leg 5 of female: absent or uniramous. Leg 5 of male in different structure67

67 (66) Leg 5 of female: absent. Leg 5 of male biramous on both legs (fig. 89)Chiridiella

Leg 5 of female uniramous or absent. Leg 5 of male uniramous on right leg and biramous on left leg (fig. 90); uniramous on one side and absent on other side (fig. 91); or uniramous on both sides (fig. 92) (Eucalanidae)68

68 (67) Some or all of pedigerous somites 2-4 and urosomite 1 with spines on posterior margin (fig. 93). Leg 5 of male: right leg uniramous; left leg biramous (fig. 90)Rhincalanus

⊕ Fig.89 Chiridiella brachydactyla male ☚   Fig.90 Rhincalanus rostrifrons male ☚   Fig.91 Subeucalanus subtenuis male ☚   Fig.92 Eucalanus hyalinus male ☚   Fig.93 Rhincalanus nasutus female ☚  

No such spines present on pedigerous somites 2-4 and urosomite 1. Leg 5 of male: uniramous on one side and absent on other side (fig. 91), or uniramous on both sides (fig. 92)69

69 (68) Antenna: exopod segments 1 & 2 fused (fig. 94). Mandible: exopod inserted terminally on basis (fig. 95). Maxillule with 3 inner lobes (praecoxal arthrite, coxal endite and one of the basal endites) (fig. 96). Leg 5 of male: left leg uniramous; right leg absent (fig. 91)Subeucalanus

⊕ Fig.94 Subeucalanus subtenuis ☚   Fig.95 Subeucalanus subtenuis ☚   Fig.96 Subeucalanus subtenuis ☚  

Antenna: exopod segments 1 & 2 separate. Mandible: exopod inserted at or beyond midlength on basis (fig. 97) Maxillule with 4 inner lobes (praecoxal arthrite, coxal endite, and both basal endites)(fig. 98). Leg 5 of male: uniramous on both legs (fig. 92)70

70 (69) Mandible: basis with 1 or 3 setae, exopod inserted beyond midlength on basis (fig. 99). Urosome of female 4-segmented. Leg 5 of male: right leg extending to or beyond distal margin of left leg segment 2 (fig. 100)Eucalanus

⊕ Fig.97 Eucalanus hyalinus ☚   Fig.98 Eucalanus hyalinus ☚   Fig.99 Eucalanus hyalinus female ☚   Fig.100 Eucalanus hyalinus male ☚  

Mandible: basis with 2 or 4 setae, exopod inserted at midlength on basis (fig. 101). Urosome of female 3-segmented. Leg 5 of male: right leg not extending beyond distal margin of left leg segment 2 (fig. 102)Pareucalanus

⊕ Fig.101 Pareucalanus attenuatus female ☚   Fig.102 Pareucalanus attenuatus male ☚  

71 (64) Legs 2-4: exopod segment 3 without teeth on outer margin72

Legs 2-4: exopod segment 3 with teeth on outer margin (fig. 103)74

72 (71) Leg 1: basis without inner marginal seta. Leg 5 of female: uniramous on both legs, 3 to 4-segmented (fig. 104). Leg 5 of male: uniramous on both legs, left leg 5-segmented and right leg 4-segmented (fig. 105). Genital double somite of female swollen, projecting laterally (fig. 106). Anal somite of male well developed and swollen, usually longer than the combined length of urosomites 2 and 3 (fig. 107)Calocalanus

⊕ Fig.103 Paracalanus nanus female ☚   Fig.104 Calocalanus contractus female ☚   Fig.105 Calocalanus contractus male ☚   Fig.106 Calocalanus contractus female ☚   Fig.107 Calocalanus contractus male ☚  

Leg 1: basis with inner marginal seta. Leg 5 of female: present on one side, or rudimentary or knob-like. Leg 5 of male: left leg uniramous, right leg absent or knob-like. Genital double somite of female not swollen to project laterally. Anal somite of male not swollen73

73 (72) Leg 5 present on left leg only: 2-segmented in female (fig. 108); 5-segmented in male (fig. 109)Delibus

⊕ Fig.108 Delibus nudus female ☚   Fig.109 Delibus nudus male ☚  

Leg 5 of female: rudimentary or knob-like (fig. 110); of male: left leg elongate and right leg knob-like (fig. 111)Bestiolina

74 (71) Leg 5 of female reduced to knobs or lacking; of male only left leg present, uniramous(fig. 112)Acrocalanus

⊕ Fig.110 Bestiolina sinica female ☚   Fig.111 Bestiolina sinica male ☚   Fig.112 Acrocalanus gibber male ☚  

Leg 5 of female 2-segmented (fig. 113); of male: right leg 2- or 3-segmented, left leg 5-segmented (fig. 114)75

⊕ Fig.113 Paracalanus parvus female ☚   Fig.114 Paracalanus parvus male ☚  

75 (74) Rostrum with fine filaments. Leg 1: inner margin of basis with 1 seta. Leg 5 of female: inner terminal seta equal to or longer than its segment (fig. 113)Paracalanus

Rostrum bifurcate, short, and solid (fig. 115). Leg 1: inner margin of basis without seta. Leg 5 of female: terminal setae about half as long as its segment (fig. 116)Parvocalanus

76 (6) Leg 2: endopod 3-segmented. Leg 5 uniramous (fig. 117)187

⊕ Fig.115 Parvocalanus crassirostris female ☚   Fig.116 Parvocalanus crassirostris female ☚   Fig.117 Mecynocera clausi female ☚  

Leg 2: endopod 2-segmented77

Leg 2: endopod 1-segmented150

77 (76) Legs 2-4: posterior surface of rami (particularly endopod of legs 3 & 4) with numbers of spines (fig. 118)78

These legs without spines on posterior surface125

78 (77) Body wide, almost globular (fig. 119)Phaenna

⊕ Fig.118 Monacilla typica female ☚   Fig.119 Phaenna spinifera female ☚  

Body elongated, elliptical79

79 (78) Leg 5 absent (♀)80

Leg 5 present, sometimes small (♂or♀)84

80 (79) Legs 2-4: exopod segment 3 with 5 inner setae81

Legs 2-4: exopod segment 3 with 4 inner setae82

81 (80) Rostrum present, bifurcate, and thick (fig. 120)Monacilla♀

Rostrum absent Spinocalanus♀

82 (80) Genital double somite projecting ventrally (fig. 121)83

⊕ Fig.120 Monacilla typica female ☚   Fig.121 Scolecithrix danae female ☚  

Genital double somite without such a projection. Rostrum with 2 points (fig. 122)Bradyidius♀

83 (82) Posterior corners of prosome rounded in lateral view (fig. 123)Scolecithrix (danae)♀

⊕ Fig.122 Bradyidius sp. female ☚   Fig.123 Scolecithrix danae female ☚  

Posterior corners of prosome pointed or forming a hook-like process in lateral view and sometimes asymmetrical (fig. 124)Macandrewella♀

⊕Fig.124 Macandrewella cochinensis female ☚  

84 (79) Urosome 5-segmented, often with very short anal somite. Leg 5: asymmetrical, uniramous or biramous, often very elongated (♂)85

Urosome 4-segmented, often with very small anal somite. Leg 5: symmetrical, uniramous, 1 to 3-segmented (♀)108

85 (84) Legs 2-4: exopod segment 3 with 5 inner setae86

Legs 2-4: exopod segment 3 with 4 inner setae87

86 (85) Leg 5: exopod 3-segmented, ending in point; endopod styliform (fig. 125)Spinocalanus♂

Leg 5: exopod 2 or 3-segmented, not pointed; right endopod styliform, left endopod lamellate (fig. 126)Monacilla♂

87 (85) Leg 5: with one (fig. 127) or two legs (fig. 128), always uniramous88

⊕ Fig.125 Spinocalanus spinosus male ☚   Fig.126 Monacilla typica male ☚   Fig.127 Xanthocalanus agilis male ☚   Fig.128 Bradyidius angustus male ☚  

Leg 5: with one or two legs, at least one leg biramous92

88 (87) Leg 5: uniramous and on one side only (fig. 127)Xanthocalanus agilis♂

Leg 5: both legs uniramous; though rarely, endopod, if present, short and tapering (fig. 128)89

89 (88) Head with or without crest. Rostrum in bifurcated plate (fig. 129). Maxilla ending in a strong claw (fig. 130). Leg 5: left leg 5-segmented, right leg 3-segmented, left leg at least 5 times length of right leg 5 (fig. 131)Onchocalanus♂

⊕ Fig.129 Onchocalanus trigoniceps ☚   Fig.130 Onchocalanus trigoniceps ☚   Fig.131 Onchocalanus trigoniceps male ☚  

Not with the above structures90

90 (89) Rostrum with 2 sharp points. Maxilla: endopod with simple setae. Posterolateral corners of prosome sharply pointed Bradyidius (angustus, armatus)♂

Rostrum differently structured. Maxilla: endopod with setae in special structure. Posterolateral corners of prosome rounded91

91 (90) Rostrum: a shallow plate equipped with 2 digitiform filaments (fig. 132). Leg 5: right leg 3-segmented; left leg 5-segmented, nearly 3 times as long as right legPseudoamallothrix ovata♂

Rostrum with 2 filaments. Leg 5: left leg with 4-5 segments, right leg with 3-4 segments, length ratio of left leg to right leg variable, from 1 to 7 Xanthocalanus♂

⊕Fig.132 Pseudoamallothrix ovata ☚  

92 (87) Leg 5: on one or both legs, uniramous93

Leg 5: on both legs, biramous94

93 (92) Maxilla: without strong worm-like appendages, often with strong spiny hooked setae (fig. 133). Leg 5: both legs uniramous, styliformXanthocalanus♂

Maxilla: with worm-like appendages, without spiny hooked setae (fig. 134). Leg 5: right leg unirmous, left leg biramous, squat and thick without terminal stylet (fig. 135)Scolecithrix♂

94 (92) Right leg 5: longer than left leg 5, exopod 3-segmented, endopod 1-segmented, small; left leg 5: exopod 3-segmented, endopod 1-segmented (fig. 136)Farrania♂

⊕ Fig.133 Xanthocalanus agilis ☚   Fig.134 Scolecithrix danae ☚   Fig.135 Scolecithrix danae male ☚   Fig.136 Farrania frigida male ☚  

Leg 5 in different form (Scolecitrichidae♂)95♂

95 (94) Left leg 5: exopod longer than endopod96

Left leg 5: endopod longer than or equal to exopod in length103

96 (95) Right leg 5: exopod segment 3 unusually bifurcate and held at right angle to exopod segment 2 (fig. 137)Macandrewella♂

Leg 5 in different form97

97 (96) Left leg 5: distal part of exopod segment 2 forming a prehensile structure with segment 3; right leg 5: endopod usually well developed, reaching distal border of segment 1 (fig. 138)Scottocalanus♂

⊕ Fig.137 Macandrewella omorii male ☚   Fig.138 Scottocalanus thomasi male ☚  

Leg 5 different from the above structures98

98 (97) Right leg 5: exopod 2-segmented; right and left leg 5: endopod absent (fig. 139)Scolecitrichopsis♂

Left leg 5: exopod 3-segmented; endopod present or absent (Neocolecithrix?)99

⊕ Fig.139 Scolecitrichopsis ctenopus male ☚  

99 (98) Right leg 5: endopod absent (fig. 135)Scolecithrix♂

Right leg 5: endopod present100

100 (99) Right leg 5 shorter than left leg 5101

Right leg 5 longer than or subequal to length of left leg 5102

101 (100) Left leg 5: endopod 2-segmented (fig. 140)Amallothrix♂

Left leg 5: endopod 1-segmented (fig. 141)Scolecithricella♂

102 (100) Head with crest (fig. 142). Right leg 5: endopod 1-segmentedScolecocalanus♂

⊕ Fig.140 Amallothrix arcuata male ☚   Fig.141 Scolecithricella nicobarica male ☚   Fig.142 Scolecocalanus spinifer ☚  

Head without crest. Right leg 5: endopod 2-segmented Mixtocalanus♂

103 (95) Right leg 5: exopod segment 1 with a protrusion at inner distal corner (fig. 143)Scaphocalanus♂

Right leg 5: exopod segment 1 without protrusion at inner distal corner104

⊕Fig.143 Scaphocalanus major male ☚  

104 (103) Right leg 5: endopod 1-segmented; left leg 5: endopod 2-segmented105

Right leg 5: endopod 2-segmented; left leg 5: endopod 1-segmented106

105 (104) Right leg 5: exopod segment 3 distal border truncated; endopod longer than exopod segment 1 (fig. 144)Archescolecithrix♂

Right leg 5: exopod segment 3 with tapering distal end; endopod nearly as long as exopod segment 1 (fig. 145)Racovitzanus♂

106 (104) Leg 5 extremely slender; right leg 5 exopod: segment 1 more than 2 times combined length of segments 2 and 3, length/width ratio of segment 1 about 25:1 (fig. 146)Pseudoamallothrix emarginata♂

⊕ Fig.144 Archescolecithrix auropecten male ☚   Fig.145 Racovitzanus levis male ☚   Fig.146 Pseudoamallothrix emarginata male ☚  

Leg 5 not structured similarily107

107 (106)  Head with crestLophothrix ( frontalis & latipes)♂

Head without crestBradfordiella♂

108 (84) Maxilla: endopod with only ordinary setae (fig. 147)109

Maxilla with special appendages, worm-like, brush-like, besides normal setae, and sometimes hooked or spiny setae110

109 (108) Rostrum absent. Leg 5: 3-segmented, with 2 or 3 terminal spines (fig. 148)Farrania♀

⊕ Fig.147 Farrania frigida ☚   Fig.148 Farrania frigida female ☚  

Rostrum lobular. Leg 5: 2-segmented, distal segment with 1 long inner seta and 1 short terminal seta (fig. 149)Bradfordiella♀

110 (108) Legs 2-4 without conspicuous spinulation on posterior surface of rami, endopods not broadened. Leg 5: 2-segmented, usually with a short basis and a long exopod (fig. 150)Tharybis♀

⊕ Fig.149 Bradfordiella fowleri female ☚   Fig.150 Tharybis compacta female ☚  

Legs 2-4 with conspicuous spinulation on posterior surface of rami, endopods usually broadened. Leg 5 differently structured111

111 (110) Leg 5 absent112

Leg 5 present113

112 (111) Genital double-somite with swelling and operculum extending beyond posterior margin on ventral surface (fig. 121)Scolecithrix (danae)♀

Genital double-somite without swelling and operculum extending beyond posterior margin on ventral surface(fig. 151)Mixtocalanus♀

113 (111) Leg 5: rudimentary and asymmetrical(fig. 152)Scolecithrix (bradyi)♀

⊕ Fig.151 Mixtocalanus alter female ☚   Fig.152 Scolecithrix bradyi female ☚  

Leg 5: present on one or both legs114

114 (113) Leg 5: right leg absent; left leg 1-segmented, with a long terminal spine, at least 2 times longer than its segment (fig. 153)Scolecocalanus♀

⊕ Fig.153 Scolecocalanus spinifer female ☚   Fig.154 Scolecithricella longispinosa female ☚   Fig.155 Scaphocalanus major female ☚   Fig.156 Scottocalanus persecans female ☚   Fig.157 Pseudoamallothrix emarginata female ☚   Fig.158 Racovitzanus levis ☚  

⊕ Fig.159 Archescolecithrix auropecten ☚   Fig.160 Scolecithrix danae female ☚  

Leg 5: present on both legs and more or less symmetrical (figs. 154-158)115

115 (114) Leg 5: 1-segmented (figs. 154, 155)116

Leg 5: 2-segmented (figs. 156, 157)118

Leg 5: 3-segmented (rarely 4-segmented) (figs. 161-168)122

⊕ Fig.161 Onchocalanus trigoniceps ☚   Fig.162 Onchocalanus trigoniceps female ☚   Fig.163 Xanthocalanus agilis female ☚   Fig.164 Scolecitrichopsis ctenopu female ☚   Fig.165 Mixtocalanus alter female ☚   Fig.166 Lophothrix frontalis female ☚   Fig.167 Scaphocalanus major female ☚   Fig.168 Amallothrix arcuata female ☚  

116 (115) Pedigerous somites 4 & 5 separateMacandrewella♀

Pedigerous somites 4 & 5 fused117

117 (116) Leg 5: plate-like, wide and flat, with 3 spines, inner longest, usually 2 times or more as long as apical spine, outer spine minute or absent (fig. 154)Scolecithricella♀

Leg 5: elongate, usually length to width larger than 3, with 3 spines, inner spine usually less than 2 times as long as apical spine, outer spine small or absent (fig. 155)Scaphocalanus♀

118 (115)  Head with crest (S. rotundatus excepted). Leg 5: terminal segment with 1 short terminal spine and 1 very long seta near inner distal corner and longer than 2 times of its segment.(fig. 156)Scottocalanus♀

Head without crest 119

119 (118) Leg 5: with 1 long inner seta, 1 large apical spine, apical spine usually shorter than inner seta (fig.157)Pseudoamallothrix♀

Leg 5: with 1 long inner seta and 1 terminal spine or with only 1 inner seta not directed backwards 120

120 (119) Rostrum lingular, terminal margin with 2 short pointed processes (fig. 158)Racovitzanus♀

Rostrum with 2 filaments121

121 (120) Rostrum short, with 2 long filaments (fig. 159)Archescolecithrix♀

Rostrum long, bifurcated, with 2 filaments (fig. 160)Scolecithrix (danae)♀

122 (115) Maxilla: endopod typically 1 vermiform and 7 brush-like sensoriform filaments (fig. 161). Leg 5: 3-segmented, surface highly ornamented with spinules (fig. 162)Onchocalanus♀

Maxilla: armature of endopod different123

123 (122) Leg 5: terminal segment much narrower, often shorter than other segments, with 3-4 short spines, often bearing with spinules (fig. 163) Xanthocalanus♀

Leg 5: 3-segmented, segment 3 nearly as wide as and 0.8 times as long as segment 2, distal end extended forming a sharp pointed process, distal inner margin with a strong spine about 1.5 times as long as its segment (fig. 164)Scolecitrichopsis (ctenopus)♀

Leg 5: terminal segment as wide as or slightly narrower than others, nearly always longer, with 2-4 spines, of which the terminal one very long. Leg 5 smooth, or at the most with some outer spinules124

124 (123) Leg 5: distal segment ending in 2 well developed spines (fig. 165)Mixtocalanus♀

Leg 5: distal segment with 3, sometimes 4, well developed spines (fig. 166)Lophothrix♀

Leg 5: often with distal two segments partially fused, distal segment with 3 or 4 spines (fig. 167)Scaphocalanus♀

Leg 5: distal segment with 3 spines, inner spine longest, terminal spine usually less than one-half length of inner spine, outer spine minute, surface sometimes with spinules (fig. 168)Amallothrix♀

125 (77) Legs 2 & 3: coxa, basis and exopod broader than those of leg 4, basis with toothed distal margin enlarged like a calyx (fig. 169)Clausocalanus

Legs 2 & 3 without these features126

126 (125) Legs 3 & 4: outer spine of exopod segment 3 comb-shaped (fig. 170)Ctenocalanus

⊕ Fig.169 Clausocalanus farrani female ☚   Fig.170 Ctenocalanus vanus ☚  

These spines of the normal form127

127 (126) Leg 5: symmetrical (sometimes slightly asymmetrical) or absent (♀)128

Leg 5 asymmetrical (♂)139

128 (127) Leg 5 present, uniramous, 2 or 3-segmented129

Leg 5 absent130

129 (128) Leg 5: slightly asymmetrical, terminal segment finger-like, distal end forming an extended pointed process with serrated margins (fig. 171)Stephos♀

Leg 5: symmetrical, terminal segment with 1 outer, 1 inner, and 2 terminal spines (fig. 172)Neoscolecithrix♀

Leg 5: symmetrical or asymmetrical (with right leg longer than left leg), 2-segmented, distal segment (exopod) usually longer than proximal segment (basis), with 3 distal spines, and one outer spine (fig. 173)Undinella♀

130 (128) Head with a dorsal median spine (fig. 174)Gaetanus♀

Head without median spines (Aetideidae & Clausocalanidae)131

131 (130) Legs 3 & 4: exopod segment 3 with 5 inner setae. Leg 1: exopod segment 1 without outer spineMimocalanus♀

Legs 3 & 4: exopod segment 3 with 4 inner setae132

132 (131) Leg 4: inner margin of coxa with spines (fig. 175). Leg 1: exopod segments 1 & 2 incompletely fusedPseudochirella♀

⊕ Fig.171 Stephos pacificus female ☚   Fig.172 Neoscolecithrix japonica female ☚   Fig.173 Undinella gricei female ☚   Fig.174 Gaetanus latifrons male ☚   Fig.175 Pseudochirella dubia ☚  

Leg 4: inner margin of coxa naked or setose133

133 (132) Posterolateral corners of prosome rounded or with an obtuse point (fig. 176)134

Posterolateral corners of prosome terminated by a sharp point135

⊕Fig.176 Pseudocalanus elongatus female ☚  

134 (133) Leg 1: exopod segment 1 without outer spine; endopod segment 1 with 4 setaeMicrocalanus♀

Leg 1: exopod segment 1 with an outer spine; endopod segment 1 with 5 setaePseudocalanus♀

135 (133) Rostrum with 2 points. Pedigerous somites 4 & 5 separate or fused136

Rostrum with 1 point or lacking. Pedigerous somites 4 & 5 fused138

136 (135) Leg 1: exopod with 2 outer spines (fig. 177). Rostrum thick, the 2 points separated down to the base (fig. 178). Pedigerous somites 4 & 5 fusedAetideus♀

⊕ Fig.177 Aetideus divergens female ☚   Fig.178 Aetideus divergens female ☚  

Leg 1: exopod with 3 outer spines. Rostrum different. Pedigerous somites 4 & 5 separate or fused137

137 (136) Rostrum large with 2 strong points (fig. 179). Legs 2-4: terminal spine of exopod segment 3 with numerous equal teeth (fig. 180)Aetideopsis♀

⊕ Fig.179 Aetideopsis armata female ☚   Fig.180 Aetideopsis armata ☚  

Rostrum small, with 2 points. Antennule: setae of last 6 segments thick and annulated (fig. 181)Bradyidius♀

⊕Fig.181 Bradyidius armatus ☚  

138 (135) Rostrum with one point. Leg 1: exopod with 2 outer spinesGaetanus♀

Rostrum absent or reduced to blunt point. Leg 1: exopod 3-segmented, with 3 outer spinesChiridius♀

139 (127) Leg 5 uniramous; left leg: penultimate segment enlarged or not, final segment with 2 or many appendages (fig. 182)Stephos♂

Leg 5: all segments narrow, endopod present on one or both legs140

140 (139) Leg 5: present on left leg only (fig. 183)Aetideus♂

⊕ Fig.182 Stephos pentacanthos male ☚   Fig.183 Aetideus armatus male ☚  

Leg 5: present on both legs141

141 (140) Leg 5: right leg: exopod 2-segmented, endopod, if present, very short, 1-segmented; left leg uniramous, 5-segmented (fig. 184)Neoscolecithrix♂

Leg 5: right leg uniramous, left leg biramous (figs. 185, 186)142

Leg 5: uniramous on both legs (figs. 187, 188, 189, 190)143

Leg 5: biramous on both legs; endopod often very shortened (figs. 191, 192)146

⊕ Fig.184 Neoscolecithrix japonica male ☚   Fig.185 Tharybis macrophthalma male ☚   Fig.186 Undinella gricei male ☚   Fig.187 Microcalanus pusillus male ☚   Fig.188 Mimocalanus crassus male ☚   Fig.189 Chiridius gracilis male ☚   Fig.190 Pseudocalanus minutus male ☚   Fig.191 Aetideopsis armata male ☚   Fig.192 Bradyidius similis male ☚  

142 (141) Left leg 5: exopod segment 3 inserted terminally on segment 2 (fig. 185)Tharybis♂

Left leg 5: exopod segment 3 inserted subterminally on segment 2 (fig. 186)Undinella♂

143 (141) Leg 1: exopod with 2 outer spines144

Leg 1: exopod with 3 outer spines145

144 (143) Leg 5: left leg 5 or 6-segmented; right leg 3-segmented (fig. 187). Leg 1: exopod segment 3 with 4 setaeMicrocalanus♂

Leg 5 essentially with 5 segments on both legs but with various degrees of fusion in segmentation (fig. 188). Leg 1 exopod segment 3 with 5 setaeMimocalanus♂

145 (143) Rostrum absent. Leg 5: right leg longer than left leg (fig. 189)Chiridius♂

Rostrum present. Leg 5: right leg needle-like, as long as left leg (fig. 190)Pseudocalanus♂

146 (141) Head with median dorsal spine (fig. 174)Gaetanus♂

Head without median dorsal spine147

147 (146) Posterolateral corners of prosome roundedPseudochirella♂

Posterolateral corners of prosome extended into points148

148 (147) Rostrum with one point (fig. 193). Leg 1: exopod with 2 or 3 outer spinesGaetanus♂

Rostrum with 2 points. Leg 1: exopod with 3 outer spines149

⊕ Fig.193 Gaetanus latifrons female ☚  

149 (148) Leg 5: endopod rounded in one leg and tapering in the other (fig. 191)Aetideopsis♂

Leg 5: both endopods tapering (fig. 192)Bradyidius♂

150 (76) Head with median dorsal spine (figs. 174)Gaetanus♀

Head without median dorsal spine151

151 (150) Leg 5 absent (♀)152

Leg 5: asymmetrical (figs. 188) (♂)164

152 (151) Posterolateral corners of prosome extended to a sharp point153

Posterolateral corners of prosome rounded or bluntly pointed159

153 (152) Leg 4: coxa with one or many spinules on the inner margin (figs. 175). Prosome with at least 5 segmentsPseudochirella♀

Leg 4: coxa without spines or spinules154

154 (153) Rostrum absentChiridius♀

Rostrum present155

155 (154) Rostrum with one point (fig. 193)156

Rostrum with two points (fig. 122)157

156 (155) Genital double somite symmetricalGaetanus♀

Genital double somite more or less asymmetrical (sometimes very little) with 1 lateral or ventral spine (fig. 194)Undeuchaeta♀

⊕Fig.194 Undeuchaeta incisa female ☚  

157 (155) Pedigerous somites 4 & 5 separateAetideopsis♀

Pedigerous somites 4 & 5 fused158

158 (157) Rostrum smallBradyidius♀

Rostrum large, points separated to the base (fig. 178)Aetideus♀

159 (152) Leg 4: coxa with one or many spines or spinules on inner margin (figs. 175)160

Leg 4: coxa without spines or spinules161

160 (159) Antenna: endopod longer than half length of exopod (fig. 195). Leg 1: exopod 3-segmentedPseudochirella♀

Antenna: endopod at the most half the length of exopod (fig. 196) Leg 1: exopod 2-segmentedEuchirella♀

⊕ Fig.195 Pseudochirella obesa ☚   Fig.196 Euchirella galeata ☚  

161 (159) Antennule: without relatively long seta on some segments. Appendicular caudal seta poorly developed, all caudal setae normally setose162

Antennule with relatively long seta on some segments. Appendicular caudal seta well-developed, two of the caudal setae always naked, and usually much longer than the others (fig. 197)163

162 (161) Rostrum uniramous (fig. 198). Antenna: exopod 1.5-2.0 times longer than endopod. Maxillule normally developedChirundina♀

⊕ Fig.197 Euchaeta indica female ☚   Fig.198 Chirundina streetsi ☚  

Rostrum absent. Antenna: exopod equal to or slightly longer than endopod. Maxillule with reduction in lobes and setation (fig. 199)Chiridiella♀

163 (161) Antenna: exopod segment 2 without seta (fig. 200). Leg 1: exopod segment 1 without outer spineEuchaeta♀

⊕Fig.199 Chiridiella macrodactyla ☚  

⊕Fig.200 Euchaeta marina ☚  

Antenna: exopod segment 2 with a small inner marginal seta (fig. 201). Leg 1: exopod segment 1 with a small outer spineParaeuchaeta♀

⊕ Fig.201 Paraeuchaeta malayensis ☚  

164 (151) Leg 5: present on one side and uniramous (fig. 183)Aetideus♂

Right leg 5: endopod 1-segmented, club-shaped; left leg 5: endopod reduced to a minute process (figs. 202, 203)165

Leg 5: endopod well developed (figs. 204, 205)166

⊕ Fig.202 Euchaeta rimana male ☚   Fig.203 Paraeuchaeta russelli male ☚   Fig.204 Chirundina streetsi male ☚   Fig.205 Undeuchaeta incisa male ☚  

165 (164) Leg 5: exopod segment 3 on both legs tapering into a long spine (fig. 202)Euchaeta♂

Left leg 5: exopod segment 3 with a vestigial terminal spine (fig. 203)Paraeuchaeta♂

166 (164) Leg 5: exopod ends in a short pointed segment with a tuft of hairs on the inside167

Leg 5: without hairs, or when hairs present never arranged in tufts; left exopod rarely pointed169

167 (166) Leg 5: left and right endopods equally developed (fig. 204)Chirundina♂

Leg 5: left endopod shorter than right endopod (fig. 205)168

168 (167) Leg 5 simple, basis little dilated (fig. 192)Bradyidius similis♂

Leg 5 complex, basis very swollen (fig. 205)Undeuchaeta♂

169 (166) Leg 1: exopod 3-segmentedGaetanus♂

Leg 1: exopod 2-segmented; sometimes with traces of the area of fusion in first segment170

170 (169) Antenna: endopod more than half the length of exopod (fig. 195)Pseudochirella♂

Antenna: endopod at most half the length of exopod (fig. 196)Euchirella♂

171 (5) Leg 1: endopod 1-segmented172

Leg 1: endopod 2-segmented177

Leg 1: endopod 3-segmented182

172 (171) Leg 2: endopod 2-segmentedEurytemora

Leg 2: endopod 1-segmented173

173 (172) Leg 5 absent174

Leg 5 present175

174 (173) Antennule: some segments with long seta. Rostrum short and bifid (fig. 206) Leg 2: exopod 2-segmentedValdiviella♀

Antennule: all segments with normal setae. Rostrum absent. Leg 2: exopod 3-segmentedChiridiella♀

⊕ Fig.206 Valdiviella minor male ☚  

175 (173) Leg 5: symmetrical or asymmetrical (with right leg longer than left leg), 2-segmented, distal segment (exopod) usually longer than proximal segment (basis), with 3 distal spines, and one outer spine (fig. 173). Leg 5 of male: left leg biramous; right leg uniramous (fig. 186)Undinella

Leg 5: biramous on both legs176

176 (175) Leg 2: exopod 3-segmentedChiridiella♂

Leg 2: exopod 2-segmentedValdiviella♂

177 (171) Leg 5: biramous and 3-segmented in both sexes. Leg 5 of female: inner distal corner of segment 2 extended forming an elongate process (fig. 40). Right leg 5 of male: inner margin of exopod segment 2 extended, forming a pincer with segment 3 (fig. 68)Centropages

Leg 5: biramous with both exopod and endopod 1-segmented in female (fig. 207), uniramous and 4-segmented in male (fig. 208)Acartiella

Leg 5: uniramous in both sexes178

⊕ Fig.207 Acartiella sinensis female ☚   Fig.208 Acartiella sinensis male ☚  

178 (177) Caudal rami length/width ratio > 4179

Caudal rami length/width ratio < 3180

179 (178) Leg 5 of female: uniramous, 2-segmented, pointed terminally (fig. 209). Leg 5 of male: basis of left leg simple, without inner expansion; right leg: basis and exopod forming a chela (fig. 210)Tortanus

⊕ Fig.209 Tortanus dextrilobatus female ☚   Fig.210 Tortanus dextrilobatus male ☚  

Leg 5 of female: exopod bearing spines (fig. 211). Leg 5 of male: basis of left leg expanded medially; right leg: basis and exopod simple, not forming a chela (fig. 212) Temora

180 (178) Leg 5 of female: 2-segmented on both legs (fig. 213); of male, left leg 4-segmented and right leg 5-segmented (fig. 214)Acartia

⊕ Fig.211 Temora turbinata female ☚   Fig.212 Temora turbinata male ☚   Fig.213 Acartia bilobata female ☚   Fig.214 Acartia bilobata male ☚  

Leg 5 of female 3 or 4-segmented on both legs; of male 4-segmented on left leg and 3 or 4-segmented on right leg181

181 (180) Urosome in female 2-segmented. Both leg 5 of female 3 or 4-segmented (fig. 215); of male 4-segmented (fig. 216)Calanopia

⊕ Fig.215 Calanopia elliptica female ☚   Fig.216 Calanopia elliptica male ☚  

Urosome in female 3-segmented. Leg 5 of female 3-segmented on both legs, distal segment with 2 setae on inner margin and with terminal finer-like process, which may be finely serrate on one or both margins (fig. 217); or ending in spine-like process, in points, or in a single, long sea-like spine (fig. 219). Leg 5 of male 4-segmented on left and 3-segmented on right (fig. 182), not chelate, ending in long feather-like seta (fig. 218) or chelate (fig. 220)Candacia

⊕ Fig.217 Paracandacia truncata female ☚   Fig.218 Candacia tuberculata female ☚   Fig.219 Paracandacia truncata male ☚   Fig.220 Candacia tuberculata male ☚  

182 (171) Urosome 1 to 3-segmented (♀)183

Urosome 5-segmented (♂)185

183 (182) Leg 5 uniramous, 2-segmented, terminating in a point (fig. 209)Tortanus♀

Leg 5 biramous, endopod sometimes very small184

184 (183) Antennule with very plumose setae. Urosome symmetrical. Right caudal ramus fused with anal somite (fig. 221). Leg 5: exopod armed with several long setae (fig. 222)Pontellina♀

⊕ Fig.221 Pontellina plumata female ☚   Fig.222 Pontellina plumata female ☚  

Antennule with setae not very plumose. Urosome asymmetrical. Right caudal ramus separate from anal somite (fig. 223). Leg 5: exopod armed with several small and large spines (fig. 224)Pontellopsis♀

185 (182) Prehensile antennule very swollen, globular in the middle (fig. 225)186

⊕ Fig.223 Pontellopsis armata female ☚   Fig.224 Pontellopsis armata female ☚   Fig.225 Pontellopsis yamadae male ☚  

Prehensile antennule little swollen, not globular in the middleTortanus♂

186 (185) Urosomite 3: hump on right margin (fig. 226). Leg 5: basis with small outer seta (fig. 227).Pontellopsis♂

⊕ Fig.226 Pontellopsis yamadae male ☚   Fig.227 Pontellopsis yamadae male ☚  

Urosomite 3 without lateral humps (fig. 228). Leg 5: basis with long and very plumose outer seta (fig. 229)Pontellina♂

⊕ Fig.228 Pontellina morii male ☚   Fig.229 Pontellina morii male ☚  

187 (76) Leg 5 5-segmentedMecynocera

Leg 5 3-segmentedParacomantenna