A dichotomous key to the 18 valid species of Noodtiella is presented below. Swimming leg setal formulae for these species are compiled in Table 2.

1 P 1 endopod 2-segmented ........................................................................... 2

– P1 endopod 3-segmented ......................................................................... 12

2 P2–P4 endopod 2-segmented ..................................................................... 3

– P2–P4 endopod 3-segmented ................................................................... 13

3 P4 exopod 2-segmented.............................................................................. 4

– P4 exopod 3-segmented.............................................................................. 6

4 P2–P3 exp-3 with 4 setae/spines; P4 exp-2 with 5 setae/spines ......... mielkei

– P2–P3 exp-3 with 5 setae/spines; P4 exp-2 with 3 or 4 setae/spines ............ 5

5 P1 exp-2 with inner seta; P1 exp-3 with 3 elements; P3 exp-2 with inner seta; P4 exp-2 with 4 setae/spines .............................................................. gracile

– P1 exp-2 without inner seta; P1 exp-3 with 4 elements; P3 exp-2 without inner seta; P4 exp-2 with 3 setae/spines ...................................... frequentior

6 P1 enp-2 with 3 elements ........................................................................... 7

– P1 enp-2 with 4 elements ......................................................................... 14

7 P4 exp-2 with outer spine ....................................................... coquimbensis

– P4 exp-2 without outer spine...................................................................... 8

8 P2–P3 exp-1 without inner seta.................................................................. 9

– P2–P3 exp-1 with inner seta ..................................................................... 10

9 P4 exp-1 with short inner seta ......................................................... pacifica

– P4 exp-1 without inner seta ..................................................... problematica

10 P4 exp-1 with inner seta ........................................................................... 11

– P4 exp-1 without inner seta ................................................. larinconadensis

11 P4 exp-2 with inner seta; P5 exopod with 3 setae in female and 4 setae in male.............................................................................................. hoodensis

– P4 exp-2 without inner seta; P5 exopod with 2 setae in female and 3 setae in male............................................................................................. tabogensis

12 P1 exp-2 with inner seta; female P5 with outer endopodal spine fused to baseoendopod................................................................................... enertha

– P1 exp-2 without inner seta; female P5 with outer endopodal spine not fused to baseoendopod............................................................................... iscensis

13 P1 enp-2 with 4 elements; P4 enp-2 with inner seta; female P5 with outer endopodal spine fused to baseoendopod ..................................... intermedia

– P1 enp-2 with 3 elements; P4 enp-2 without inner seta; female P5 with outer endopodal spine not fused to baseoendopod................................... chilensis

14 P1–P4 exp-3 with 3 elements ....................................................... lusitanica

– P1–P4 exp-3 with 4 elements ................................................................... 15

15 P2–P4 enp-2 with 4 elements; P4 exp-3 with 4 elements..... arenosetelloides

– P2–P4 enp-2 with 5 elements; P4 exp-3 with 4 elements.......................... 16

– P2–P4 enp-2 with 6 elements; P4 exp-3 with 3 elements............... pectinata

16 Anal somite without paired multidentate lamellae; female P5 with outer endopodal spine not fused to baseoendopod............................................ wellsi

– Anal somite with paired multidentate lamellae; female P5 with outer endopodal spine fused to baseoendopod............................................. ornamentalis