Microthalestris Sars, 1905

Huys, Rony & Mu, Fanghong, 2021, Johnwellsia, a new intertidal genus of Parastenheliidae (Copepoda, Harpacticoida) from the Taiwan Strait, China, including a review of the family and key to genera, Zootaxa 5051 (1), pp. 236-318 : 282

Key to species of Microthalestris Sars, 1905

As pointed out above, Brady’s (1910) description of M. gracilis is rudimentary, his illustrations are far from precise and the armature formula of P2–P5 is misleading. The species is consequently omitted from the key and the reader is advised to consult the original description. The same applies to M. littoralis which is only known from the female and for which no information on swimming leg armature exists.

1. P3–P4 exp-1 without inner seta, exp-3 with eight and seven spines/setae, respectively; P 5 ♀ exopod with elements; P5 exopod ♂ 1-segmented with seven elements........................................ M. forficuloides ( Scott & Scott, 1894) .

– These characters not combined..........................................................................2.

2. P2–P3 enp-1 without inner seta; P3 endopod ♂ with inner seta on enp-3 [0.1.12 + apo]; caudal ramus seta IV with distinctly bulbous, basal swelling..................................................... M. bulbosa ( Gee, 2006) comb. nov.

– P2–P3 enp-1 with inner seta; P3 endopod ♂ without inner seta on enp-3 [1.1.02 + apo]; caudal ramus seta IV not modified.3.

3. P3 exp-3 armature 0.0.123; P5 exopod ♀ with six elements, inner margin and proximal two-thirds of outer margin virtually straight; P5 exopod ♂ 1-segmented, with six elements.................................... M. santacruzensis sp. nov.

– These characters not combined..........................................................................4.

4. P3 enp-3 with one inner seta............................................................................5.

– P3 enp-3 with two inner setae...........................................................................6.

– P3 enp-3 with three inner setae..........................................................................8.

5. P2–P3 exp-2 with inner seta; P2 enp-3 without inner seta; P4 exp-3 with three inner setae; P4 enp- 3 ♀ with two inner setae (021 in ♂); P5 exopod ♂ 1-segmented........................................... M. minuta ( Pallares, 1982) comb. nov.

– P2–P3 exp-2 without inner seta; P2 enp-3 with inner seta; P4 exp-3 with one inner seta; P4 enp-3 with one inner seta in both sexes; P5 exopod ♂ 3-segmented......................................................... M. variabilis sp. nov.

6. P3 exp-1 without inner seta; P5 exopod ♀ with six elements............................... M. campbelliensis sp. nov.

– P3 exp-1 with inner seta; P5 exopod ♀ with eight elements....................................................7.

7. P3–P4 exp-3 with three inner setae; P5 exopod ♂ with seven elements............................. M. polaris sp. nov.

– P3–P4 exp-3 with two inner setae; P5 exopod ♂ with six elements, outer seta of exp-1 absent or extremely reduced............................................................................................... M. sarsi sp. nov.

8. P4 enp-3 with one inner seta.............................................. M. antarctica ( Scott, 1912) comb. nov.

– P4 enp-3 with two inner setae............................................. M. costata ( Pallares, 1982) comb. nov.