Petalophthalminae, Czerniavsky, 1882

Wittmann, Karl J., 2020, Lophogastrida and Mysida (Crustacea) of the “ DIVA- 1 ” deep-sea expedition to the Angola Basin (SE-Atlantic), European Journal of Taxonomy 628, pp. 1-43 : 33-35

Key to genera and species of the subfamily Petalophthalminae

Distribution data modified and updated from San Vicente et al. (2014).

Petalophthalmidae with mandibular palp long, powerful, and prehensile; thoracopods 1–2 without exopod, thoracopods 3–8 with well-developed exopods; powerful subchelae formed by thoracic endopods 1–2; merus of endopod 1 with large endite; ischium of endopod 2 with again larger, subquadrangular endite; endopod 5 normal-sized or elongate; endopods 3–4, 6–8 normal or reduced to different degrees; female pleopods uniramous or biramous, male pleopods biramous; exopods of uropods with subterminal suture. Subfamily Petalophthalminae Czerniavsky, 1882 (panoceanic, depth 0–5500 m, mainly 100–500 m) ............................................................................................... 1

1. Outer margin of antennal scale with smooth portion ending at a single spine; eyes well developed .......................................................................................................................................... 9

– Antennal scale setose all around; cornea well developed or reduced ............................................... 2

2. Eyes without or with strongly reduced visual elements; terminal margin of telson without setae, with spines and in most species also with small teeth. Genus Petalophthalmus Willemoës-Suhm, 1874 . ........................................................................................................................................................... 6

– Cornea well developed, functional; terminal margin of telson with setae, spines, and with small teeth in between. Ipirophthalmus gen. nov............................................................................................... 3

3. Antennal scale 2-segmented; disto-lateral corner of the basal segment of the exopod of uropods with spines only, without seta; coxa of thoracic endopod 1 without endite ............................................... Ipirophthalmus liui ( Wang, 1998) gen. et comb. nov. (northern South China Sea, depth 194–219 m)

– Antennal scale unsegmented; disto-lateral corner of the basal segment of the exopod of uropods with several spines and one seta; coxa of thoracic endopod 1 with endite ............................................... 4

4. Telson mid-terminally emarginated by, if at all, up to 1% of its length, lateral margins with 21–22 spines each, terminal margin with two long setae, nine large, toothed spines and small teeth in between ..................................................... Ipirophthalmus macrops (Tchindonova & Vereshchaka, 1991) gen. et comb. nov. (W-Indian Ocean: off Madagascar, benthopelagic, depth 360–555 m)

– Telson mid-terminally emarginated by, if at all, up to 5% of its length, lateral margins with less than 20 spines each, terminal margin with four long setae, seven large, toothed spines and small teeth in between ............................................................................................................................................. 5

5. Telson mid-terminally emarginated by about 5% of its length, lateral margins with 12–15 spines each; eyestalk without ocular papilla; female pleopods biramous ............................ Ipirophthalmus caribbeanus (O.S. Tattersall, 1968) gen. et comb. nov. (Caribbean, mesopelagic, depth 329–366 m)

– Telson mid-terminally emarginated by about 2% of its length; lateral margins with 17–18 spines each; eyestalk with ocular papilla; female pleopods uniramous ...................................................... ................................................................ Ipirophthalmus oculatus ( Illig, 1906) gen. et comb. nov. (NW-Arabian Sea, W-Indian Ocean, off Japan, mesopelagic to bathybenthic, depth Ĺ 1200 m according to Illig 1906, compatible with 220–430 m indicated by San Vicente et al. 2014)

6. Anterior margin of carapace truncate, without rostrum; eyes without or with some small, scattered visual elements .................................................................................................................................. 8

– Anterior margin of carapace with triangular rostrum forming a longitudinal crista; eyes without visual elements .................................................................................................................................. 7

7. Eyes leaf-like; merus of thoracic endopod 2 with outer margin smooth, carpopropodus with three short setae on outer margin; thoracic endopod 5 with subequal praeischium, ischium and merus; carpus not shorter than propodus ........................................... Petalophthalmus armiger Willemoës- Suhm, 1875 (panoceanic, 56 ° N to 46° S, bathypelagic to abyssobenthic, depth 900–4572 m)

– Eyes elongate ovoid, dorsoventrally flattened by a factor of 1.4; merus of thoracic endopod 2 with five large setae on outer margin, carpopropodus with three long and six short setae on outer margin; merus of thoracic endopod 5 longer than combined praeischium and ischium; carpus less than half length of propodus .............................................................................................................................. ............................ Petalophthalmus cristatus sp. nov. (SE-Atlantic: Angola Basin, depth Ĺ 5497 m)

8. Eyes without eyestalks and without visual elements. Merus of thoracic endopod 2 with outer margin smooth, carpopropodus with three setae on outer margin; thoracic endopod 5 with subequal ischium, merus and carpus, each longer than praeischium, propodus 2-segmented with proximal segment half length of the distal one; telson with 25–37 spines on distal ¾ of each lateral margin ....................... .................................................................................... Petalophthalmus papilloculatus San Vicente, Frutos & Cartes, 2014 (NE-Atlantic: Galicia Bank off Iberian Peninsula, depth 1536–1809 m)

– Eyes with definite eyestalks, globular cornea containing some scattered visual elements not forming a compound sensory organ; merus of thoracic endopod 2 with outer margin bearing seven setae, carpopropodus with three long and six short setae along outer margin; endopod 5 with subequal praeischium, ischium and merus, carpus ¾ length of propodus; telson with 20–22 spines on distal half of each lateral margin ...................................................................................... Petalophthalmus papuaensis San Vicente & Corbari, 2015 (tropical W-Pacific: Bismarck Sea, depth 800–1065 m)

9. Thoracic endopods 6–8 rudimentary, with only 1–2 segments; thoracic endopods 3–4 terminating in two setae ......................................monotypic genus Parapetalophthalmus Murano & Bravo, 1998 ; species P. suluensis Murano & Bravo, 1998 (central Indo-Pacific: Sulu Sea, depth 285–306 m)

– Thoracic endopods 3–8 with more than four segments terminating in strong claw. Genus Pseudopetalophthalmus Bravo & Murano, 1997 .......................................................................... 10

10. Claw of thoracic endopods 1–2 fused with dactylus; thoracic endopods 3–5 with carpopropodus longer than merus; lateral margins of telson with four spines ..................... Pseudopetalophthalmus australis ( Panampunnayil, 1982) (west coast of Australia, nocturnal surface to subsurface plankton)

– Claw of thoracic endopods 1–2 not fused with dactylus; thoracic endopods 3–5 with carpopropodus shorter than merus; lateral margins of telson with 7–8 spines ..................... Pseudopetalophthalmus japonicus Bravo & Murano, 1997 (east coast of central Japan, epibenthic, depth 74–130 m)