Platorchestiinae, Lowry & Myers, 2022

Lowry, J. K. & Myers, A. A., 2022, Platorchestiinae subfam. nov. (Amphipoda, Senticaudata, Talitridae) with the description of three new genera and four new species, Zootaxa 5100 (1), pp. 1-53 : 2-3

Subfamily Platorchestiinae subfam. nov.

Type genus. Platorchestia Bousfield, 1982 , original designation.

Included genera. Platorchestiinae includes 15 genera: Cariborchestia Smith, 1998 ; Chroestia Marsden & Fenwick, 1984 ; Cocorchestia gen. nov.; Demaorchestia gen. nov.; Insularorchestia gen. nov.; Laniporchestia Lowry & Myers, 2019 ; Mauritiorchestia Green, Appadoo, Lowry & Myers, 2021 ; Mexorchestia Wildish & LeCroy, 2014 ; Miyamotoia Morino, 2020 ; Morinoia Lowry & Myers, 2019 ; Pickorchestia Lowry & Myers, 2019 ; Platorchestia Bousfield, 1982 ; Tethorchestia Bousfield, 1984 ; Vallorchestia Lowry, 2012 and Yamatorchestia Takahashi & Morino, 2020 .

Ecological types. Beach-hoppers, marsh-hoppers, sand-hoppers, driftwood-hoppers, moss-hoppers, field-hoppers, forest-hoppers, riparian-hoppers and cave-hoppers.

Diagnostic description (male). Based on Miyamoto & Morino (2004) and Lowry & Myers (Delta Database to World Talitroidea )

Head. Antenna 2 peduncular articles slender or incrassate; article 3 without plate ventrally. Mandible left lacinia mobilis 4-, 5, or 6- cuspidate. Maxilliped palp article 2 with distomedial lobe. Labium with or without inner lobes or with possible vestigial inner lobes.

Pereon. Gnathopod 1 subchelate; posterior margin of carpus and propodus each with lobe covered in palmate setae; dactylus simplidactylate or cuspidactylate. Gnathopod 2 subchelate; propodus palm acute or transverse, evenly rounded, rounded distally, sigmoidal or irregular, without large recurved robust setae lining palm, with or without sinuses along palmar margin, with or without a proximal spine or thumb defining palm; dactylus not modified distally and blunt or short or recurved distally, attenuated distally or slender, distally acute. Pereopods 3–7 bicuspidactylate. Pereopod 4 significantly shorter than pereopod 3 or subequal or slightly shorter than pereopod 3; carpus similar in length to pereopod 3 or significantly shorter than carpus of pereopod 3; dactylus amplidactylate or homobasidactylate, dactylus similar to pereopod 3 dactylus, not thickened proximally or notched or thickened proximally with notch midway along posterior margin or short with mini-wavy posterior margin. Pereopod 6 incrassate or not, basis expanded or moderately expanded. Pereopod 7 incrassate or not. Oostegites (female) setae with simple smooth tips or with spatulate tips.

Pleon. Pleopods 1–3 all well-developed or all reduced. Epimera 1–3 without slits along ventral margins. Uropods 1–2 rami without apical spear-shaped setae. Uropod 1 peduncle distolateral robust seta present or distolateral robust seta absent; exopod without marginal robust setae; endopod with marginal robust setae in 1 or 2 rows. Uropod 2 exopod with marginal robust setae in 1 or 2 rows; endopod with marginal robust setae in 1 or 2 rows. Uropod 3 peduncle with or without 1 or 2 long robust setae dorsal margin. Telson with 3 to 10 robust setae per lobe.

Remarks. The Platorchestiinae differ from the Floresorchestiinae in having no slits along the ventral margins of the epimera. They differ from the Pseudorchestoideinae in having no distal spear-shaped setae on the uropodal rami. The Platorchestiinae differ from the Talitrinae in having the combination of gnathopod 1 subchelate; with palmate lobes on the carpus and propodus but absent on the merus; uropod 1 without marginal robust setae on the exopodite.

Talitrinae that exhibit some combination of these character states are Talorchestia , Sinorchestia and Vietorchestia but they have a parachelate gnathopod 1 and Pyatokovestia, that has a palmate lobe on the merus. Aokiorchestia Morino, 2020 differs from the Platorchestiinae in having a row of marginal setae on the exopod of uropod 1. Talorchestia Dana, 1852 , also differs from the Platorchestiinae in having the male gnathopod 2 palm strongly acute with large, recurved robust setae along the palm. Vietorchestia is poorly described but apparently has no distomedial lobe on article 2 of the maxilliped palp. This character state would seemingly exclude the genus from the Talitridae , but its similarity to Talorchestia would suggest that if the structure is truly missing it is probably convergent with Talorchestia the loss being a homoplasy rather than a synapomorphy.

Distribution. Atlantic Ocean. USA Atlantic coast ( Bousfield 1973), Gulf of Mexico ( Wildish & LeCroy, 2014) and Caribbean Sea ( Smith 1998, Wildish & LeCroy 2014). Brazil, Venezuela ( Stebbing, 1903, Stephensen 1948). Atlantic Ocean Saint Helena Island ( Stock 1996), Ascension Island ( Stock & Biernbaum 1994) and the Azores (Mateus, Mateus & Afonso 1986). Baltic Sea, European coast, Mediterranean Sea ( Chevreux & Fage 1925, Bellan- Santini & Krapp-Schickel 1993); Israel ( Morino & Ortal, 1995). Pacific Ocean. Canada. China ( Hou & Li 2005), Hawaii ( Richardson 1991), Galapagos (Monod 1970), Costa Rica ( Stebbing, 1903, Shoemaker 1932, Monod 1970). Tonga ( Lowry & Bopiah, 2013). Australia: Queensland ( Marsden & Fenwick 1984), New South Wales, South Western Australia ( Serejo & Lowry 2008). Fiji ( Myers 1985). Eastern Russia ( Derzhavin 1937), Korea ( Kim & Kim 1987), Japan ( Jo 1988, Morino 2020, Takahashi et al. 2021), Taiwan ( Miyamoto & Morino 2004, Cheng et al. 2011, Kim, Jung & Min 2013). Indian Ocean. Mauritius (Green et al. 2021). Iraq ( Salman & Abdullah 1997). India ( Chilton 1921); South Africa ( Griffiths 1975).