Chroestia Marsden and Fenwick, 1984

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 : 5-6

Chroestia Marsden and Fenwick, 1984

Chroestia Marsden & Fenwick, 1984: 843 .

Type species. Chroestia lota Marsden & Fenwick, 1984 , monotypy.

Included species. Chroestia contains 1 species: C. lota Marsden & Fenwick, 1984 .

Category. Mascupod.

Ecological type. Beach-hoppers.

Habitat. In thick mats of Zostera and mangrove debris on a small sand-gravel beach at the top of an extensive mud flat area.

Diagnostic description (male). Based on Marsden & Fenwick, 1984.

Head. Antenna 2 peduncular articles slender or slightly incrassate. Mandible left lacinia mobilis 4-cuspidate. Labium without inner lobes. Maxilliped palp article 2 with distomedial lobe; article 4 reduced, button-shaped.

Pereon. Gnathopod 1 sexually dimorphic; subchelate; coxa much smaller that coxa 2; posterior margin of carpus and propodus each with lobe covered in palmate setae; propodus anterior margin with 3 or 4 groups of robust setae, ‘subtriangular’ with well-developed posterodistal lobe, palm transverse; dactylus simplidactylate. Gnathopod 2 subchelate; propodus palm acute, evenly rounded or sigmoidal, with or without proximal sinuses, without distal sinus; without proximal spine or thumb defining palm; dactylus short, recurved distally or attenuated distally. Pereopods 3–7 dactyli bicuspidactylate. Pereopod 4 significantly shorter than pereopod 3; carpus significantly shorter than that of pereopod 3; dactylus amplidactylate, thickened proximally with notch midway along posterior margin or short, thickened. Pereopod 6 shorter than pereopod 7, not incrassate; basis moderately expanded; male merus expanded, carpus not expanded. Pereopod 7 not incrassate; basis broadly expanded; posterior margin smooth or minutely serrate margin with numerous small robust setae, posterodistal lobe present, shallow, narrowly rounded; merus slightly expanded distally, subtriangular, anterior margin slightly convex; carpus unexpanded, subrectangular, subequal to or shorter than propodus; propodus broad, length 5.9 × width, propodus without large distal tuft of setae. Oostegites (female) setae with curled tips.

Pleon. Pleopods 1–3 all well-developed. Uropod 1 peduncle distolateral robust seta present (large); exopod without marginal robust setae; endopod with marginal robust setae in 1 row. Uropod 2 exopod with marginal robust setae in 1 row; endopod with marginal robust setae in 1 row or with marginal robust setae in 2 rows. Uropod 3 ramus shorter than peduncle. Telson completely cleft, apically incised, with at least 10 robust setae per lobe.

Remarks. Chroestia has no obvious relationship with any other platorchestiine genus. Based on the slender second antenna, simplidactylate first gnathopod and large number of setae on the telson it is most similar to the Japanese genus Miyamotoia . They differ most obviously in the pleopod development (all well-developed in Chroestia , all reduced in Miyamotoia ).

Distribution. Australia. Lota, Queensland ( Marsden & Fenwick 1984).