Tethorchestia

Wildish, David J. & Lecroy, Sara E., 2014, Mexorchestia: a new genus of talitrid amphipod (Crustacea, Amphipoda, Talitridae) from the Gulf of Mexico and Caribbean Sea, with the description of a new species and two new subspecies, Zootaxa 3856 (4), pp. 555-577 : 569

Key for known Tethorchestia and Mexorchestia n. gen taxa from the Gulf of Mexico and Caribbean Sea

1. Peraeopods 3 – 7, articles with slender marginal robust setae; peraeopod 7, basis subquadrate, much broader than those of peraeopods 5–6; fossil forms (in amber)........................................................... T. palaeorchestes

- Peraeopods 3 – 7, articles with stout marginal robust setae; peraeopod 7, basis subrectangular, slightly broader than those of peraeopods 5–6; extant forms.............................................................................. 2

2. Antenna 2, flagellum longer than peduncle articles 3–5; telson with fewer than 10 dorsal and marginal robust setae............................................................................. T. karukerae (known from Guadeloupe)

- Antenna 2, flagellum shorter than, or subequal to, peduncle articles 3–5; telson with>12 dorsal and marginal robust setae. 3

3. Female gnathopod 2, basis with anterior margin evenly expanded; male peraeopod 7 with 2–4 distal groups of “comb” setae on propodus, with the largest less than half the length of the dactylus; uropod 1, peduncle lacking well-developed dorsolateral robust seta distally; dorsal pigment patterns usually present on anterior body...................................... 4

- Female gnathopod 2, basis with anterior margin narrowing distally; male peraeopod 7 with 4–7 distal groups of “comb” setae on the propodus, with the largest greater than half the length of the dactylus; uropod 1, peduncle with well-developed dorsolateral robust seta distally; dorsal pigment patterns lacking on anterior body....................................................................... T. antillensis (known from Bahamas, Cuba, Guadeloupe, Mexico, Florida south of 29 °N)

4. Adult male antenna 2 flagellum with 13–18 articles; adult female antenna 2 flagellum with 11–13 articles; oostegite 2 with 17–35 marginal setae; telson, each lobe with 1 dorsolateral robust seta; Up1 PL ratio>0.13; DPP in both sexes delimited as a diamond shape on the cephalon or may be absent, mid-line pleon pigments linear, quadrate or diamond-shaped, always present..................................................................................................... M. c. carpenteri n. subsp. (known from the Gulf of Mexico, from Florida, including the Atlantic coast—south of 28°32’N (Titusville), to Texas)

- Adult male antenna 2 flagellum with 18–21 articles; adult female antenna 2 flagellum with 14–17 articles; oostegite 2 with 15–19 marginal setae; telson, each lobe with 2 distal dorsolateral robust setae; Up1 PL ratio <0.13; DPP in both sexes diffused throughout the cephalon or may be absent, mid-line pleon pigments either linear, club-shaped or absent.................................... M. c. raduloviciae n. subsp. (known from the Caribbean Sea, including Belize and Chetumal, Mexico)