Gondwanorchestia Myers & Pérez-Schultheiss 2020, gen. nov.

• Main Authors: Myers, James K. Lowry Alan A., Pérez-Schultheiss, Jorge
• Format: Text
• Language: unknown
• Published: Zenodo 2020
• Subjects: Biodiversity; Taxonomy; Animalia; Arthropoda; Malacostraca; Amphipoda; Talitridae; Gondwanorchestia; Lowry; Myers; Seta; Tristan; South Atlantic Ocean; Tierra del Fuego
• Online Access: https://dx.doi.org/10.5281/zenodo.3704871; https://zenodo.org/record/3704871

Gondwanorchestia gen. nov. Type species. Gondwanorchestia tristanensis sp. nov. , original designation. Included species. Gondwanorchestia includes 2 species: G. scutigerula (Dana, 1852) and G. tristanensis sp. nov. Category. Mascupod. Ecological type. Beach-hoppers, field-hoppers. Etymology. Gondwana reflecting the origin of this genus coupled with the stem orchestia . Diagnostic description ( male ). Head. Eye medium (1/5–1/3 head length). Antenna 1 long, reaching to at least midpoint of peduncular article 5 of antenna 2 . Antenna 2 peduncular articles slender or slightly incrassate (expanded) in male; article 3 without plate or process ventrally. Labrum epistome without many large robust setae over surface; median groove with robust setae. Mandible left lacinia mobilis 5-cuspidate, fifth article rudimentary. Maxilliped palp article 2 with distomedial lobe; article 4 apparently fused with article 3. Pereon. Gnathopod 1 sexually dimorphic; subchelate; posterior margin of carpus and propodus each with lobe covered in palmate setae propodus ‘subtriangular’ with well-developed posterodistal lobe, palm transverse. Gnathopod 2 subchelate; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; propodus palm oblique; dactylus not modified distally, blunt or acute, shorter than posterior margin of propodus. Oostegites setae with simple smooth tips. Pereopods 3–7 bicuspidactylate. Pereopod 4 subequal or slightly shorter than pereopod 3; dactylus thickened proximally with notch midway along posterior margin. Pereopod 5 short, less than 2/3 length of pereopod 6; dactylus long, slender. Pereopods 6–7 without row of short setae along posterior margin of dactyli. Pereopod 6 not sexually dimorphic; basis expanded; shorter than pereopod 7. Pereopod 7 sexually dimorphic basis broadly expanded, plate-like; merus and carpus very weakly expanded. Pleon. Pleonites 1–3 without dorsal spines. Pleopods 1–3 all well-developed. Epimera 1–3 slits absent; a row of slender setae along ventral margin of each epimeron. Uropod 1 male exopod not sexually dimorphic; peduncle distolateral robust seta absent; endopod with marginal robust setae in 2 rows; exopod with marginal robust setae in two rows. Uropod 2 rami without apical spear-shaped setae; exopod with marginal robust setae in 1 row; endopod with marginal robust setae in 2 rows. Uropod 3 ramus linear, weakly narrowing distally; shorter than peduncle . Telson as broad as long, tapering distally, entire, without groove, with marginal and apical robust setae, with 7–9 robust setae per lobe. Remarks. Gondwanorchestia is most similar to Orchestia, a genus that also occurs in southern South America (undescribed species, Myers & Lowry, in prep.). The main difference between these two genera is in the form of sexual dimorphism in male pereopod 7 and a prominent row of ventral setae on epimera 1–3 in Gondwanorchestia . In Gondwanorchestia , the basis is expanded, plate-like, and the merus and carpus are only slightly expanded. In Orchestia , the basis is unexpanded, while the merus and carpus are variously expanded and the ventral epimeral setae are absent. Distribution. Tristan da Cunha (Stephensen 1949); Tierra del Fuego (Dana 1852), South Atlantic Ocean. : Published as part of Myers, James K. Lowry Alan A. & Pérez-Schultheiss, Jorge, 2020, Gondwanorchestia tristanensis gen. nov. sp. nov., a new southern hemisphere genus and species of talitrid amphipod (Amphipoda, Senticaudata, Talitridae), pp. 375-381 in Zootaxa 4748 (2) on page 376, DOI: 10.11646/zootaxa.4748.2.9, http://zenodo.org/record/3698917 : {"references": ["Dana, J. D. (1852) Crustacea. Part II. United States Exploring Expedition during the years 1838, 1839, 1840, 1841, 1842 under the command of Charles Wilkes, U. S. N., 14, 689 - 1618.", "Stephensen, K. (1949) The Amphipoda of Tristan Da Cunha. Results of the Norwegian Scientific Expediton to Tristan Da Cunha 1937 - 1938, 19, 1 - 62."]}