Euryrhynchoides Powell, 1976

Pachelle, Paulo P. G. & Tavares, Marcos, 2018, The freshwater shrimp family Euryrhynchidae Holthuis, 1950 (Crustacea: Decapoda: Caridea) revisited, with a taxonomic revision of the genus Euryrhynchus Miers, 1878, Zootaxa 4380 (1) : 12

Genus Euryrhynchoides Powell, 1976

Euryrhynchoides Powell, 1976: 885 . Gender masculine.

Euryrhynchoides — Powell 1977: 650; Holthuis 1993: 184; Pereira 1997: 3, tab. 5; De Grave 2007: 193; De Grave et al. 2008: 291; De Grave et al. 2009: 17; De Grave & Fransen 2011: 309; De Grave et al. 2015: 4; De Grave et al. 2017: 120.

Recognition characters. Rostrum with 2–3 teeth on dorsal margin, ventral margin smooth, non-dentate. Distomesial region of ocular peduncles not produced anteriorly, not reaching distal margin of cornea. Distolateral margin of stylocerite with cluster of simple setae. Accessory ramus of antennule with aesthetacs distributed on distal 3 articles. Third maxilliped with 2 arthrobranchs. Third and fourth pereopod carpus with cuspidate seta on distoventral margin. Third to fifth pereopod dactylus with cuspidate setae on dorsal margin. Male second pleopod with endopod not spatulate, modified into gonopod with accessory branch; appendices masculina and interna lacking. Uropodal exopod with more than 3 cuspidate setae on diaeresis, decreasing in size towards lateral margin.

Type species. Euryrhynchoides holthuisi Powell, 1976 , by monotypy.

Species included. Genus monotypic.

Distribution. Sierra Leone (Moyamba district) and Nigeria (Rivers State) ( Powell 1976; Nwadiaro 1984) ( Figs. 2 , 62 , blue circles).

Remarks. The genus includes the largest representatives of the family, with adult specimens up to 10.3 mm of carapace length (based on the examined specimens). Euryrhynchoides is unique within the family in having a dorsally dentate rostrum, the aesthetascs of the accessory ramus of antennule present on the distal and antepenultimate articles, and the second male pleopod with a biramous gonopod, but lacking an appendix interna ( Powell 1976: fig. 1B, F; Fig. 5 A, D, E ). Euryrhynchoides shares with Euryrhynchus the distomesial region of the ocular peduncles not anteriorly produced, the stylocerite with a cluster of setae on the distolateral margin, the presence of arthrobranch on the third maxilliped, the second male pleopod with a gonopod, and the uropodal diaeresis with more than 3 cuspidate setae ( Powell 1976: figs. 1C, D, 2H, 4B–D; see also Figs. 9 A , 11D, E, G , 13B , 17B–E ).

Figures

FIGURE 2. Distribution map of the family Euryrhynchidae Holthuis, 1950, illustrating the known geographic distribution of the genera Euryrhynchina Powell, 1976 (yellow circles) and Euryrhynchoides Powell, 1976 (blue circles) in West Africa, and Euryrhynchus Miers, 1878 (green circles) in South America.

FIGURE 5. A–F, Euryrhynchoides holthuisi Powell, 1976: male holotype (cl 10.3 mm), Jong (Taia) River, Sierra Leone (RMCA 53069). (A) Left antennule, main and accessory rami, lateral view; (B) Fourth sternite of pereon, median region, ventral view; (C) Fifth sternite of pereon, median region, ventral view; (D) Left second pleopod, exopod and gonopod (endopod), dorsal (frontal) view; (E) Same, gonopod (endopod), mesial view; (F) Left uropod, lateral process of protopodite, dorsal view.Arrows in D and E indicate the accessory branch.

FIGURE 9. A–I, Euryrhynchus amazoniensis Tiefenbacher, 1978: (A–H) male (cl 7.5 mm), Barcelos, Amazonas, Brazil (MZUSP 20014); (I) female (cl 5.7 mm), Igarapé Japiina, Amapá, Brazil (MZUSP 21431). (A) Anterior region of the body, dorsal view; (B) Same, eye and part of frontal margin of carapace, setae omitted; (C) same, lateral view; (D) Pereon, fourth to eighth sternites, ventral view; (E) Same, fourth sternite of pereon, median region, vental view; (F) Same, fifth sternite of pereon, median region, vental view; (G) Pleon, lateral view, setae omitted; (H) Same, sixth sternite of pleon, ventral view; (I) Pleon, lateral view, setae omitted.

FIGURE 11. A–G, Euryrhynchus amazoniensis Tiefenbacher, 1978: (A, B, D) male (cl 7.5 mm), Barcelos, Amazonas, Brazil (MZUSP 20014); (C) female (cl 5.7 mm), Igarapé Japiina, Amapá, Brazil (MZUSP 21431); (E) male (cl 2.5 mm), Igarapé Santa Fé, Amazonas, Brazil (MZUSP 34520); (F, G) male holotype (cl 5.0 mm), Ilha do Careiro, southeast of Manaus, Amazonas, Brazil(ZSM406/1).(A) Telson,dorsal view, distalplumose setaeomitted;(B) Same, distal region,dorsal view; (C) Telson, dorsal view, setae omitted; (D) Right uropodo, dorsal view, distal plumose setae omitted; (E) Same, exopod and part of protopodite, dorsalview, setaeomitted;(F)Same,lateral process of protopodite,dorsal view,setae omitted; (G) Same, diaeresis of exopod, dorsal view, setaeomitted.

FIGURE 13. A–E, Euryrhynchus amazoniensis Tiefenbacher, 1978: male (cl 7.5 mm), Barcelos, Amazonas, Brazil (MZUSP 20014).(A) Right second maxilliped, outer (frontal) view; (B) Right third maxilliped, lateral view; (C) Same, ultimate and part of penultimate article, mesial view; (D) Right first pereopod, lateral view; (E)Same, chela, dorsal (mesial) view.

FIGURE 17. A–M, Euryrhynchus amazoniensis Tiefenbacher, 1978: (A–H) male (cl 7.5 mm), Barcelos, Amazonas, Brazil (MZUSP 20014); (I–M) female (cl 5.7 mm) Igarapé Japiina, near Porto Grande, Amapá, Brazil (MZUSP 21431). (A) Right first pleopod, ventral view; (B) Right second pleopod, ventral view; (C) Same, gonopod (endopod) and exopod, dorsal view; (D) Same, lateral view; (E) Same, mesial view; (F) Right third pleopod, ventral view; (G) Right fourth pleopod, ventral view; (H) Right fifth pleopod, ventral view; (I) Right first pleopod, ventral view; (J) Right second pleopod, ventral view; (K) Right third pleopod, ventral view; (L) Right fourth pleopod, ventral view; (M) Right fifth pleopod, ventral view. Distal setae omitted.

FIGURE 62. Distribution maps for the African euryrhynchids. (A–B) Euryrhynchoides holthuisi Powell, 1976 (blue circles). (B) Euryrhynchina edingtonae Powell, 1976 (yellow circles) and Euryrhynchina puteola De Grave, Piscart, Tuekam Kayo & Anker, 2017 (orange circle).The corresponding localities for each point on the maps are indicated on the Appendix 1A–C.