Euryrhynchus taruman, Pachelle & Tavares, 2018

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) : 57-65

Euryrhynchus taruman sp. nov.

( Figs. 38–43 , 44A , 64B )

Euryrhynchus amazoniensis — Tiefenbacher 1978: 183 [partim]; Magalhães 1988: 46, tab. I [partim]; Magalhães & Walker 1988: 281, tab. I [partim].

Material examined. Holotype: ♂ (cl 6.0 mm), MZUSP 34330 , Brazil, Roraima, Igarapé Pupunha , 00°59.413'S 62°05.945'W, in submerged leaflitter and loose trunks, coll. J.B. Mendonça Jr., 05.ix.2011. Paratypes: Brazil: 12♂ (6.1– 3.9 mm), 8♀ (cl 5.1– 2.8 mm), 3♀ov (cl 4.7– 4.1 mm), MZUSP 34331, same collection data as for the holotype; 2♂ (cl 3.5, 2.8 mm), 2♀ (cl 4.8, 3.1 mm), MZUSP 34182, Roraima, Igarapé Caicubi, 00°58'18.3''S 62°06'35.5''W, in submerged leaflitter, coll. J.B. Mendonça Jr., ix.2011; 2♀ (cl 4.6, 3.7 mm), MZUSP 34183, Roraima, Igarapé Caicubi, 00°57.835'S 62°07.793'W, coll. J.B. Mendonça Jr., 11.ix.2011; 4♂ (cl 5.7– 4.1 mm), 4♀ (cl 4.4– 3.5 mm), MZUSP 34184, Roraima, Igarapé Kanaiuni, coll. J.B. Mendonça Jr., 29.viii.2011; 4♂ (cl 4.9–4.0 mm), MZUSP 34185, Roraima, Igarapé Pretinho, 00°56'23.0''S 62°06'16.0''W, in submerged leaflitter, coll. J.B. Mendonça Jr., 31.viii.2011; 5♂ (cl 6.0– 3.6 mm), 2♀ (cl 4.3, 3.3 mm), MZUSP 34186, Roraima, Igarapé Pretinho, 00°57'07.0''S 62°06'34.0''W, in submerged leaflitter and under loose trunks, coll. J.B. Mendonça Jr., 31.viii.2011; 3♂ (cl 6.0– 4.2 mm), 1♀ (cl 3.2 mm), MZUSP 34187, Roraima, Igarapé Branquinho, 00°56.370'S 62°06.253'W, coll. J.B. Mendonça Jr., 09.ix.2011; 4♂ (cl 6.4– 3.2 mm), 2♀ (cl 4.3, 2.9 mm), 1♀ov (cl 4.8 mm), MZUSP 34189, Roraima, Igarapé Caicubi, 00°59.957'S 62°06.314'W, in submerged leaflitter and vegetation, col. J.B. Mendonça Jr., 02.ix.2011; 1♂ (cl 6.0 mm), 1♀ (cl 4.0 mm), MZUSP 34190, Roraima, Igarapé Branquinho, 00°56'23.5''S 62°06'10.7''W, in submerged leaflitter and loose trunks, coll. J.B. Mendonça Jr., 31.viii.2011; 1♂ (cl 5.0 mm), MZUSP 34191, Roraima, Igarapé Pretinho, 00°55.875'S 62°06.566'W, coll. J.B. Mendonça Jr., 09.ix.2011; 2♀ (cl 4.8, 4.0 mm), MZUSP 34192, Roraima, Igarapé Pretinho, 00°56'23.0''S 62°06'16.0''W, in submerged leaflitter, coll. J.B. Mendonça Jr., 31.viii.2011; 3♂ (cl 5.8– 3.6 mm), 5♀ (cl 4.2–4.0 mm), MZUSP 34193, Roraima, Igarapé Pretinho, 00°55.988'S 62°06.511'W, coll. J.B. Mendonça Jr., 09.ix.2011; 1♂ (cl 4.6 mm), 2♀ (cl 5.0, 4.5 mm), MZUSP 34194, Roraima, Igarapé Paricá, 01°08'36.0''S 61°59'52.6''W, coll. J.B. Mendonça Jr., 10.ix.2011; 3♂ (cl 5.8– 5.2 mm), 1♀ (cl 4.7 mm), MZUSP 34195, Roraima, Igarapé Branquinho, 00°56'23.5''S 62°06'10.7''W, in submerged leaflitter and loose trunks, coll. J.B. Mendonça Jr., 31.viii.2011; 16♂ (cl 5.5– 3.2 mm), 8♀ (cl 4.6– 3.4 mm), 2♀ov (cl 4.5, 4.1 mm), MZUSP 34196, Roraima, Igarapé Caicubi, 00°58.717'S 62°06.211'W, in submerged leaflitter, coll. J.B. Mendonça Jr., 02.ix.2011; 3♂ (cl 6.7– 4.6 mm), 4♀ (cl 5.0– 3.9 mm), MZUSP 34197, Roraima, Igarapé Pretinho, 00°55.988'S 62°06.511'W, in submerged leaflitter, coll. J.B. Mendonça Jr., 09.ix.2011; 9♂ (cl 6.8– 3.2 mm), 13♀ (cl 6.3– 2.8 mm), MZUSP 34198, Roraima, Igarapé Pupunha, 01°00'36.4''S 62°05'19.6''W, in submerged leaflitter and loose trunks, coll. J.B. Mendonça Jr., 05.ix.2011; 9♂ (cl 6.5– 3.1 mm), 13♀ (cl 6.2– 2.6 mm), MZUSP 34199, Roraima, 1.9 Km from Vila de Caicubi, 01°01.538'S 62°05.079'W, temporary pool, in leaflitter, coll. J.B. Mendonça Jr., 11.ix.2011; 1♂ (cl 4.4 mm), MZUSP 34526, Roraima, Igarapé Caicubi, 01°01.418'S 62°06.277'W, in leaflitter, coll. J.B. Mendonça Jr., 03.ix.2011; 1♂ (cl 4.1 mm), 2♀ (cl 3.9, 2.9 mm), MZUSP 34527, Roraima, Igarapé Santa Fé, 01°00.571'S 62°06.191'W, coll. J.B. Mendonça Jr., 06.ix.2011; 2♂ (cl 5.8, 3.8 mm), 1♀ (cl 4.5 mm), MZUSP 34525, Roraima, Igarapé Caicubi, 00°59.264'S 62°06.191'W, in leaflitter, coll. J.B. Mendonça Jr., 02.ix.2011; 1♂ (cl 6.5 mm), OUMNH.ZC.2016-01-023, Roraima, Igarapé Pretinho, 00°55.988'S 62°06.511'W, in submerged leaflitter, coll. J.B. Mendonça Jr., 09.ix.2011; 1♂ (cl 6.3 mm), 1♀ov (cl 5.2 mm), OUMNH.ZC.2016-01-024, Roraima, Igarapé Caicubi, 00°59.957'S 62°06.314'W, in submerged leaflitter and vegetation, col. J.B. Mendonça Jr., 02.ix.2011; 2♂ (cl 5.9, 5.0 mm), 2♀ (cl 4.3, 4.2 mm), OUMNH.ZC.2016- 01-025, Roraima, Igarapé Pretinho, 00°57'07.0''S 62°06'34.0''W, in submerged leaflitter and under loose trunks, coll. J.B. Mendonça Jr., 31.viii.2011. Additional material: Brazil: 2♂ (cl 4.0, 3.1 mm), 2♀ (cl 3.6, 2.5 mm), MZUSP 34188, Amazonas, Igarapé Bandeira, 01°02.934'S 62°08.714'W, in submerged leaflitter and tree branches, coll. J.B. Mendonça Jr., 03.ix.2011; 1♂ (cl 5.1 mm), 1♀ (cl 3.3 mm), MZUSP 34200, Amazonas, São Gabriel da Cachoeira, left bank of Rio Negro, Igarapé Sabure, in submerged leaflitter, coll. J. Zuanon, J.M. Cunha & E. Trajano, 15.xii.2005; 1♂ (cl 4.3 mm), 1♀ (cl 2.5 mm), MZUSP 34329, Amazonas, São Gabriel da Cachoeira, right bank of Rio Negro, Igarapé Barixia, 00°07'24.6''S 67°08'04.8''W, in submerged leaflitter, coll. J.M. Cunha, E. Trajano & J. Zuanon, 14.xii.2005; 1♂ (cl 4.6 mm), MZUSP 34528, Amazonas, Igarapé Santa Fé, 01°00'29.1''S 62°12'20.6''W, in submerse leaflitter and loose trunks, coll. J.B. Mendonça Jr., 06.ix.2011; 2♂ (cl 4.0, 2.9 mm), 2♀ (cl 4.2, 3.5 mm), MZUSP 34529, Amazonas, Igarapé Santa Fé, 01°00.310'S 62°12.182'W, coll. J.B. Mendonça Jr., 01.ix.2011; 1♂ (cl 5.9 mm), MZUSP 34530, Amazonas, Igarapé Tubana, in leaflitter, 01°04.953'S 62°07.755'W, coll. J.B. Mendonça Jr., 29.viii.2011; 10♂ (cl 5.5–3.0 mm), 9♀ (cl 5.1–4.0 mm), MZUSP 34531, same collection data as previous lot; 1♂ (cl 3.3 mm), 1♀ (cl 3.7 mm), MZUSP 34532, Amazonas, Igarapé Tubana, 01°04.953'S 62°07.755'W, in submerged loose trunk, coll. J.B. Mendonça Jr., 29.viii.2011; 1♂ (cl 3.1 mm), MZUSP 34557, Amazonas, Igarapé Tubana, 01°04.953'S 62°07.755'W, in leaflitter, coll. J.B. Mendonça Jr., 29.viii.2011; 1♂ (cl 3.0 mm), 2♀ (cl 2.9, 2.9 mm), MZUSP 34558, Amazonas, Barcelos, Rio Negro, stomach content of Potamotrygon sp., coll. J.B. Mendonça Jr., 23.x.2008; 1♂ (cl 5.0 mm), MZUSP 34559, Amazonas, Manaus, Tarumã-Mirim, 02°55'S 60°13'W, in well, leaflitter, coll. J. Zuanon, 21.x.2004; 11♂ (cl 5.9– 4.4 mm), 5♀ (cl 5.1– 4.1 mm), INPA 2169, Amazonas, near Manaus, Igarapé Tarumã-Mirim, in submerged leaflitter, coll. C. Magalhães, 23.vi.1983; 1♂ (cl 6.0 mm), 5♀ (cl 4.0– 4.5 mm), INPA 2170, Amazonas, Manaus, Rio Negro, Igarapé do Almofada, coll. O. Collart, 24.ii.1989; 8♂ (cl 6.5– 4.6 mm), 5♀ (cl 4.4–4.0 mm), NHM 1988.84.14 (in part), Amazonas, Igarapé Tarumãzinho, in submerged leaflitter bank, coll. P.A. Henderson, 24.x.1984; 2♂ (cl 3.8, 3.5 mm), 3♀ (cl 4.0– 2.2 mm), MZUSP 22767, Rondônia, Porto Velho, Rio Pardo village, 09°32'55.6''S 63°57'11''W, in a 5.7 m depth well, coll. J. Cunha & J. Zuanon, 30.x.2006. Paratypes of E. amazoniensis ( sensu Tiefenbacher, 1978 ): Brazil: 6 ♀ (cl not measured), RMNH.CRUS.D.21749, Amazonas, right bank of Rio Amazonas, Lago Redondo, about 03°16'S 59°48'W, in roots and floating vegetation, coll. Antonio dos Santos, 20.viii.1963; 5♂ (cl not measured), 2♀ (cl not measured), ZSM 407/1, Amazonas, left bank of Rio Amazonas, igapó on lower Igarapé Tarumã-Mirim, about 20 km from Manaus, near confluence with Rio Negro, coll. U. Irmler, 19.vi.1971 – 04.v.1972.

Type locality. Igarapé Pupunha and surrounding igarapés on the left bank of Rio Jufari, south-west of Roraima ( Brazil).

Distribution. Brazil (Amazonas, Rondônia, Roraima) (present study) ( Fig. 64B ).

Description. Carapace smooth, non-setose. Branchiostegite finely granulated in large specimens, anterior margin produced beyond infra-orbital angle, branchiostegal groove weakly marked. Pterygostomial region rounded or broadly angular, not produced anteriorly. Antennal spine conspicuous, placed at same level than infra-orbital angle, partially obscuring infra-orbital angle. Hepatic and branchiostegal spines absent. Rostrum triangular in dorsal view, depressed dorsally, almost reaching or slightly overreaching distal margin of eyes, with row of few long simple setae along each dorsolateral margin ( Figs. 38A–C , 39A, C , 41A ).

Fourth thoracic sternite with transversal ridge slightly deepening medially, not produced. Fifth thoracic sternite with transversal ridge produced into broadly acute lobe medially.Sixth and seventh thoracic sternites with transversal ridge incomplete, interrupted medially. Eigth thoracic sternite with transverse ridge complete, median region produced anteriorly, V-shaped ( Fig. 38D, E ).

Pleon smooth, non-setose. First to fifth pleurae with postero-ventral margin rounded. Second pleura expanded in both sexes, overlapping both first and third pleurae by almost half width. Third to fifth pleurae with long simple setae on antero-ventral margins. Sixth pleura with postero-ventral margin angular, ventromesial margin with fringe of plumose setae. First to third sternites of males and immature females with median process, third one smallest, sometimes inconspicuous. Fourth to sixth sternites smooth, unarmed. Pre-anal plate smooth, lacking longitudinal carina, distally straight.

Telson broad, up to twice as long as wide. Lateral margins of telson nearly straight, parallel, not noticeably tapering towards distolateral angle. Distal region of telson broadly rounded, sometimes varying in length, fringed with numerous long, annulate, plumose setae. Distolateral margins of telson with row of few simple setae of variable length. Distolateral angle of telson with pair of cuspidate setae, mesial seta about twice as long as lateral seta. Dorsal surface of telson with two pairs of cuspidate setae, anterior pair usually placed on proximal third of telson length, posterior pair usually placed on medial third of telson length, inserted more mesially than anterior pair. Lateral margin of telson with few long, simple setae. Anal tubercles absent ( Fig. 38F ).

Eyes short, not overreaching proximal half of basal article of antennular peduncle. Cornea somewhat kidneyshaped in dorsal view, occupying the entire distal region and most of lateral region of ocular peduncle, basal line weakly marked, ommatidia hexagonal, ocellar spot (“ocellus”) absent. Ocular peduncles nearly immobile, basal articulation reduced, inconspicuous ( Fig. 38A–C ).

Antennular peduncle with stylocerite blunt, not produced distally, with cluster of long, simple setae on distodorsal region. Basal article with distolateral angle produced into sharp tooth, reaching or slightly overreaching distolateral projection of medial article, mesial margin fringed with plumose setae, proximal third with ventromesial sharp spine. Medial article almost as long as wide, fringed with plumose setae on both mesial and lateral margins, distolateral and distomesial angles bluntly produced. Distal article quadrate. Lower antennular flagellum long and uniramous. Upper antennular flagellum divided into two rami fused at base by one article; main ramus similar to lower antennular flagellum; accessory ramus shorter and thicker than other antennular flagella, with 3 to 6 free articles, increasing in number in large specimens, length of articles variable, aesthetascs restricted to distal margin of apical article ( Fig. 38A–C, G ).

Antenna with scaphocerite broad, about 1.5 times as long as wide, slightly overreaching antennular peduncle, lamella fringed with plumose setae, lateral margin straight or slightly convex, with sharp distal tooth reaching or slightly overreaching lamella. Carpocerite about 3 times as long as wide, reaching distal third of scaphocerite. Basicerite with sharp distolateral tooth reaching proximal fourth of carpocerite, ventral margin of basicerite produced anteriorly into broad, triangular tooth ( Fig. 38A, C ).

Mouthparts typical for genus. Third maxilliped pediform. Coxa with broad lateral plate, single arthrobranch present. Basis short, about 1/3 length of antepenultimate article of endopod. Endopod with 3 articles, furnished laterally with long simple setae; antepenultimate article longest, furnished mesially with simple setae; penultimate article about 0.7 times length of antepenultimate article, furnished mesially with rows of serrate setae; ultimate article shortest, about 0.8 times length of penultimate article, furnished mesially with rows of serrate setae. Exopod long, reaching proximal third of penultimate article of endopod, fringed with long plumose setae ( Fig. 38H ).

First pereopod slender, short, carpus and chela overreaching scaphocerite when fully extended. Merus about twice as long as ischium. Carpus about same length or slightly longer than merus. Chela about 0.7 times length of carpus, distal half furnished ventrally with tufts of long serrulate setae, fingers equal in length with palm, fingertips corneous ( Figs. 38I , 39D ).

Second pereopod stout, long, pair similar in form, equal or subequal in size in both sexes. Articles varying in size with age, usually slender in small individuals and stout in large individuals. Surface of ischium to propodus (sometimes also proximal region of dactylus) finely granulated, more conspicuous in large specimens. Merus fused with ischium, distoventral angles unarmed, smooth. Carpus in adults elongated in dorsal view, approximately 2.5 to 3 as long as wide, about same length or slightly longer than palm, distomesial angle with distal spine. Chela with proximal transverse constriction near articulation with carpus, fingers with pair of teeth on proximal half of each cutting edge, teeth varying in shape and size with age, fingertips corneous ( Figs. 40 , 41B–E , 44A ).

Third pereopod stouter than fourth and fifth pereopods. Merus about 1.5 as long as ischium. Carpus about 0.5 as long as merus. Propodus about 1.7 as long as carpus, ventral margin with 8 to 16 cuspidate setae, some more closely spaced on distal third of propodus, dorsal margin usually without cuspidate setae. Dactylus biunguiculate, at least 0.4 as long as propodus, dorsal margin indented, with single cuspidate seta, placed on mesial side ( Fig. 42A, B ).

Fourth pereopod similar to third pereopod, but thinner. Propodus with ventral margin furnished with 8 to 13 cuspidate setae, dorsal margin usually with single dorsomesial cuspidate seta on distal third, distodorsal angle without cuspidate seta. Dactylus dorsal margin indented, with subdistal pair of cuspidate setae ( Fig. 42C–E ).

Fifth pereopod similar to fourth pereopod, but longer. Carpus about 0.75 as long as merus. Propodus about 1.4 as long as carpus, ventral margin furnished with 9 to 13 cuspidate setae, distal third with 3 to 6 rows of serrate setae, dorsal margin without cuspidate seta. Dactylus about 0.4 as long as propodus, dorsal margin indented, with subdistal pair of cuspidate setae ( Fig. 42F, G ).

Male first pleopod protopodite furnished with short row of cuspidate setae on distomesial margin. Exopod at least twice as long as endopod, fringed with few plumose setae. Endopod furnished with cuspidate setae along distomesial margin, plumose setae absent, appendix interna absent. Second pleopod exopod longer than endopod, fringed with plumose setae. Endopod stout, twisted, modified into gonopod, distal half carinate dorsoventrally, tapering into triangular apex, mesial region with 3 rows of cuspidate setae, median row longer than ventral row, almost reaching distal third of endopod, dorsal row continuing on lateral margin of dorsal carina, setae curve irregularly as row approaches apex of endopod, blocking exopod mesially, mesial margin of dorsal carina with triangular lobe, appendix interna reduced, appendix masculina absent. Third to fifth pleopods protopodites furnished with few long setae on lateral margin. Endopod shorter than exopod, both fringed with plumose setae, appendix interna absent ( Fig. 43A–F ).

Female first and second pleopod endopods shorter than exopods, margins smooth or fringed with fewer plumose setae than exopod, appendix interna absent. Third to fifth pleopod protopodites furnished with few long setae on lateral margins. Endopods shorter than exopods, both fringed with plumose setae, appendix interna absent ( Fig. 43G–K ).

Uropod broad. Protopodite with well-developed lateral process, at least twice as long as mesial process, curving mesially, furnished distodorsally with transverse row of long simple setae, distomesial angle rounded or angular (sometimes produced into small tooth). Endopod narrower than exopod, fringed with long, annulate, plumose setae, distolateral margin with few long simple setae. Exopod fringed with long, annulate, plumose setae, distal margin somewhat truncated, straight, with cluster of few long simple setae on distolateral margin, diaeresis incomplete, with 4 to 10 cuspidate setae, growing in size towards mesial margin, increasing in number with age ( Figs. 38J , 39E, F ).

Etymology. The specific name “ taruman ” is a noun in apposition taken from Igarapé Tarumã-Mirim (or Tarumãzinho), a water course tributary of the Rio Negro, located west of Manaus (Amazonas, Brazil), from where the species has been often collected during ecological studies, albeit it not recognized as new.

Remarks. Euryrhynchus taruman sp. nov. shares similar key characters with E. amazoniensis and E. tuyuka sp. nov., including the armature of the second pereopod carpus and merus, and the male second pleopod with stout, twisted gonopod (see also Table 2 ). Nevertheless, E. taruman sp. nov. can be differentiated from the other two above mentioned species by the combination of the following characters: (i) pterygostomial region of carapace rounded or broadly angular, not produced anteriorly into a sharp tooth ( Figs. 38C , 39C ); (ii) appendices internae absent in both male and female pleopods (except for second pleopod of male) ( Fig. 43 ); and (iii) second pereopod carpus elongated in dorsal view, about 2.5 to 3 times as long as wide in large specimens ( Fig. 40 ). Euryrhynchus taruman sp. nov. differs from E. burchelli , E. pemoni and E. wrzesniowskii in having a stout and twisted gonopod, Fig. 43B, C (versus gonopod elongated and straight in the later three species, Figs. 29B, C , 30 , 37B, C , 60B, C, L , 61 ). The specimens of E. taruman sp. nov. from Rondônia ( Brazil) (MZUSP 22767) have reduced cornea on the ocular peduncles (see Fig. 39A–C ), a characteristic commonly found in young individuals of Euryrhynchus (see also Magalhães 1988). Indeed, the specimens from Rondônia present additional juvenile morphological traits, such as small carapace length (up to 4.0 mm), slender chelipeds, low number of rows of serrate setae on fifth pereopod, and predominantly few, slender cuspidate setae on uropodal diaeresis ( Fig. 39E, F ).

Figures

FIGURE 29. A–J, Euryrhynchus burchelli Calman, 1907:(A–F) male (cl 6.0 mm), Sítio São Bento, Roraima, Brazil (MZUSP 34207); (G–K) female (cl 6.0 mm) same lot as previous specimen. (A) Right first pleopod, ventral view; (B) Right second pleopod,ventral view;(C)Same,gonopod (endopod) and exopod, dorsalview; (D)Right third pleopod,ventral view;(E)Right fourth pleopod, ventral view; (F) Right fifth pleopod, ventral view; (G) Right first pleopod, ventral view; (H) Right second pleopod, ventral view; (I) Right third pleopod, ventral view; (J) Right fourth pleopod, ventral view; (K) Right fifth pleopod, ventral view. Plumose setae omitted.

FIGURE 30. A–F, Euryrhynchus burchelli Calman, 1907: male, Igarapé Sabure, left bank of Rio Negro, São Gabriel da Cachoeira, Amazonas, Brazil (MZUSP 34201). (A) Right second pleopod, ventral view; (B) Same, dorsal view; (C) Same, mesial view; (D)Same, detail of apex, dorsalview; (E)Same, appendix interna,lateral view;(F)Same,rows of cuspidatesetae, dorsal view.

FIGURE 37. A–K, Euryrhynchus pemoni Pereira, 1985: (A–F) male (cl 5.8 mm), Montagne des Singes, Cayenne, French Guiana (OUMNH.ZC.2013-05-0047); (G–K) female paratype (cl 5.3 mm), creek on the La Gran Sabana road, Venezuela (USNM 216242).(A) Right firstpleopod, ventral view; (B) Right second pleopod,ventral view; (C)Same, gonopod (endopod) and exopod, dorsal view; (D) Right third pleopod, ventral view; (E)Right fourth pleopod, ventral view;(F)Right fifth pleopod, ventral view; (G) Right first pleopod, ventral view; (H) Right second pleopod, ventral view; (I) Right third pleopod, ventral view; (J) Right fourth pleopod, ventral view; (K) Right fifth pleopod,ventral view.Plumose setae omitted.

FIGURE 38. A–J, Euryrhynchus taruman sp. nov.: male paratype (cl 6.0 mm), Igarapé Pupunha, Roraima, Brazil (MZUSP 34331). (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) Fourth sternite of pereon, median region, ventral view; (E) Fifth sternite of pereon, median region, ventral view; (F) Telson, dorsal view, setae omitted; (G) Right antennule, main and accessory rami, ventral view; (H) Right thirdmaxilliped, lateral view; (I) Right first pereopod,lateral view;(J) Right uropod,exopodand lateral process of protopodite, dorsal view, setae omitted.

FIGURE 39. A–F, Euryrhynchus taruman sp. nov.: (A–E) female (cl 3.8 mm), Rio Pardo village, Porto Velho, Rondônia, Brazil (MZUSP 22767); (F) female paratype (cl 5.1 mm), Igarapé Pupunha, Roraima, Brazil (MZUSP 34331). (A) Anterior regionof the body, dorsalview;(B)Same, eye and part of frontalmargin of carapace,setae omitted; (C)Same,lateral view;(D) Right first pereopod, lateral view; (E, F) Right uropod, exopod and lateral process of protopodite, dorsal view, setae omitted.

FIGURE 40. A–E, Euryrhynchus taruman sp. nov.: male paratype (cl 6.0 mm), Igarapé Pupunha, Roraima, Brazil (MZUSP 34331). (A) Left second pereopod, lateral view; (B) Same, chela and carpus, dorsal (mesial) view; (C) Right second pereopod, lateral view; (D) Same, carpus and distal region of merus, mesial view,setae and granulesomitted; (E)Same, chela and carpus, dorsal (mesial) view.

FIGURE 41. A–E, Euryrhynchus taruman sp. nov.: male (cl 3.0 mm), Igarapé Tubana, Amazonas, Brazil (MZUSP 34557). (A) Anterior margin of carapace, right pterygostomial region of carapace, lateral view; (B) Left second pereopod, lateral view; (C) Same, chela and carpus, dorsal (mesial) view; (D) Right second pereopod, lateral view; (E) Same, chela and carpus, dorsal (mesial) view.

FIGURE 42. A–G, Euryrhynchus taruman sp. nov.: male paratype (cl 6.0 mm), Igarapé Pupunha, Roraima, Brazil (MZUSP 34331).(A) Right third pereopod,lateral view; (B) Same, dactylus anddistal regionof propodus,lateral view; (C) Right fourth pereopod, lateral view; (D) Same, dactylus and distal region of propodus, lateral view; (E) Same, mesial view; (F) Right fifth pereopod, lateral view; (G) Same, dactylus and distal region of propodus, lateral view.

FIGURE 43. A–K, Euryrhynchus taruman sp. nov.: (A–F) male paratype (cl 6.0 mm), Igarapé Pupunha, Roraima, Brazil (MZUSP 34331); (G–K) female paratype (cl 5.1 mm), same lot as previous specimen. (A) Right first pereopod, ventral view; (B) Right second pereopod, ventral view; (C) Same, gonopod (endopod) and exopod, dorsal view; (D) Right third pereopod, ventral view; (E) Right fourth pereopod, ventral view; (F) Right fifth pereopod, ventral view; (G) Right first pereopod, ventral view; (H) Left second pereopod, ventral view; (I) Right third pereopod, ventral view; (J) Right fourth pereopod, ventral view; (K) Right fifth pereopod, ventral view.Plumose setae omitted.

FIGURE 60. A–L, Euryrhynchus wrzesniowskii Miers, 1878: (A–F) male (cl 5.4 mm) temporary pool in Skull Point, Mazaruni-Potaro district, Guyana (USNM 195308); (G–K) female(cl 5.0 mm), same lot as previous specimen; (L)male (cl 5.3 mm), tributary of Kuribrong River, Potaro-Siparuni, Guyana (MZUSP 26174).(A) Right first pleopod, ventral view; (B) Right second pleopod, ventral view; (C) Same, gonopod (endopod) and exopod, dorsal view; (D) Right third pleopod, ventral view; (E) Right fourth pleopod, ventral view; (F) Right fifth pleopod, ventral view; (G) Right first pleopod, ventral view; (H) Right second pleopod, ventral view; (I) Right third pleopod, ventral view; (J) Right fourth pleopod, ventral view; (K) Right fifth pleopod, ventral view; (L) Right second pleopod, gonopod (endopod) and exopod, dorsal view. Plumose setae omitted.

FIGURE 61. A–F, Euryrhynchus wrzesniowskii Miers, 1878: male, tributary of Kuribrong River, Potaro-Siparuni, Guyana (MZUSP 26174). (A) Right second pleopod, ventral view; (B) Same, mesial view; (C) Same, dorsal view; (D) Same, detail of apex, dorsal view; (E)Same, appendix interna, ventral view; (F) Same, medianrows of cuspidate setae, dorsal view.

FIGURE 64. Distribution maps for the South American euryrhynchids Euryrhynchus pemoni Pereira, 1985 (A) and Euryrhynchus taruman sp. nov. (B). The corresponding localities for each point on the maps are indicated on the Appendix 1F, G.

FIGURE44. A–B, Euryrhynchus taruman sp. nov., male (cl 5.9 mm) from Igarapé Tubana,tributary of Rio Jufari,Amazonas, Brazil (MZUSP 34530), lateral view (A); Euryrhynchus tomasi De Grave, 2007, male holotype (cl 5.0 mm), Crique Timothy, north-west of St Georges de l’Oyapock, French Guiana (NHM 2007.62), lateral view (B). Photographs kindly provided by Joel Braga de Mendonça Jr.(A) and Joachim Tomas (B).