A new tribe, two new genera and three new species of Cypridopsinae (Crustacea, Ostracoda, Cyprididae) from Brazil Author Almeida, Nadiny Martins de 0C9E2B69-3A99-4185-9E24-017286D9D353 State University of Maringá (UEM), Centre of Research in Limnology, Ichthyology and Aquaculture (Nupélia), Graduate Programme in Ecology of Inland Water Ecosystems (PEA). Av. Colombo, 5790, CEP 87020 - 900. Maringá, PR, Brazil. Royal Belgian Institute of Natural Sciences, Freshwater Biology, Vautierstraat 29, 1000 Brussels, Belgium and Ghent University, Biology, K. L. Ledeganckstraat 35, 9000 Ghent, Belgium. nadinymartinsdealmeida@gmail.com Author Higuti, Janet 3A5CEE33-280B-4312-BF6B-50287397A6F8 State University of Maringá (UEM), Centre of Research in Limnology, Ichthyology and Aquaculture (Nupélia), Graduate Programme in Ecology of Inland Water Ecosystems (PEA). Av. Colombo, 5790, CEP 87020 - 900. Maringá, PR, Brazil. Royal Belgian Institute of Natural Sciences, Freshwater Biology, Vautierstraat 29, 1000 Brussels, Belgium and Ghent University, Biology, K. L. Ledeganckstraat 35, 9000 Ghent, Belgium. janethiguti@gmail.com Author Ferreira, Vitor Góis 1D07BA7A-7475-49CC-AD80-54FB2BF7CD61 State University of Maringá (UEM), Centre of Research in Limnology, Ichthyology and Aquaculture (Nupélia), Graduate Programme in Ecology of Inland Water Ecosystems (PEA). Av. Colombo, 5790, CEP 87020 - 900. Maringá, PR, Brazil. Royal Belgian Institute of Natural Sciences, Freshwater Biology, Vautierstraat 29, 1000 Brussels, Belgium and Ghent University, Biology, K. L. Ledeganckstraat 35, 9000 Ghent, Belgium. vgferreira@outlook.com Author Martens, Koen 9272757B-A9E5-4C94-B28D-F5EFF32AADC7 Royal Belgian Institute of Natural Sciences, Freshwater Biology, Vautierstraat 29, 1000 Brussels, Belgium and GhentUniversity, Biology, K. L. Ledeganckstraat 35, 9000 Ghent, Belgium. darwinula@gmail.com,kmartens@naturalsciences.be text European Journal of Taxonomy 2021 2021-08-04 762 1 48 http://dx.doi.org/10.5852/ejt.2021.762.1451 journal article 5012 10.5852/ejt.2021.762.1451 00a6c00a-00f0-4d37-9b84-c1f30c1b7341 2118-9773 5176858 10F0CC31-6B9D-4F67-B5E8-C2E72D560643 Brasilodopsis amazonica gen. et sp. nov. urn:lsid:zoobank.org:act: 52B493C0-AC19-49EB-95BD-77E4805A9957 Figs 13–17 “ Cypridopsis ” n. gen. 1 n. sp. – Higuti & Martens 2016 : appendix 1. Diagnosis LV and RV with well-developed anterior calcified inner lamella, with greatest height in both valves situated in the middle of the smoothly curved dorsal margin. A2 with the natatory setae reaching beyond the tip of the end claws and seta g absent. Valve surface densely set with rimmed pores in shallow pits. T1 with seta d present in female, absent in male. CR present in female only. Male prehensile palps asymmetrical; Rpp with first segment rather stout and second segment with triangular lobe; Lpp with first segment elongated and second segment sickle shaped. Hemipenis with ventral lobe of ms rounded and ventral lobe of ls bird head-shaped; with two loops in post-labyrinthal spermiduct. Table 4 (continued on next page). Localities (and some environmental characteristics) where the new genera and new species were collected. Bold represents the type localities of the new species. Abbreviations: WT = water temperature; EC = electrical conductivity; DO = dissolved oxygen; nd = no data; Bb = Brasilodopsis baiabonita gen. et sp. nov. ; Ba = Brasilodopsis amazonica gen. et sp. nov. ; Pr= Paranadopsis reducta gen. et sp. nov. ; Az = Azolla sp. ; Ea = Eichhornia azurea Kunth. ; Ec = Eichhornia crassipes (Mart.) ; Le = Lemna sp. ; Li = Limnobium sp. ; Lu = Ludwigia sp. ; Pa = Paspalum sp. ; Pi = Pistia sp. ; Ps = Pistia stratiotes L.; Ri = Ricciocarpus sp. ; Sap = Salvinia spp. ; Sa = Salvinia auriculata Aubl. ; Sm = Salvinia minima Baker ; Ut = Utricularia sp.

Locality name	Sample nr	S°	S’	S”	W°	W’	W”	Floodplain	Date	Substrate type	WT	EC	pH	DO	Bb	Ba	Pr
(ºC)	(µS. cm- 1 )	(mg. L- 1 )
1. Monte Cristo Lake	AMA 42	3	6	43.4	60	40	28	Amazon	15 May 2012	Ec	31.7	67.1	6.5	0.4	♀
2. Grande Lake	AMA 56	3	22	24.8	60	35	4.7	Amazon	16 May 2012	Ec, Pi, Sa, Az	31.5	54.1	6.6	1.2	♂ ♀
3. Poço Curuça Lake	AMA 59	3	3	17.6	60	34	6	Amazon	16 May 2012	Ec, Sap, Lu, Le, Az	31.5	51.8	6.6	1.4	♂ ♀
4. Cadete Lake	AMA 63	3	24	9.7	60	33	19.1	Amazon	16 May 2012	Pa, Az, Li, Sa	32	48.9	6.6	1.7	♀
5. Fuxico Lake	AMA 69	3	25	21.5	60	29	13	Amazon	16 May 2012	Ec	32.9	41.5	6.5	1.31	♀
6. Grande II Lake Jamauacá	AMA 73	3	22	33.1	60	17	55.1	Amazon	17 May 2012	Ec, Sm, Az	32.3	42.5	6.5	3	♀
7. Castanho Lake	AMA 79	3	24	4.6	60	13	26.9	Amazon	17 May 2012	Az, Sa, Lu	32.5	43.5	6.4	0.9	♂ ♀
8. Comprido Lake	AMA 82	3	14	0.3	59	57	53.8	Amazon	17 May 2012	Ec	31.5	65.1	6.7	1.8	♀
9. Crixas IV Lake	ARA 05	13	20	37.5	50	36	40	Araguaia	2 Nov. 2011	Pa, Pi, Ri	30	54.4	6.7	6.7	♀
10. Japonês Lake	ARA 09	13	21	33.1	50	36	42.9	Araguaia	3 Nov. 2011	Ec, Pa	29.8	38.8	6.8	5.4	♀
11. Japonês II Lake	ARA 63	13	25	23.6	50	38	57.4	Araguaia	10 Mar. 2012	Ec	29.8	50.2	6.9	5.8	♀
12. Piratinga Lake	ARA 24	13	3	58.9	50	34	57.6	Araguaia	4 Nov. 2011	Pa	29.5	26.5	7	6.8	♀
13. Luiz Alves I Lake	ARA 35	13	13	52.1	50	34	12.3	Araguaia	6 Nov. 2011	Pa, Sa, Az	29.2	33.8	6.7	5.9	♀
14. Luiz Alves II Lake	ARA 38	13	13	34.2	50	34	39.8	Araguaia	6 Nov. 2011	Pa	29.4	44.1	6.4	1.7	♀
15. Montaria I Lake	ARA 66	13	24	7.9	50	43	10.2	Araguaia	10 Mar. 2012	Pa	30.9	31.1	7	7.6	♀
16. Montaria II Lake	ARA 72	13	23	43.1	50	42	17.3	Araguaia	10 Mar. 2012	Pa	30.9	33.4	6.9	7.8	♀
17. Piranha Lake	ARA 77	13	2	53.5	50	37	32.2	Araguaia	11 Mar. 2012	Ut	29.3	46.5	6.8	3.8	♀
18. Varal Lake	ARA 80	13	0	58.4	50	36	12	Araguaia	11 Mar. 2012	Pa	28.5	39.1	6.6	3.9	♀
19. Comprido I Lake	ARA 93	12	52	2.3	50	35	37.9	Araguaia	12 Mar. 2012	Pa	28.9	21.8	6.5	4.3	♀
20. Comprido II Lake	ARA 99	12	51	8.8	50	34	4.8	Araguaia	12 Mar. 2012	Pa	29.5	27.6	6.64	6.24	♀
21. Curva Doleque Road, lake 4	PAN 8	19	31	34	57	2	27	Pantanal	3 Jun. 2003	Macrophytes	24	161	6	nd	♀
22. Carenda Forest Road, lake 1	PAN 9	19	43	39	57	4	19	Pantanal	4 Jun. 2003	Macrophytes	20.5	215	7	nd	♀
23. Carenda Forest Road, lake 2	PAN 11	19	41	33	57	2	34	Pantanal	4 Jun. 2003	Macrophytes	21	215	7	nd	♀
24. Corumba Road, lake 1	PAN 12	19	35	33	57	8	19	Pantanal	4 Jun. 2003	nd	20.8	185	7	nd	♀
25. Corumba Road, pool 2	PAN 14	19	35	38	57	8	3	Pantanal	4 Jun. 2003	nd	19.2	292	7	nd	♀
26. Corumba Road, lake 2	PAN 15	19	37	9	57	5	11	Pantanal	4 Jun. 2003	nd	18.5	nd	7	nd	♀
27. Corumba Road, pool 3	PAN 16	19	36	17	57	6	46	Pantanal	5 Jun. 2003	nd	21.1	nd	7	nd	♀
28. Corumba Road, lake 4	PAN 18	19	37	13	57	5	3	Pantanal	5 Jun. 2003	Macrophytes	22.8	415	7	nd	♀
29. Corumba Road, lake 5	PAN 20	19	37	53	57	3	43	Pantanal	5 Jun. 2003	Ec	23.5	235	7	nd	♀
30. Curva Doleque Road, lake 5	PAN 21	19	37	15	57	2	4	Pantanal	5 Jun. 2003	Macrophytes	24	225	7	nd	♀

Table 4 (continued).

Locality name	Sample nr	S°	S’	S”	W°	W’	W”	Floodplain	Date	Substrate type	WT	EC	pH	DO	Bb	Ba	Pr
(ºC)	(µS. cm- 1 )	(mg. L- 1 )
31. Curva Doleque Road, cattle pond	PAN 22	19	34	55	57	2	14	Pantanal	5 Jun. 2003	Mud	24	269	7	nd	♀
32. Vermelho River	PAN 23	19	37	2	56	57	48	Pantanal	5 Jun. 2003	Ea	20	59	6	nd	♀
33. Medalha Lake	PAN 25	19	34	32	57	0	51	Pantanal	7 Jun. 2003	Ea, Sap	24	155	6	nd	♀
34. BEP wetland 1	PAN 26	19	34	38	57	1	11	Pantanal	7 Jun. 2003	Macrophytes	24	192	7	nd	♀
35. Camp Road, pool 2	PAN 29	19	34	30	57	1	23	Pantanal	7 Jun. 2003	Grass	25	210	7.5	nd	♀
36. Camp Road, pool 4	PAN 31	19	34	34	57	1	7	Pantanal	7 Jun. 2003	Macrophytes	23	209	7	nd	♀
37. Formoso River	PAN 33	21	10	26.5	56	26	56	Bonito	10 Jun. 2003	Sand, mud	nd	nd	nd	nd	♂ ♀
38. Baia Bonita River	PAN 36	21	9	57.4	56	26	26	Bonito	10 Jun. 2003	Macrophytes	nd	nd	nd	nd	♂ ♀
39. Roadside pool	PAN 41	21	9	45.7	56	27	44.2	Pantanal	10 Jun. 2003	nd	nd	38	5	nd	♀
40. Arrozal Lake	PAN 43	19	2	3.7	57	28	13.9	Pantanal	20 Aug. 2011	Sa, Ea	24.9	84.8	7.4	0.3	♀
41. Tuiuiu Lake	PAN 45	18	48	30.2	57	39	20.4	Pantanal	21 Aug. 2011	Ec, Sa, Pi	21	54.3	7	5.1	♀
42. Caceres Lake	PAN 48	18	58	42.3	57	43	43.3	Pantanal	21 Aug. 2011	Ec, Sa, Pi	21.1	82.7	8.9	5.8	♀
43. Odila I Lake	PAN 52	19	27	47.6	57	24	52.6	Pantanal	22 Aug. 2011	Ec, grass, Sm, Pi	19.9	59.2	7.5	0.1	♀
44. Odila II / Jaburú Lake	PAN 54	19	28	28.5	57	24	57.7	Pantanal	22 Aug. 2011	Pi, Sa, Ec	22	56.9	7.5	4.8	♀
45. Baía Ponte Lake	PAN 58	19	30	11.7	57	25	39.1	Pantanal	22 Aug. 2011	Ec, Sa, Lu	21.3	57.7	7.5	3.5	♀
46. Baía Bugre Lake	PAN 60	19	30	43.3	57	23	27.3	Pantanal	22 Aug. 2011	Ec, Ea, Sap	20.4	119.4	7.6	4.6	♀
47. Miranda I River	PAN 63	19	25	38.2	57	18	58.4	Pantanal	23 Aug. 2011	Ea, Ec	20.1	162.2	8	4.9	♂ ♀
48. Miranda II River	PAN 66	19	25	7.7	57	18	49	Pantanal	23 Aug. 2011	Ea, Pi, Sap, Lu	19.7	140	8.1	4.5	♀
49. Miranda III River	PAN 69	19	26	23.1	57	18	21.4	Pantanal	23 Aug. 2011	Ec	20.3	162	7.9	3.9	♀
50. Miranda IV River	PAN 72	19	25	49	57	19	12	Pantanal	23 Aug. 2011	Sap, Ec	21	162.1	7.8	3.6	♀
51. Mirandinha Lake	PAN 75	19	24	16.6	57	18	3.5	Pantanal	24 Aug. 2011	Ec, Ea	20.3	51.1	7.3	4.1	♀
52. Figueira Lake	PAN 78	19	24	24	57	18	49.3	Pantanal	24 Aug. 2011	Sap, Ec	20.9	52.8	7.4	4.2	♀
53. Ilha Grande Lake	PAN 81	19	25	33.3	57	21	11.7	Pantanal	24 Aug. 2011	Ec	21.5	53.5	7.5	4	♀
54. Piuva Lake	PAN 87	19	26	52.7	57	23	9.9	Pantanal	24 Aug. 2011	Sap, Ec	21.4	63.8	7.8	4.5	♀
55. Corixão Lake	PAN 90	19	32	9.7	57	3	3.3	Pantanal	25 Aug. 2011	Ea, Pi, Li	21.5	102.1	7.8	1.5	♀
56. Paraguay River	PAN 130	19	24	48.9	57	18	51.3	Pantanal	27 Mar. 2012	Ec	nd	nd	nd	nd	♀
57. Albuquerque Lake	PAN 137	19	24	29.1	57	22	12.9	Pantanal	27 Mar. 2012	Ec	26.5	58.2	6	5.5	♀
58. Rebojão Lake	PAN 153	19	35	9.9	56	59	29.7	Pantanal	29 Mar. 2012	Lu	24.7	118.5	6.5	1.6	♀
59. Jacare Lake	PAR 21	22	47	10	53	29	56	Paraná	13 Mar. 2004	Littoral	27.3	48.6	6.4	5.3	♀
60. Caracu Stream	PAR 100	22	46	6	53	15	28	Paraná	17 Mar. 2004	Sand	27.2	54.3	6.9	6.4	♀
61. Manezinho Backwater	EC1	22	46	45.3	53	20	56.4	Paraná	2 Mar. 2007	Ec	28.9	52.6	6.8	4.1	♀	♀
62. Pombas Lake	PAR 1520	22	47	56.8	53	21	36.6	Paraná	22 Mar. 2018	Az	28.3	61	7	7.6	♀	♀
63. Ilha Pacu Lake	PAR 1522	22	47	28.3	53	19	53.6	Paraná	22 Mar. 2018	Ec	29	57	6.3	3.1	♀
64. Porcos Lake 65. Gavião Lake	PAR 1499 PAR 1514	22 22	41 40	57.6 49.3	53 53	14 12	39.4 59.8	Paraná Paraná	21 Mar. 2018 21 Mar. 2018	Ec Ec	31.3 32.6	20 14	6 5.8	1.5 2.3	♀	♀ ♀

Etymology The species is named after the area from which it is here described, namely Amazonia, Brazil . Material examined Holotype BRAZIL • ♂ ; Amazon River floodplain, Castanho Lake ; 3°24′4.6″ S , 60°13′26.9″ W ; 17 May 2012 ; J. Higuti leg.; with soft parts dissected in glycerine in a sealed slide, valves stored dry in a micropalaeontological slide; sample AMA 79; MZUSP 41852 . Allotype BRAZIL • ♀ ; Amazon River floodplain, Castanho Lake ; 3°24′4.6″ S , 60°13′26.9″ W ; 17 May 2012 ; J. Higuti leg.; with soft parts dissected in glycerine in a sealed slide, valves stored dry in a micropalaeontological slide; sample AMA 79; MZUSP 41853 . Paratypes BRAZIL • 2 ♂♂ ; Amazon River floodplain , Castanho Lake ; 3°24′4.6″ S , 60°13′26.9″ W ; 17 May 2012 ; J. Higuti leg.; with soft parts dissected in glycerine in sealed slides, LV and RV lost; sample AMA 79; MZUSP 41854 , MZUSP 41855 • 1 ♂ ; Amazon River floodplain , Castanho Lake ; 3°24′4.6″ S , 60°13′26.9″ W ; 17 May 2012 ; J. Higuti leg.; with soft parts dissected in glycerine in a sealed slide, LV stored dry in a micropalaeontological slide after use for SEM; sample AMA 79; MZUSP 41856 • 3 ♂♂ ; Amazon River floodplain , Castanho Lake ; 3°24′4.6″ S , 60°13′26.9″ W ; 17 May 2012 ; J. Higuti leg.; carapaces stored dry in micropalaeontological slides after use for SEM; sample AMA 79; MZUSP 41857 to MZUSP 41859 • 1 ♀ ; Amazon River floodplain , Castanho Lake ; 3°24′4.6″ S , 60°13′26.9″ W ; 17 May 2012 ; J. Higuti leg.; with soft parts dissected in glycerine in a sealed slide, both LV and RV lost; sample AMA 79; MZUSP 41861 • 1 ♀ ; Amazon River floodplain , Castanho Lake ; 3°24′4.6″ S , 60°13′26.9″ W ; 17 May 2012 ; J. Higuti leg.; with soft parts dissected in glycerine in sealed slides, valves stored dry in micropalaeontological slides; sample AMA 79; MZUSP 41860 • 1 ♀ ; Amazon River floodplain , Castanho Lake ; 3°24′4.6″ S , 60°13′26.9″ W ; 17 May 2012 ; J. Higuti leg.; with soft parts dissected in glycerine in sealed slides, valves stored dry in micropalaeontological slides after use for SEM; sample AMA 79; MZUSP 41862 • 3 ♀♀ ; Amazon River floodplain , Castanho Lake ; 3°24′4.6″ S , 60°13′26.9″ W ; 17 May 2012 ; J. Higuti leg.; carapaces stored dry in micropalaeontological slides after use for SEM; sample AMA 79; MZUSP 41863 to MZUSP 41865 . Other material examined BRAZIL • 2 ♀♀ ; Amazon River floodplain , Fuxico Lake ; 3°25′21.5″ S , 60°29′13″ W ; 16 May 2012 ; J. Higuti leg.; UEM-AMA 69; JH729 , JH730 • 3 ♀♀ ; Amazon River floodplain , Jamauacá Lake ; 3°22′33.1″ S , 60°17′55.1″ W ; 17 May 2012 ; J. Higuti leg.; UEM-AMA 73; JH731 to JH733 . Measurements of illustrated specimens See Table 2 . Description Remark: most of the material was slightly to considerably decalcified, so that dissections and SEM illustrations were difficult. The holotype male has two intact valves, but these were not used for SEM, because of the risk of damaging them. Other specimens were used for illustration, but no intact RV was available. Male LVi ( Fig. 13A–C – slightly distorted owing to decalcification) with well-developed anterior calcified inner lamella, posterior calcified inner lamella narrow; an inner list running along and parallel to anterior, ventral and posterior valve margin, inwardly displaced anteriorly and posteriorly; anterior inner list running almost to the dorsal margin, posterior inner list running to the dorsal margin. RVi (not illustrated) with well-developed anterior calcified inner lamella, posterior calcified inner lamella narrow; short anteroventral trace of an inner list and posteroventrally with an elevated inwardly displaced inner list and a submarginal selvage, both running parallel to the valve margin. Greatest height in both valves situated in the middle of the smoothly curved dorsal margin. CpRl ( Fig. 13E ) elongated; dorsal margin smoothly arched; with the greatest height in the middle; external valve surface densely set with rimmed pores in shallow pits ( Fig. 13D ). CpD ( Fig. 13F, H ) and CpV ( Fig. 13G ) sub-ovate; with greatest width situated behind the middle; anterior margin pointed, posterior margin rounded; LV overlapping RV along the anterior, ventral and posterior margins, with a broad flap in the middle. A1 (not illustrated) with seven segments. First segment large, ventrally with two long apical hirsute setae; dorsally with one short subapical hirsute seta, and with small Wouter’s organ. Second segment subquadrate, with one short dorsal seta and a small ventral Rome organ. Third segment with two apical setae (the shorter ventral seta almost reaching the tip of the fourth segment; the longer dorsal seta reaching the edge of the fifth segment). Fourth segment with three apical setae, two long dorsal ones, and one ventral seta, the latter slightly shorter than the length of the fifth segment. Fifth segment with three apical setae, two long dorsal setae and one short ventral seta, the latter reaching half the length of the sixth segment. Sixth segment with four long apical setae. Terminal segment with two long setae, one shorter, but still elongated, aesthetasc Ya and one shorter seta, the latter almost the same length of the aesthetasc Ya. A2 ( Fig. 14A–B ) with protopodite, exopodite and three-segmented endopodite. Protopodite ventrally with three setae: two unequal but short setae, one long apical seta reaching beyond the tip of the terminal segment. Exopodite reduced to a small plate with one long seta (reaching beyond the tip of the terminal segment) and two sub-equal short setae. First endopodal segment ventrally with aestethasc Y (more than ⅓ of the length of this segment), one long hirsute ventral seta (reaching beyond the tip of the terminal segment), and five hirsute natatory setae, reaching beyond the tip of the end claws, and one short accompanying seta, about ½ of the length of the second endopodal segment. Second endopodal segment with two unequal but long dorsal setae, one short hirsute ventral seta t; apically with three claws (G1, G2, z1) and three setae (G3, z2, z3). Terminal segment ( Fig. 14B ) with two claws, one long (GM) and one short (Gm) and one aesthetasc y3 with accompanying seta (slightly longer than the aesthetasc y3). Seta g absent. Rake-like organ (not illustrated) stout, solid, T-shaped, with seven apical teeth. Md-palp (not illustrated) with four segments. First segment with two long plumose setae (S 1 and S 2 ), one long smooth seta and one short smooth seta α. Second segment with three dorsal setae (two long and one shorter, ca ⅔ the length of the two longer ones); ventrally with one hirsute seta β and four long setae (three equally long, and one slightly shorter). Third segment with three groups of setae; dorsally one group of three unequal but long setae; laterally with one hirsute and stout apical seta γ and three smooth setae; ventrally with three unequal shorter setae. Terminal segment with three claws and three setae. Md-coxa (not illustrated) elongated, dorsally with a short seta, and with strong and apical teeth, interspaced with some setae. Mx1 (not illustrated) consisting of three masticatory lobes (endites), a two-segmented palp and a large branchial plate (not illustrated). Branchial plate elongated, with ca 16 respiratory rays, some quite short, others longer. First segment of palp with five setae (apically with four unequal but long setae and one short subapical seta, about ¼ of the longest one). Terminal segment of palp ca twice as long as basal width, apically with two claw-like setae and two setae. Third endite apically with two serrated claws and several setae. First endite at its base with two unequal setae and apically with ca five unequal, sideways directed bristles. Fig. 13. Brasilodopsis amazonica gen. et sp. nov. from Amazon River floodplain, ♂. A . LVi (MZUSP 41856). B . LVi, detail of anterior part (MZUSP 41856). C . LVi, detail of posterior part (MZUSP 41856). D . CpRl, detail of Cp surface (MZUSP 41857). E . CpRl (MZUSP 41857). F . CpD (MZUSP 41858). G . CpV (MZUSP 41859). H . CpD, detail of Cp surface (MZUSP 41858). Scale bars: A, E–G = 300 µm; B–D, H = 100 µm. Fig. 14. Brasilodopsis amazonica gen. et sp. nov. from Amazon River floodplain, ♂. A . A2, without the terminal segment (MZUSP 41854). B . A2, terminal segment (MZUSP 41854). C . T3 (MZUSP 41854). Abbreviations: see text and Material and methods. Scale bars: 50 µm. T1 protopodite ( Fig. 15A–C ) apically with a group of eight hirsute setae, and two short setae a inserted in the middle, seta d absent. Endopodites ( Fig. 15B–C ) asymmetrical prehensile palps: Rpp ( Fig. 15B ) with first segment rather stout, with two small subapical spines, second segment with triangular lobe, with uneven dorsal and slightly curved distal margin. Lpp ( Fig. 15C ) with first segment elongated, with two sub-apical spines, second segment sickle-shaped, with swollen basis and blunt distal part. T2 (not illustrated) with protopodite, a ‘knee’-segment and four endopodite segments. Protopodal segment without seta d1. ‘Knee’-segment with one short subapical seta d2. First endopodal segment with one apical hirsute seta e, reaching the middle of the second endopodal segment. Second endopodal segment with one apical hirsute seta f, reaching beyond the tip of the fifth segment. Third endopodal segment with one subapical hirsute seta g, approximately half of the length of the seta f. Terminal segment with one apical serrated claw h2, one short hirsute subapical seta h1 and a very short seta h3. T3 ( Fig. 14C ) with three segments. First segment with two unequal long setae d2 and dp and one shorter seta d1. Second segment with one subapical seta e, reaching beyond the middle of the third segment. Third segment medially with one seta f, about ½ the length of the third segment. Distal part of third segment with a pincer structure, one small spine-like structure (h1), one long subapical seta h3, about 1.5× the length of the broad seta h2, the latter set with spine-like setulae. Zenker’s organ ( Fig. 15D ) about 4 times as long as wide, with approximately 10 series of sw. Hemipenis ( Fig. 15E–M ) with ventral lobe of ms rounded, ventral lobe of ls bird head-shaped with bluntly pointed distal beak. Post-labyrinthal spermiduct with two loops: one large, one much smaller ( Fig. 15E ). Remark: the outline of the hemipenis can show some variability within one specimen and between specimens. Therefore, the hemipenis outlines of four males have been illustrated in Fig. 15F–M . Female Remark: also here, some specimens were decalcified and this caused some distortion of the single valves in the SEM illustrations. LVi ( Fig. 16A, C–D ), RVi ( Fig. 16B, E–F ), CpRl ( Fig. 16G ), CpD ( Fig. 16H ) and CpV ( Fig. 16I ) as in the male. A1, Rake-like organ, Md-coxa, Mx1 and T2 (not illustrated) as in the male. A2 ( Fig. 17A–B ) with protodopodite, exopodite and three-segmented endopodite. Protopodite ventrally with three setae: two unequal but short setae, one long apical seta reaching beyond the tip of the terminal segment. Exopodite reduced to a small plate with one long seta (reaching beyond the tip of the terminal segment) and two sub-equal short setae. First endopodal segment ventrally with aestethasc Y (ca ¼ of the length of this segment), one long hirsute ventral seta (reaching beyond the tip of the terminal segment), and five hirsute natatory setae, reaching beyond the tip of the end claws, and one short accompanying seta, about ½ of the length of the second endopodal segment. Second endopodal segment with two unequal, but long dorsal setae, four ventral setae t (two unequal but long, one ca e half of the length of the longest setae, and one short, approximately ¼ of longest setae); apically with three claws (G1, G2, G3) and three setae (z1, z2, z3). Terminal segment ( Fig. 17B ) with two claws, one long (GM) one short (Gm) and one aesthetasc y3 with accompanying seta, slightly longer than y3. Seta g absent. Fig. 15. Brasilodopsis amazonica gen. et sp. nov. from Amazon River floodplain, ♂. A . T1 (MZUSP 41852). B . Rpp (MZUSP 41852). C . Lpp (MZUSP 41852). D . Zenker’s organ (MZUSP 41852). E–G . Hemipenis (MZUSP 41852). H–I . Hemipenis (MZUSP 41856). J–K . Hemipenis (MZUSP 41854). L–M . Hemipenis (MZUSP 41855). Abbreviations: see text and Material and methods. Scale bars: 50 µm. Fig. 16. Brasilodopsis amazonica gen. et sp. nov. from Amazon River floodplain, ♀. A . LVi (MZUSP 41862). B . RVi (MZUSP 41862). C . LVi, detail of posterior part (MZUSP 41862). D . LVi, detail of anterior part (MZUSP 41862). E . RVi, detail of anterior part (MZUSP 41862). F . RVi, detail of posterior part (MZUSP 41862). G . CpRl (MZUSP 41863). H . CpD (MZUSP 41864). I . CpV (MZUSP 41865). Scale bars: A–B, G–I = 300 µm; C–F = 100 µm. Fig. 17. Brasilodopsis amazonica gen. et sp. nov. Amazon River floodplain, ♀. A . A2, without the terminal segment (MZUSP 41853). B . A2, terminal segment (MZUSP 41853). C . T1 (MZUSP 41861). D . T3 (MZUSP 41862). E . CR (MZUSP 41861). Abbreviations: see text and Material and methods. Scale bars: 50 µm. T1 ( Fig. 17C ) protopodite with a group of eight hirsute setae; two short seta a, one long seta d. Endopodite consisting of three long plumose setae. T3 ( Fig. 17D ) with three segments. First segment with two unequal long setae d2 and dp and one shorter seta d1. Second segment with one subapical seta e, almost smaller than the half of the third segment. Third segment medially with one seta f, about ⅓ the length of the third segment. Distal part of third segment with a pincer structure, one small spine-like structure h1, one long subapical seta h3, slightly longer than the broad seta h2, the latter set with spine-like setulae. CR ( Fig. 17E ) with elongated base (2–3 times as long as wide), one subapical short seta and one long apical seta (ca 3–5 times the length of the base). Differential diagnosis Cp sub-ovate, slightly more elongated and with smoothly curved dorsal margin (with blunt dorsal corner in Brasilodopsis baiabonita gen. et sp. nov. ). Posterior inner list in LV more slender than in B. baiabonita gen. et sp. nov. (see Table 3 ). External valve surface densely set with rimmed pores in shallow pits (smooth, with sparse setae and pores in B. baiabonita gen. et sp. nov. ). Hemipenis outline similar in both species, but distal segments of prehensile palps with subtle differences. Ecology and distribution Brasilodopsis amazonica gen. et sp. nov. was recorded only from the Amazon River floodplain, in association with several aquatic macrophytes. The range of the water temperature was between 31.5 and 32.9°C. The pH range remained slightly acid (6.4 and 6.7 – hence possibly the decalcified valves). The ranges of electrical conductivity and dissolved oxygen were from 41.5 to 67.1 µS. cm-1 , and from 0.4 to 3 mg .L- 1 , respectively (see Table 4 ).