A new tribe, two new genera and three new species of Cypridopsinae (Crustacea, Ostracoda, Cyprididae) from Brazil

We describe one new tribe, two new genera and three new species of the subfamily Cypridopsinae Kaufmann, 1900 from Brazilian fl oodplains. Brasilodopsis gen. nov. belongs in the nominal tribe Cypridopsini, and both new species in this new genus were found in both sexual and asexual populations. Brasilodopsis baiabonita gen. et sp. nov. has a wide distribution and was found in three of the four major Brazilian fl oodplains. Brasilodopsis amazonica gen. et sp. nov. was recorded only from the Amazon fl oodplain. Brasilodopsis baiabonita gen. et sp. nov. has a subtriangular shape in lateral view, whereas Brasilodopsis amazonica gen. et sp. nov. is more elongated and has more rounded dorsal margins in both valves, as well as more pronounced external valve ornamentation, consisting of rimmed pores in shallow pits. Paranadopsis reducta gen. et sp. nov. was found in asexual populations in the Upper Paraná River fl oodplain only and differs from other Cypridopsinae in the more elongated carapace, an A1 with strongly reduced chaetotaxy (hence the specifi c name) and the total absence of caudal rami in females. Because of these strong reductions in valve and limb morphology, Paranadopsini trib. nov. is created within the Cypridopsinae for this intriguing new genus and species.


from Brazil
Baker, Utricularia sp. were manually sampled, placed in plastic buckets (see Higuti et al. 2007;Campos et al. 2017) and washed to remove the ostracods associated with macrophytes. The samples were fi ltered in a net (160 μm mesh size) and were fi xed in alcohol, buffered with sodium tetraborate. The ostracods were sorted under a stereoscopic microscope and stored in 70% alcohol.

Morphological analyses
The valves were opened with entomological needles, the soft parts were removed from the carapace and the appendages separated and mounted on a slide in a drop of glycerine, covered with cover slip and sealed with nail polish. The separated valves and the illustrated carapaces were stored dry in micropalaeontological slides.
The illustrations (drawings) of the appendages of the ostracods were made with the aid of a camera lucida (Olympus UDA) attached to transmission light microscope (Olympus CX-41). The valves were illustrated with scanning electron microscopy (SEM, Fei Qanta ESEM, RBINS, Brussels) in different views (valves: internal and details; carapaces: lateral, dorsal, ventral and details). Illustrations of limbs for each species were made from different specimens, because no single dissection had all limbs in the right position, owing to the very small size of the animals. The type material and all illustrated specimens are stored in the Museum of Zoology of the University of São Paulo (MZUSP), São Paulo, Brazil. Some non-type and non-illustrated specimens will be stored at the State University of Maringá (UEM).

Abbreviations used in text, tables and fi
The nomenclature of the chaetotaxy of the limbs follows t he model proposed by Broodbakker & Danielopol (1982), revised for the A2 by Martens (1987) and for the T3 by Meisch (2000). Higher taxonomy of the Ostracoda follow the synopsis by Horne et al. (2002).

Etymology
The name of the new genus is a contraction of 'Brasilo', after Brazil, the country from which it is here described, and 'dopsis', referring to the stem of Cypridopsis.

Diagnosis
Cp sub-triangular in lateral view, with LV mildly overlapping RV along all sides. LV anteriorly, ventrally and posteriorly with a well-developed, largely inwardly displaced inner list, anteriorly with a submarginal selvage. RV anteriorly with submarginal inner list, posteriorly with one inner list and a marginal selvage. A2 with natatory setae well-developed, reaching well beyond the end claws. T1 in female with two short setae a; seta d present in female, absent in male; setae b absent in both sexes. T2 with one short seta d2, seta d1 absent. T3 distally with incompletely developed pincer organ, fourth segment fused with third segment. CR in female with cylindrical base.

Differential diagnosis
Brasilodopsis gen. nov. belongs to the cypridopsine genera where the LV overlaps the RV; only six other genera belong to that group (see Table 1). The new genus differs from Austrocypridopsis McKenzie, 1982, Cavernocypris Hartmann, 1964and Pseudocypridopsis Karanovic, 1999 by the long natatory setae on the A2 (short to very short in the other three genera). It further differs from Austrocypridopsis in the shape of the base of the CR, (triangular in Austrocypridopsis, cylindrical in Brasilodopsis gen. nov.) and in the shape of the valves in lateral view (rectangular in Austrocypridopsis). Cavernocypris also has a triangular base of the CR and furthermore lacks all inner lists and selvages on both valves, while the T1 has a seta b (missing in Brasilodopsis gen. nov.). Pseudocypridopsis also lacks inner lists and ALMEIDA N.M. et al., Cypridopsinae (Crustacea, Ostracoda) from Brazil selvages; while the CR is missing in both males and females. Brasilodopsis gen. nov. further differs from Cypridopsis s. str. Brady, 1867 by the general shape of the Cp (much broader in dorsal view in Cypridopsis), while the posteroventral inner list in the LV does not run (sub-)parallel to the valve margin in this latter genus (it does so in Brasilodopsis gen. nov.), while the anterior inner list in this valve runs less than halfway the anterior valve margin (all the way to the dorsal margin in Brasilodopsis gen. nov.). The base of the CR in Cypridopsis is triangular, while it is elongated in Brasilodopsis gen. nov. Neocypridopsis Klie, 1940 has a very different shape of the Cp (rather high and swollen in dorsal view), but more importantly has the fourth segment of the T3 separate from the third segment, much like in Candonidae. Tungucypridopsis Victor, 1983, fi nally, is ill-described which makes a comparison with the present new genus diffi cult. It appears to lack the inner lists on both valves, which are moreover much larger than in Brasilodopsis gen. nov. (0.6 mm versus 0.4 mm -see Table 2).
Cyprettadopsis Savatenalinton, 2020 (placed in a separate tribe by this author) has a similar valve shape, including inner lists, but has (incomplete) marginal septae and a series of large ventral pores along the outer lists, which are both absent in Brasilodopsis gen. nov., while the T3 also has a separate fourth segment (fused into an incomplete pincer in Brasilodopsis gen. nov.).

Diagnosis
Cp in dorsal view with LV overlapping RV at anterior and posterior sides. LV and RV with welldeveloped anterior calcifi ed inner lamella, with the greatest height in both valves situated in the middle of the dorsal margin. A2 with the natatory setae reaching beyond the tip of the end claws; seta g absent. T1 with seta d absent in males, present in females. CR present only in female. Male prehensile palps asymmetrical. Rpp with fi rst segment elongated and second segment with triangular lobe, Lpp with fi rst segment elongated and second segment sickle shaped. Hemipenis with ventral lobe of ms rounded and ventral lobe of ls bird head-shaped and with two loops in the post-labyrinthal spermiduct.

Etymology
The species is named after its type locality, Baia Bonita River in the State of Mato Grosso do Sul (Brazil).

Measurements of illustrated specimens
See Table 2.

Male
LVi ( 3G) with a triangular shape, with greatest height in the middle. CpD (Fig. 3H) external surface sparsely set with shallow pits and short setae and CpV (Fig. 3I) sub-ovate, with greatest width slightly behind the middle; anterior margin more pointed, posterior margin more rounded; LV overlapping RV along anterior, ventral and posterior margins, with an extended fl ap in the middle of the ventral side. A1 ( Fig. 4A) 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 (Wo). Second segment subquadrate, with one short dorsal seta and a small ventral Rome organ (R). Third segment with two apical setae (the shorter ventral seta almost reaching the tip of the fourth segment; the longer dorsal seta slightly shorter than the length of the fi fth segment). Fourth segment with three apical setae, two long dorsal ones, and one ventral seta, the latter slightly shorter than the length of the fi fth segment. Fifth segment with three apical setae, two long dorsal setae and one short ventral seta, the latter reaching half the length of the terminal segment. Sixth segment with four long apical setae. Terminal segment with two unequally long setae, aesthetasc Ya and one shorter seta, the latter almost the same length of the aesthetasc Ya. A2 ( Fig. 4C-D) 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 fi ve 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. 4D) 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.
Md-palp ( Fig. 5B) 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 ( Fig. 5A) elongated, dorsally with a short seta, and with strong and apical teeth, interspaced with some setae. Mx1 ( Fig. 5C -chaetotaxy not complete) 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 fi ve setae (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 fi ve unequal, sideways directed bristles.    6D) 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 tip of the second endopodal segment. Second endopodal segment with one apical hirsute seta f, reaching beyond the tip of the terminal 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. 6E) with three segments. First segment with two unequal long (d2, dp) and one shorter setae d1. Second segment with one subapical seta e, reaching 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 twice of the length of the broad seta h2, the latter set with spine-like setulae.
Zenker's organ (Fig. 6F) about four times as long as wide, with ca 10 sw. Hemipenis ( Fig. 6G) with distal lobe of ms rounded, distal lobe of ls bird head-shaped, with rounded margins, and a bluntly pointed distal beak. A1, Rake-like organ, Md-coxa and Mx1 (not illustrated) as in the male. A2 (Fig. 9A-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 fi ve 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 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. 9B) with two claws, one long (GM) one short (Gm) and one aesthetasc y3 with accompanying seta, slightly longer than y3. Seta g absent. T1 (Fig. 9C) Protopodite apically with a group of eight hirsute setae; two short setae a and one long seta d. Endopodite apically with three subequal long and plumose setae. T2 (Fig. 10A) largely as in the male, 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 tip of the second endopodal segment. Second endopodal segment with one apical hirsute seta f, just reaching the tip of the fi fth segment. Third endopodal segment with one subapical hirsute seta g, approximately ⅔ 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 (not visible here). T3 (Fig. 10B) largely as in the male, with three segments. First segment with two unequal long (d2, dp) and one shorter setae d1. Second segment with one subapical seta e, reaching 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 twice the length of the broad seta h2, the latter set with spine-like setulae. CR ( Fig. 10C) with cylindrical base, one subapical short seta and one long apical seta (ca 3 times the length of the base).   Table 3). External valve surface smooth, with sparse setae and pores in Brasilodopsis baiabonita gen. et sp. nov., (densely set with rimmed pores in shallow pits in B. amazonica gen. et sp. nov.). Hemipenis outline similar in both species, but distal segments of prehensile palps with subtle differences.

Ecology and distribution
Brasilodopsis baiabonita gen. et sp. nov. was recorded from three tropical Brazilian fl oodplains (Araguaia, Pantanal and Paraná), associated with different species of macrophytes and sediment (mud, sand). The water temperature ranged between 18.5 and 32.6°C. The pH ranged from acid (5) to basic (8.9). The range of electrical conductivity was between 14 and 415 μS.cm -1 and the values of dissolved oxygen varied from 0.1 to 7.8 mg.L -1 (see Table 4).

Remar ks
In order to show that valve and Cp morphologies are similar in all three fl oodplains, we here also illustrate this in Figs 11 (Araguaia) and 12 (Paraná), albeit for all-female populations only.

Measurements of illustrated specimens
See Table 2.

Description
Remark: most of the material was slightly to considerably decalcifi ed, so that dissections and SEM illustrations were diffi cult. 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. RVi (not illustrated) with well-developed anterior calcifi ed inner lamella, posterior calcifi ed 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.

Male
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 fl ap 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 fi fth segment). Fourth segment with three apical setae, two long dorsal ones, and one ventral seta, the latter slightly shorter than the length of the fi fth 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 fi ve 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.
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 fi ve 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 fi ve unequal, sideways directed bristles. 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 fi rst 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 fi rst 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 fi fth 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 decalcifi ed 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 fi ve 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. 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 fl oodplain, 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 decalcifi ed 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).

Diagnosis
Cp elongated and bean-shaped, with curved ventral margin. LV largely overlapping RV, especially along the anterior side. LV with weak anterior and ventral inner list, posterior inner list fully absent. RV without anterior inner list, posteriorly with weakly inwardly displaced selvage. Several limbs with segments reduced in length and/or in chaetotaxy: A1 with four distal segments highly reduced in both length and chaetotaxy; A2 with one short natatory seta (or its accompanying seta) only and reduced length of two distal segments. Idem for Md-palp, Mx1, T1 and T2 (where both setae d1 and d2 are missing). Male unknown.

Remarks
Because of the structural reduction in both valves (inner lists mostly absent) and the limbs (especially in the A1, but also in most other limbs) it is clear that this new genus and its species do not belong in the tribe Cypridopsini and require a new tribe, which might in time even be elevated to the rank of subfamily.

Diagnosis
As for the new tribe.

Etymology
The new genus is named after the state and the river from which it is here described, namely Paraná, and 'dopsis', referring to the stem of Cypridopsis.

Differential diagnosis
Paranadopsis gen. nov. can be distinguished from all other cypridopsine genera by the combination of the valve and limb morphology, including the strong reduction of size and chaetotaxy of segments in various limbs, especially in the A1 (see above, diagnosis of new tribe) (see Table 3).

Diagnosis
As for the tribe and genus. As the tribe is monogeneric and the genus is monospecifi c, it is diffi cult to allocate the different characters and character states to the different taxonomic levels. It is expected that other species in this genus and other genera in this tribe will have basically the same body plan, with slight modifi cations in shape, size and chaetotaxy of segments in various limbs.

Etymology
The new species is named after the fact that much of the size, shape and chaetotaxy of the segments in the limbs is reduced, especially in the A1.

Measurements of illustrated specimens
See Table 2.

Description
Female LVi (Fig. 18A, C-D) with broad anterior calcifi ed inner lamella and narrower posterior calcifi ed inner lamella; weak inner list present anteriorly and ventrally, absent posteriorly. R Vi (Fig. 18B, E-F) with broad anterior calcifi ed inner lamella and narrower posterior calcifi ed inner lamella; inner list fully absent, posteriorly with an inwardly displaced selvage. Both valves elongated and bean-shaped, with curved ventral margin, evenly rounded dorsal margin and with anterior margin more broadly rounded than posterior one. CpRl (Fig. 18G) elongated; with the greatest height situated in front of the middle; LV overlapping RV anteriorly (widely so) and posteriorly. External valve surface smooth and set with isolated setae. CpD (Fig. 18H) sub-ovate; with greatest width in the middle, and with LV widely overlapping RV anteriorly and less so posteriorly. CpV (Fig. 18I) also sub-ovate; with the greatest width in the middle; LV overlapping RV especially anteriorly, but also ventrally and posteriorly and with a gap between the two valves in the anterior third of the length, immediately followed by a central fl ap of the LV extending beyond the RV. A1 (Fig. 19A) with seven segments. First segment with two long subapical ventral setae; Wouter's organ not seen. Second segment with one long dorso-lateral seta; Rome organ not seen. Third segment with one ventro-lateral and one dorso-apical setae, the latter slightly shorter than the former one. Fourth to seventh segment greatly reduced in length and chaetotaxy. Fourth segment without setae. Fifth segment with one dorso-apical seta. Sixth segment with three long apical setae. Terminal (seventh) segment with two apical setae, one long and one half that length, and one aesthetasc Ya, about ⅔ of the shorter seta. A2 (Fig. 19B, D) with prodopodite, exopodite and three-segmented endopodite. First segment with one long subapical seta reaching well beyond the tip of the terminal segment. Exopodite reduced to a small plate (not illustrated), with only one long seta reaching the tip of the fi rst endopodal segment; two short accompanying setae missing. First endopodal segment with a ventral aesthetasc Y (approximately half the length of the segment), one subapical long seta, about 2.5 × the length of aesthetasc Y and hirsute in its distal one fi fth, and medially with one short (natatory) seta, almost reaching the tip of the second endopodal segment. Second endopodal segment ventrally with three setae t (one short seta, about twice the length of the terminal segment; one long ca twice the length of the shortest setae, and one of ca ¾ the length of the longest seta); medio-dorsally with two setae, one short and one long (ca twice the length of the short one); apically with three claws (G1, G2, G3) and three setae (z1, z2, z3). Terminal segment (Fig. 19D) with two claws, one long (GM), one short (Gm) and one aesthetasc y3 with one accompanying seta, the fi rst one slightly shorter than the latter; seta g missing. Rake-like organ (Fig. 19C) stout, solid, T-shaped, with ca ten apical teeth.
Md-palp ( Fig. 20B) 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 two unequal, but long dorsal setae; ventrally with one seta β, and one long seta (ca 2 × the length of seta β). Third segment with three groups of setae; dorsally with one group of three long setae and one short (hirsute) seta; apically with a group of three setae, one of which being seta γ; ventro-apically with two unequal setae. Terminal segment with three claws and three setae.
Md-coxa (Fig. 20A) elongated, with strong apical teeth, interspaced with some setae. Mx1 (Fig. 20C -chaetotaxy not completely illustrated) consisting of three masticatory lobes (endites), a two-segmented palp and a large branchial plate (the latter not illustrated). Branchial plate elongated, with ca 12 respiratory rays, some quite short, others long. First segment of palp subapically with two long setae. Terminal segment of palp with two claw-like setae and two short setae. Third endite apically with several setae, two with a distal tuft of setulae, and one basal, long seta. First endite apically with one basal seta and ca four sideways directed bristles. T1 (Fig. 21A) protopodite with a group of six hirsute setae and two short setae a; setae b and d absent. Endopodite consisting of two apical plumose setae (one long and one short about ½ the length of the long one). T2 (Fig. 21B) with one protopodite segment, one 'knee' segment and four endopodite segments. Protopodite and knee-segment with setae d1 and d2 absent. First endopodal segment with one subapical seta e, not reaching the tip of the second endopodal segment. Second endopodal segment with one apical seta f, reaching beyond the tip of the fi fth segment. Third endopodal segment with one sub-apical seta g. Terminal endopodal segment with one apically serrated claw h2; setae h1 and h3 absent. T3 (Fig. 21C) with three segments. First segment with three long setae (d1, d2, dp). Second segment with one apical seta e, reaching the middle of the third segment. Third segment medially with one seta f, about ⅓ of the length of the third segment. Distal part of third segment fused with fourth segment into a pincer structure, with a claw h2, one short seta h1 and one long seta h3, about 2 × the length of seta h2. CR absent.

Male
Unknown.

Ecology and distribution
Paranadopsis reducta gen. et sp. nov. was found associated with the root system of E. crassipes, located in some lakes of the Upper Paraná River fl oodplain. The temperature range of these lakes at the time of sampling was 28.3 to 32.6°C, while the pH range was 5.8 to 7. The electrical conductivity range was 14 to 61 μS.cm -1 , and the dissolved oxygen range was 1.5 to 7.6 mg.L -1 (see Table 4).
The species can be considered as rare in the area.

Discussion
Taxonomic position of the Cypridopsinae Kaufmann (1900) described the subfamily Cypridopsinae in the family Cyprididae, based mainly on the presence of a fl agellum-like CR. Hartmann & Puri (1974) escalated this taxon to the family Cypridopsidae, in which they included, following Hartmann (1963), both the original Cypridopsinae, with CR reduced to a fl agellum, and the Cyprettinae Hartmann, 1963, in which the CR shows various degrees of reduction, but never to the state of a fl agellum. In the nominal subfamily Cypridopsinae, they included genera such as Cypridopsis Brady, 1867, Potamocypris Brady, 1870 and Zonocypris G.W. Müller, 1898, presently still considered as belonging to this subfamily, but also Oncocypris G.W. Müller, 1898 and Pseudocypretta Klie, 1932, both of which also have a fl agellar CR. Oncocypris has meanwhile been transferred to the subfamily Oncocypridinae De Deckker, 1979 in the family Notodromadidae Kaufmann, 1900by De Deckker (1979a, 1979b, while Pseudocypretta has meanwhile been transferred to the Cyprettinae, but might belong in the Cyprettadopsini Savatenalinton, 2020. Because at that stage, at least one other family in the Cypridoidea, the Notodromadidae, comprised a genus with fl agellar CR, the main characteristic of the family Cypridopsidae was no longer unique to this family, and therefore De Deckker (1979a) argued (albeit implicitly) that this family should be merged (lowered to the rank of subfamily) in the family Cyprididae. Other researchers had already taken that position (McKenzie 1977 and others), however without further justifi cation. One year later, Shornikov (1980) described the terrestrial genus Callistocypris Shornikov, 1980 with reduced CR and placed it in a separate subfamily, the Callistocypridinae in the family Cypridopsidae. Meanwhile, this subfamily is placed outside of the Cypridopsinae in the Cyprididae (see Meisch et al. 2019). The CR in Callistocypris is also not fl agellar European Journal of Taxonomy 762: 1-48 (2021) but reduced to a clear ramus and one claw-like seta (Shornikov 1980;Pinto et al. 2005), as in some species of Cypretta Vavra, 1895.
Within the Cypridoidea, the fl agellar CR is rather an exception, as most species in this superfamily have a solid CR, consisting of a stout ramus and (generally) two claws and two setae. However, the other two superfamilies with representatives in non-marine habitats (Cytheroidea and Darwinuloidea) all have fl agellar caudal rami, so either fl agellar caudal rami in the Cypridoidea are the plesiomorphic character state, or they are an apomorphic condition resulting from a secondary reduction. The fact that several cypridoid lineages have such fl agellar caudal rami does not help in deciding between these two evolutionary scenarios, as these lineages could either have retained the plesiomorphic state independently from each other or could have experienced parallel secondary reduction, or both processes could have been active. Either way, the presence of fl agellar caudal rami is not a good character state on which to base a higher taxon, and even at the level of a subfamily, the monophyletic nature of the Cypridopsinae remains doubtful.

Taxonomy of the Cypridopsinae
An overview of the present generic taxonomy of the Cypridopsinae is given in Table 1. Five tribes (including Paranadopsini trib. nov.) and 21 genera (including Brasilodopsis gen. nov. and Paranadopsis gen. nov.) are presently included in this subfamily. The largest, and without doubt polyphyletic, tribe is still the Cypridopsini with 16 genera, divided in two groups: genera comprising species where the RV overlaps the LV and genera in which species have the LV overlapping the RV; the latter comprising the nominate genus Cypridopsis Brady, 1867. The Potamocypridini, rather obscurely defi ned in Ghetti & McKenzie (1981), only comp rise the genus Potamocypris Brady, 1870, the only cypridopsine genus with a spatulate second segment of the Mx1-palp (all other genera have a cylindrical segment there). Higuti & Martens (2012) erected the tribe Zonocypridini, to comprise the genera Zonocypris G.W. Müller, 1898, mainly from Africa, and Cabelodopsis Higuti & Martens, 2012 from Brazil. This tribe is characterised by a hyper developed claw G2 in the female A2. Savatenalinton (2018) added the genus Thaicypridopsis to this tribe. Recently, Savatenalinton (2020) added the tribe Cyprettadopsini for the enigmatic genus Cyprettadopsis Savatenalinton, 2020, which combines features of Cypridopsinae (fl agellar CR), Cyprettinae (marginal septae) and even Candonidae (separate terminal segment of the T3). The relevance of the latter character will be discussed elsewhere, but Cyprettadopsis is probably a result of parallel evolution.
The above summary shows that delineating taxa in the Cypridopsinae, even at the level of tribes, generally relies on small differences in valve and/or soft part morphology, although there are exceptions, such as the remarkable species Thaicypridopsis longispinosa Savatanalinton, 2018 with unique spatulate and distally hirsute setae on all three endites of the Mx1. Siamopsis Savatenalinton, 2017, on the other hand is a case in point, where a species fl ock of fi ve species in South East Asia is (correctly) united by a small 'plate' (expansion of the posterior calcifi ed lamella) in the LV (Savatenalinton 2017). Also, the description of Brasilodopsis gen. nov. mainly relies on valve characters, nl. the presence /absence of inner lists in the valves.

Position of Paranadopsis gen. nov.
The situation of Paranadopsis gen. nov., however, is completely different as it shows reductions in size and chaetotaxy of segments in almost all limbs, but especially in the A1, whereas the CR is completely absent.
In the A1, segments 4 to 7 are reduced to tiny segments, with only a few setae. This is unique in the Cypridopsinae, and even in the Cyprididae. Such drastic reductions with loss of segments and setae, on the other hand, is not uncommon in interstitial Candonidae (for example Danielopol (1978);Martens ALMEIDA N.M. et al., Cypridopsinae (Crustacea, Ostracoda) from Brazil