Hemicypris posterotruncata Bate, 1970

Smith, Robin James & Chang, Cheon Young, 2020, Taxonomic assessments of some Cyprinotinae Bronstein, 1947 species (Crustacea: Ostracoda) from Japanese and Korean rice fields, including (re-) descriptions of six species and a review of the type species of the subfamily, Zootaxa 4795 (1), pp. 1-69 : 24-34

Hemicypris posterotruncata Bate, 1970

( Figs 4 D–F, 11–16)

1970 Hemicypris posterotruncata sp. nov. —Bate: 289, 292–295, pl. 52, text-fig. 3.

1972 Hemicypris posterotruncata Bate 1970 —Bate: 184–185, text-fig. 1.

non 1980 Hemicypris posterotruncata Bate—McClure & Swain: Pl. 2, fig. 6 (fide Mohammed et al. 2018).

1981 H. posterotruncata —Victor & Fernando: 24.

1983 Hemicypris posterotruncata Bate, 1970 —Broodbakker: Table 1.

1984a Hemicypris posterotruncata Bate, 1970 nov. syn. —Martens: 10–11, checklist.

1984b H. posterotruncata Bate, 1970 —Martens: 149, as possible syn. of Hemicypris kliei .

1989 Hemicypris sp. A.—Okubo & Ida: 106, pl. 3k–n.

1990 Hemicypris vulgaris sp. nov. —Okubo: 10–11, figs 3l–j.

1990 Hemicypris nipponica sp. nov. —Okubo: 10, figs 3g-i, (fide herein).

2004 Hemicypris vulgaris Okubo, 1990 —Okubo: 27, figs 11a–d.

2004 Hemicypris ovata Moniez, 1892 [sic]—Okubo: 27, figs 11e-h (fide herein).

2008 Hemicypris posterotruncata Bate, 1970 —Savatenalinton & Martens: Table 1, as syn. of Hemicypris kliei .

2008 Hemicypris nipponica Okubo, 1990 —Savatenalinton & Martens: 22, table 1.

2008 Hemicypris vulgaris Okubo, 1990 —Savatenalinton & Martens: 22, table 1.

2009 Hemicypris nipponica Okubo, 1990 —Hayashi et al.: 77.

2009 Hemicypris vulgaris Okubo, 1990 —Hayashi et al.: 77.

2010 Hemicypris posterotruncata Sars,1903 [sic]—Al-Da’amy: No page numbers.

2011 Hemicypris vulgaris Okubo, 1990 —Martens & Savatenalinton: Table 2.

2011 Hemicypris posterotruncata Bate, 1970 —Martens & Savatenalinton: Table 2, as syn. of Hemicypris kliei .

2012 H. posterotruncata Bate 1970 —Karanovic: 438, as syn. of Hemicypris kliei .

2012 Hemicypris nipponica Okubo, 1990 —Hayashi et al.: 62.

2012 Hemicypris vulgaris Okubo, 1990 —Hayashi et al.: 62.

2012 H. nipponica Okubo 1990 b—Karanovic: 439, 441.

2012 H. vulgaris Okubo 1990 b—Karanovic: 439, 441.

2013 Hemicypris nipponica Okubo, 1990 —Martens et al.: No page numbers.

2013 Hemicypris posterotruncata Bate, 1970 —Martens et al.: No page numbers, as syn. of Hemicypris kliei .

? 2015 Hemicypris megalops Sars, 1903 —Tanaka et al.: 33, figs 2F, 3K & L, 5E, 8B & C, table 2 (fide herein).

2017 Hemicypris vulgaris Okubo, 1990 —Rasouli & Aygen: 422, 424–430, Figs 2–5 .

2019 Hemicypris posterotruncata Bate, 1970 —Meisch et al.: 64, as syn. of Hemicypris kliei .

2019 Hemicypris vulgaris Okubo, 1990 —Meisch et al.: 65.

Diagnosis. Posterior margin of carapace slightly more inflated than anterior margin, ventral margin approximately straight, maximum height at about mid-length. Left valve with well developed marginal denticles along posteroventral and antero-ventral margins. Surface of valves smooth, with exception of area near anterior margin of left valve; here crescent-shaped area of small, shallow, but well-defined pits. Antennal aesthetasc Y 20% length of dorsal sclerotised margin of first endopodal segment, swimming setae long, reaching beyond ends of claws. Antenna, claw G2 long, ca. 84% length of claw G1, claw Gm slender, ca. 64% length of GM. Mandibular gamma seta short and triangular, with wide base and long, numerous, fine setules on distal half of outer edge. Maxillula third endite with one smooth and one very finely serrated Zahnborsten. Sixth limb first segment with d1 seta, second segment with e seta reaching to distal end of third segment, third segment with f seta reaching to distal end of fourth segment. Seventh limb (cleaning limb) with seta dp on first segment shorter than both d1 and d2 of same segment, second segment with long e seta, not reaching to distal end of third segment. Caudal ramus with claw Ga noticeably larger than claw Gp, both claws slender, seta sp about 94% as long as claw Gp, seta sa about one third length of Ga.

Material examined. Topotypes. KENYA • 2 specimens, fossil whole carapaces stored in micropalaeontological cavity slides; Turkana County, Lothagam Hill ; [2.9213º N, 36.0648º E]; M. D. Gwynne leg.; age uncertain, possibly Holocene or Pleistocene; NHMUK PM os 19882 to 19883 . • 2 specimens, fossil right valves stored in micropalaeontological cavity slides; same data as for preceding; NHMUK PM os 19884 to 19885 . • 3 specimens, fossil left valves stored in micropalaeontological cavity slides; same data as for preceding; NHMUK PM os 19886 to 19888 .

Other figured material. JAPAN • 2 ♀♀, with soft parts dissected in glycerine and sealed in slides, valves stored dry in micropalaeontological cavity slides; Shiga Prefecture, Nagahama, Tomecho ; 35.43866º N, 136.32637º E; alt. 150 m; 24 May 2009; Robin J. Smith leg.; rice field; LBM 1430009519 , LBM 1430009520 . • 1 ♀, whole, stored dry in a micropalaeontological cavity slide; same data as preceding; LBM 1430009521 . • 2 ♀♀, with soft parts dissected in glycerine and sealed in slides, valves stored dry in micropalaeontological cavity slides; Shiga Prefecture, Otsu, Kurozu ; 34.94011º N, 135.91667º E; alt. 85 m; 17 Jun. 2009; Robin J. Smith leg.; rice field; LBM 1430009522 , LBM 1430009523 . • 1 ♀, with soft parts dissected in glycerine and sealed in slides, valves stored dry in micropalaeontological cavity slides; Shiga Prefecture, Kusatsu, Oroshimo, Lake Biwa Museum ; 35.07471º N, 135.93401º E; alt. 90 m; 20 Jun. 2012; Robin J. Smith leg.; rice field; LBM 1430009525 . • 1 ♀, whole, stored dry in a micropalaeontological cavity slide; same data as preceding; LBM 1430009524 . • 1 ♀, valves stored dry in a micro- palaeontological cavity slide; Shiga Prefecture, Kusatsu, Oroshimo, Lake Biwa Museum ; 35.0746º N, 135.93402º E; alt. 90 m; 10 Sep. 2014; Robin J. Smith leg.; plastic container with mud and rice plants; LBM 1430009526 .

Other material. JAPAN • 1 ♀, “ Hemicypris vulgaris 010615 ”, valves and appendages mounted on a glass slide in an unknown matrix, distal parts of antennae and sixth limbs aberrant; [Okayama, Mantomi ]; [34.75814º N, 134.08065º E]; [alt. ca. 12 m]; Ichiro Okubo leg.; LBM 1430009516 . • 1 ♀, “ Hemicypris ovate 010615 ”, valves and appendages mounted on a glass slide in an unknown matrix; same data as for preceding; LBM 1430009517 .

Other material collected by authors, see Table 1.

Description. Carapace length 833–1250 µm, height 519–719 µm, height /length = 0.57–0.62. Ovoid in lateral view, anterior margin evenly rounded ( Fig. 11A, E ). Posterior margin slightly more inflated than anterior margin and most tightly curved along posterior-ventral margin. Dorsal margin unevenly curved with maximum height just posterior of muscle scars. Ventral margin straight to slightly sinuous. Dorsal view ovoid, posterior margin more inflated than anterior margin, left valve slightly pinched inwards anteriorly (marked with white triangle on Fig. 12A ). Right valve overlaps left valve. Surface of valves mostly smooth, but with distinctive crescent of shallow pits running near anterior margin of left valve, fading out towards the ventral and dorsal margins ( Figs 11A, B, E & F , 12D , 13A & B , 16G ). Left valve with denticles running along anterior and posterior-ventral margins; denticles change to list at middle section of ventral margin ( Figs 11C & G , 12 B–D, F & G, 13D, E, 14C, E & F). Right valve with two lines of shallow marginal sockets towards edge of calcified inner lamella, one line running near anterior margin and one near posterior-ventral margin; sockets align with marginal denticles of left valve when carapace closed ( Figs 12E , 13G ). Right valve with faint outer list along central ventral area ( Fig. 14D ). Inner calcified lamella narrow, wider anteriorly, posteriorly widest along posterior-ventral margin ( Figs 11C, D, G & H , 13D & F ). Muscle scars typical of family. Colour yellowish, with brown pigmented patches towards dorsal and anterior margins; patches vary from weakly to strongly developed, missing altogether in some specimens ( Figs 4 D–F, 16G). Hepatopancreas colour ranges from greenish-grey to yellowish-brown. In transmitted light microscopy, valves with well developed fine granular background (granules slightly smaller than normal pores), but without larger reticulation ( Fig. 32A ).

Antennule ( Fig. 15A ) with seven articulated segments. First segment with small, bulbous Wouters organ and seta on dorsal margin, and two long sub-apical setae on ventral margin. Second segment with small Rome organ, and apical-dorsal seta. Third segment with one apical-dorsal seta and one apical-ventral seta. Fourth segment with two long apical-dorsal setae, and two apical-ventral setae, one of which slightly offset towards centre of segment. Fifth segment with two long apical-dorsal setae, and two apical-ventral setae, one of which slightly offset towards centre of segment. Sixth segment with four long and one very short (alpha) setae; alpha seta about two times length of dorsal margin of terminal segment. Terminal segment apically with one stout, short seta, two long setae and aesthetasc ya.

Antenna, longest setae on exopodite reaching to approximately end of first endopodite segment or slightly beyond ( Fig. 15B ). Aesthetasc Y 20% length of dorsal sclerotised margin of first endopodal segment (marked with dotted arrowed line on Fig. 15B ). Natatory setae long, noticeably extending beyond tips of terminal claws. Claw G2 long, ca. 84% length of claw G1 ( Fig. 16A ). Claw Gm slender, ca. 64% length of GM.

Mandible palp, first segment with small, slender alpha seta, tapering distally to setule-like distal end ( Fig. 15D ). Second segment 3+1+beta setae on inner edge, and three setae on outer edge. Beta seta setulous, slightly longer than alpha. Third segment with group of four sub-apical setae on outer edge, gamma + 3 setae along distal edge, and one long and one very short setae on inner sub-apical edge. Gamma seta short but robust, with long setules on outer edge. Terminal segment with three stout claw-like setae and three thinner setae. Mandibular coxa robust, with ca. seven teeth of various sizes ( Fig. 15E ).

Maxillula palp, first segment with group of five setae on outer apical edge, all of varying lengths, and two sub-apical setae, one of which long, located on outer edge, and other, much shorter seta displaced inwards ( Fig. 15G ). Second segment sub-quadrate, slightly widening distally, apically with three claw-like robust setae, and three smaller setae. Third endite with one smooth and one lightly serrated Zahnborsten.

Rake-shaped organ with eight to 11 teeth (mostly with nine) ( Fig. 15F ).

Fifth limb (maxilliped) basis with two a setae, and relatively long d and b setae; c seta missing, typical of subfamily ( Fig. 16B ). Endite with ca. 12 apical setae. Exopodite (branchial plate) with six rays. Palp with three apical setae of unequal lengths.

Sixth limb (walking leg) robust with five articulated segments ( Fig. 16C ). First segment with d1 seta. Second segment with e seta reaching to approximately end of third segment. Third segment with f seta reaching to approximately end of fourth segment. Fourth segment with one relatively long, and one tiny g setae. Fifth segment with h1 and h3 setae similar in length, and h2 claw long.

Seventh limb (cleaning limb) with seta d1 on first segment shorter than d2 and dp of same segment ( Fig. 16D ). Second segment with relatively long e seta. Third segment with f seta at mid-length, almost reaching to end of segment. Terminal segment part of pincer structure typical of the family.

Caudal ramus slender, with claw Ga noticeably larger than claw Gp, both claws slender ( Fig. 16E ). Seta sp long, but shorter than claw Gp. Seta sa very slender and relatively long. Caudal ramus attachment proximally straight, curving distally, with small dorsal branch distal at mid-length ( Fig. 16F ).

Males unknown and no evidence of males (e.g. spermatozoa in females).

Remarks. Japanese specimens collected during this study are a very close match to topotype material of Hemicypris posterotruncata ( Figs 11 E–H, 12 H). This species was first reported as a sub-fossil collected from lacustrine deposits near Lake Turkana, Kenya ( Bate 1970). At the time, Bate (op. cit.) was unaware of a publication of Lindroth (1953) in which several new species of Cyprinotus from Lake Turkana were described (and later transferred to the genus Hemicypris ). To compensate for this oversight, Bate (1972) compared his species with those of Lindroth, considering Hemicypris kliei as the most morphologically similar to Hemicypris posterotruncata . He distinguished the two species by the more steeply angled postero-dorsal slope, less angular antero-dorsal margin and more distinctly concave ventral margin of the carapace of Hemicypris kliei . He also noted that the surface ornament of the two species is different; Hemicypris kliei is covered with broad, shallow pits, which are absent in Hemicypris posterotruncata . Martens (1984a) considered that the differences listed by Bate (1972) were minor and within the variability seen in species of the genus. Based on the published figures of the two species, Martens (1984a) concluded that Hemicypris posterotruncata is a junior synonym of Hemicypris kliei .

For this study syntype material of Hemicypris kliei from the Uppsala Museum, Sweden was compared with topotype material of Hemicypris posterotruncata from the Natural History Museum in London, and Japanese specimens collected by the authors. In the female specimen of Hemicypris kliei used in this study, the middle area of the left valve around the adductor muscle scars is smooth, but shallow, ill-defined pits are visible on the rest of the valve surface, with the exception of the anterior margin; here, the pits are deeper and better defined, and in size, morphology and distribution, strongly resemble the crescent of pits seen in Hemicypris posterotruncata (see the description of Hemicypris kliei below, Fig. 20 ). This crescent of well-defined pits in both species suggests that they are at least closely related, but the difference in surface ornamentation elsewhere questions whether they should be considered synonyms. Hemicypris kliei has more rounded posterior and dorsal margins than Hemicypris posterotruncata , and although this is a subtle difference, it does seem to be consistent. Additionally, Hemicypris kliei has a groove on the calcified inner lamella of the right valve ( Fig. 21D ), whereas this is absent in the types of Hemicypris posterotruncata . The appendages of the two species mostly correspond quite closely, although some setae are noticeably longer in Hemicypris kliei , such as the h3 seta on the walking leg. Two differences are significant: 1. the Y aesthetasc of the antenna is longer in Hemicypris kliei , 33% of the length of the posterior margin of the first endopodal segment ( Fig. 23B ), compared with 24–26% in Hemicypris posterotruncata . 2. The gamma seta on the mandible palp is much wider in Hemicypris kliei ( Fig. 23D ) compared with that in Hemicypris posterotruncata . Although these two species are morphologically similar, both species are considered separate based on clear differences in the carapace and appendages, i.e. Hemicypris posterotruncata is not a junior synonym of Hemicypris kliei .

Okubo (1990) briefly described four new species of Hemicypris found in Japanese rice fields: Hemicypris mizunoi Okubo, 1990 , Hemicypris kibiensis Okubo, 1990 , Hemicypris nipponica Okubo, 1990 and Hemicypris vulgaris Okubo, 1990 . The last three of these species are very similar in morphology; Hemicypris kibiensis was reported to be smaller than the other two, and Hemicypris nipponica and Hemicypris vulgaris could be distinguished from each other by carapace colouration and subtle features of the caudal ramus. Later, Okubo (2004) considered Hemicypris kibiensis and Hemicypris nipponica to be junior synonyms of Hemicypris megalops and Hemicypris ovata respectively, a view rejected herein (see above and below for more details). Type specimens were designated but the location of type material is unknown. However, one specimen of each of these species provided by Ichiro Okubo were examined for this study.

Hemicypris kibiensis is overall similar to Hemicypris posterotruncata in valve shape and appendages ( Fig. 4M & N ). The valves of the specimen is mounted in an unknown medium, so could not be investigated with SEM, but it appears not to have a similar crescent of pits on the left valve as seen in Hemicypris posterotruncata . This could be due to preservation of the specimen (the mounting medium could have partly decalcified the valves), but additionally, in transmitted light microscopy, the valves have a reticulated pattern (ca. 14–25 µm across) overlying a finer, poorly defined granular background ( Fig. 4O ). A reticulate pattern is not seen in Hemicypris posterotruncata (only the fine granular background, better defined, Fig. 32A ), and therefore this specimen is considered not to be conspecific with Hemicypris posterotruncata .

Hemicypris vulgaris is also very similar to Hemicypris posterotruncata , only differing in size and a slightly more elongate carapace. Okubo (1990) gave no mention of the crescent of pits on the anterior margin of the left valve, but the pits are visible in the photograph of the left valve of Hemicypris vulgaris provided by Okubo (2004). These pits are also faintly visible in the specimen of Hemicypris vulgaris from Okubo that was examined by us. In the material collected for this study, both large (corresponding to Hemicypris vulgaris ) and small (corresponding to Hemicypris posterotruncata ) specimens were recovered in addition to others that were in between the two size types. Measurements of Asian specimens show a continuous range of sizes from 915 µm through to 1250 µm, with no clear distinction between the two forms ( Fig. 16H ). Fossil specimens range from 833 µm to 970 µm in length. Larger specimens tend to be slightly more elongate, but height / length ratios again do not show any discrete groups. Appendages and areas of pigmentation on the carapace are also very similar between larger and smaller forms ( Fig. 4 D–F). With no clear distinctions between specimens, we conclude that all are conspecific. This variation in size, albeit large, is comparable with some other Cyprinotinae species (e.g. Heterocypris incongruens ( Ramdohr, 1808), 1200 –1900 µm; Heterocypris rotundata ( Bronstein, 1928) , 900–1300 µm; and Heterocypris salina ( Brady, 1868) 800–1300 µm; Meisch 2000). Additionally, large differences in size have been noted for another ostracod species inhabiting rice fields, with larger specimens slightly more elongate ( Ilyocypris japonica Okubo, 1990 ; Smith et al. 2019).

Differences between Hemicypris vulgaris (considered to be large forms of Hemicypris posterotruncata herein; see above) and Hemicypris nipponica are restricted to the carapace colouration and the length of the sp seta on the caudal ramus ( Okubo 1990). The colouration of Hemicypris nipponica was reported to be darker brown compared with that of Hemicypris posterotruncata ( Okubo 1990) , but this study has found that intensity of colouration is variable in Hemicypris posterotruncata , ranging from very weak to very strong, and it may be related to environmental as well as temporal factors. This character therefore cannot reliably discriminate the two species. Okubo (1990) noted that the sp seta of the caudal ramus was “shorter” than claw Gp in Hemicypris nipponica , and “nearly as long” as claw Gp in Hemicypris posterotruncata , although no difference in lengths is evident in the accompanying figures. In the one specimen of Hemicypris nipponica (labelled as Hemicypris ovate (sic)) provided by Okubo and examined for this study, pits are vaguely visible in the anterior area of the left valve. The antennae, sixth limbs, and to a lesser extent, the caudal rami are deformed in this specimen so cannot be compared, but there are no differences in the other appendages. Hemicypris nipponica is therefore considered herein to also be a junior synonym of Hemicypris posterotruncata .

Hemicypris posterotruncata is very similar to Hemicypris ovata Sars, 1903 from South East Asia, with a very similar carapace (both having a crescent of pits near the anterior margin of the left valve) and appendages (see description of Hemicypris ovata below, Fig. 14H & I ), but there are features that can discriminate the two species. Compared to Hemicypris posterotruncata , Hemicypris ovata has a more prominent anterior overlap of the right valve, lacks pigmentation of the carapace ( Sars 1903), and has some longer setae on the appendages, notably, but not restricted to, the alpha seta on the antennule, the t-setae on the antenna, the h3 seta on the walking leg and the sa seta on the caudal ramus. Both species have one serrated and one smooth Zahnborsten on the maxillula, but in Hemicypris ovata the serration is more robust. The gamma setae of the mandibles also differ; in Hemicypris posterotruncata the main part of the gamma seta (not including the setules) reaches to about the distal end of the terminal segment of the palp, whereas it is considerably shorter in Hemicypris ovata . The setules on the gamma setae are mostly on the distal outer edge in Hemicypris posterotruncata , but also on the inner edge in Hemicypris ovata .

Smaller specimens of Hemicypris posterotruncata are also similar to Hemicypris megalops . At the present time the carapace of Hemicypris megalops is not clearly known due to poor preservation of type material. Other authors who have looked at type material (e.g. Sars 1903; Bate 1970; Victor & Fernando 1981) have not reported a crescent of pits on the anterior margin of the left valve for Hemicypris megalops (and which is present in Hemicypris posterotruncata and Hemicypris ovata ), but the pits could have been overlooked as they are difficult to observe without SEM. There are small differences in the appendages, such as the seventh limb with a compact and rounded distal end and a reflexed h2 seta in Hemicypris megalops , and the caudal ramus attachment (with a small dorsal branch in Hemicypris posterotruncata , without this branch in Hemicypris megalops ) (also see Table 2). Other Japanese reports of Hemicypris megalops ( Tanaka et al. 2015) are possibly Hemicypris posterotruncata or Hemicypris kibiensis , and need to be confirmed.

Distribution and ecology. This species’ known living distribution is restricted to Japan (Okayama, Gumma, Shiga Prefectures), South Korea (Gyeongsangbuk-do and Gyeongsangnam-do provinces), and the western part of Turkey near Gönen ( Okubo 1989; 1990; 2004; Rasouli & Aygen 2017; this study) ( Fig. 17 ). The Japanese and Korean records correspond to temperate to cold Köppen climatic zones with no dry season and hot summers (zones Dfa and Cfa; Peel et al. 2007). The Turkish record, although far from East Asia, is from a similar Köppen climatic zone: temperate, with dry and hot summers (zone Csa; Peel et al. 2007). The South Korean records are the first of this species for that country.

In Japan and South Korea, this species has so far been found in rice fields, a pond, a ditch, and a water-filled plastic container with rice plants next to rice fields ( Table 1). Okubo (1990) noted that it is the most common species of the genus and that it is abundant in rice fields from spring to autumn. Material examined for this study was collected from late May through to August in rice fields (and during September in a plastic container next to rice fields). Its presence is probably heavily determined by the schedule of rice farming, and disappears when the rice fields are left to dry prior to harvesting. Males are unknown and reproduction is assumed to be parthenogenetic. The Turkish specimens were found in a rice field and from a nearby spring that feeds the Gönen River ( Rasouli & Aygen 2017).

Figures

FIGURE 2. Cyprinotus cassidula sp. nov. A, left valve, internal view, female (LBM 1430009506). B, left valve, internal view, male (LBM 1430009496). C, right valve, internal view, female, detail of antero-ventral area (LBM 1430009506). D, right valve, internal view, female, detail of postero-ventral area (LBM 1430009506). E, left valve, internal view, female, detail of posteroventral area (LBM 1430009506). F, left valve, internal view, female, detail of antero-ventral area (LBM 1430009506). G, right valve, internal view, female, detail of central ventral area (LBM 1430009506).All specimens from type locality (Table 1, sample 4). Scale bar = 500 µm for A & B, 108 µm for C–G.

FIGURE 3. Cyprinotus cassidula sp. nov. A, right valve, ventral view, female (LBM 1430009506, sample 4; see Table 1). B, left valve, ventral view, female (LBM 1430009506, sample 4). C, right valve, ventral view, female, detail of marginal denticles (LBM 1430009506, sample 4). D, right valve, ventral view, female, detail of ventral area (LBM 1430009506, sample 4). E–J, whole carapaces, left views, females, each from different locations, E–G from Japan (LBM 1430009495, sample 3, LBM 1430009508, sample 4, LBM 1430009507, sample 10 respectively), H–J from Korea (LBM 1430009511, sample 22, LBM 1430009512, sample 25, LBM 1430009513, sample 28 respectively). Scale bar = 500 µm for A & B, 28 µm for C, 108 µm for D, 817 µm for E–J.

FIGURE 4. A & B, Cyprinotus cassidula sp. nov. (sample 10; see Table 1).A, left lateral view of whole carapace, female. B, left lateral view of whole carapace, male. C, Hemicypris megalops, whole carapace, right lateral view, female (paralectotype from Sumatra, Indonesia F12292c2, before dissection). D–F, Hemicypris posterotruncata. D & E, left lateral views of whole carapaces, females. F, dorsal view of whole carapace, anterior to left, female. G & H, Hemicypris ovata. G, paralectotype (NHMO F12264c), right view of whole carapace, female (prior to SEM). H, paralectotype (NHMO F12264b), internal view of right valve, female (before dissection). I & J, Hemicypris barbadensis (LBM 1430009514). I, left valve, internal view, female. J, right valve, internal view, female. K & L, Heterocypris savatenalintonae sp. nov. K, left lateral view of whole carapace, female. L, left lateral view of whole carapace, male. M–O, Hemicypris kibiensis (LBM 1430009515). M, left valve, internal view, female. N, right valve, internal view, female. O, high magnification transmitted light microscopy of valves. A–H, K & L, photographed while specimens submerged in water. I, J, M–O, mounted in unknown medium on glass slide.All photographs focussed stacked. Scale bar = 1506 µm for A & B, 1000 µm for C to N, 238 µm for O.

FIGURE 5. Cyprinotus cassidula sp. nov. A, antennule, male (LBM 1430009504). B, antenna, male (LBM 090524-01-014). C, mandibular palp, male (LBM 1430009502). D, alpha, beta and gamma setae of mandibular palp, male (LBM 1430009502). E, mandibular coxa, male (LBM 1430009502). F, maxillula palp and endites (setae on endites not drawn) (LBM 1430009502). G, left fifth limb palp, male (LBM 1430009502). H, right fifth limb palp, male (LBM 1430009502). All specimens from type locality (Table 1, sample 4).

FIGURE 11. Hemicypris posterotruncata Bate, 1970. A–D, specimens from a rice field in Japan. E–H, topotype sub-fossil material from lacustrine sediments in Kenya. A, whole carapace, left lateral view (LBM 1430009524, sample 32; see Table 1). B, whole carapace, left lateral view, detail of anterior margin (LBM 1430009524, sample 32). C, left valve, internal view (LBM 1430009525, sample 32). D, right valve, internal view (LBM 1430009525, sample 32). E, whole carapace, left lateral view (NHMUK PM Io 1450A-002). F, whole carapace, left lateral view, detail of anterior margin (NHMUK PM Io 1450A-002). G, left valve, internal view (NHMUK PM Io 1451A-001). H, right valve, internal view (NHMUK PM Io 1450B-001).All Japanese specimens female, sex of Kenyan specimens unknown. Scale bar = 500 µm for A, C–E, G & H, 89 µm for B & F.

FIGURE 12. Hemicypris posterotruncata Bate, 1970. A–G, specimens from a rice field in Japan. H, topotype sub-fossil material from lacustrine sediments in Kenya.A, whole carapace, dorsal view, anterior to left (white triangle marks indentation) (LBM 1430009524, sample 32; see Table 1). B, left valve, internal view, detail of postero-ventral margin (LBM 1430009525, sample 32). C, left valve, external ventral view (LBM 1430009525, sample 32). D, left valve, external ventral view, detail of antero-ventral margin (LBM 1430009525, sample 32). E, right valve, internal view, detail of central anterior margin (LBM 1430009525, sample 32). F, left valve, external ventral view, detail of ventral margin (LBM 1430009525, sample 32). G, left valve, external ventral view, detail of denticles (LBM 1430009525, sample 32). H. whole carapace, dorsal view, anterior to left (NHMUK PM Io 1450A-002). All Japanese specimens female, sex of Kenyan specimens unknown. Scale bar = 500 µm for A, C & H, 132 µm for B & E, 145 µm for D & F, 30 µm for G.

FIGURE 13. Hemicypris posterotruncata Bate, 1970. A, whole carapace, left view (LBM 1430009521). B, detail of pits on anterior of left valve (LBM 1430009521). C, whole carapace, dorsal view, anterior to left (LBM 1430009521). D, left valve, internal view (LBM 1430009520). E, left valve, internal view, detail of postero-ventral margin (LBM 1430009520). F, right valve, internal view (LBM 1430009520). G, right valve, internal view, detail of central anterior margin (LBM 1430009520).All specimens female, from sample 4 (Table 1). Scale bar = 500 µm for A, C, D & F, 77 µm for B, E & G.

FIGURE 14. A–F, Hemicypris posterotruncata Bate, 1970. A, left valve, external ventral view (LBM 1430009522, sample 14; see Table 1). B, right valve, external ventral view (LBM 1430009522, sample 14). C, left valve, external ventral view, detail of ventral margin (LBM 1430009522, sample 14). D, right valve, external ventral view, detail of ventral margin (LBM 1430009522, sample 14). E, left valve, external ventral view, detail of antero-ventral margin (LBM 1430009522, sample 14). F, left valve, external ventral view, detail of denticles (LBM 1430009522, sample 14). H & I, Hemicypris ovata Sars, 1903. H, whole carapace, left view (paralectotype NHMO F12264c). I, detail of pits on anterior of left valve (paralectotype NHMO F12264c). All specimens female. Scale bar = 500 µm for A, B & H, 141 µm for C–E, 23 µm for F, 84 µm for I.

FIGURE 15. Hemicypris posterotruncata Bate, 1970. A, antennule (LBM 1430009520, sample 4; see Table 1). B, antenna (LBM 1430009519, sample 4). C, mandibular palp (LBM 1430009520, sample 4). D, alpha, beta and gamma setae of mandibular palp (LBM 1430009520, sample 4). E, mandibular coxa (LBM 1430009519, sample 4). F, rake shaped organ (LBM 1430009523, sample 14). G, maxillula palp and endites (setae on endites not drawn) (LBM 1430009520, sample 4). All specimens female.

FIGURE 16. Hemicypris posterotruncata Bate, 1970. A, antenna, detail of last two segments (LBM 1430009519, sample 4; see Table 1). B, fifth limb (LBM 1430009520, sample 4). C, sixth limb (LBM 1430009519, sample 4). D, seventh limb (LBM 1430009519, sample 4). E, caudal ramus (LBM 1430009519, sample 4). F, caudal ramus attachment (LBM 1430009520, sample 4). G, sketch of left valve, external view, showing position of crescent of pits and pigmentation. H, length and height of right valves, filled black circles Kenyan sub-fossils, open black circles Asian living material. All living specimens female, sex of Kenyan specimens unknown.

FIGURE 17. Distribution map of Hemicypris posterotruncata and Hemicypris ovata.? indicates uncertain records. Abbreviations and colours of points refer to Köppen climatic zones, following Peel et al. (2007). Data from: 1, Akindele 2013. 2, Schöning (1994) as Hemicypris sp., identified as H. ovata by Karanovic (2012). 3, Deb (1972a). 4, Deb (1972b). 5, Savatenalinton (2014), Savatenalinton & Suttajit (2014). 6, Sars (1903) (approximate as no specific locality given). 7, Victor & Fernando, 1981. 8, Bate (1970; 1972). 9, Rasouli & Aygen (2017). 10, this study. 11, Kume (2013). 12, Okubo (1990). 13, this study. 14, Tanaka et al. 2015.

FIGURE 20. Hemicypris kliei Lindroth, 1953. A, left valve, external view. B, right valve, external view. C, left valve, external view, detail of antero-ventral area. D, left valve, external view, detail of antero-ventral area. E, left valve, external ventral view. F, right valve, external ventral view. G, left valve, external ventral view of antero-ventral margin. H, left valve, external ventral view of postero-ventral margin. I, left valve, external ventral view, detail of ventral margin. Scale bar = 500 µm for A, B, E & F, 298 µm for I, 125 µm for C, G, H, and 31 µm for D. (All figures female topotype specimen UUZM Typ 603x.)

FIGURE 21. Hemicypris kliei Lindroth, 1953. A, left valve, internal view. B, right valve, internal view. C, left valve, internal view, detail of anterior margin. D, right valve, internal view, detail of anterior margin. E, left valve, internal view, detail of postero-ventral margin. F, right valve, internal view, detail of postero-ventral margin. Scale bar = 500 µm for A & B, 125 µm for C–F. (All figures female topotype specimen UUZM Typ 603x.)

FIGURE 23. Hemicypris kliei Lindroth, 1953.A, antennule, female (UUZM Typ 603 x). B, female antenna (UUZM Typ 603 x). C, mandibular palp, female (UUZM Typ 603 x). D, alpha, beta and gamma setae of mandibular palp, female (UUZM Typ 603 x). E, mandibular coxa, female (UUZM Typ 603 x). F, maxillula palp and endites (setae on endites not drawn), female (UUZM Typ 603 x). G, right fifth limb palp, male (UUZM Typ 603 j). H, left fifth limb palp, male (UUZM Typ 603 f).

FIGURE 32. High magnification transmitted light microscopy of valves.A, Hemicypris posterotruncata, showing a well developed fine granular background (LBM 1430009526). B, Heterocypris savatenalintonae sp. nov., showing a weakly developed fine granular background (LBM 1430009538). C, Heterocypris salina, showing a weakly developed fine granular background with a larger, overlying reticulation (LBM 1430009529). Photographed while valves submerged in water. All photographs focussed stacked.