Cyprinotus, Brady, 1886
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publication ID |
https://doi.org/ 10.5852/ejt.2019.566 |
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publication LSID |
lsid:zoobank.org:pub:0A180E95-0532-4ED7-9606-D133CF6AD01E |
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persistent identifier |
https://treatment.plazi.org/id/695C879E-FFD5-FFB2-FF12-F9BFFB9E8682 |
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treatment provided by |
Plazi |
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scientific name |
Cyprinotus |
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Taxonomy of the genus Cyprinotus View in CoL
Meisch et al. (2019) retained 17 species in the genus Cyprinotus . However, a literature survey conducted in the present paper showed that actually only seven species, including Cyprinotus drubea sp. nov., really belong in the genus ( Table 2 View Table 2 ). Based on the illustrations in the original descriptions, several of the other species could be allocated to other genera ( Table 3 View Table 3 ). Cyprinotus crenatus (Turner, 1893) , C. flavescens Brady, 1898 , C. ohanopecoshensis Ferguson, 1966 and C. sulphurous Blake, 1931 belong in the genus Heterocypris , because of a clear lack of a dorsal hump on the RV. Cyprinotus scytodus (Dobbin, 1941) most likely also belongs in the genus Heterocypris .
For C. pellucidus ( Sharpe, 1897) , it is impossible to see to which genus it belongs based on the original illustrations in Sharpe (1897). However, Sharpe (1918) provided new illustrations which indicate that these specimens belong to Heterocypris . However, it is uncertain if both sets of specimens, those of Sharpe (1897) and those of Sharpe (1918) really belong to the same species.
Cyprinutus dentatus ( Sharpe, 1910) certainly refers to several species. The species described by Sharpe (1910) certainly belongs to Heterocypris , even to the ‘ rostrata ’ type, but it is clear that males of two different species are figured here (compare Sharpe, 1910: figs 2b and 2c, the latter could be Heterocypris incongruens (Ramdohr, 1808)) . The illustrations in Sharpe (1918: 816, fig. 1271a–c) refer most likely to the species figured by Sharpe (1910: fig. 2b). Cyprinotus newmexicoensis Ferguson, 1967 certainly belongs in Heterocyrpis, but the specimens might be juvenile.
Cyprinotus unispinifera Furtos, 1936 clearly belongs in the genus Cypricercus Sars, 1895 . Cyprinotus tenuis Henry, 1923 , C. fuscus Henry, 1919 and C. carinatus (King, 1855) do not belong in Cyprinotus , maybe not even in the Cyprinotinae . Müller (1912) already ranked C. carinatus as “doubtful species” and we here propose to consider all three species as ‘doubtful’ and to exclude them from further consideration. They would thus belong in the list of “excluded species” in Meisch et al. (2019: 110), using the “taxonomic filter” of Müller (1912).
The new species can be distinguished from most of the Cyprinotus s. str. species by the size and shape of the dorsal hump, which is much smaller and more elongated in C. cingalensis ( Fig. 8A View Fig ), C. edwardi McKenzie, 1978 ( Fig. 8B View Fig ), C. indica Battish, 1981 ( Fig. 8C View Fig ), C. dahli Sars, 1896 ( Fig. 8D View Fig ) and C. uenoi Brehm, 1936 ( Fig. 8G, H View Fig ). In C. kimberleyensis McKenzie, 1966 ( Fig. 8E View Fig ), the hump is also large but of a more rectangular shape. The most closely related species is the fossil Cyprinotus scholiosus ( Fig. 8F View Fig ), originally described by Sohn & Morris (1963) as Cheikella scholiosa from the Pliocene of Saudi Arabia, and later also reported from the Pleistocene of Yemen by Malz (1976).
Cyprinotus drubea sp. nov. closely resembles C. scholiosus (see above, differential diagnosis). However, to us it is not entirely clear what the identity of C. scholiosus really is, as various illustrations in Sohn & Morris (1963) and in Malz (1976) show a variety of shapes and sizes of the dorsal hump. For example, fig. 1(7) in Malz (1976) shows a very different shape of the LV than fig. 1(3). The holotype of the species (nr USNM648125; Sohn & Morris 1963: 329, pl. 1, figs 7–10) has a smaller and fully symmetrical dorsal hump, while this structure in C. drubea sp. nov. is higher and asymmetrically curved to the posterior side, while also the posterior margin of the carapace is slightly different. We therefore decide to keep the two species separate, although they are indeed closely related. Together with the population from the Pilbara ( Karanovic 2008), C. scholiosus and C. drubea sp. nov. form a clear species group within the genus.
The allocation of C. indica to the genus Cyprinotus s. str. is still doubtful, as the shape and external ornamentation with dense setae are rather aberrant and unlike any of the other species in the genus. The type materials of this species should be re-investigated.
Karanovic (2008) sank C. dahli , C. uenoi , C. kimberleyensis and C. edwardi into synonymy of C. cingalensis . This was most likely done, because she interpreted the variability in the size and shape of the dorsal hump on the RV in her Pilbara populations as a result of one highly variable species, i.e., C. cingalensis . However, there are two other possible interpretations of the difference in size and shape of the dorsal hump as illustrated by her.
Firstly, her material could have contained specimens from two species: one population of C. cingalensis (smaller species) and one population of a new (larger) species. In this respect, the smaller specimen in her fig. 6F–G might belong to C. cingalensis and the larger specimens in her figs 6A–E and 9A–E would belong to a new species.
A similar situation has occurred when Daday (1913) described Cyprinotus inversus Daday, 1913 from the Kalahari Desert ( South Africa). His material contained two species from two genera, namely a sexual population of a species of Heterocypris (possibly H. giesbrechti Müller, 1898 ) and an asexual population of a species of Hemicypris Sars, 1903 (see Martens 1984). This description lead to decades of confusion regarding the validity of these two genera, as in Heterocypris the LV overlaps the RV and the RV has the marginal tubercles, while in Hemicypris it is just the opposite. After the description of C. inversus , several authors no longer accepted Hemicypris as a separate and valid genus.
Secondly, the smaller specimens might also simply be the A- 1 juveniles (see fig. 6A, F in Karanovic: adult specimen in fig. 6A with marginal tubercles = 1.3 mm; smaller specimen in fig. 6F with fewer marginal tubercles = 1.05 mm). We here illustrate the A- 1 females of C. drubea sp. nov. ( Fig. 7 View Fig ), which indeed resemble the smaller species illustrated by Karanovic (2008).
If either of these hypotheses turns out to be true, then C. cingalensis is not so highly variable and possibly not all four synonymies proposed by Karanovic (2008) might be valid. For these reasons, we do not follow these synonymies here.
The A- 1 juvenile of Cyprinotus drubea sp. nov.
In ostracod taxonomy, juvenile morphology is rarely illustrated, unless the juveniles are seen as a different species or even genus than the adults. Indeed, juvenile and adult morphologies can be very different and have in some cases mislead authors. For example, Eucypris serratomarginata Kiss, 1960 is the last juvenile stage of Sclerocypris multiformis Kiss, 1960 (see Martens 1986) while Candonocypris serratomarginata Furtos, 1935 is most likely the juvenile of Chlamydotheca unispinosa (Baird, 1862) (discussed in Martens & Savatenalinton 2011). Extensive examples of the differences between adult and juvenile morphologies are given for species of the Australian genus Bennelongia De Deckker & McKenzie, 1981 by De Deckker & Martens (2013).
Here, the clearest differences in the valves between adults and A- 1 juveniles are in the much smaller dorsal helmet and the stronger external ornamentation in the juveniles. The strong selvage in the LV is also remarkable. This selvage is completely absent in the RV, which shows the narrow, calcified lamella, typical of juveniles in Cyprididae . The RV is also devoid of tubercles.
The A-1 stage in Cyprididae can be clearly identified by the number of natatory setae on the A2: the adult has five long and one shorter setae (in those species where the natatory setae are well developed). In stage A-1, the shorter seta is still missing.
Distribution
The seven Recent species presently retained in Cyprinotus ( Table 2 View Table 2 ) occur in the Afrotropical, Oriental, Australasian and Pacific realms, and in parts of the southern Palaearctic (North America, Japan) ( Meisch et al. 2019). The actual distribution of the genus is most likely circumtropical so that it is also expected to occur in the northern part of South America and in Central America, from which it has not yet been reported (Higuti & Martens in press). Cyprinotus drubea sp. nov. is possibly an endemic to the New Caledonian archipelago.
Neale (1979) indicated that the collections of the British Museum (now Natural History Museum, London) contained a female specimen, labelled as C. cingalensis , from St. Joseph, Uvea, Loyalty Islands. However, Neale (loc. cit.) found differences in the limb morphology between this specimen and the material from Ceylon and doubted the identification. But if these specimens from Uvea would have belonged to C. drubea sp. nov., then Neale (loc. cit.) would certainly have noted this. It is thus likely that a second species of Cyprinotus occurs in the New Caledonia archipelago.
Morphology
This is the first time that a species of Cyprinotus is described in such detail, especially with regard to the valves. Neale (1979) provided some SEM images of C. cingalensis that show that the anterior marginal tubercles of the RV are not covered by the selvage in this species, but the posterior ones are (i.e., just the opposite of the situation in Cyprinotus drubea sp. nov.) and that the dorsal hump on the RV is indeed also slightly leaning towards the right side. Most surprising in the description of C. cingalensis by Neale (1979), however, is that he drew the proximal seta on the caudal ramus in the middle of the ramus, which is highly unusual in Cyprididae . Karanovic (2008), in what she called C. cingalensis , drew this seta in approximately the same position as we do here in Cyprinotus drubea sp. nov. Surprisingly, she did not find seta d1 on the first segment of T1 and she drew two types of attachments of the caudal ramus: one with a single rod for the male and one with a distally bifurcated rod for the female; both belong to the larger species in her material. Halse & Martens (2019) already suggested that there may be an asymmetry or sexual dimorphism in this structure in this subfamily.
Conclusions
The Recent species of the genus Cyprinotus Brady, 1886 are re-assessed and only seven extant species are retained in the genus. A new species, C. drubea sp. nov. from New Caledonia is included in this list and is compared to all extant taxa as well as to the fossil C. scholiosus , to which it has the closest resemblance. Also, the carapaces and valves of the last juvenile stage of the new species are described and these descriptions are used to re-assess some previous records of species of Cyprinotus . Together with the population from the Pilbara, described by Karanovic (2008) as C. cingalensis , C. drubea sp. nov. and C. scholiosus form a clear species group within the genus Cyprinotus .
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