We describe Malawidopsis gen. nov., a new genus of Cypridopsinae Kaufmann, 1900 from the African ancient Lake Malawi. The genus comprises at least 17 new species, which makes it a significant ostracod radiation in this lake, parallel to a similar (but independent) cypridopsine radiation in Lake Tanganyika. Three of these new species are here described: Malawidopsis stellae gen. et. sp. nov., the type species of the new genus; M. ruwaydae gen. et. sp. nov. and M. antoniae gen. et. sp. nov.. The other new species are briefly illustrated and described, but are left in open nomenclature (sp. A, B, C, etc.). Cypridopsis cunningtoni Sars, 1910 and Potamocypris fuelleborni Daday, 1910 are transferred to Malawidopsis gen. nov. and are identical to Malawidopsis spec. F and Malawidopsis spec. N, respectively. The new tribe Plesiocyprisopsini trib. nov. is erected, and comprises the cypridopsine genera previously in the Cypridopsini s.l. with the right valve overlapping the left valve, at least anteriorly. Potential drivers of speciation within this endemic clade in Lake Malawi are briefly discussed. Bathymetry might have been important, with most species being restricted to shallower depths and only four species also occurring at depths of 75 m or more, but very few specimens were retrieved from greater depths. Most species occurred on coarse sand, but this sediment category coincides with shallower stations. Overall, most species appear to have a wide geographical distribution in the lake, so no geographical parapatric speciation is apparent. The occurrence of all species in sexual populations and the significant differences in the male sexual organs and the valves suggest that sexual selection might have been the most important driver in the speciation process of this species flock, but this should be further explored. Following deep coring results in Lake Malawi, the present clade could be (at least) c one million years old.
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The New Caledonian Archipelago is a hot spot for biodiversity and endemism. Whereas popular groups such as birds and plants are well-studied, invertebrate groups such as ostracods remain ill-known. Here, Caledromus robinsmithi gen. et sp. nov. is described from a single locality on ‘Grande Terre’, the main island of the archipelago. The new genus belongs to the Psychrodromini, one of the four tribes in the subfamily Herpetocypridinae (family Cyprididae). Caledromus gen. nov. can be distinguished from all other herpetocypridinids by a combination of the following factors: the absence of marginal septa in both valves, the mildly developed marginal valve structures, the small Rome organ on the A1, the total reduction of the five natatory setae on the A2, the rectangular second palp segment of the Mx1, the broad and asymmetrical palp on the female T1, the absence of additional postlabyrinthal coils in the Hp and the seta Sp of the CR which is a fixed spine. Because of the close similarity to the genus Psychrodromus, the new genus is thought to have Palaearctic affinities, contrary to other ostracod species in New Caledonia, which are either circumtropical or with Australian zoogeographical connections.
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