Neopotamocypris, Savatenalinton, 2024

Savatenalinton, Sukonthip, 2024, A new Potamocypridini genus of Cypridopsinae (Crustacea, Ostracoda) from Thailand, with a discussion on taxonomic characters and morphological evolution in the tribe, Zootaxa 5537 (4), pp. 475-492 : 488-489

Origin of Neopotamocypris gen. nov.

Neopotamocypris gen. nov. is very similar to Potamocypris in external morphology. For example, the general shape of the Cp in lateral view is subtriangular, the RV overlaps the LV ventrally, and the valve surface is usually set with tiny pits and setae. In addition, the similarity also exists in the valve structure, especially on the LV, which has inwardly displaced selvages on both, the anterior and posterior parts. The discrimination between these two genera thus mainly relies on the soft parts morphology, especially the T2, T3, Md-palp, Mx1 and genital hook of the female. As both genera belong to the same tribe ( Potamocypridini ), such differences existing in the new genus could be constituted via divergent evolution from the Potamocypris ancestor and the new genus might be of a more recent origin evidenced by its derived characters (see discussion above).

Neopotamocypris indivisa gen. nov. sp. nov. is the only species of the tribe Potamocypridini recorded in Southeast Asia and Thailand. It generally resembles P. acuminata , which was described based on Pleistocene fossil specimens ( Fuhrmann & Pietrzeniuk 1990; Fuhrman & Goth 2011). However, recently, the first living specimens of this species were reported from Japan and the description of soft body parts was provided for the first time ( Smith et al. 2024). Thus far, P. acuminata has been recorded from the Palaearctic region. Nonetheless, Smith et al. (2021) reported on exotic species, from Japanese pet shops, including Pseudostrandesia tenebrarum which is very similar to the endemic Thai P. phetchabunensis (see Savatenalinton & Martens 2010; Smith et al. 2021), and also proposed that its origin is most likely in Southeast Asia, with transportation occurring via the pet trade. Moreover, Smith et al. (2024) recently presented six more exotic species of Japan, including P. acuminata and Siamopsis sudzukii (Okubo, 1992) , collected from pet shops and hobbyist’s aquaria. The record of the latter species in Japan is remarkable in that Siamopsis is no longer endemic to Thailand. Such evidence most likely suggests the possibility of transportation of ostracod faunas between these two regions. Hence, it could be assumed that N. indivisa gen. nov. sp. nov. evolved from an ancestor in Potamocypris , like P. acuminata .

Another possibility is that N. indivisa gen. nov. sp. nov. evolved from an Oriental Potamocypris ancestor. In the Oriental region, only one identified Potamocypris species has been recorded, the Indian P. narayanani (see George & Martens 2002). Further findings of Potamocypris , either living or fossil, in Thailand or Southeast Asia would provide more explanation on this phenomenon.

Distribution

In the last two decades, extensive surveys of freshwater ostracods in Thailand have been carried out mainly in three parts of the country: northern, northeast and western parts. About 410 water bodies, ranging from various types of habitats in 37 provinces (from a total of 77 provinces) were sampled and ca. 620 samples were obtained. The examination of such a large number of sampled localities unveils that N. indivisa gen. nov. sp. nov. is very rare as it has so far been found only in 10 localities in eight provinces, namely Nakhon Ratchasima, Chaiyaphume , Lopburi, Phetchabun, Kanchanaburi, Ratchaburi, Phetchaburi and Prachuap Khiri Khan ( Table 1, Fig 6 ) .

Figures

FIGURE 6. Distribution map of Neopotamocypris indivisa gen. nov. sp. nov., numbers see Table 1. (Modified from NordNordWest, Thailand adm location map.svg - https://commons.wikimedia.org/wiki/File:BlankMap-Thailand-provinces. svg)