|Siamopsis renateae Savatenalinton, 2017|
Siamopsis gen. nov., described here, belongs to a group of genera with the right valve overlapping the left valve in the subfamily Cypridopsinae Kaufmann, 1900 of the family Cyprididae Baird, 1845. The distinguishing characters of the new genus are in the morphology of its valves and soft parts. The postero-dorsal margin of the internal left valve is plate-like protruded. The morphology of this plate varies in different species, e.g., some species bear a tooth-like tubercle on the plate. The posterior margin of the right valve is recurved inwardly at ca mid-height, resulting in the occurrence of a lobe-like expansion that can clearly be seen in the dorsal and caudal views of the carapace. In addition, the other diagnostic soft part features of the new genus are the cylindrical caudal ramus, the presence of two t-setae on the female A2 penultimate segment, the very elongated terminal segment of the Mx1 palp, the morphology of the two large bristles (tooth bristles) of the Mx1 third endite (one smooth, one serrated) and the absence of d-seta on T1. In the present paper, five new species are described under this new genus: Siamopsis renateae gen. et sp. nov., S. suttajiti gen. et sp. nov., S. conspecta gen. et sp. nov., S. khoratensis gen. et sp. nov. and Siamopsis planitia gen. et sp. nov. A key to the species of Siamopsis gen. nov. is also provided.
Keywords: Cypridopsinae; biodiversity; taxonomy; new species; Thailand
Class Ostracoda Latreille, 1802
Subclass Podocopa G.O. Sars, 1866
Order Podocopida G.O. Sars, 1866
Suborder Cypridocopina Jones, 1901
Superfamily Cypridoidea Baird, 1845
Family Cyprididae Baird, 1845
Subfamily Cypridopsinae Kaufmann, 1900
Siamopsis gen. nov.
Type species: Siamopsis renateae gen. et sp. nov. (here designated)
Diagnosis: RV overlapping LV anteriorly, ventrally and posteriorly. LV in internal view with postero-dorsal plate. Posterior margin of RV recurved inwardly. Wouters organ on A1 present, aesthetasc ya long. Terminal segment of Mx1 palp cylindrical, very elongated (length > 2 × width). A2 with well developed claws, long natatory setae, with two t-setae in females. T1 with a-setae (b, c and d setae absent). T2 with d2 seta (d1 seta absent). CR reduced, fl agellum-like, cylindrical in shape.
Etymology: The genus is named after the country “Siam”, the former name of Thailand, where the new taxa were discovered. The name is combined with the suffix of the existing generic name Cypridopsis.
Differential diagnosis Siamopsis gen. nov. can be distinguished from other genera of the subfamily Cypridopsinae by the presence of a postero-dorsal internal plate of the LV and the morphology of the posterior inner valve margin of the RV, which is recurved inwardly. Additionally, it differs from its closest genus, Plesiocypridopsis Rome, 1965, by the presence of the A1 Wouters organ, the two t-setae of the female A2 (there are four t-setae in Plesiocypridopsis) and the morphology of the two large bristles (teeth bristles) on the Mx1 third endite, of which one bristle is smooth while the other one is serrated (both setae are serrated in Plesiocypridopsis).
Species included Siamopsis renateae gen. et sp. nov., S. suttajiti gen. et sp. nov., S. conspecta gen. et sp. nov., S. khoratensis gen. et sp. nov., S. planitia gen. et sp. nov.
Distribution: Thailand (present study).
Siamopsis renateae gen. et sp. nov.
Etymology This species is named after Dr. Renate Matzke-Karasz (Munich University, Germany) in appreciation of her outstanding work on ostracods and also for a long friendship.
Type locality: THAILAND: Nakhon Ratchasima Province, Muang District, irrigation ditch ..., 5 Oct. 2010. Accompanying ostracod fauna: Cypris subglobosa Sowerby, 1840, Cyprinotus uenoi Brehm, 1936, Stenocypris cf. orientalis Victor & Fernando, 1981, Siamopsis khoratensis gen. et sp. nov., S. conspecta gen. et sp. nov. and S. planitia gen. et sp. nov.
Ecology The new species has thus far been recorded from eight localities in the Northern and Northeastern provinces: Nakhon Ratchasima, Chaiyaphum, Phayao, Chiang Rai, Phitsanulok and Phetchabun. It occurs at a pH range of 6.5–7.2, a temperature range of 26.1–29.5°C and a dissolved oxygen (DO) range of 3.20–7.80 mg/l.
Siamopsis suttajiti gen. et sp. nov.
Etymology: This species is named after Prof. Dr. Maitree Suttajit (University of Phayao, Thailand) in appreciation of his encouragement and moral support over the years, especially during my research project on nonmarine ostracods in the southern part of Northeast Thailand.
Siamopsis conspecta gen. et sp. nov.
Etymology: The Latin word ‘conspecta’, meaning conspicuous, refers to the markedly well-developed tooth-like tubercle on the postero-dorsal plate of internal LV. This is the most prominent character of the new species.
Siamopsis khoratensis gen. et sp. nov.
Etymology: The species is named after Nakhon Ratchasima Province, also called “Khorat”, where the new species was discovered.
Siamopsis planitia gen. et sp. nov.
Etymology: The specific epithet “planitia” refers to the appearance of a dorsal margin at the middle part of the carapace in lateral view, which is similar to the summit of a plateau. This is the most prominent character of the new species.
Sukonthip Savatenalinton. 2017. Siamopsis gen. nov. and Five New Species of the Subfamily Cypridopsinae Kaufmann, 1900 (Crustacea: Ostracoda) from Thailand. European Journal of Taxonomy. 384; 1–39. DOI: 10.5852/ejt.2017.384