Species: Dineutus unidentatus Aubé, 1838
Classification
Phylum: Arthropoda
 Class: Insecta
  Order: Coleoptera
   Family: Gyrinidae
    Genus: Dineutus

Morphology:
Adult:
 - Dineutus unidentatus is closest to D. australis but can be distinguished by both sexes of D. unidentatus have the narrowly oval body form and smaller size (male: 6.0–6.7 mm; female: 6.4–6.9 mm) than that D. australis, male elytral apices with longer and more developed epipleural spines. The median lobe of D. unidentatus aedeagus is broader, more parallel-sided, which is abruptly constricted at its apex in dorsal view. The females of both species can be distinguished by D. unidentatus has the elytral apices with epipleural spines, and more elongate gonocoxae with the apex obliquely truncate and the lateral angle acuminate.


Figure
Dorsal habitus of Dineutus unidentatus male (Photo: Benjamart Suksai).


Habitat: - In Thailand, D. unidentatus was found near the margins of a stagnant stream and in ponds.

Distribution:
 - Amnat Charoen Province: Kork Stream, Chanuman District.
- Khon Kaen Province: Khon Kaen University.
- Khon Kaen Province: Phong River, Si Chomphu District.
- Khon Kaen Province: Pond at Ban Kho, Mueang Khon Kaen District.
- Krabi Province: Pond at Ban Paga Sai, Nuea Khlong District.
- Mukdahan Province: Huai Lao Waterfall, Khamcha-I District.
- Mukdahan Province: Tadton Waterfall, Nong Sung District.
- Nakhon Ratchasima Province: Sakaerat Environmental Research Station.
- Phetchabun Province: Nam Churn Stream, Nam Nao District.
- Trang Province: Sikao District.

Work cited:
 - Suksai, B., Gustafson, G.T., Sites, R.W. and Sangpradub, N. 2021. The Gyrinidae (Coleoptera) fauna of Thailand: Key to tribes and genera, with new records and keys to species of Dineutini and Gyrinini. Zootaxa 5071(1): 097–117.

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