Species: Porrorhynchus marginatus Laporte, 1835
Classification
Phylum: Arthropoda
 Class: Insecta
  Order: Coleoptera
   Family: Gyrinidae
    Genus: Porrorhynchus

Morphology:
Adult:
 - Porrorhynchus marginatus is the only Thai Porrorhynchus. This species can be distinguished from other Gyrinidae in Thailand by large body size and long (male: 15.6–18.6 mm; female: 15.4–17.4 mm), triangular labrum, and the lateral margin of the orbital ridge yellow or white in color.


Figure
Dorsal habitus of Porrorhynchus marginatus male (Photo: Benjamart Suksai).


Habitat: - In Thailand, Porrorhynchus marginatus was found only in streams with shaded areas and slow current with substrates including pebble, gravel and sand, at elevations ranging from 11 to 1,800 m a.s.l., but most often at 100–900 m a.s.l.

Distribution:
 - The northeastern: Amnat Charoen Province, Chaiyaphum Province, Loei Province, Mukdahan Province, Nakhon Ratchasima Province, Sakon Nakhon Province, Ubon Ratchathani Province.
-The eastern: Chanthaburi Province, Prachin Buri Province, Rayong Province, Sa Kaeo Province.
-The northern: Chiang Mai Province, Mae Hong Son Province, Nan Province, Phetchabun Province.
-The southern: Chumphon Province, Phang Nga Province, Phatthalung Province, Satun Province, Songkhla Province, Surat Thani Province, Yala Province.
-The western: Kanchanaburi Province.
-The central: Nakhon Nayok Province, Saraburi Province, Suphan Buri Province.

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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