Description: A left-eyed flatfish with large, clearly visible scales that is reported to grow up to 18 cm in length. It has a single, very elongated, fin ray just beside the mouth which is a key identification feature for this species. This fin ray is very conspicuous and is usually pale in colour. The colouration of the fish itself is quite distinctive, with blotches and blocks of pale brown to dark brown, with some paler patches and usually some blue, giving this fish good disruptive camouflage.

Habitat: Usually recorded on sand or muddy sand but can be found in more coarse habitat too. Reported from 10 m – 200 m but doesn’t seem to be overly common within diving depths.

Distribution: Few records exist but this may be due to under-recording. There are currently two records for the UK and Ireland on NBN, one from Belfast Lough and one from Rathlin Island.

Similar Species: The single elongated fin ray should distinguish this species from Arnoglossus imperialis (4-5 elongate fin rays) or Arnoglossus laterna (no elongate fin rays).

Key Identification Features:

• Left-eyed flatfish with large scales.
• Diagnostic single elongated fin ray near mouth, which is usually pale in colour and highly conspicuous.
• Usually patterned with blotchy, blocks of colour (pale to dark browns with some patches of blue).

Distribution Map from NBN: Arnoglossus thori at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Arnoglossus thori at iNaturalist World Species Observations database.

GBIF data for Arnoglossus thori

WoRMS: Arnoglossus thori at World Register of Marine Species. Accepted name: Arnoglossus thori Kyle, 1913. AphiaID: 127128.

Classification: Biota; Animalia; Chordata; Vertebrata; Gnathostomata; Osteichthyes; Actinopterygii; Actinopteri; Teleostei; Pleuronectiformes; Bothidae; Arnoglossus