Description: Colonial; tiny polyps arising from basal encrusting carpet. Each polyp is up to 4 mm tall, 2 mm diameter, with 19-22 tentacles. Colour dark brown, tentacles often with pale tips. Base and polyp walls encrusted with fine sand.

Habitat: On shore in open rock pools amongst Corallina, etc. or on silty rocks, stones and shells in the shallow sublittoral. Very sensitive, closing at the slightest disturbance and well hidden due to its small size and dull coloration.

Distribution: Recorded in the British Isles from south Devon, south Wales, Calf of Man and the west coast of Ireland north to Fair Head. Elsewhere from north and west France and Denmark. Probably more widely distributed but easily overlooked.

Similar Species: Smaller than, and differently coloured from Parazoanthus and Epizoanthus couchii.

Key Identification Features:

• Small size of polyps.
• 19-22 tentacles.
• Chocolate brown colour.

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

iNaturalist: Isozoanthus sulcatus at iNaturalist World Species Observations database.

WoRMS: Isozoanthus sulcatus at World Register of Marine Species. Accepted name: Isozoanthus sulcatus (Gosse, 1860). AphiaID: 101053.

Classification: Biota; Animalia; Cnidaria; Anthozoa; Hexacorallia; Zoantharia; Macrocnemina; Parazoanthidae; Isozoanthus