Description: Grows from a small discoid holdfast with short stipe no longer than 1.5 cms long which expands into a strong blade up to 30 cms long and 18 cms broad. Irregular blades may grow from the margins.

Habitat: Common. Epilithic and on the stipes of Laminaria in the upper sublittoral to 27 m deep.

Distribution: Western shores of the British Isles: south-west England, Wales, around most of Ireland save the east coast, west of Scotland and the Shetlands. Europe: Mediterranean, Azores, Portugal, Atlantic coasts of Spain and France, Baltic Sea. Atlantic coasts of North America: Massachusetts. Further afield: Canary Islands .

Similar Species: Callophyllis laciniata is distinctly branched more or less dichotomously.

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

iNaturalist: Kallymenia reniformis at iNaturalist World Species Observations database.

WoRMS: Kallymenia reniformis at World Register of Marine Species.