Phymatolithon

Phymatolithon is a genus of non geniculate coralline red algae, known from the UK,^[1] and Australia.^[2] It is encrusting, flat, and unbranched; it has tetrasporangia and bisporangia borne in multiporate conceptacles.^[1] Some of its cells bear small holes in the middle; this distinctive thallus texture is termed a "Leptophytum-type" thallus surface, and has been posited as a taxonomically informative character.^[1] It periodically sloughs off its epithallus, reducing its overgrowth by algae by as much as 50% compared to bare rock.^[3]

Phymatolithon
Phymatolithon calcareum
Scientific classification
Domain:	Eukaryota
Clade:	Archaeplastida
Division:	Rhodophyta
Class:	Florideophyceae
Order:	Corallinales
Family:	Hapalidiaceae
Genus:	Phymatolithon Foslie, 1898
Species
At least 11, including Phymatolithon bornetii Phymatolithon calcareum Phymatolithon elatum Chamberlain, 1990 Phymatolithon laeve Phymatolithon lenormandii (Areschoug) W.H.Adey
Synonyms
Leptophytum Adey, 1966