Phyllacanthus irregularis

Western slate-pencil urchin
Phyllacanthus irregularis
Phyllacanthus irregularis, Rottnest Is, WA, Photo: Andrew Green
Phyllacanthus irregularis
Phyllacanthus irregularis, Rottnest is, WA, Photo: Andrew Green
1 / 2
Phyllacanthus irregularis
Phyllacanthus irregularis


Temperate Australasia


Very similar in general appearance to P. parvispinus and lives in a similar habitat. It can, however, be distinguished from the eastern species by possessing small pointed spinelets at the top of the test, rather than broad and scale-like spinelets. It is most commonly found in shallow undercut caves in limestone reefs.


Max Size: 11 cm

Sea Temperature Range: 13.3-23.5°C

Depth: 1-20m

Habitat Generalization Index: N/A

Also referred to as the SGI (Species Generalisation Index), this describes the habitat niche breadth of the species. Species with values less than 15 are found in a relatively narrow range of reef habitat types (specialists), while those over 25 may be found on most hard substrates within their range (generalists). Learn more here.

Conservation and Rarity

IUCN Status: Not Evaluated

Occurrence: Widespread (54.2% of sites)

Occurrence describes how often the species is found on surveys within its distribution. It is calculated as the % of reef sites surveyed by RLS divers across all the ecoregions in which the species has been observed

Abundance: Few (3 per transect)

Abundance is calculated as the average number of individuals recorded per RLS transect, where present.

Edit by: GJ Edgar. 2008. Australian Marine Life. New Holland, Sydney