Mottled appearance, with rows of large spines surrounded by discs along its upper surface. The number of arms is usually 11, but can vary from 7 to 14. While the species can also act as a scavenger, Coscinasterias muricata is such an active predator of molluscs in sheltered marine habitats that it is considered a keystone species; it can alter community structure by preventing the establishment of beds of mussels, scallops, etc. The species was called C. calamaria until recently. That name is now reserved for a close tropical relative, which has slightly differently shaped plates on the arms. If broken off, each arm can regenerate into a complete animal.

• Max Size: 50 cm
• Sea Temperature Range: 10.3-23.6°C
• Depth: 0-150m
• Habitat: Rocky Reef, Soft sediment

• IUCN Threat Status: Not Evaluated
• Occurrence: Common (21% 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 (4 per transect)
  Abundance is calculated as the average number of individuals recorded per RLS transect, where present.