[1] Described as Patiriella mortenseni in 2002,[2] it is named after T. Mortensen, who recorded it as distinct from Patiriella regularis, the New Zealand common cushion star, in 1925.

[3] According to genetic evidence, P. mortenseni was moved from the Patiriella genus to Meridiastra in 2004.

[4] Reciprocal transplant experiments in Fiordland have shown it is less tolerant of hyposaline conditions than the sympatric (but distantly related) P. regularis.

This is reflected in its distribution: it lives in deeper waters (at depths of roughly 10±3 m in Milford and Doubtful Sounds), below the low salinity layer.

[5] In laboratory conditions, they die after 24-hour exposure to water with salinities below 25‰.