Eucidaris metularia is a primitive species of sea urchin and comes from an ancient lineage that has hardly changed over the past 150 million years.

It is a common species among seagrasses and in rocky back-reef lagoons, usually in shallow water, but sometimes at depths of down to 500 metres (1,600 ft).

At metamorphosis, which takes place after the larvae have settled on the seabed, the rearrangement of tissues is much less extensive in these primitive species than is the case in more advanced echinoids.

[8] Eucidaris metularia was one of several sea urchins used in research designed to examine the feasibility of using non-invasive magnetic resonance imaging technology to study internal anatomy.

[9] MRI was found to be a useful tool for comparative studies of the morphology of echinoids which extended the range of techniques available for use without destroying the specimen.