An urchin with thick blunt spines like pencils, wedged in rock crevices by day. The qualifier separates it from the Atlantic species of the same name.
Test diameter is not given in any source consulted. Thick blunt pencil spines, usually fouled, and it wedges under rock by day.
The Galapagos pencil urchin is now treated as a separate species for the Galapagos, Cocos and Clipperton populations. Where that leaves a Revillagigedo animal is not settled in the sources, so an identification here should be treated as genus-level.
Nought to forty-five metres, from Baja California to Panama. It grazes coral heavily enough to measurably reduce reef growth. The spines are blunt and it is harmless to handle.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.