''Heterocentrotus trigonarius'', commonly known as the slate pencil urchin or red slate pencil urchin, is found in the tropical waters of the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

region. ''

Heterocentrotus mamillatus ''Heterocentrotus mamillatus'', commonly known as the slate pencil urchin, red slate pencil urchin, or red pencil urchin, is a species of tropical sea urchin from the Indo-Pacific region. Description This species is a large sea urchin, capp ...

'' is a similar, related species. ''Heterocentrotus trigonarius'' can grow to in diameter (spine-to-spine). The spines are potentially harmful to humans if trodden on.

References

trigonarius Echinoderms of the Indian Ocean Echinoderms of the Pacific Ocean Echinoderms described in 1816 Taxa named by Jean-Baptiste Lamarck {{echinoidea-stub