slate pencil urchin
Alternative names: red slate pencil urchin, red pencil urchin, Heterocentrotus mamillatus
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Heterocentrotus mamillatus is a species of tropical sea urchin from the Indo-Pacific region. This particular urchin is quite large, with some specimens measuring over 8 cm in diameter and spikes up to 10 cm. They are colored in bright red, but some are purple or brown.