Photographer: Paul Osmond
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Known by several common names including the Pincushion Tuxedo Urchin and the Shortspine Urchin, this is generally known as the Globular Sea Urchin (Mespilia globulus).
This species is generally found on shallow sand reefs, and is regularly covered with sea grasses as shown in this image.
Image taken on a coral reef close to Mabul Island in Sabah, Malaysia.