Purple turtle urchin

This purple turtle urchin ( Colobocentrotus atratus ), also known as the helmet urchin, is a species of echinoderm notable for its unique morphology. Its shell is thick and rounded, giving it a "helmet" or "turtle shell" appearance. It lacks the long spines typical of sea urchins and instead has thick, flat plates covering its body. Its dominant color is a dark purple, sometimes almost black, which can vary depending on the individual.