keyhole urchin
The 'keyhole urchin' is a type of sea urchin known for its distinctive keyhole-shaped openings and its resemblance to sand dollars.
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Definition
C1Marine Biology
(technical)A flat sea urchin with keyhole-shaped openings in its shell, belonging to genera like Melitta, Rotula, and Encope.
Example
- The keyhole urchin can often be found burrowing in sandy or muddy ocean floors.
- Scientists study keyhole urchins to understand their unique respiratory system.