Colleplax – a structure present in chileate brachiopods.
It is a triangular plate in the umbonal region of the ventral valve, covering an area that is otherwise externally exposed through the resorption of a part of the ventral valve.[1] This aperture is supposed to have been covered by adhesive tissue,[2] but no similar structure exists in any living brachiopod, so other interpretations have also been proposed.[1]