colleplax

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.{{Cite book |title=Treatise on Invertebrate Paleontology. Part H, Brachiopoda (revised), Volume 1. |last=Kaesler |first=Roger L. |date=1997 |publisher=Geological society of America |isbn=978-0-8137-3108-7 |edition= |location=Boulder (Colo.) |pages=359, 360, 427}} This aperture is supposed to have been covered by adhesive tissue,{{Cite web |title=The external surface of Dictyonella and of other pitted brachiopods {{!}} The Palaeontological Association |url=https://www.palass.org/publications/palaeontology-journal/archive/24/3/article_pp443-481 |access-date=2023-07-20 |website=www.palass.org}} but no similar structure exists in any living brachiopod, so other interpretations have also been proposed.