Which ancient sponge fossils have been found in the Burgess Shale?

The Burgess Shale of the Middle Cambrian contains significant fossil evidence of early sponges, which are well-represented in this formation. Specifically, the ancient sponge fossils identified in the Burgess Shale include:1

• Protospongia: A member of the class Hyalospongiae (glass sponges).1
• Eiffelia: A member of the extinct class Heteractinellida.1

These organisms typically resembled pouches with very thin walls, featured spicules arranged in a single layer, and likely possessed an ascon-type water-current system. While the Burgess Shale is renowned for its exceptional preservation of soft-bodied biota, these sponge fossils provide critical insight into the diversity of marine life during the Middle Cambrian Epoch.12