Chancelloriids: slugs or sponges?

Chancelloriids are one of the most difficult groups of Cambrian fossils to understand, because there are two completely opposed interpretations of them. They are generally sponge-like in overall form, but have details that seem much more like molluscs. Resolving these issues is challenging, but potentially has far-reaching implications for the whole of animal evolution... Some of the important references: Porter 2008: https://onlinelibrary.wiley.com/doi/f... Botting et al. 2013: https://palaeo-electronica.org/conten... Bengtson and Collins 2015: https://palaeo-electronica.org/conten... Botting and Muir 2018: https://www.sciencedirect.com/science... Cong et al. 2018: https://royalsocietypublishing.org/do... Botting et al. 2019: https://palaeo-electronica.org/conten... Yun et al. 2021: https://www.diva-portal.org/smash/get... Yun et al. 2025: https://www.nature.com/articles/s4200...