Allonnia

Allonnia is a genus of extinct sponge belonging to the class Heteractinida. These sponges are characterized by their distinctive heteractine spicules, which are six-rayed spicules with rays of different lengths and shapes. Allonnia fossils have been found in Cambrian-age rocks, primarily in North America, specifically in the Burgess Shale Formation of British Columbia, Canada. The genus is significant because it provides insight into the early evolution and diversity of sponges during the Cambrian explosion. Fossils suggest Allonnia were sessile, filter-feeding organisms that attached to the seafloor. They contribute to our understanding of the paleontology of early sponges and the composition of ancient marine ecosystems.