Well-Preserved Utah Cambrian Sponge Fossil

Description: The Demosponge Crumillospongia belong to the family Hazeliidae. Because no attachment structures have ever been found, it remains unclear whether or not this early poriferan lived attached to the seafloor. Crumillospongia are somewhat rare in the Middle Cambrian of Utah, and very rare in the Burgess Shale. The Crumillospongia spongs on this plate has unusually good contrast, and is very 3-D in aspect. Note the two Peronopsis agnostid trilobites superimposed near the top.
Sponge fossils from the Cambrian Explosion are found in various Cambrian sites in North America, most notably the Burgess Shale of Canada, and the Cambrian strata of Utah, like this specimen. Many sponges are also described from the Chengjiang biota of China. Sponges are believed to have undergone repeated radiations in the Phanerozoic, and probably attained their largest diversity in the Cretaceous.