Cambrian Explosion Fossil Sponge Crumillospongia

Crumillospongia biporosa

Phylum Porifera, Class Demospongia; Family Hazeliidae

Geological Time: Early Middle Cambrian (~525 million years ago)

Size: Fossil is 24 mm by 19 mm

Fossil Site: Pioche Formation, Comet Shale Member, Lincoln County, Nevada

Crumillospongia biporosaDescription: 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 Nevada, and very rare in the Burgess Shale. The genus derives its name from the resemblance of the sponge to a purse, while the specific name refers to the fact that the sponge has pores of two sizes.

Sponge fossils from the Cambrian Explosion are found in various Cambrian sites in DemospongiaNorth America, most notably the Burgess Shale of Canada, and the Cambrian strata of Utah, unlike this specimen, which comes from a new location. 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.

This one comes from the Comet Shale Member of the Pioche Formation of Nevada. This deposit spans the transition of Early to Middle Cambrian which saw the extinction of the Olenellid trilobites. It is just younger than the comparable material from the Chengjiang Maotianshan Shales of Yunnan Province, China and just older than the Burgess Shale Fauna of British Columbia, Canada.

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