Demospongea (Order: Monaxonida)
Fieldospongia is considered to be a primitive demosponge related to the Anthaspidellidae (Rigby, 1986). Demosponges, the same group that are harvested as bath sponges, represent the largest class of sponges today.
Fieldospongia – from Field, the mountain peak (2,643 m) and small town near Fossil Ridge, British Columbia, Canada. The name was given by William Cornelius Van Horne (General Manager of the Canadian Pacific Railway), to honor Cyrus West Field a promoter of the first telegraph cable across the Atlantic Ocean; and from the Latin spongia, “sponge.”
bellilineata – from the Latin bell, “charming,” and linea, “pertaining to lines.” The name makes reference to the linear-like skeleton of this sponge.
Holotype –USNM66454, in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Burgess Shale and vicinity: none.
Other deposits: none.
Middle Cambrian, probably from the Glossopleura Zone or the Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
The northwest shoulder of Mount Stephen and the Monarch Peak in Kootenay National Park.
Brief history of research:
Described in 1920 as Tuponia bellilineata by Walcott in his monograph on sponges from the Burgess Shale, this form has now been placed within a separate genus, Fieldospongia, erected by Rigby in 1986. The only known specimen purportedly came from the Mount Whyte Formation (Walcott, 1920), just below the Northwestern shoulder of Mount Stephen. This formation is older than any of the rock units containing Burgess Shale-type fossils in the vicinity and is not characterized by exceptional preservation. Examination of the specimen suggests that this sponge probably comes from younger rock units with Burgess Shale-type fossils (Glossopleura to Bathyuriscus-Elrathina Zones) that are known in this area. It is likely that this specimen was derived from upper sections and was collected at the base of talus slopes coinciding with levels of the Mount Whyte Formation. A second specimen was described by Rigby and Collins in 2004 from The Monarch, a mountain Peak at the border between Mount Assiniboine Provincial Park and Kootenay National Park.
This species has a conical shape with gentle horizontal wrinkles. The thin walls are composed of similarly spaced bundles of spicules arranged vertically and horizontally, forming a regular skeletal net with rectangular cells. Vertical strands are usually more prominent than the horizontal ladders. The root tuft is relatively long and narrow.
Fieldospongia is very rare, known from only two specimens.
Fieldospongia would have lived attached to the sea floor. Particles of organic matter were extracted from the water as they passed through canals in the sponge’s wall.