Choia belongs to an early branch of siliceous sponge, the protomonaxonids at the base of the Demospongea (Rigby, 1986). Demosponges, the same group that are harvested as bath sponges, represent the largest class of sponges today.
Choia – derivation unknown, but probably from the Spanish word cholla referring to spiny cacti of the genus Opuntia which resembles the sponge Choia in shape and spiny elements.
carteri – in honor of H. J. Carter, a famous nineteenth century hexactinellid sponge specialist.
Burgess Shale and vicinity: C. ridleyi (Walcott, 1920) from the Walcott Quarry; C. hindei (Dawson, 1896) from the Raymond Quarry.
Other deposits: C. utahensis (Walcott, 1920) from the Middle Cambrian Wheeler and Marjum Formations in Utah (Rigby et al., 2010); C. xiaolantianensis from the Lower Cambrian Chengjiang biota (Hou et al., 1999), C. sp. from the same formation near Haikou, Yunnan Province (Luo et al., 1999); and C.? sriata from the Lower Cambrian Hetang Formation, Anhui Province (Xiao et al., 2005). Choia is also known from the Ordovician of Morocco (Botting, 2007).
Burgess Shale and vicinity: The Walcott and Raymond Quarries on Fossil Ridge. The Collins Quarry and Trilobite Beds on Mount Stephen.
Other deposits: C. hindei (Dawson, 1896) from the Ordovician of Quebec at Little Métis to the Middle Cambrian Burgess Shale; C. carteri, C. hindei from the Middle Cambrian Wheeler and Marjum Formations in Utah (Rigby et al., 2010).
Choia was first described by Walcott (1920) based on specimens from the Burgess Shale, Utah and Quebec. The material from the Burgess Shale was re-examined in detail by Rigby (1986) and Rigby and Collins (2004).
Choia carteri consists of a flattened elliptical disc, up to 2 cm in diameter (5 cm including the long spicules), formed by fine radiating spicules from which stronger and long spicules up to 30 mm in length radiate. Other species differ in size and spine coarseness. C. ridleyi is generally smaller (less than 1.5 cm) and C. hindei larger (up to 8 cm).
Choia is not common in the Walcott Quarry where it represents only 0.2% of the Walcott Quarry community (Caron and Jackson, 2008). Only one specimen of C. hindei is known from the Burgess Shale (Rigby and Collins, 2004).
The sponge was not anchored to the sediment, but simply sat unattached on the sea floor. The long spicules are interpreted to have maintained the sponge above the sediment-water interface. Particles of organic matter were extracted from the water as they passed through canals in the sponges wall.
BOTTING, J. P. 2007. ‘Cambrian’ demosponges in the Ordovician of Morocco: insights into the early evolutionary history of sponges. Geobios, 40: 737-748.
CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.
DAWSON, J. W. 1896. Additional notes on fossil sponges and other organic remains from the Québec Group of Little Métis on the lower St. Lawrence; with notes on some of the specimens by Dr. G.J. Hinde. Transactions of the Royal Society of Canada, 2: 91-129.
HOU, X., J. BERGSTRÖM, H. WANG, X. FENG AND A. CHEN. 1999. The Chengjiang fauna exceptionally well-preserved animals from 530 million years ago. Yunnan Science and Technology Press, Kunming, 170 p.
LUO, H., S. HU, L. CHEN, S. ZHANG AND Y. TAO. 1999. Early Cambrian Chengjiang fauna from Kunming region, China. Yunnan Science and Technology Press, Kunming, 162 p.
RIGBY, J. K. 1986. Sponges of the Burgess Shale (Middle Cambrian), British Columbia. Palaeontographica Canadiana, 2: 1-105.
RIGBY, J. K. AND D. COLLINS. 2004. Sponges of the Middle Cambrian Burgess Shale and Stephen Formations, British Columbia, 1, 155 p.
RIGBY, J. K., S. B. CHURCH AND N. K. ANDERSON. 2010. Middle Cambrian Sponges from the Drum Mountains and House Range in Western Utah. Journal of Paleontology, 84: 66-78.
WALCOTT, C. D. 1920. Middle Cambrian Spongiae. Smithsonian Miscellaneous Collections, 67(6): 261-364.
XIAO, S., J. HU, X. YUAN, R. L. PARSLEY AND R. CAO. 2005. Articulated sponges from the Lower Cambrian Hetang Formation in southern Anhui, South China: their age and implications for the early evolution of sponges. Palaeogeography, Palaeoclimatology, Palaeoecology, 220: 89-117.