Choia

Choia is a genus of extinct demosponge ranging from the Cambrian until the Lower Ordovician periods. Fossils of Choia have been found in the Burgess Shale in British Columbia; the Maotianshan shales of China; the Wheeler Shale in Utah; the Itajaí Basin in Brazil; and the Lower Ordovician Fezouata formation.^[2][3] It was first described in 1920 by Charles Doolittle Walcott.^[4]

Choia Temporal range: Cambrian Stage 3–Arenig PreꞒ Ꞓ O S D C P T J K Pg N [1]
Fossil of Choia carteri from the Burgess Shale
Scientific classification
Kingdom:	Animalia
Phylum:	Porifera
Class:	Demospongiae
Order:	†Protomonaxonida
Family:	†Choiidae
Genus:	†Choia Walcott, 1920
Type species
†Choia carteri Walcott, 1920
Species
†C. carteri Walcott, 1920 †C. hindei (Dawson, 1896) †C. utahensis Walcott, 1920 †C. ridleyi Walcott, 1920 †?C. striata Xiao et al., 2005 †C. xiaolantianensis Hou et al. 1999

Life habit

Reconstruction of C. carteri, as according to the Fezouata specimens^[2]

Choia was originally thought to be not attached to the sea bed: the living animal was originally thought to rest directly on the substrate, with the radiating spines from the edge of its flattish, conical body, giving an appearance not unlike that of the peak of a big top, with guy lines. Recently discovered fossils from Lower Ordovician Morocco show that the living animal was actually suspended high above the seafloor, attached via stalk-like spines derived from spicules.^[5] Water is assumed to have entered the sponge parallel to the spines, being expelled, presumably, from a central opening.^[6] Species reached up to an average of 28 mm in diameter.^[6]

Distribution

127 specimens of Choia are known from the Greater Phyllopod bed, where they comprise 0.2% of the community.^[7]

• 
  Fossils of C. ridleyi from the Burgess Shale
• 
  Fossil of C. xiaolantianensis from the Maotianshan Shales
• 
  Fossil of C. sp from the Fezouata biota
• 
  Fossil of C. utahensis from the Wheeler Shale