Brachiospongia
digitata
Brachiospongia is a highly-distinctive fossil sponge. It is a
glass sponge, a member of Class Hexactinellida. Glass sponges make a
skeleton consisting of a network of opaline siliceous spicules (SiO2·nH2O).
They occur in deep-water ocean environments today but occupied shallow water
marine facies during the Paleozoic. All fossil and living hexactinellid
sponges are sessile, benthic filter-feeding organisms. Brachiospongia
has an unusually-shaped skeleton consisting of a cup-like structure with a
series of six to twelve, bent finger-like extensions.
Classification: Animalia, Porifera, Hexactinellida, Lyssacinosa,
Brachiospongiidae
Brachiospongia digitata (Owen, 1858) (top view) from the Bigby Limestone
(Trenton Group, upper Middle Ordovician (sensu traditio)) at Bridgeport,
Kentucky, USA (FMNH P59, Field Museum of Natural History, Chicago, Illinois,
USA).