Hexactinellida (Order: Reticulosa)
Stephenospongia is placed in the Family Hintzespongiidae (primitive hexactinellids). Hexactinellid sponges (glass sponges) have a skeleton composed of four to six-pointed spicules. They are considered to be an early branch within the Porifera phylum due to their distinctive composition.
Stephenospongia – from Mount Stephen (3,199 m), a mountain peak in Yoho National Park, named after George Stephen (1829 – 1921), first president of the Canadian Pacific Railway and the Latin spongia, meaning “sponge.”
magnipora – from the Latin magnus, “great,” and porus, “pore.” The name makes reference to the large pores present in the skeleton of this sponge.
Holotype –ROM43127 in the Royal Ontario Museum, Toronto, Canada.
Burgess Shale and vicinity: none.
Other deposits: none.
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
The Trilobite Beds on Mount Stephen.
Brief history of research:
Stephenospongia was described by Rigby (1986) (see also Rigby and Collins 2004) based on a single specimen discovered by the Royal Ontario Museum in 1982.
Stephenospongia has a conical and almost cylindrical shape. The skeleton is composed of six rayed spicules (called hexactines) typical of the hexactinellid sponges. The spicules mesh together to form a single layer and are arranged in an irregular fashion especially around holes in the sponge wall. Prominent holes organized in vertical and horizontal rows are separated by tracts of spicules with ray lengths reaching more than one centimetre. The basal and top parts are not preserved.
Only a single specimen is known and comes from the Trilobite Beds.
Stephenospongia 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.