Stephenospongia magnipora (ROM 43127) – Holotype. Fragment of the only known specimen of the species showing large holes in the wall of this sponge. Specimen height = 44 mm. Specimen dry – polarized light. Trilobite Beds on Mount Stephen.
© ROYAL ONTARIO MUSEUM. PHOTO: JEAN-BERNARD CARON
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.
Burgess Shale and vicinity: none.
Other deposits: none.
The Trilobite Beds on Mount Stephen.
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.
RIGBY, J. K. 1986. Sponges of the Burgess shale (Middle Cambrian), British Columbia. Palaeontographica Canadiana, 2: 105 p.
RIGBY, J. K. AND D. COLLINS. 2004. Sponges of the Middle Cambrian Burgess Shale and Stephen Formations, British Columbia. Royal Ontario Museum Contributions in Science (1): 155 p.
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