Anthozoa? (Order: Actiniaria(?), stem group cnidarians)
Mackenzia is thought to be a cnidarian (a group which includes modern coral and jellyfish) and appears most similar to modern sea anemones (Conway Morris, 1993).
Mackenzia – from Mount Mackenzie (2,461 m) near Revelstoke, southwest of the Burgess Shale. Mount Mackenzie was named in honor of Alexander Mackenzie (1822-1892), Canada's 2nd Prime Minister.
costalis – from the Latin costalis, “pertaining to ribs.” The name refers to the lineations along the length of the animal.
Lectotype – USNM 57556 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Burgess Shale and vicinity: none.
Other deposits: none.
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
The Walcott and Raymond Quarries on Fossil Ridge. The Tulip Beds (S7) on Mount Stephen.
Brief history of research:
Mackenzia was first described as a holothurian, a group of echinoderms commonly known as the sea-cucumbers (Walcott, 1911). Additional fossils collected by the Geological Survey of Canada and restudy of Walcott’s collection led Conway Morris (1989, 1993) to reinterpret this animal as a cnidarian.
Mackenzia is a large saclike animal, up to 16 cm in height, which was anchored to hard substrates with a disc or holdfast via a short stalk; it probably stood upright. The surface of the body is folded longitudinally into 8-10 ridges. There is a large gut cavity and some evidence of internal partitioning, but little else is known of the anatomy. Tentacles are absent; the mouth was probably at the end opposite the stalk.
Mackenzia is very rare and represents only 0.03% of the Walcott Quarry community (Caron and Jackson, 2008).
Suspension feeder?, carnivorous?
Mackenzia probably lived on the seabed and may have attached to animal remains such as brachiopod shells for stability. Its mode of feeding is uncertain.