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Mackenzia costalis

A Burgess Shale sea anemone-like animal

Image of Mackenzia costalis.

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Mackenzia costalis (ROM 61115). The largest specimen known. Note the base is attached to isolated shells of the hyolith Haplophrentis carinatus (close ups to the right). Specimen height = 200 mm. Specimen dry – direct light (far left), dry – polarized light (middle left), wet – polarized light (middle right, top right), wet – direct light (bottom right). Walcott Quarry.

© Royal Ontario Museum. Photos: Jean-Bernard Caron

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Taxonomy

Kingdom:

Animalia

Phylum:

Cnidaria

Class:

Anthozoa? (Order: Actiniaria(?), stem group cnidarians)

Affinity:

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).

Species name:

Mackenzia costalis

Described by:

Walcott

Description date:

1911

Etymology:

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.

Type Specimens:

Lectotype –USNM57556 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.

Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

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Age

Period:

Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).

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Localities

Principal localities:

The Walcott and Raymond Quarries on Fossil Ridge. The Tulip Beds (S7) on Mount Stephen.

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History of Research

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.

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Description

Morphology:

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.

Abundance:

Mackenzia is very rare and represents only 0.03% of the Walcott Quarry community (Caron and Jackson, 2008).

Maximum size:

200 mm

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Ecology

Life habits:

Epibenthic, sessile

Feeding strategies:

Suspension feeder?, carnivorous?

Ecological Interpretations:

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.

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References

Bibliography:

CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.

CONWAY MORRIS, S. 1989. Burgess Shale faunas and the Cambrian explosion. Science, 246: 339-346.

CONWAY MORRIS, S. 1993. Ediacaran-like fossils in Cambrian Burgess Shale-type faunas of North America. Palaeontology, 36(3): 593-635.

WALCOTT, C. D. 1911. Middle Cambrian holothurians and medusae. Cambrian Geology and Paleontology II. Smithsonian Miscellaneous Collections, 57(3): 41-68.

Other links:

None

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