The Burgess Shale

Portalia mira

A sea-cucumber-like animal covered in tentacles

Portalia mira (USNM 83927) – Holotype, part and counterpart. Complete specimen preserved with Mackenzia costalis. Anterior possible to the right. Specimen length = 100 mm. Specimen dry – polarized light. Walcott Quarry.



Kingdom: Animalia
Phylum: Unknown
Higher Taxonomic assignment: Non applicable
Species name: Portalia mira

Portalia is regarded as a problematic organism awaiting a full redescription (Briggs and Conway Morris, 1986).

Described by: Walcott
Description date: 1918

Portalia – from Portal Peak (2,911 m), north of the Burgess Shale in Banff National Park.

mira – from the Latin mirus, “wonderful,” in reference to the morphology of the animal.

Type Specimens: Holotype –USNM83927 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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

The Walcott Quarry on Fossil Ridge.

History of Research:

Brief history of research:

The only known specimen of Portalia was first illustrated by Walcott in a brief communication published in 1918 and refigured in a posthumous publication (Walcott, 1931). Walcott interpreted this fossil as a holothurian, a member of a group of echinoderms better known as sea-cucumbers. Madsen (1957) suggested Portalia might be a primitive sponge, but Durham (1974) thought that the holothurian affinity could not be rejected without further studies (see also Conway Morris, 1979). The relationships of Portalia remain difficult to establish (Briggs and Conway Morris, 1986).



The body of Portalia is sausage-shaped and the most distinctive features are a series of elongate tentacle-like structures covering the entire surface. These structures tend to split into several simple branches. A central strand within the body has been interpreted as part of the gut and the head has been tentatively identified as a darker indistinct area at one end.


Portalia is known from a single specimen.

Maximum Size:
100 mm


Life habits: Epibenthic, Mobile
Feeding strategies: Unknown
Ecological Interpretations:

Not enough is known about this organism to interpret its feeding strategy.


BRIGGS, D. E. G. AND S. CONWAY MORRIS. 1986. Problematica from the Middle Cambrian Burgess Shale of British Columbia, p. 167-183. In A. Hoffman and M. H. Nitecki (eds.), Problematic fossil taxa (Oxford Monographs on Geology and Geophysics No. 5). Oxford University Press & Clarendon Press, New York.

CONWAY MORRIS, S. 1979. The Burgess Shale (Middle Cambrian) fauna. Annual Review of Ecology and Systematics, 10(1): 327-349.

MADSEN, F. J. 1957. On Walcott’s supposed Cambrian holothurians. Journal of Paleontology, 31(1): 281-286.

WALCOTT, C. 1918. Geological explorations in the Canadian Rockies. From “Explorations and Field-Work of the Smithsonian Institution in 1917”. Smithsonian Miscellaneous Collections, 68: 4-20.

WALCOTT, C. 1931. Addenda to descriptions of Burgess Shale fossils. Smithsonian Miscellaneous Collections, 85(3): 1-46.

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