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.
© SMITHSONIAN INSTITUTION – NATIONAL MUSEUM OF NATURAL HISTORY. PHOTOS: JEAN-BERNARD CARON
Portalia is regarded as a problematic organism awaiting a full redescription (Briggs and Conway Morris, 1986).
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.
Burgess Shale and vicinity: none.
Other deposits: none.
The Walcott Quarry on Fossil Ridge.
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.
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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