Past lives: Chronicles of Canadian Paleontology |
Proactive disclosure Print version ![Print version Print version](/web/20061103052245im_/http://www.gsc.nrcan.gc.ca/esst_images/_printversion2.gif) ![ÿ](/web/20061103052245im_/http://www.gsc.nrcan.gc.ca/esst_images/_spacer.gif) | ![ÿ](/web/20061103052245im_/http://www.gsc.nrcan.gc.ca/esst_images/_spacer.gif) | ![Geological Survey of Canada Geological Survey of Canada](/web/20061103052245im_/http://www.gsc.nrcan.gc.ca/esst_images/gsc_e.jpeg) Natural Resources Canada > Earth Sciences Sector > Geological Survey of Canada > Past lives: Chronicles of Canadian Paleontology
Past lives: Chronicles of Canadian Paleontology An Ediacaran Pompeii
Turbidites of ash roiling downslope into deep water killed and
preserved a suite of Ediacaran organisms as surely as air-borne ash killed
and preserved unfortunate humans at Pompeii
![Field photograph of spindle-shaped fossils from Mistaken Point (David Rudkin, Royal Ontario Museum) Field photograph of spindle-shaped fossils from Mistaken Point (David Rudkin, Royal Ontario Museum)](/web/20061103052245im_/http://www.gsc.nrcan.gc.ca/paleochron/images/mistak3a.jpg) Field photograph of spindle-shaped fossils from Mistaken Point
(David Rudkin, Royal Ontario Museum) |
Of all the places to collect fossils in Canada, the rain-slicked cliffs
above the Atlantic Ocean at Cape Race in Newfoundland certainly ranks
among the most challenging. Mistaken Point forms a small headland on the
Avalon Peninsula, just southwest of Cape Race. Here, the steeply dipping
sandstone and shale beds are perennially wet and the cliffs are often
shrouded in cold fog rolling in from the sea ice off-shore. But if you are
lucky to be there on a rare sunny day in summer, you might see hundreds of
peculiar spindle-shaped and feather-like impressions on the upper surfaces
of many of the shale beds highlighted by the late afternoon rays. These
imprints are the oldest Ediacaran fossils known in the world and the only
ones that lived in deep water.
Ediacaran fossils were first discovered in the Flinders Range, South
Australia in coarse sandstones lying beneath rocks with the first shelly
fossils of Early Cambrian age. These are large, flat and carpet-like
fossils. The initial work indicated that they were metazoans; that is,
true animals -- medusoids, sea pens and annelid worms, possibly even
arthropods and echinoderms -- and that they were soft-bodied precursors to
animal groups found in Cambrian rocks. This traditional view was
challenged by Dolf Seilacher, an iconoclastic German academic
paleontologist, who declared that the Ediacaran fossils were not animals
because none shows any evidence of having organs, muscles, mouth, anus,
gut or legs. Instead he interpreted the Ediacarans as unique quilted and
immobile organisms constructed as a series of fluid- or jelly-filled cells
-- like air-mattresses -- that must have absorbed sunlight and nutrients
directly from seawater through their skin. Seilacher suggested that these
fossils represent a new kingdom of organisms called Vendobionta that
became extinct before the beginning of the Cambrian.
The emblematic Mistaken Point fossil is a unique and still unnamed
spindle-shaped form consisting of leaf-like compartments growing out
off-set from a conspicuous mid-line. As this organism grew, the number of
compartments remained constant, but each expanded and folded in a fractal
pattern according to the terminology of the mathematician Benoit
Mandelbrot. In this way these organisms were able to grow from a length of
5 cm to 30 cm and as wide as 9 cm. These fossils are occasionally found
broadly flexed, but because they are never creased or kinked, the living
organism must have been rather tough and stiff.
Dolf Seilacher called up rather compelling Biblical imagery when he
referred to a peaceful Garden of Ediacara where organisms lived side by
side without conflict and without predators. The life in this Garden was
annihilated by the emergence of mobile animals with shells, exoskeletons
and eventually claws and teeth. The naked immobile Ediacarans were
defenceless and they perished worldwide.
Further reading:
Monastersky, R. |
1998: |
Life grows up. National Geographic Magazine, vol. 193, no. 4, p. 100-115. |
Seilacher, A. |
1997: |
Fossil Art. Royal Tyrrell Museum of Palaeontology, 64 p. |
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