![Geological Survey of Canada Geological Survey of Canada](/web/20061103060139im_/http://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 Climactichnites: reaching for land in the Cambrian
The Climactichnites
trackway constitutes evidence of the first time any animal tentatively reached
out from the sea to claim the land. The attempt was unsuccessful,
but deserving of recognition
![The Climactichnites slab taken down from the wall of Logan's office. (GSC photo 201284B (c)) The Climactichnites slab taken down from the wall of Logan's office. (GSC photo 201284B (c))](/web/20061103060139im_/http://gsc.nrcan.gc.ca/paleochron/images/climac.jpg) The Climactichnites slab taken down from the wall of Logan's office.
(GSC photo 201284B (c)) |
The first director of the
Geological Survey of Canada lived very simply. Sir William Logan
occupied a single room at the Survey offices at 76 St. Gabriel
Street in the heart of old Montreal. This room served as his
office and bedroom, as well as for reception and storage. One
wall was entirely covered by an immense slab of sandstone
displaying six overlapping tracks. Each track was 15 cm wide and
marked by a chevron cross pattern repeated with almost
machine-like regularity between crenulated marginal ridges. In
all, the trackway looks disturbingly like dirt-bike tire tracks.
This trackway came from the
Potsdam Formation at Perth, halfway between Kingston and Ottawa.
These rocks were thought to be some of the oldest fossiliferous
sedimentary rocks anywhere -- now they are known to be Upper
Cambrian. In 1860 Logan described and named this trackway Climactichnites.
The presence of this large and strikingly patterned trackway in
such ancient rocks caused quite a stir among paleontologists who
immediately began to speculate on the identity of the track maker.
Some suggested arthropods -- either horseshoe crabs or trilobites
-- or perhaps worms; others thought mollusks such as snails or
chitins were responsible. However, none of these is likely. An
arthropod would leave discrete footprints and a snail or chitin a
smooth trail quite unlike the high chevron ribs and crenulated
lateral ridges of Climactichnites. Size also presents a
problem. All Cambrian snails are smaller than 2 cm, and no fossil
worm is as wide as even a small Climactichnites. But
mollusks received renewed support when ovoid slug-like
impressions were discovered at the end of some exceptionally
preserved trails in New York.
Recently, Yochelson and Fedonkin
set out to reconstruct the anatomy of this animal from the nature
of its trackway. The animal must have been about twice as long as
wide, covered by tough upper skin with its lower surface composed
of a strongly muscled sole with oblique rows of cilia. On each
side hung a pair of wing-like flaps. The animal used its cilia to
sort through sand grains for microorganisms and its lateral wings
to grip the sediment. In the process of feeding, the sand was
packed into oblique rows.
![GSC lapidary and fossil collector T.C. Weston next to Climactichnites slab. (GSC photo 81450A) GSC lapidary and fossil collector T.C. Weston next to Climactichnites slab. (GSC photo 81450A)](/web/20061103060139im_/http://gsc.nrcan.gc.ca/paleochron/images/climact1.jpg) GSC lapidary and fossil collector T.C. Weston next to Climactichnites slab.
(GSC photo 81450A) |
Although the Climactichnites animal
was able to swim with its lateral flaps, it spent most of its
life moving across the tidal sand flats that must have been
periodically exposed because the track ways occur on bedding
surfaces with ripple marks and mud cracks. Climactichnites,
therefore, records a signal event -- the first time that any
animal reached out from the sea to move onto the land. The
attempt was ultimately unsuccessful, but it deserves
acknowledgement, at least by land dwellers such as ourselves. The
animal itself appears to belong to an unnamed phylum that lived briefly
on the vast tidal sand flats that existed in eastern North America
around 500 million years ago.
Further reading:
Yochelson, Ellis and Fedonkin, Mikhail. |
1993: |
Paleobiology of Climactichnites, an enigmatic Late Cambrian fossil. Smithsonian Contributions to Paleobiology, No. 74. |
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