The Tree Stump Animals
The first reptiles on Earth emerged 300 million
years ago and their remains have been found at Joggins, inside the trunks of lycopod
trees. Dawson and Lyell discovered Hylonomus lyelli, a tiny reptile, or
microsaur, as Dawson dubbed them, about 30 centimetres long. These tiny reptiles would,
over the next 100 million years, evolve into dinosaurs. One widely held theory, first
proposed by Dawson, was that animals such as Hylonomus lyelli became trapped in hollow tree stumps which had been snapped off and the exterior
surrounded with sediment until the openings were at ground level. The unsuspecting animal
would have then fallen into the hollowed tree trunk. Once trapped, Hylonomus lyelli
and others either drowned immediately, starved to death or survived for a time scavenging
on previous victims, only to be eaten by the next. Up to seventeen skeletons have been
found inside one trunk! A more recent theory suggests that the animals lived and made
their dens inside the hollow stumps.
Also found by Dawson and Lyell in the tree stumps were the
remains of a primitive amphibian, Dendrerpeton acadianum. This animal reached
lengths of one metre and probably looked very much like a large salamander.
Other creatures that have been found in the stumps include the world's oldest land
snails (Pupa sp. and Zonites sp.) and a small, articulated worm-like
creature called a gally worm.
The largest creature at Joggins was an
arthropod (an invertebrate with a hard jointed exoskeleton) called Arthropleura sp.
At nearly two metres long, these animals resembled an extremely large sow bug. Arthropleura
may have had as many as 30 pairs of legs, and their tracks, resembling Caterpillar tractor
tracks, have also been found at Joggins. They were never trapped in the hollow tree stumps
because either they never lost their balance and fell into them or they were large enough
to scuttle their way right over the gaping holes.
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