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ENTERPRISE
A new theory has been proposed for what might have created what appear to be large ancient tracks just above Alexandra Falls, south of Enterprise.

One of the circular impressions in a rocky ledge along the Hay River south of Enterprise. - NNSL file photo

When they were first spotted in 2009, it was believed the impressions in the rock along the edge of the Hay River may have been formed by a dinosaur walking in the area about 100 million years ago.

Now, Donald Henderson, curator of dinosaurs at the Royal Tyrrell Museum of Palaeontology in Drumheller, Alta., has reconsidered his opinion and thinks they may have been created by an early lungfish walking underwater much further back in time – an estimated 360-370 million years ago.

If that is the case, it would be a significant discovery, since there is only one other example of such tracks in the world.

"It could be a big deal, yes," said Henderson, noting it would be the first such find in North America. "But let's not get too far ahead of ourselves."

Henderson has not yet visited the site, but is offering his opinion based on photographs sent to him by the Department of Industry, Tourism and Investment (ITI), which operates Twin Falls Gorge Territorial Park, where the suspected tracks are located.

However, he plans to visit the site in May once the ice is off the Hay River to examine the impressions in the rock more closely.

"If these rocks are the right age – this Devonian age between about 360 and 400 million years ago – they could be made by these fishes, but we have to be really sure about the rocks and their age," he said. "So with better geology maps and being able to go and check the rock type directly, we might be able to say something a bit more definitive."

There is a row of about 10 circular impressions – each close to a foot in diameter – along a rocky ledge just above the Hay River.

Tom Colosimo, ITI's manager of tourism and parks in the South Slave, noted GNWT geologists have looked at photos of the impressions and judged them to be random erosional features.

However, Colosimo said he is "very skeptical" of that assessment.

Instead, he personally thinks the impressions in the rock look like something once walked in the area.

"Obviously, if it was a walking fish, it would be very rare," he said.

Colosimo hopes experts can provide answers upon examining the site.

Henderson said he reconsidered his assessment based on the fact the area is a mix of rocks from the dinosaur age and more ancient rocks from about 400 million years ago.

"I got a better geology map and started thinking maybe these rocks are older, because they look like limestones instead of sandstones or mudstones, which dinosaur tracks would have been in," he explained. "And I wasn't totally thrilled with them being dinosaur tracks because you couldn't see any real good toe impressions."

Plus, he noted a scientific paper was published a couple of years ago about a discovery in Poland of tracks of large lobed-fin fish from the Devonian geologic period.

Those fish, which included the sauripterus, ranged from one to six metres in length.

Henderson explained that, unlike living fish, they had bones in their limbs, in the front and hind fins, and they would have had muscles going out into their fins.

"They would have been in the shallows," he said. "The body may have been partly out of the water. They weren't fully supported by water, so their weight was starting to be felt through their limbs and they would be propelling themselves along the bottom."

Henderson said it would be incorrect to describe the limbs as legs because they weren't jointed, but they had muscles coming off their shoulders and hip bones going into the limbs.

"So these limbs could move forward and backward, up and down," he said. "Now it seems some of these really big ones were heavy enough and they were in shallow enough water that they were actually leaving tracks."

Colosimo said, if the impressions above Alexandra Falls turn out to have been caused by an ancient walking fish, it would be an opportunity to create a series of interpretive displays and perhaps a themed walking trail.

It would also mean the tracks would deserve protection, he said, adding that might mean moving them to a more secure location to protect them from erosion and the Hay River's water and ice, which continue to deteriorate the site.

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