It might not sound normal to search for signs of the earliest animals in a city centre, but then St. John’s is not a normal city. You really can find downtown fossils if you know where to look, and not just any old fossils: critters that date back to the very beginnings of animal life.
The beasts in question are called Aspidella terranovica, or ‘the little shield from the new land’, and St John’s is truly their home: Elkanah Billings – Canada’s first state palaeontologist – coined the name in 1872 based on specimens he found on Duckworth Street.
The origins of these dimpled blobs has caused much controversy, not least because they are unequivocally from Precambrian strata and, for much of the 19th and 20th centuries, rocks of such age were thought to be unfossiliferous.
We now know this to be erroneous. The late Precambrian – or the Ediacaran period, to give it its proper name – has yielded all sorts of interesting specimens of lithified complex organisms. At the Mistaken Point Ecological Reserve, Newfoundland serves up some of the most spectacular examples anywhere on Earth.
Aspidella can be found in the rocks at Mistaken Point, though it is rather overwhelmed by its larger, freakier-looking cousins, such as Fractofusus and Charniodiscus. In the overlying Fermeuse Formation, however, Aspidella takes centre stage. At Ferryland, the low coastal cliffs abound with the things: wave-smoothed rock surfaces are speckled with little discs.
Keep the Aspidella flying
In St John’s, the same unit of rocks underlies the town centre, so one summer afternoon I went Fermeuse fossil-hunting. On Duckworth Street, the formation forms the back wall of a car park. I spent a few minutes scouring the rocks, hoping to turn up an urban Ediacaran, but didn’t spot anything. Ah well, I thought, it was always a long shot. I began trudging up the vertiginous ascent of Holloway Street.
It transpired that slow climbs have their upsides, though, as I spotted a pile of scree and weeds beneath a newly erected telegraph pole. In among the detritus was a dark grey block of muddy sandstone, and there on the face, glinting in the sun, was a cluster of Aspidella!
OK, they were diminutive, nothing like as impressive as the specimens you find in Ferryland, but what the heck? These were 550-odd million-year-old fossils and I’d just picked them up on a paved street in downtown St John’s! I picked the block up with a childlike delight and wended my way home with a spring in my step.
Inspecting the rock more closely later, I began to figure out how the fossils had been preserved. Looking at the block’s internal structure, it was possible to see cross-cutting layers of muddy sand, the remnants of ancient ripples, one climbing over the back of the next. It had probably been a big storm, scouring the seabed, smothering the organisms that dwelt there.
But just what was Aspidella?
A recent study by scientists at Oxford and Memorial universities has offered an amazing new possibility: Aspidella might have been one of the first animals on Earth. Research led by Latha Menon found evidence that Aspidella could move upwards through sediment. Specimens from the Avalon Peninsula (not mine, sadly) preserve tell-tale disturbances of Aspidella adjusting its life position, possibly in response to being partly buried by small influxes of sand or mud.
This might not sound especially remarkable, but as I’ve discussed before, one of the fundamental aspects of animals is the ability to move. Stationary creatures are highly vulnerable; mobile ones less so. Aspidella seems to be one of the first things on Earth to have been animated.
Such behaviour requires a body that had muscles it could contract. This is found in modern life as simple as a sea anemone, but 560 million years ago, it would have been the height of sophistication.
So next time you’re out and about in town, keep your eyes peeled. If you find an exposed patch of bedrock, move slowly across it: you might find traces of a distant relative that was doing much the same thing an unfathomably long time ago.
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