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“If they could scream I’m sure they would.”
Paleontologist Tim Ewin stands in a quarry, remembering the calamity that is written in the rocks under his mud-covered boots.
“They tried to protect themselves by adopting the stressful position of pulling the arms in,” he continues. “But it was in vain; you can see where their arms opened, up to the crown. They were pushed into the sediment and buried alive.”
There is a small smile on Tim’s face, and he has reason to be happy.
The misfortune that befell this place 167 million years ago has delivered an extraordinary collection of fossil animals in what is arguably one of the most important Jurassic excavation sites ever discovered in the UK.
We cannot be specific on the location of the excavation for safety reasons, but you will recognize by the beautiful honey colored limestone that we are somewhere in Cotswold country.
Things have changed a bit since the Jurassic, however.
No picturesque villages and dry stone walls at the time; these parts were covered by shallow sea, perhaps 20 to 40 m deep. And that was a damn hotter sight than your traditional English summer. The movement of the tectonic plates means that Britain was pretty much where North Africa is today.
So you can imagine the types of creatures that would have lived on this ancient almost tropical seabed.
Rod animals called sea lilies were tied to the bed in large “meadows.” Their floating cousins, the feathered stars, passed by, seeking to catch the same particles of food. And in the sediment, starfish and brittle stars made their way through the bottom with their five arms, no doubt bumping into any urchins or sea cucumbers that passed every now and then.
It is exactly this scene that has persisted in the rocks of our mysterious quarry.
The quantities involved are astonishing. Not hundreds, not thousands, but perhaps tens of thousands of these animals that scientists collectively call “echinoderms”. It is a great name, derived from the Greek for “hedgehog”, or “prickly”, “skin”. What is a sea urchin if not an “underwater hedgehog”?
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Some may look like plants but they are all animals
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Skeletons are made from calcite (calcium carbonate)
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They exhibit radial symmetry, in multiples of five
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They don’t have a brain but have a nervous system
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Tubular arms and feet are moved by pumping sea water
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Lost parts can be pushed back, much like a gecko’s tail
Most of what we know about the deep history of echinoderms from British fossils comes from the few specimens that emerged from railroad cuttings and quarries in the Victorian era.
Tim Ewin’s institution, the Natural History Museum in London, has hidden these objects in a small space which will now be quite insufficient to accommodate the truck of new examples to come.
“At this Middle Jurassic rock age, only two species of starfish were known, represented by five specimens,” he says. “In a few days of collecting here, we have 12 specimens of starfish and we expect to find many more.
“And the same goes for comatulids, or rodless crinoids (feathered stars) – 200 years of collection is represented in the museum by about 25 specimens. Here we have probably 25 specimens right under our feet, and we ‘ I collected over 1,000 of them. “
But it is also the quality of the conservation that is breathtaking.
Approach a slab of rock that has just been cleaned and you will observe what at first glance reminds you of a plate of noodles. It is in fact a great mass of fossil weapons coming from who knows how many water lilies.
You can clearly discern the individual calcite plaques, or ossicles, that made up the skeletal frameworks of these animals when they were alive. In addition, the specimens are fully articulated. That is, all the parts are still intact. Everything is captured in three dimensions.
“We’re talking about the five (radial symmetry) in echinoderms. They’re all there; you can see them,” says Mark Graham, NHM’s senior fossil preparer.
Fossil echinoderm specialists believe that the Cotswold quarry will help them better categorize the different life stages of species, their ecology and their proper place in the history of evolution.
To paraphrase that old cliché: textbooks may not need to be rewritten, but you will almost certainly need to add detailed notes in the margins.
And the new learning will go even further, says echinoderm specialist Jeff Thompson.
“We live in a changing world today, and if we are to understand how climate change could affect not only the future of humanity but all life on the Earth’s surface, then echinoderms are the place to be. one of the best groups to study, ”he tells me. .
“We know very well what happened to them through a variety of mass extinctions, so their experience can be very useful as we try to understand major changes in biodiversity through geological time.”
Click here to see the interactive BBC
Sally Hollingworth is half-standing, half-seated on the edge of a pool of muddy water. She’s busy trying to remove more feather stars from the clay layers that dot the limestone units of the quarry.
She pushes gently with a spatula, trying to get under the specimens to lift them without breaking them.
“I call them ‘squiggly wigglies’,” she laughs. “The hunted crinoids, I call these ‘walkie stalkies’.”
It is Sally and her husband, Neville, that the NHM must thank for finding this wonderful site.
Both are passionate amateur paleontologists. They spend their weekends exploring the Cotswold Hills and surrounding areas, looking for interesting rocks. The most promising items they take home to “for him and for her” studios (a shed and garage) where they use air abrasion tools to remove any obscuring sediment.
It was while they were locked up during the lockdown that Sally and Neville first identified career potential.
After reviewing the location on Google Earth and comparing it with geological maps of the area, they sought permission from the landowner for reconnaissance, which Sally said seemed somewhat disappointing at the time.
“We only found tiny fragments of Jurassic sea creatures and we said, ‘Okay, okay, let’s take a slab home and see what we can reveal if we can clean it up,'” she recalls. .
“I remember Nev yelling from the garage, ‘Sal, Sal! You have to come check this out!’ It was this beautiful water lily emerging, coming to life, from the slab. “
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Water lilies are the stalked variety of crinoids
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Adult animals anchor to the bottom of the sea
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Their crowns are pointed in the stream of water
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Feathery pinnae catch floating food particles
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This rubbish is propelled towards a mouth
When Tim Ewin was informed, he immediately recognized the importance of the career and brought in a team of experts to do a systematic research.
Sally and Neville, far from being pushed aside by the professionals, are an integral part of the group. Their local knowledge and homemade elderflower syrup are greatly appreciated.
Working on the site is a muddy affair. Recent rains have turned the quarry floor into a mud bath, and the precise and painstaking process of excavating the fossils means researchers have no choice but to get on all fours in the sticky mess.
“Beautiful things are protected by overturned trays of food. It might not look like it in all this mud, but there are actually places where we are not supposed to set foot,” explains NHM curator Zoe Hughes. “But there is such an abundance, it is perhaps not such a concern”, quips her colleague Katie Collins. “There is such a bonanza of stuff.”
The focus is on these layers of clay. These contain the mass of echinoderms.
The setting appears to be a busy strip of seabed where nutrients were constantly being delivered to the site.
You see it in the occasional piece of Jurassic wood sticking out of the mud. Perhaps there was a delta nearby that was directing food-laden waters towards this scene.
This may explain the abundance of fossil animals, but it does not explain their supreme preservation. For that, we have to come back to the idea of a calamity. The clue of the drama is recorded in the harder, sand-richer bands of clay – a signal of a sudden shift to a more energetic environment.
“What we have is something very suggestive of a dramatic mudslide,” says Zoe. “We have this happy little ecosystem and then, boom! – something catastrophic happens.
“Maybe there was an earthquake that caused the mudslide and it happened and covered everything up. That’s why the preservation is so amazing, because the scavengers couldn’t reach all of these then. animals to separate them. “
As Neville Hollingworth likes to say, “What we have here is sort of Jurassic Pompeii.”
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