In the summer of 1956, a teenage girl named Tina Negus stumbled upon an utterly impossible fossil.
She was visiting Charnwood Forest - a hilly and rugged landscape in Leicestershire,
England, with some of the oldest exposed rocks in the country.
They date back to the Precambrian, with some more than 600 million years old.
And, while exploring an old quarry in the forest, Tina found herself at the right
place at the right time to spot something in the wrong place at the wrong time.
A fossil - and a pretty beautiful one at that - kind of shaped like the frond of a fern.
But there was just one problem. It was almost
a geological law that rocks this old could never contain fossils.
Because it was common knowledge that multicellular organisms with complex body
plans only emerged later, in the Cambrian explosion around 541 million years ago.
Yet here was a fossil that would eventually make us reconsider
much of what we thought we knew about the earliest complex life.
And it wouldn’t be the last big find in the forest.
More than 60 years later, another discovery would shine a light on an
adaptation that today we take for granted - but it might have been a first for its time.
Hidden in the rocks once thought too old to contain complex life,
we may have found the animal kingdom’s oldest known predator.
Sadly, Tina would never get credit for spotting that frond-shaped fossil. Her report was dismissed
by her geography teacher’s emphatic claim that “there are no fossils in Precambrian rocks!”
The credit would go instead to another local kid
named Roger Mason who came across the same fossil the following year.
He made a rubbing of the imprint and finally convinced a local geology professor that it
really was a Precambrian fossil - the first one ever recognized as such.
It was named Charnia masoni, after both Charnwood Forest and Roger Mason,
who would grow up to become a geology professor himself.
It dates to around 570 million years ago,
and it sparked a revolution of our understanding of Precambrian life.
Before the discovery of Charnia, scientists thought that life in this period was basically
all microbial - too small, simple, and squishy to leave behind any real fossil evidence.
Even Sir David Attenborough, who grew up nearby, had avoided looking in these
particular rocks while fossil hunting in his youth. He assumed that they were just too old.
But almost as soon as Charnia was officially described, researchers began to realize that other
finds from around the world were also fossilized macro-scale organisms from the Precambrian.
In some cases, these finds had previously been dismissed as patterns created by
ancient geological forces, rather than being biological in origin.
Others had been recognized as fossils, but the rocks they were in hadn't been
reliably dated. So, they were assumed to be from the Cambrian because…well,
all fossils could only be as old as the Cambrian, right?
But the news of Charnia triggered a radical reassessment of many of our
old assumptions. Suddenly, the concept of a Precambrian world of complex lifeforms
went from being impossible to being impossible to ignore.
And in the years since then, many more of these weirdos have been
described from around the world - from Canada to Namibia to Australia.
This collection of ancient creatures became known as the ‘Ediacaran Biota,’ named for
the geological period they inhabited – the one right before the Cambrian.
They’ve revealed to us a previously unknown chapter in the history of
life. One in which groups of complex, macroscopic,
and bizarre organisms diversified and thrived well before the Cambrian explosion.
And Charnwood Forest has continued to be an exceptionally valuable window
into the life forms of this period. Many of the oldest and best-preserved
fossils from the Ediacaran have been found there.
Some of the most abundant belong to a group called the Rangeomorphs, which includes Charnia.
Like most Ediacaran life,
these soft-bodied organisms were totally unlike anything alive today.
They were bound to the sea floor via a holdfast and didn’t move around.
And they had a fern-like frond structure that branched off their central stem that
gave them a plant like-appearance. But they weren't plants at all.
They lived too deep for much light to reach them, so they didn’t photosynthesize.
But they also lacked a clear mouth, gut, or any other kind of feeding apparatus.
In fact, they don't seem to have actively done anything to feed.
Predation hadn't been invented yet,
beyond a few Ediacaran groups that may have grazed on microbial mats and algae.
Actively catching and eating other organisms only became common with
the rise of modern animal groups in the Cambrian.
Instead, our best guess at the moment is that
they passively absorbed dissolved organic carbon from the seawater.
But while rangeomorphs like Charnia are some of the earliest and most abundant
Ediacaran lifeforms, a diverse range of other weirdos also appeared alongside them later on.
Some lived at other depths, some were mobile,
and they came in a range of shapes and sizes, including tubes, discs, bags, and quilts.
They’re generally so strange and alien-looking that it’s
been a real struggle to figure out both how they relate to each other
and how they relate to later animal groups that became dominant in the Cambrian.
Some have been tentatively interpreted as primitive
members of those animal groups - though not without controversy.
But most seem like entirely separate evolutionary
experiments with no direct link to any animals living today.
But in that crowd of ancient strangers, we have seen one familiar face.
In 2022, scientists reported a new out-of-place
fossil from Charnwood Forest that once again broke all the rules.
It was found preserved alongside some rangeomorphs,
close to the site where Tina had found the first Charnia.
And it dated to around 560 million years ago,
nearly 20 million years before the Cambrian explosion.
While the vast majority of Ediacaran fossils from this period seemed completely alien,
this one seemed instantly familiar to some animals living today.
Like the rangeomorphs, it probably anchored itself to the sea floor. But unlike those
soft-bodied strangers, it had a skeleton - the oldest one ever seen in the fossil record.
And it forked into two goblet-shaped structures that contained dense clusters
of tentacles, a lot like some living animals.
The researchers realized that this was the earliest Precambrian
fossil to clearly show the body plan of a modern animal group.
And, potentially, the oldest animal with direct living descendants in the fossil record.
The researchers concluded that it was the earliest known cnidarian,
a phylum of animals that includes anemones, corals, and jellyfish.
Now, cnidarians have long been considered one of the most ancient animal lineages,
and previous molecular analyses had hinted that they had already evolved
and begun to diverge prior to the Cambrian explosion.
But this had never been confirmed, because unambiguous fossils of
Precambrian cnidarians - or any other modern animal group - had been missing, until now.
Within that phylum, this new find seemed to be a member of the subgroup Medusozoa,
making it an ancient jellyfish relative.
It closely resembled a life-cycle stage common to many medusozoans,
during which they form an immobile stalked polyp before eventually becoming free-swimming.
Though, whether this ancient critter also had a free swimming stage,
or if that evolved later, we don’t know yet.
And rather than passively absorbing nutrients from the water, it likely used its tentacles
for the same thing modern medusozoans use them for - capturing prey, probably plankton and protists.
This makes it potentially the oldest animal predator ever found,
pushing back the evolution of predation by around 20 million years!
The researchers named it Auroralumina attenboroughii,
meaning Attenborough’s Dawn Lantern, after the local legend himself.
‘Dawn’ referenced its immense age - the fossil’s,
not Attenborough’s - and ‘lantern’ honored the cupped tentacles’ resemblance to a flaming torch.
While the discovery of Charnia unexpectedly showed that large complex life pre-dated the Cambrian,
the discovery of Auroralumina went a step further.
It showed that at least one recognizable animal group - cnidaria - was also around during
this period, living and diversifying alongside other Ediacaran weirdos.
And, even this early on, they had already established a modern cnidarian body plan and
a predatory lifestyle - two innovations that were previously only known from the Cambrian onwards.
It was an out-of-place fossil in a wider group of out-of-place fossils. While those other Ediacaran
species had surprised us by being so weird, this one surprised us by being so familiar.
More than 60 years after Tina’s discovery,
Charnwood Forest continues to blow our minds, shift our paradigms, and show us
just how little we really understand about the rise of large complex life.
Exciting announcement! We just released a puzzle.
For our first-ever puzzle, we're celebrating carcinization with a
reconstruction of what's thought to be the oldest false crab: Platykotta.
It's available now at DFTBA.com!
Thanks to this month’s impossibly awesome Eontologists! They help
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can get fun perks - like submitting a joke for us to read. Like this one from Grayson Bo Guthrie.
How does a rock get a girl to like him? He quartz her!
I got it, quart - quart... quartz. That was good. Good!
And as always thank you for joining me in the Adam Lowe studio. Subscribe
at youtube.com/eons for more epic epochs.
Somebody's coming down the stairs, that's crazy you can hear them coming
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