In 1931, paleontologist Robert Broom announced an exciting new discovery.
It was a 257 million-year-old skull, found on a farm in what’s now South Africa.
It was pretty small, but that little cranium was the only piece left of this animal.
But even without the rest of its body, Broom could tell that this fossil came from a therapsid,
a diverse group of vertebrates that may have arisen as far back as the late Carboniferous
Period.
And mammals belong to this group, too, although we didn’t show up until much later.
But there was something strange about this particular therapsid.
On either side of its upper jaw - right behind each canine tooth - there was what’s called
a fossa, a shallow indentation in the surface of the bone.
Broom named the animal Euchambersia mirabilis and his best guess was that those fossae held
large salivary glands.
But two years later, one of Broom’s colleagues suggested something more radical.
Baron Franz Nopcsa - an Austro-Hungarian aristocrat who was also a paleobiologist - proposed that
Euchambersia actually carried a secret weapon: venom.
For decades, scientists have puzzled over whether the Baron was right.
And they’ve also wondered if Euchambersia was, in fact, the first known land vertebrate
to have a venomous bite.
If true, it would mean that this little animal possessed venom about 20 million years before
the first lizards, and over 150 million years before the first snakes, evolved.
And it might also tell us something about the roots of this trait in our own group - because,
yes! venomous mammals do exist.
Now, some recent research has shed new light on the mystery surrounding this old fossil.
And to help us investigate, we’ve teamed up with my friend Sarah Suta from Bizarre
Beasts to explore the story of venomous mammals, both living and extinct.
Maybe you’ve heard someone say: “If it bites you and you die, then it’s venomous.
But if you bite it and you die, then it’s poisonous.”
Now, that’s not always how things work in real life, but it covers the basic difference
between poison and venom.
Both are toxic weapons used by living things.
What separates the two is their method of delivery.
Poisons take effect when the victim inhales, swallows, or absorbs them through the skin,
while venoms have to be injected.
Venomous creatures alive today, like vipers and scorpions, use fangs or stingers to shoot
toxins into other animals.
And while poison is mainly used for defense, venom can have both an offensive and a defensive
function.
If you’re hungry, venom can help you bring down your prey.
Or, it can help you not become prey.
Venom is widespread across the animal kingdom, from invertebrates like spiders and snails,
to vertebrates, like fish and amphibians.
And venomous reptiles are really common.
Many snakes and a few different lizards, like the Gila monster and the Komodo dragon, pack
venom, too.
And we can’t forget about venomous mammals, like the vampire bat and the solenodon.
But how far back could this adaptation go?
And where does Euchambersia fit in?
Blake, what’s the fossil side of this story?
Well, Euchambersia wasn’t a true mammal.
But it was a mammal relative.
Remember, it’s a therapsid, a group of vertebrates whose oldest known members probably lived
about 310 million years ago, and who became more common by the mid-Permian Period, around
270 million years ago.
Now, you and I are therapsids too, just so ya know, along with every mammal that’s
ever existed.
I mean, can't you see the resemblance?!
If I maybe go like this so my fangs stick out?
maybe it's just me
But anyway Euchambersia lived almost 50 million years before mammals appeared.
It’s part of an extinct lineage of therapsids called the therocephalians, or the “beast
heads.”
Which, hey, I’ve been called worse than that.
But Euchambersia seems to be unique in some ways, based on the couple of fossils that’ve
been found.
Its braincase was small, and it had an unusually broad snout.
And on each side of the upper jaw, it had five incisors lined up in front of a large
canine tooth.
But that’s where the teeth stopped.
While many therapsids have premolars and molars, this one didn’t.
Instead, it had those two big, deep and very bizarre fossae in its snout.
And no other vertebrate - living or extinct - has this strange combination of features.
Robert Broom captured the weirdness of this animal in a drawing of its skull that he published
in 1932.
And by 1964, three other illustrators had released their own drawings based on Broom’s
picture.
But as time passed and even more sketches came out, inaccuracies crept in and became
part of the story of this fossil.
For example, one of these newer sketches appeared in a book published in 1986.
And the text wrongly claims that Euchambersia had deep grooves on its canines.
That sounded like solid evidence for the venom hypothesis, because some venomous animals
alive today have prominent grooves on their teeth.
Those little trenches help them inject their toxins.
But here’s the thing: none of the previous researchers - including Broom and Baron Nopcsa
- ever actually said that Euchambersia had such grooves on those teeth.
So, to get a better handle on this mysterious fossil, in 2016, Julien Benoit, a paleontologist
working in South Africa, reviewed more than eighty years’ worth of papers about it.
And what he realized was that instead of deep grooves, Euchambersia actually has prominent
ridges on its canines.
Broom and Nopcsa knew this too.
But when later authors looked at Broom’s sketch from 1932 - and the other drawings
inspired by that sketch - some of them mistook the ridges for tooth grooves.
Eventually, a kind of scientific urban legend was born - that its canines were grooved and
therefore possibly venomous - which influenced our thinking about this animal for decades.
Then, as part of a 2017 study of the fossils, Benoit and his colleagues CT scanned the only
two skulls of Euchambersia that’ve ever been found and spotted some tantalizing new
clues.
Those unexplained fossae in its upper jaw?
Turns out, they had small openings at the base.
And the scans showed that these little openings fed into tubes that ran through a feature
called the maxillary canal.
In modern amphibians, reptiles, birds, and mammals, that canal acts as a pathway for
nerves and blood vessels.
And in Euchambersia, the tooth sockets of its canines are also connected to this canal.
So, based on the anatomy of living venomous animals, it’s possible that venom could’ve
flowed out of glands in the weird cavities in its snout, passed through the maxillary
canal, and then gotten mixed in with its saliva.
And those tooth ridges might’ve helped it wound its prey, allowing that venomous saliva
to seep into the injuries.
According to Benoit and his co-authors, venom glands are probably the best explanation we
have right now for the odd anatomy of this Permian animal.
Now, of course, other explanations are still possible.
Maybe those fossae held heat-sensitive organs or some other kind of sensory organ that’s
just unknown to modern science.
But we do know that venom arose in therapsids - possibly even in our friend Euchambersia
- at some point.
Because today, at least four different orders of mammals include venomous species.
Sarah!
Why don’t you introduce us?
Well, there’s the platypus, an egg-laying monotreme with venomous spurs.
And believe it or not, vampire bats are venomous, too.
The slow loris, a small primate from Southeast Asia, is also venomous.
And then we have the order the solenodon belongs to, which it shares with shrews, moles, and
hedgehogs.
At least three different genera of shrews are venomous.
And some of them use their dangerous bites to kill larger snakes.
Genetic evidence shows us that shrews and solenodons split from a common ancestor some
70 million years ago or more.
And a study in 2019 found that their common ancestor probably wasn’t venomous.
Venom may have independently evolved at least four separate times within this group.
And with how widespread venom is across mammals, from the platypus to primates, well, it would
be pretty strange if there weren’t extinct mammal relatives that were venomous, too.
Thanks, Sarah!
If you want to know more about the solenodon and other venomous mammals, check out this
month’s episode of Bizarre Beasts.
And who knows what else paleontologists might discover about this fossil in the decades
to come.
In the meantime, we can learn two big lessons from the story of Euchambersia.
First, it’s a reminder of why it's so important for scientists to have access to important
fossils and to independently review each other’s work.
Going back over the studies on this fossil helped correct a misconception about its teeth
- and opened the door for new research.
And second, it looks like venom might run deep in the tree of life, including within
our extended family, the therapsids.
Now, for more on therapsid family tree watch our episode, “When the Synapsids Struck
Back”.
You may not see the family resemblance between yourself and these early mammal relatives,
but we share features that still connect us to those long-forgotten animals, even after
more than a quarter of a billion years.
And its my lucky day because Kallie couldn’t think of a venomous pun.
So "fangs" to this month’s Eontologists. Boy I love puns.
Sean Dennis, Jake Hart, Annie & Eric Higgins, John Davison Ng, and Patrick Seifert!
By becoming an Eonite at patreon.com/eons you can get fun perks like submitting a joke
for us to read.
Like this one from Stephen O'Leary.
Air Sacs gave Dinosaur Evolution a second wind.
Is there a laughter and applause sign around here?
And as always thanks for joining me in the Konstantin Haase studio.
Subscribe at youtube.com/eons for more fantastic fossils.