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.
