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In 2002, researchers studying fossils from Transylvania dating to around 70 million years ago
reported an unusual discovery.
They were analyzing a few big bone fragments - bits of a skull and
humerus - which had first been described a decade earlier.
At the time, they were thought to belong to a huge theropod dinosaur - possibly
some kind of tyrannosaur, on account of their enormous size.
But upon their re-analysis, the researchers realized that these
bones weren’t those of a theropod at all, or any other kind of dinosaur.
Instead, they belonged to a colossal pterosaur -- easily one of the largest ever discovered.
They named it Hatzegopteryx [HOTS-egg-OP-ter-icks].
Its huge size wasn’t the only remarkable thing about it.
Unlike other pterosaurs that had a generally slender build,
the bones of this specimen seemed uniquely stocky, robust, and built for strength.
And its initial mistaken identity as a giant theropod is pretty understandable because today,
it’s thought that Hatzegopteryx was basically a pterosaur playing the role of a giant theropod.
As it turns out, its bizarre proportions were likely the result of a particular ecological
situation -- one that turned a pterosaur into a giant apex predator
and the dinosaurs it hunted into dwarfs.
In the Late Cretaceous Period, Europe was a fragmented archipelago - a collection of islands,
some large, some small, that had become isolated due to rising sea levels.
And while Europe’s fossil record from this time is often patchy,
the Hateg basin region of Romania where Hatzegopteryx was discovered
has provided some key insights into the area’s weird animal life.
Back then, the basin was one of the archipelago’s islands, Haţeg Island, which was a little
smaller than Ireland in size and 200 to 300 kilometers away from the nearest landmass.
And as far back as a hundred years ago, paleontologists excavating in the basin
realized that there was something strange about its dinosaurs: they seemed….miniaturized.
It was proposed that Hateg’s dinosaurs shrank in response to the limited
resources available on the island in a process called insular dwarfism.
Now, you might’ve heard of this before.
It’s happened many times over the history of life,
when large animals found themselves isolated on islands and rapidly shrank
in response. And this resulted in islands of things like dwarf mammoths and hippos.
But these examples are relatively recent -within the last few hundred thousand years or so.
Hateg Island was the first example of this process affecting dinosaurs in the much deeper past.
And the fossils we’ve found from the region - as well as the fossils
we haven’t found - paint a picture of an ecosystem that was just the weirdest.
One that created a unique opportunity for a pterosaur to become the apex predator.
Among Hateg’s strange fauna were tiny sauropods.
Now, sauropods are generally known for being some of the biggest land animals of all time,
sometimes growing more than 30 meters long.
But the sauropods from Hateg Island shrank to only around
6 meters long - making them some of the smallest species of sauropods ever found.
And as small as these sauropods were,
they’re still the biggest dinosaurs we know of from the Island...
Because insular dwarfism seems to have affected many of the Island’s
other herbivorous dinosaurs too, like the around-4-meter-long dwarf hadrosaur called
Telmatosaurus. It was around half the size of your average mainland hadrosaur.
And you’d think that these little dinos would have been easy prey for
large- or even medium-sized carnivorous dinosaurs.
After all, we know many predatory theropods were at the top of the food chain across much of the
rest of the planet at the time, like T. rex in North America and Carnotaurus in Argentina.
Yet, we’ve found no evidence to date of any big theropods from Hateg.
And this suggests that the ecological niche of apex predator was empty,
waiting to be occupied by something large, mobile, and powerful enough to fill it.
Enter Hatzegopteryx: a pterosaur with an estimated wingspan of up to 12 meters
and a skull nearly 3 meters long.
One pterosaur expert even described it as “a giant mix of a shoebill stork, a ground hornbill,
and the Terminator.”
The idea that Hatzegopteryx was basically a pterosaur turned T. rex was first proposed
in 2017 by researchers studying one of its neck vertebrae.
The bone was particularly short, wide, thick and robust compared to other known giant pterosaurs.
And this led them to think that, while Hatzegopteryx was truly massive,
its neck would have actually been proportionally quite short,
but thick and heavily muscled - trading length for strength.
By modeling the biomechanics of Hatzegopteryx’s neck,
they concluded that it might be the strongest of any known pterosaur.
This would allow it to withstand the kind of stresses experienced
by a terrestrial predator that used its enormous head to bite,
bash, and stab prey that was too big to swallow whole - like dwarf dinosaurs.
And while a huge, chunky pterosaur might seem like it should be pretty clumsy on the ground, it’s
been suggested in recent years that pterosaurs were actually capable and efficient walkers.
Analysis of fossil trackways and skeletal features of other giant
pterosaurs suggest they weren’t catching food in flight. Instead many would have
been terrestrial generalist foragers that ate small animals and scavenged on carrion.
But Hatzegopteryx is thought to have taken this lifestyle up another notch - taking down
proportionally much larger prey than any other known pterosaur,
thanks to its uniquely robust build.
Based on its size, Hatzegopteryx would have probably been big and powerful enough to prey on
all of the island’s known dinosaurs, other than maybe fully-grown dwarf sauropods.
Now, you might be thinking: if Hatzegopteryx was a terrestrial apex predator and had
such a massive, stocky build, could it still fly?
Well, there are reasons to think, yeah, it probably could!
Based on the few bone fragments we have from its wings, they seem to have still been
functional. The proportions of its humerus match those of a normal flying pterosaur.
And despite being so robust, it actually would have been surprisingly light.
The internal structure of its bones have a series of weight-saving adaptations, like
tiny and densely packed hollow structures called alveoli that
kinda look like polystyrene - rigid but light.
In fact, its weight has been estimated at only around 250 kg!
That's an animal the size of a giraffe, with the wingspan of a small plane,
weighing only roughly the same as a large black bear.
So it seems that Hatzegopteryx landed in an evolutionary sweet spot - able to grow big
and powerful enough to hunt dwarf dinosaurs, while still probably staying lightweight enough to fly.
And flight might have been a key factor that allowed Hatzegopteryx to get and stay so gigantic,
while many of the Island’s other animals shrank.
If it could fly, then its food resources wouldn’t have been limited to only one island, the way
they were for the dwarf dinosaurs. Hatzegopteryx could’ve ranged across the European archipelago,
avoiding insular dwarfism.
And this also makes Hatzegopteryx not just a contender for the most imposing
pterosaur of all time, but also one of the largest things that ever flew.
The largest flying animal around today, the wandering albatross, has a wingspan
up to 3.7 meters -- Hatzegopteryx’s was a little over 3 times that.
And throughout the entire fossil record it’s rivaled by only two other pterosaurs,
one of which was Quetzalcoatlus from North America,
which was also enormous, but much more slender.
Despite rising to the top of the food chain and ruling Hateg Island for
millions of years - and probably the rest of the European archipelago,
too - Hatzegopteryx’s reign came to a catastrophic end 66 million years ago.
Like the dwarf dinosaurs it preyed upon,
it didn’t survive the mass extinction at the end of the Cretaceous.
But the story of its rise shows us that being at the right place
at the right time can be a major driving force in evolution -- one
that could turn a pterosaur into the Hateg Island version of a T. rex.
We’ve gotta thank this month’s pterrific Eontologists!
Become an Eonite at patreon.com/eons and you can get fun perks like submitting a joke for us to read,
like this one from Matt Hepler: What do you call a pterasaur that can't fly?
A Terra-saur! ...Firma-Terra, a TERRAsaur!
And as always thanks for joining me in the Konstantin Haase studio.
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