In 1912, a fossil collector discovered some
strange beautiful fragments in the eerie, beautiful
Cretaceous Bahariya rock formation of Egypt.
The fragments looked like they belonged to
some kind of predatory dinosaur, but it was
unlike anything experts had ever seen.
It was later described, in 1915, by a paleontologist
with the awesome name of Ernst Freiherr Stromer
von Reichenbach.
Stromer named the new dinosaur Spinosaurus
aegyptiacus, Latin for “Egyptian spine lizard.”
And for a long time, that name was the only
information you could find about Spinosaurus.
It took nearly a hundred years for scientists
to even begin to figure out what this animal
really was, how it looked, and why it lived
the way it did.
But eventually, that handful of fossil fragments
would reveal to scientists one of the strangest
dinosaurs that ever existed -- the world’s
only known semi-aquatic dinosaur.
When Stromer first described Spinosaurus,
he didn’t have much to go on -- just a handful
of vertebrae, several giant dorsal spines,
a lower jaw fragment, and some teeth.
Clearly, this thing was big, rivalling the
biggest predatory dinosaurs ever found at
the time.
But beyond that, all Stromer could determine
was that it was some kind of theropod, and
it was… different.
For instance, there were those huge spines,
the longest reaching up to two meters in length.
At first, Stromer thought they might have
supported a fatty hump like in a modern-day
bison.
But he later concluded that they were more
likely part of a giant sail, which proved
to be the more popular interpretation.
But why a predator might need a giant sail
on its back, he didn’t know.
The jaw was also weird
The shape of the lower jaw fragment seemed
to indicate that Spinosaurus had a longer,
narrower snout than most theropods.
The snout squared off at the end, and contained
long, cone-shaped teeth instead of the short,
serrated ones that other carnivorous theropods
usually had.
It wasn’t until 1936 that Stromer published
a reconstruction of what he thought Spinosaurus
looked like.
And his rendering resembled, basically, a
T. rex with big forelimbs and a sail on its
back.
It was really awkward looking, but accurate
or not, Stromer’s version of the dinosaur
became the popular, accepted vision of Spinosaurus.
And soon, it became the only version.
Because, in 1944, Allied forces bombed the
museum in Munich where the Spinosaurus fossils
were held, and the specimen was destroyed.
Suddenly, Stromer’s descriptions and a few
photos of the fragments were the world’s
only records of this bizarre creature.
As time went on, other researchers tried to
develop a more complete picture of Spinosaurus,
but their work was all still based on the
same old evidence.
It wasn’t until the late 20th century that
the idea began to take shape that Spinosaurus
was a dinosaur with a truly unique lifestyle.
Because, during that time, new fossils were
discovered in Africa, Europe, and South America
that shared some similarities with Spinosaurus.
For example, a theropod called Baryonyx walkeri
was described in 1986 by a pair of British
researchers who noticed that it, too, had
an elongated jaw with conical teeth — not
unlike the lower jaw fragment described by
Stromer all those years ago.
Because of its long snout, plentiful teeth,
and some fish teeth and scales that were found
mixed in with its remains, the researchers
suggested that Baryonyx might be the first-known
piscivorous, or fish-eating, theropod.
Then in the 1990s, more species were uncovered
with a similar, croc-like jaw.
One small specimen was described in 1996 from
a single skull fragment found in Brazil.
Another was described from a more complete
skeleton reported in Africa in 1998.
By that time, enough evidence of these odd
creatures had turned up that scientists decided
to assign them all to a single group.
Paleontologists added all of these narrow-snouted
Cretaceous theropods to the family called
Spinosauridae, after Stromer’s Spinosaurus.
But during all this time, no new fossils of
Spinosaurus itself had been found, except
for a handful of bone fragments.
Then, it finally happened.
In 2008, paleontologist Nizar Ibrahim was
working on his doctorate in Morocco when a
local fossil collector approached him with
a box of fossils.
One fossil in particular caught Ibrahim’s
eye — it looked like Stromer’s illustration
of a Spinosaurus spine.
Ibrahim convinced the man to lead him and
his team to the original site of the fossils.
The collector took them to a cliffside in
the Kem Kem fossil beds, and sure enough,
it was a Spinosaurus treasure trove.
There they found both hind limbs, much of
the pelvis, several neural spines, and a large
portion of the lower jaw from what was likely
a juvenile Spinosaurus.
The team took CT scans of the newly discovered
fossils and created digital models based on
Stromer’s original descriptions.
Then, they put all the pieces together and
published a paper announcing their findings
in 2014.
Nearly 100 years after Stromer first described
Spinosaurus, paleontologists got a fresh look
at the famous dinosaur.
And it was even weirder than anyone thought
possible.
For one thing, its nostrils were on the top
of the snout.
And it also had evidence of croc-like pressure
receptors on the tip of its snout.
Its limbs seemed suited to horizontal swimming,
in addition to walking, and its bones were
also more dense than other dinosaurs’.
All of these clues put together led Ibrahim
and his colleagues to suggest that Spinosaurus
actually spent at least part of its time in
the water, making it the first-known semi-aquatic
dinosaur of any kind.
As for the sail?
Paleontologists still can’t agree on what
it’s for, but there have been some interesting
ideas.
Some think it was used as a threat display
or to attract mates, while others think it
could have regulated the creature’s body
temperature.
A paper from 2016 suggests that it might even
have functioned like the sail on a sailfish,
helping Spinosaurus maneuver in the water
or corral schools of fish.
So, Spinosaurus turned out to be totally unique
and fascinating.
But of course, the question remains: Why?!
Why did this thing exist?
What sort of environmental pressures could
produce a giant sail-backed, semi-aquatic
dinosaur?
Well, northern Africa wasn’t always a giant
desert.
During the Cretaceous Period, it was home
to a river that stretched from what’s now
Morocco all the way to Egypt.
Some researchers refer to this waterway as
the “River of Giants,” because it had
an abundance of prey in the river and its
surrounding tropical forests, as well as an
unusually high density of big predators.
Aquatic reptiles, giant sawfish, and coelacanths
the size of buses swam in this ancient river,
while crocodiles sunned themselves on the
shores.
And giant theropods like Carcharodontosaurus
roamed nearby.
This kind of environment would have offered
a lot of prey for Spinosaurus, but also a
lot of fierce competition, both on land and
in the water.
So, being able to take advantage of food sources
in both places would have been a huge advantage.
By spending much of its time in the water,
it could avoid direct competition with other
large theropods, but it could also prey on
land animals if it needed to.
The adaptations of Spinosaurus proved to be
exquisitely useful, but nevertheless, as far
as we know, they seem to be unique.
There’s no fossil evidence of any other
aquatic dinosaurs, semi- or otherwise.
But maybe there are others out there waiting
to be found!
After all, Spinosaurus wasn’t the only dinosaur
that lived in a competitive environment.
Until we find more like it, however, Spinosaurus
will remain a truly distinctive character
in the history of our planet -- one of the
most unique and fascinating apex predators
the world has ever seen.
Thanks for joining me for this foray into
the Cretaceous!
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