153 million years ago in Montana, the giant
dinosaur known as Diplodocus wandered through a seasonal wetland looking for its lunch. Like most other sauropod dinosaurs, Diplodocus
was pretty big - it weighed almost as much as 4 elephants, and was about as long as three
school buses. And: a full 25% of that length was its neck,
far longer than any mammal’s neck would - or could - ever be. If it sat back on its haunches to rear up,
like some paleontologists have hypothesized that it could have, then Diplodocus might’ve
reached a full 11 meters up into the trees. So, you might understand why some paleontologists
were surprised after studying the teeth of a Diplodocus. Based on the scratch marks they found on the
teeth, it turned out that the primary diet of Diplodocus wasn’t the leaves of trees;
it was ground cover, like ferns and horsetails. And it’s not just Diplodocus that ate this
way. Other sauropods that lived in the same area
-- a region known today as the Morrison Formation -- had unexpected diets, too. Like, the 25 metric ton, 23 meter-long Apatosaurus,
which also ate mostly ground-level plants. Or the 15 meter long Camarasaurus, which ate
tougher, shrub-sized plants and short trees - despite being around 4 meters tall at the
shoulder, which is almost two and a half Kallies tall. Each of these dinosaurs had a neck that was
much longer than the animal was tall - way longer than it needed to be for the dinosaur’s
mouth to reach the ground. But if so many sauropods were eating ground-level
plants, why did they all have such long necks? It turns out that it did give them a huge
advantage when it came to food, but not in the way you think. And this benefit would allow them to become
the biggest terrestrial animals of all time! Being big comes with a fair number of advantages. It makes you harder to attack and eat, for
one. And larger animals tend to lose heat more
slowly, which means they can spend less energy regulating their body temperature. Bigger bodies can also store more energy for
later, which helps them make it through tough times. They can also move farther, and faster, than
most small bodies can - so they can survive in environments where food sources are farther
apart. And if bigger is better, then sauropods were
the best, as they became the largest animals that ever walked on land. Some, like Argentinosaurus from the Cretaceous
of -- wait for it -- Argentina, got to be 35 meters long and could have weighed up to
70 metric tons. But while they would end up evolving to be
absolutely enormous, the sauropod dinosaurs had some pretty humble beginnings. Sauropods are part of a larger group of dinosaurs
called the sauropodomorphs, or sauropod-like dinosaurs. Scientists are still arguing about what the
precise distinction is between the two. But the most common definition is that once
sauropodomorphs had to stand on all four legs and stopped having grasping fingers, they
were officially sauropods. Still, all of the similarities between sauropods
and sauropodomorphs means that it’s a little hard to tell exactly when sauropods themselves
evolved. The first possible sauropod tracks show up
toward the end of the Triassic Period, around 210 million years ago, in North America. But the earliest known definitely-probably-sauropod
bones appear about 5 million years later in Thailand. And, based on those bones and the partial
skeleton of another, slightly younger species, paleontologists think that the first sauropods
probably looked something like the Early Jurassic dinosaur from Zimbabwe known as Vulcanodon Vulcanodon was not as big as its later relatives,
but it was a lot bigger than you: estimates vary, but suggest it was around 9 or so meters
long, and around 10 metric tons. And it looked a lot like the sauropodomorphs
that it coexisted with, having a somewhat shorter neck and generally smaller body size
than later sauropods. But Vulcanodon had one subtle but important
new feature: Unlike other sauropodomorphs, its front legs
were about as long as its back legs, and it probably spent all of its time on all fours. That shift to four-leggedness was an important
glimpse of what was to come. Being big requires a lot of stable support
- and once they acquired the stability they needed, they pretty quickly started to increase
in size. By the middle Jurassic, sauropods like Patagosaurus
were almost twice the length of Vulcanodon. But that was just the beginning. By the end of the Jurassic, sauropods had
become truly massive. For example, Giraffatitan, was a 26-meter
long monster from Tanzania, and is estimated to have weighed as much as 78 tons. And as sauropods got bigger and heftier, their
necks did too. The 10-meter long neck of Giraffatitan had
nothing on the 15 meter long neck of Supersaurus, the longest-necked sauropod found so far. Now, paleontologists think that those long
necks weren’t just some weird byproduct of their large body size; instead, they actually
made it possible for sauropods to become as massive as they did. The best-accepted hypothesis for why long
necks evolved in the first place is that having a long neck expanded a dinosaur’s feeding
envelope. Essentially, a feeding envelope is the space
within which an animal can reach food without having to move too much. After all, moving consumes energy – so the
less you have to move in order to get to your food, the better! Maximizing your feeding efficiency is a key
step for getting big, so long necks and big bodies are pretty closely linked in sauropod
dinosaurs. There were, of course, always exceptions,
but on the whole - the bigger the body, the longer the neck. Long necks were such a successful adaptation
that, in the Late Jurassic, sauropods were represented by 19 different genera worldwide. And 10 of those can be found in the Morrison
Formation in Montana, where Diplodocus and many others lived. But while long necks are a good clue that
a sauropod was eating a lot, they aren’t actually a good indication of what exactly
it was eating. Sure, there were sauropods that fed on tree-tops:
Brachiosaurus, for example, had wear on its teeth that matched well with a tree-munching
lifestyle. But the ones that ate at ground level like
Diplodocus had equally long necks and big bodies. And while that might seem a little strange,
it makes more sense when you understand the environment that Diplodocus lived in. It didn’t rain much in the Morrison Formation. Instead, most water flowed in from nearby
mountains, channeled by seasonal streams that often flooded their banks. Without rain, most of this big basin was home
to an open, dry environment and very few trees. Scientists compare it to a savannah - but
with cycads and short ferns, instead of grass, which hadn’t evolved yet. But the low-lying areas formed small lakes
and vast wetlands, and these were ringed with trees. So all of these different environments meant
that the Morrison could support those 10 different genera of sauropods - because they were eating
different things and living in slightly different places. For example, the high-browsing Brachiosaurus
and shrub-eating Camarasaurus likely spent most of their time eating trees that grew
near the lakes and streams. But Diplodocus was eating plants that grew
in the wetlands. And, if you’re a large dinosaur, wetlands
aren’t a very safe place. Getting stuck in the mud and having to fight
your way back out would’ve been exhausting and potentially deadly. In fact, some muddy rocks of the Morrison
Formation seem to preserve sauropods that died in just this way! But Diplodocus’s long neck made it easy
to reach deep into these wetlands and eat ferns and other plants without ever getting
its toes muddy. As a result, Diplodocus was able to access
food that other large herbivores like Stegosaurus couldn’t, and carve out a space for itself
where it didn’t compete with other herbivores. So long sauropod necks for the win: They allowed
some of these giant dinos to have a huge feeding envelope - even if for some of them, that
envelope was, horizontal, rather than vertical. And necks are one area where the current ruling
class of animals, the mammals, will never be better than the dinosaurs. The giraffe, of course, has the longest neck
of any living mammal. But it’s only about a third as long as a
Diplodocus neck – and there’s one big constraint that no giraffe in the past or
future can overcome. Almost all mammals, including you and giraffes,
have only 7 neck vertebrae. Instead of having more bones in their necks,
giraffes just have longer ones. But, sauropods and other dinosaurs didn’t
have that limitation. They could have up to 19 vertebrae in their
necks! That’s why, today, the surviving dinosaurs
-- also known as birds -- are the ones carrying on that long-necked tradition. Birds have even more uses for their necks
than sauropods did. They use them for specialized feeding in wetlands,
for preening their hind feathers, and for helping their heads stay level as they walk
and fly. Some birds, like parrots, even use their necks
as an additional limb to help them climb trees. And if we’re just counting the number of
vertebrae, today’s dinosaurs have the extinct ones totally beat: Some birds have up to 25
vertebrae in their necks! But, lucky for us, those long-necked birds
haven’t evolved to contend with sauropods for the title of biggest dinosaur. A regular sized goose is bad enough - but
one the size of a Supersaurus? No thank you. Ready to increase your digital feeding envelope? Be sure to check out PBS Digital Studios’
new food channel, PBS Zest!— all about exploring food through culture, community and science. Its new series, Good Gumbo, dives deep to
uncover the stories (and cultures) behind iconic southern foods; Serving up Science
delivers research-backed tips to make your favorite foods even tastier. Fair warning… This channel might make you hungry... Also extra long high-fives to this month’s
Eontologists: Patrick Seifert, Jake Hart, Jon Davison Ng, Sean Dennis, Hollis, and Steve! To become an Eonite, pledge your support at
patreon.com/eons! And as always, thank you for joining me in
the Konstantin Haase Studio. Be sure to subscribe at youtube.com/eons!
What show is this?