How Did Prehistoric Animals Get So Big?

Today's megafauna are tiny compared with history's largest dinosaurs. Learn a few theories about how these animals got so big in this episode of BrainStuff, based on this article: https://animals.howstuffworks.com/extinct-animals/why-were-prehistoric-animals-big.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of iHeart Radio, Hey
brain Stuff Lauren Vogelbaum. Here. There's ongoing debates about which
dinosaur might be the largest animal to have ever RealMed
the Earth. One candidate is a ninety eight million year
old skeleton of a long necked titanosaur discovered in northwest

(00:22):
Patagonia in in research published one in the journal Cretaceous Research.
The authors said that they believe it could be one
of the largest sauropods ever found, even larger than the
one on display at the American Museum of Natural History.
That's a hundred and twenty two ft long. That's thirty
seven ms. But why did priest work animals like these

(00:44):
get so big in the first place? After all, we
do still have megafauna that reached towering sizes, like elephants, rhinoceros,
and hippopotamus, But most of the largest land animals living
today would still look like little buddies next to the
literal mammoths of prehistory. And there are several hypotheses about
why these creatures grew so massive. Several studies have linked

(01:08):
environmental factors such as higher oxygen content in the air
to the expansion of huge sauropod dinosaurs in North America.
For example, a study published in twenty nineteen reported the
researchers using a new technique to analyze tiny amounts of
gas trapped inside two hundred and fifteen million year old
rocks from the Colorado Plateau and the Newark Basin. Jumps

(01:29):
in oxygen levels in layers of the rock correlate with
the first dinosaurs appearing in the area and then massive sauropods.
The existence of sauropods leads us to a second hypothesis
about why these animals grew so gigantic efficient food uptake.
The thought behind this idea is that because sarropods had

(01:49):
such long necks, they must have been more efficient eaters
than other large herbivores, meaning they could cover much larger
feeding grounds and reach food that was inaccessible to other
dinosaur wars. So, in theory, the massive sauropods must have
been able to grow larger than other dinosaurs because they
fed more efficiently. Then there's Cope's rule, which is the

(02:11):
hypothesis formulated by paleontologist Edward Cope that says that animals
in evolving lineages tend to get larger over time, and
a twelve study by the Department of paleo Biology at
the National Museum of Natural History found that Cope was
right well some of the time. Using advanced statistical methods,
the team used dinosaur femur bones to estimate animal size.

(02:35):
They then used that data in their statistical model to
look for too things, directional trends in size over time,
and whether there were any detectable upper limits for body size.
What they found was some groups or clades of dinosaurs,
including the long necked sauropods, do grow larger over time,
as Cope's rule suggests. However, others like therapods, which include

(02:57):
the popular Tyrannosaurus rex, did not. Other evidence points to
why prehistoric animals that flew grew so massive, and specifically,
it points to their bones and lungs. Parasaurs, for instance,
started out small, but some species ballooned to unbelievable proportions.
This could have been due in part to a highly

(03:18):
effective float through respiratory system, which allowed them the ability
to sustain flight. Take one of the largest flying pterosaurs
in the world as Dark Kids and I do hope
on saying that right. They had wingspans of thirty three
feet that's ten meters and weighed as much as four
hundred and forty pounds that's two hundred kilos. Studies have

(03:39):
shown that their bones were made up of intricate structures
that made them both super strong and stable, but also
super light. They may have been able to fly as
far as ten thousand miles that's sixteen thousand kilometers without
resting or eating, and the supersaurus is also thought to
have had extraordinarily light bones and a complex system of

(04:00):
air sacks, which could have allowed it to grow huge
without collapsing in on itself. They also had very efficient lungs,
so their respiration and heat exchange could better support their
larger size. Of course, all of the animals we've mentioned
were the top predators of their time, which made them
a lot less susceptible to becoming other animals dinner. One

(04:22):
exception to the animals being smaller these days rule are whales.
For example, the blue whale makes the supersourus seem small.
Blue whales grow on average to between seventy five and
nine ft in length that's about twenty three to twenty
seven and way about two hundred tons. Though it is
difficult to measure such a huge creature underwater. Being ocean bound,

(04:45):
they have buoyancy on their side, which makes it possible
for them to weigh three times with the supersourus wave
without their bodies collapsing. Today's episode is based on the
article why were so many prehistoric animals So big? On
how stuff works dot Com, written by Karen Kirkpatrick and
Sarah glime A. Brain Stuff is production by Heart Radio

(05:08):
in partnership with how stuff Works dot Com is produced
by Tyler Clang. Four more podcasts my Heart Radio viausit,
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