Planet Dinosaur – The Great Survivors
Bradycneme, Magyarosaurus & Hatzegopteryx
In this episode we explore the dinosaur’s extraordinary ability to survive
and witness how they have transformed over millions of years into some of
the most alien-looking animals the world has ever seen.
This astonishing
capacity to evolve into ever more diverse and bizarre forms meant that it
helped them, not only spread throughout the world, but also dominate life
upon it.
Dinosaurs lived on Earth for more than 160 million years. Most
famously, throughout the Jurassic Period, but it was the later Cretaceous
Period that the biggest, baddest and most bizarre dinosaurs lived.
By the end of the Cretaceous, dinosaurs were flourishing in every
continent. Even dinosaurs that had been around for over 100 million
years, like the giant plant-eating Sauropods, were still thriving.
Magyarosaurus
Back then, Europe was a series of large islands. On one of them,
Hateg Island, a giant dinosaur showed a most surprising adjustment to
island life. Cut off from everywhere else, Hateg Island had its own
unique collection of animals. Bradycneme is one of the predators here.
Magyarosaurus, a plant-eater, is the potential prey and its the youngest
that are at the greatest risk from predators.
Hateg is an island where much is not as it appears.
Bradycneme
This is a world turned upside down. They may look like giants, but
Magyaroaurus, from Hateg Island, stood no taller than a pony. Weighing
around 1 ton, they are a fraction of the aize of their mainland
relatives and weigh at least 70 times less than their cousin
Argentinosaurus.
On the island of Hateg, there simply wasn’t enough food to support a
plant-eating giant. So, over many tens of thousands of years they
adapted creating a world where many of the dinosaurs were pocket-sized
versions of their relatives.
But, some animals are still huge.
The largest flying vertebrate ever known is a pterosaur with a 10m
wingspan. Its as tall as a giraffe, standing over five and a half metres.
Discovered in 2002, its skull alone is 3m long. This is Hatzegopteryx. A
giant we assumed hunted from the skies.
Hatzegopteryx
That was until the discovery of a series of fossil footprints, in
South Korea, unlike any found before. The footprints were those of a
giant pterosaur and they showed that these creatures did not just fly,
but could comfortable walk on all fours. It seems these monsters
actually hunt on the ground. Able to hunt with impunity, Hatzegopteryx
are the top predators, able to fly from island to island, this is their
kingdom.
Hateg Island is just one example of the strange paths evolution can
take. But, all over the world, bizarre shaped dinosaurs continually evolved
throughout their long reign.
Perhaps the strangest of all dinosaurs is one particularly weird group –
Therizinosaurs. And the best example of these peculiar animals was announced
in 2009. A skeleton revealed the secrets of this strange creature that lived
in New Mexico 92 million years ago.
Nothronychus
The swamps we are shown are home to zinu-tyrannus, a mid-sized
tyrannosaur, and they’re also home to this weird creature – Nothronychus.
Its actually a close relative of the tyrannosaur, but with one major
difference. Nothronychus has given up eating meat. Here, the tyrannosaur is
the top predator. Therizinosaur had been a mystery for decades known only
from tantalising fragments. That all changed with the discovery of
Nothronychus. It gave us our clearest look at this strange group of
dinosaurs.
It walked upright on short stocky legs. It had wide hips and a long neck.
Its teeth showed that these weren’t the teeth of a killer. Far from its
ferocious tyrannosaur cousins, this pot-bellied dinosaur had evolved into a
strict vegetarian. But, armed with viciously long claws on its
forearms, it was by no means defenceless.
By becoming a plant-eater Nothronychus has easy access to food. And
because it walks on two legs, it can use its claws to pull down branches to
reach leaves. Nothronychus thrives here because it doesn’t compete
with tyrannosaurs for food. But, just because you’re not competing for food
does not mean you’re not seen as food These are dangerous places to
be bottom of the food chain. Tyrannosaurs are predators that will eat
anything, even one of their own, whether they’ve killed it or not.
And a discovery found in Montana of a number of meat-eating dinosaurs
appeared to show that being such an unfussy eater could have dramatic
consequences. It seems scavenging can hold hidden dangers.
Tyrannosaur remains
This Tyrannosaur wasn’t killed by Nothronychus. There’s a moew deadly
killer at work here. All the predators’ bones were found alongside the edge
of an ancient, stagnant lake and all of them died at the same time. Similar
mass killings have been found today among birds and the killer is – a
fast-acting, naturally occurring, deadly disease – botulism. Botulism is
caused by a bacteria that can thrive in rotting carcasses. We think that the
dinosaurs too might have been been victims of this lethal and invisible killer.
Once a carcass is poisoned it is quickly passed on to any animal that eats
it, with lethal results. But, plant-eaters like Nothronychus are usually
safe from such deadly killers.
By completely changing its diet Nothronychus shows the extraordinary
adaptability of the group known as the therapod dinosaurs. These two-legged
dinosaurs were the most diverse of all the dinosaur groups.
For predators like Mapusaurus and Majungasaurus to the bizarre
Therizinosaurus the extraordinary tree-living Microraptor to the weird
Gigantoraptor they evolved into an incredible range of shapes and sizes. The
tyrannosaurs were the most successful of the therapod dinosaurs and once
tyrannosaurs dominated in an area many other meat-eating dinosaurs simply
disappeared. But, thoase that had changed their diets flourished.
Mongolia, 85 million years ago. One group of dinosaurs are thriving here,
despite the fact that they live in the shadow of a deadly tyrannosaur. These
are Oviraptorids, omnivores that eat animals and plants and so don’t compete
directly for food with the biggest of killers.
The benefits are clear becuase some of there creatures become huge, like
the 8m Gigantoraptor. But, this group have another trick to help them
survive, the way they nest.
In Mongolia in 1994, a nest of very large dinosaur eggs was discovered.
An array of more than 20 eggs in pairs around the edge of a shallow pit.
They were the biggest dinosaur eggs ever found. When an embryo was found
preserved within an egg, it proved that the nest, eggs and embryo were
almost certainly those of Gigantoraptor.
Oviraptorids
In 2005, one particular fossil was found to contain two eggs within the
body cavity, ready to be laid. Even more amazing were a number of other
finds that revealed the nesting behaviour of these dinosaurs.
Three dinosaurs were discovered all sitting on top of nests of eggs. The
dinosaurs sitting in the centres of the nests with their long arms spread
out to protect the pairs of eggs arranged around them. These dinosaurs were brooding!
Looking after their eggs increases the chance of them hatching. And, having
large eggs means the hatchling is more developed making it less vulnerable
to predators. But, it takes longer to hatch – up to 80 days for
Gigantoraptor. A time when both eggs and the brooding parent are permanently
at risk.
Unwilling to leave the nest, in the presence of a tyrannosaur, the adult
protects its offspring, first by hiding, then if that fails be going on the
offensive. Protecting the nest means that Gigantoraptor young are more likely
to survive. It now seems clear that the instinct to nurture and care for a
nest of eggs had its origins with the dinosaurs. Its a behavious that was so
successful its still widespread today with birds.
But, the fossils show something else. These animals all died sitting on
their nests. It seems that threats don’t always come from predators,
sometimes the real danger comes from the most unlikely place. These
dinosaurs were all buried alive after a massive sandstorm.
Planet Dinosaur was an incredibly diverse and varied place, with these
creatures able to colonise every continent on Earth. Continually evolving
and changing, their dominance of life on Earth was absolute. Yet, they were
doomed!
Approaching Armageddon
Their downfall was caused by an asteroid smashing into Earth. Travelling
20 times faster than a speeding bullet, 15 kilometres across, it slammed
into the Gulf of Mexico. The impact released more energy than a billion
atomic bombs. The initial impact triggered wildfires, massive earthquakes
and tsunamis. But most devastating was the debris blasted high into
the atmosphere. This shrouded the planet in darkness that lasted for monrh.
The
impact resulted in the collapse of the whole food chain and, the extinction
didn’t just affect the dinosaurs. Virtually all life on Earth was affected.
