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Offensive Adaptations

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Dino 101: палеобиология динозавров

Альбертский университет

4.9 (оценок: 925) | Зарегистрировано учащихся: 20K

Dino 101: Dinosaur Paleobiology is a 12-lesson course teaching a comprehensive overview of non-avian dinosaurs. Topics covered: anatomy, eating, locomotion, growth, environmental and behavioral adaptations, origins and extinction. Lessons are delivered from museums, fossil-preparation labs and dig sites. Estimated workload: 3-5 hrs/week.

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Получаемые навыки

Biodiversity, Biology, Evolution, Paleontology

Рецензии

4.9 (оценок: 925)

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TW

Dec 16, 2017

The instructors' explanation are very clear and easy to understand. Would definitely recommend this to anyone who is interested in Paleontology or dinosaurs in general. I really had fun learning.

TW

Sep 23, 2017

This course (and the other Paleontology Offerings) have given me a new interest in the subject. Thank you, University of Alberta for providing so much information in such an interesting format.

Из урока

Attack and Defense

Examines the behaviours and structures that may have served for attack or defence through the lifetime of a dinosaur.

Defensive Adaptations13:50

Offensive Adaptations15:24

Intraspecific Interactions7:34

Преподаватели

Philip John Currie, PhD
Professor and Canada Research Chair, Dinosaur Paleobiology

Текст видео

What are some of the behaviors and

adaptations that predators use to catch prey?

Can you think of some of the adaptations that carnivorous dinosaurs might have had

for locating, catching, and devouring their prey?

Check all the answers you think are correct.

Was it A, sharp serrated teeth?

B, binocular vision?

C, strong odor?

D, sharp retractable claws?

E, the ability to run fast?

Or F, armor?

Many of these are useful adaptations for predators.

Some of them, like the serrated teeth and sharp claws, are useful for

actually catching and eating the prey.

While others like binocular vision and speediness are most useful for

tracking down the prey.

Things like strong odor and

armor are better defense mechanisms than they are predatory adaptations.

So answers A, B, D, and E are correct.

>> Many living carnivorous birds and

mammals have binocular vision, which helps them accurately determine distances.

Humans have binocular vision too.

Our eyes are situated on the front of our heads, and

the field of view of each eye overlaps slightly.

This is what allow us to have depth perception.

It lets us see in 3D.

Binocular vision lets us know the distance between us and something we're looking at.

You can see how this would be useful if you need to chase down another animal and

leap to catch it.

Many herbivores have eyes on the sides of their heads, like this horse.

They can see to the front, sides, and behind them.

They have a greater field of view, so

that they can easily see when a predator is approaching.

Horses, as well as most other herbivores, do not have binocular vision.

So they do not have good depth perception.

But they do have a wide field of view.

Let's contrast that with the skull of this tyrannosaur.

Its eyes face forward.

So it would have had binocular vision and good depth perception.

>> This is a drawing of a very famous fossil specimen recovered in

Mongolia's Gobi Desert back in 1971.

The fossil is called The Fighting Dinosaurs.

It is a truly remarkable specimen.

The dinosaur skeletons are complete and articulated, and

the fossil seems to preserve an interaction between two different species.

The Velociraptor is one its side, and the Protoceratops is crouching.

The Protoceratops has the Velociraptor's hand in its mouth, but

the Velociraptor has its sickle claw in the Protoceratops's throat and

is holding part of the Ceratopsian's frill with its other hand.

What predatory adaptations does Velociraptor have that you would be

able to observe in the actual fossil?

A, pack hunting.

B, sharp claws and teeth.

C, high intelligence.

D, speed.

E, binocular vision.

Check all the answers you think are correct.

We're pretty sure that Velociraptor exhibited all of these adaptations, but

looking at this fossil we can only observe three of them.

Sharp claws and teeth, speed, based on limb proportions, and binocular vision.

It is important to understand and differentiate between our

direct observations of a fossil and our broader understanding of an organism.

Looking at the fighting dinosaurs fossil,

there are a number of things we can observe.

We can see that the Velociraptor had sharp claws and

teeth, binocular vision, and was likely fast based on its limb proportions.

Based on other fossils, we know that theropod dinosaurs are sometimes found in

groups, something we'll come back to shortly.

Also we postulate that Velociraptor was intelligent,

based on the size of its skull.

However, deducing intelligence in extinct animals is tricky and contentious.

Regardless, Velociraptor and other theropods like it

had some of the largest brain size to body ratios of any dinosaur group.

Were they smarter than other dinosaurs?

We can only postulate.

Finally, there is one more important fact we can observe in

the fighting dinosaurs fossil.

That is, these two dinosaur species lived at the same time and

did indeed interact with one another.

Determining close dinosaur interactions is incredibly difficult,

even in modern environments.

Animals may live near one another, but never regularly interact.

In the fossil record, animals may be found within a few feet of each other, but

those few feet could represent millions of years of displacement in time.

But we do know that Protoceratops and Velociraptor lived at the same time and

interacted with one another as predator, and prey.

To catch and

kill their prey, predatory animals have evolved an array of hunting strategies.

Some predators, like crocodiles, and many venomous snakes, are ambushers.

Think of them like nature's landmines.

They first seek out a good hiding spot.

And then they lie in wait for unsuspecting prey to wander into striking distance.

Ambushing is a strategy best suited to predators who can afford to wait for

a long time between meals and who are capable of a single fast and

deadly strike, but not a prolonged chase.

Stealthy stalking is another hunting strategy, exemplified by modern big cats.

They're the masters of finding and

sneaking close to their prey without being seen.

Naturally, even the stealthiest hunter can usually only sneak in so far.

So, stealth predators still need to be able to outrun their prey,

even if only for a short sprint.

Pursuit predators, like wolves and wild dogs, are endurance hunters.

They may not be as quick as their prey, but they can remain hot on its heels for

a long time.

They have the endurance necessary to eventually exhaust and overtake it.

Some predators have another strategy, cooperation.

Hunting in a group can allow predators to surround prey,

to drive prey into an ambush, or

to take on prey that would otherwise be too dangerous to attack alone.

However, hunting in a group has a downside.

Predators that work together also have to split the spoils of their labor.

A single kill provides a predator with a lot less food when

the predator has to share it with multiple members of its pack.

When food resources are tight, there may not be enough to go around.

Lions are a great example of social predators.

Lion prides use sophisticated hunting strategies to

kill fleet-footed prey like gazelle and zebra.

And lion prides can also bring down really big and dangerous game.

Such as buffalo, rhinoceros and even on rare occasions, elephants.

Tigers and leopards are solitary hunters.

They don't reap the benefits of cooperation, but

they also don't have to share what they kill.

Cheetahs are flexible in their approach to team work.

Sometimes, cheetahs form groups called consortiums, and hunt cooperatively.

And sometimes cheetahs opt to hunt alone.

Notice that the three examples I have just given of a social,

a solitary, and a socially variable predator are all big cats.

Social hunting behaviors tend to be diverse,

even among closely related animals.

Were any predatory dinosaurs capable of social hunting?

How can we tell?

Here's Dr. Phil Curry to talk about Albertosaurus.

Maybe they were social hunters too.

>> As I mentioned before,

sometimes we have concentrations of single species of animals in one place.

And sometimes those are carnivores or theropods.

Now, let's try and

think of reasons why carnivores might be concentrated in one single place.

Maybe this was a predator trap.

So, for example, you might have a duck-billed dinosaur that's in its

death throes because it's been trapped in quicksand.

And the carnivores are attracted to this animal that can't get away from them.

Unfortunately, the carnivores that come in first also get trapped.

And then that attracts more carnivores, and

you keep getting more and more carnivores attracted to

the same site as the site gets reset with fresh meat essentially.

These predator traps are known occur in some parts of the world.

But there are other possible explanations too.

So, for example we may have a concentration of carnivores and

there's no evidence of a predator trap.

There's no evidence of tar or quicksand or anything like that.

No evidence of an animal that they were eating.

How do explain that?

Possibly these animals were trapped in flood waters.

Or a fire, or they died of disease.

Or maybe they were concentrated around a water hole and

slowly dying of thirst during a drought.

It's very hard sometimes to interpret what these sites are.

It was very important then, when Barnum Brown,

back in 1910, found a site near the city of Red Deer in Alberta.

There he collected parts of nine skeletons of Albertosaurus,

one of the Tyrannosaurs.

Now Brown took those specimens back to New York and they were put in collections, and

he never got around to writing about the sites, so we didn't know

where the site was and we didn't even know about it to any great degree.

Until the mid 1990s.

At that time when we looked at the evidence, we realized that Brown had

a site where it was only Albertosaurus, and these were articulated skeletons.

Skeletons that were partially together at least,

and we made an effort to go and find that site.

And in 1997, we re-opened the quarry that Brown had been working in 1910.

There was so much material left in the field that we continued to

work that site for more than 12 years.

And during that time, we took the number of possible skeletons of

Albertosaurus from the nine specimens that Brown found.

To at least a dozen, and more likely into the low 20s.

And those animals ranged in size from small animals about my size,

to big ones that were 12 meters long.

And in terms of age, the youngest one was about two years old, and

the oldest one was 24 years old.

Now, we've collected a lot of evidence from that particular quarry.

It's not just paleontological evidence, it's also geological.

And we have developed a scenario where we feel that these animals were in fact,

together at the time of death.

And because so many animals died in one single place, and

there's no evidence of any Herbivores around them, we think that in fact,

this may have been a pack of Albertosaurus.

And they encountered some kind of a mass catastrophe.

The best explanation right now is that the region may have been hit by a hurricane,

some 70 million years ago, and

that these animals were caught in the flood waters of a river at that time.

>> Do you think Albertosaurus was a solitary hunter, or did it hunt in groups?

Check one answer that you think is correct.

In fact, there's no way for us to be sure how Albertosaurus hunted.

We have to be careful when we interpret dinosaur bone beds.

Just because we may find multiple individuals of the same species in

the same place, does not mean that they necessarily lived together in a group.

Just like with the fossil of the Velociraptor and

the Protoceratops, we have to be cautious about differentiating between what we

can observe and the conclusions we draw from an observation.

The geology of the Albertosaurus bone bed tells us

only that these animals were all together after they died and

that they were deposited in a certain spot by a flood.

Why these animals were all together is still not fully clear.

These animals could have all been drawn together by a carcass, and

then got caught in a flood.

Alternatively, they may have tolerated one another, but not actually hunted together.

We just don't know for sure.

>> Studying another group of fossils has led us to believe that some dinosaurs may

have changed their defensive behaviours depending on their stage of growth.

A group of baby Ankylosaurs called Pinacosorus, were found in China.

There are at least five individuals preserved lined up next to each other in

crouching positions.

They looked like they had hunkered down for the night.

Let's think about why these dinosaurs may have been found together.

Maybe they came together looking for water and were washed together in a flood.

Or maybe they sought safety in numbers, a defensive herding behavior.

These baby Pinacosaurus and had very little armor compared to adult forms.

The sediment these dinosaurs were preserved in did not suggest that

the Pinacosaurus were attracted to a dwindling resource like water.

As well, we know of at least one other Pinacosaurus bone bed in Mongolia.

The information from this and

other juvenile Ankylosaur bone beds suggests that they lived in

groups while they were young, but that adult Ankylosaurs may have been solitary.

Adult Pinacosaurus had tail clubs and

lots of osteoderms, but these juveniles had formed no armor of note.

This leads us to believe that young Pinacosaurus herded

as a defensive behavior, and then switched to be more solitary animals once they

had developed the armor that would protect them for the rest of their lives.

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