Know Your Bones: July 2015

[Blog of Reason]

Discussion thread for the blog entry "Know Your Bones: July 2015" by he_who_is_nobody.

Permalink: http://blog.leagueofreason.org.uk/science/know-your-bones-july-2015/

 

[Inferno]

Sadly I don't have the time to do copious amounts of research right now to look for the fossil, but I'd like to challenge you, he_who_is_nobody, on the use of the fenestrae.

I simply can't believe the first option:
"The fenestrae found on the frill were most likely away for cutting down the weight of the skull"
Why would you want that? Of what use would that be? I know, I'm making the "consciousness fallacy" aka I assign consciousness to evolution, but you know what I mean. Why would that be beneficial?
If the skull is used for defensive purposes, you need something heavy so it neither shatters nor gives you a concussion. The bone would have to be extremely flexible so as not to break which would seriously affect the brain through vibrations.

I also don't believe this:
"The frill and horns were most likely used for display, with the possibility of blood being pumped into the frill to change its color slightly."
Now I'm no expert in dino-skin, but I've seen a fair amount of human skin. Changing the color of skin by pumping blood through it takes insane amounts of blood. No problem there, but that would mean you'd need large vessels there. Large vessels in a place you're likely to get attacked at.
See where I'm going with this? I seriously doubt that'd work well...

All of the above would be especially dumb if "The frill and horns were also probably used in defense as well as jousting between each other".
Which other animals do we know that bump heads? Well considering the Dinosaurs we're talking about Pachycephalosaurus, today it's deer and goats, basically animals with antlers.
The first is protected by its extremely thick skull, both the second and third are protected by a skull and antlers where next to no blood runs through it.



I'd postulate something different: Dinosaurs were endotherms, weren't they? Has it been considered that the fenestrae serve the same purpose as the ears of elephants? i.e. they're responsible for keeping them cool?
Because then I could accept the other two additional explanations: Display and defence. Cooling down is vital, so I could accept that the head is in a bad position for defence but it's in an excellent one to cool the animal.

 

[Dragan Glas]

Greetings,

Interesting points, Inferno.

I'd agree with the cooling hypothesis, as - rather appropriately with this month's challenge - the plates on Stegasaurus are likely to have been used as a cooling aid rather than for defence. The Stegasaurus would face into the wind, allowing the breeze passing between the two rows of plates to cool it.

Having said that, it's likely that such adaptations had more than one function - cooling and defence, perhaps through misdirection (through the predator being attracted to biting the large, colourful plates in both Stegasaurus and the Ceratopsins?) Also, since the plates and frills would not contain any vital organs, there's no real damage done to the animal itself...!? Although the frill would provide a certain amount of protection for the neck.

PS The dinosaur in this month's challenge is Allosaurus. As you said, it was easy!

Kindest regards,

James

 

[Inferno]

Also, since the plates and frills would not contain any vital organs, there's no real damage done to the animal itself...!? Although the frill would provide a certain amount of protection for the neck.

Tell that to people with ruptured "A. femoralis". Technically it's no "vital organ", but it pumps huge amounts of blood, just as any animal that wants to cool itself or change the color would need.

I absolutely agree on the "multiple uses" idea, maybe I didn't make it clear enough:
If we assume only one use, I'd be hard pressed to think the benefit outweighs the risk. If there are multiple uses, including "cool down", I could get behind them.
I just have a problem with them on their own.

 

[Dragan Glas]

Greetings,

Also, since the plates and frills would not contain any vital organs, there's no real damage done to the animal itself...!? Although the frill would provide a certain amount of protection for the neck.

Tell that to people with ruptured "A. femoralis". Technically it's no "vital organ", but it pumps huge amounts of blood, just as any animal that wants to cool itself or change the color would need.

Given that elephants lose ears without bleeding to death, it's unlikely that this would happen to either dinosaurs mentioned - clearly, blood-clotting had already evolved.

It would be interesting if someone has done - does!? - a study on the volume of blood that passes through Stegasaurus' plates and how efficient they'd be as temperature control. This would give an idea of likely blood-loss before clotting occurs. As the plates have fossilised, this should be possible - it'd be more difficult with the Ceratopsids as the skin stretched between the frill's bone obviously hasn't survived.

I absolutely agree on the "multiple uses" idea, maybe I didn't make it clear enough:
If we assume only one use, I'd be hard pressed to think the benefit outweighs the risk. If there are multiple uses, including "cool down", I could get behind them.
I just have a problem with them on their own.

Agreed - who knows, there might be uses for which no-one's considered.

Kindest regards,

James

 

[Isotelus]

Quickly responding to some of the comments here:

The purpose of fenestration has not been nailed down, but it may reduce the weight of the skull by reducing the amount of bone without compromising its overall structural integrity. There's also the chance of them being involved in muscle alignment and such. If you're already a heavy animal, lightening the load in some manner without making your skeleton weaker is potentially a good thing, especially if you're a predator that needs to move about and lug its chunky face around. Even if you're a Ceratopsian, losing some head weight might not be that bad of an idea either. None of this conclusive or shown to actually been the case conclusively, but it's a place to start.

Dinosaur endothermy. Feathered theropods almost certainly were endothermic, as well as the really really big dinosaurs. The latter were likely inertial homeotherms; which just means that they were so god damn big, they could maintain a more or less constant body temperature with little effort. This is due to the surface area/volume ration, where larger animals lose heat way more slowly than smaller ones. As for the other dinosaurs, many lines of evidence certainly point to endothermy, but probably not conclusively. There is some recent work suggesting it was kind of intermediate between ectothermy and endothermy.

Cooling down! A grand idea that is indeed being looked into. A number of dinosaurs may have grown some weird structures for the purpose of thermoregulation: Spinosaurus, Ouranosaurus, possibly Amargasaurus, Deinocheirus, etc.

So yes. I may add more later.

 

[he_who_is_nobody]

Sadly I don't have the time to do copious amounts of research right now to look for the fossil, but I'd like to challenge you, he_who_is_nobody, on the use of the fenestrae.

I simply can't believe the first option:
"The fenestrae found on the frill were most likely away for cutting down the weight of the skull"
Why would you want that? Of what use would that be? I know, I'm making the "consciousness fallacy" aka I assign consciousness to evolution, but you know what I mean. Why would that be beneficial?

The skull in last month’s challenge is ~ 2 meters long and a little under 1 meter at its widest. That is a lot of bone, which means a lot of weight, which needed to be supported by the neck of the animal if the frill was made of solid bone. Thus, being able to lift the head seems like benefit enough, but you do make some great points.

If the skull is used for defensive purposes, you need something heavy so it neither shatters nor gives you a concussion. The bone would have to be extremely flexible so as not to break which would seriously affect the brain through vibrations

When the skull is being used for defensive purposes, the first line of defense is not being attacked in the first place. How does one do that? Looking large without actually being large. In addition, Have a look at the image below, that is what you would see facing down an animal like this. You would not attack that head on, with or without the frill. Any attack on an animal like this would come from behind, just as predators do with modern bovine (unless they are ambush predators).

I also don't believe this:
"The frill and horns were most likely used for display, with the possibility of blood being pumped into the frill to change its color slightly."
Now I'm no expert in dino-skin, but I've seen a fair amount of human skin. Changing the color of skin by pumping blood through it takes insane amounts of blood. No problem there, but that would mean you'd need large vessels there. Large vessels in a place you're likely to get attacked at.
See where I'm going with this? I seriously doubt that'd work well...

First you are assuming they had skin as unremarkable as ours. Why could they not have skin like a chameleon? In addition, there is some evidence that appears to show that ceratopsians had some sort of dino-fuss as well. Thus, the frill could have also been a place for extra surface for extra “feather” display. Moreover, nothing is attacking these animals head on, that would be suicide.

All of the above would be especially dumb if "The frill and horns were also probably used in defense as well as jousting between each other".
Which other animals do we know that bump heads? Well considering the Dinosaurs we're talking about Pachycephalosaurus, today it's deer and goats, basically animals with antlers.
The first is protected by its extremely thick skull, both the second and third are protected by a skull and antlers where next to no blood runs through it.

First off, deer do not bump heads; they slowly bow their heads and lock their antlers together. They do not bash each other’s brains out; their fights are more like glorified pushing matches with interlocking knives. That is how I would imagine a ceratopsian jousting match. The goal is not to kill your rival, just prove that you are stronger. Now, this is not a perfect method and sometimes male deers will kill their rival, but nothing in this world is perfect. Moreover, it is not as if they were using their frills as shields during any form of combat, the frill sits very far back on the skull. In addition, goats have horns, not antlers.

I'd postulate something different: Dinosaurs were endotherms, weren't they? Has it been considered that the fenestrae serve the same purpose as the ears of elephants? i.e. they're responsible for keeping them cool?
Because then I could accept the other two additional explanations: Display and defence. Cooling down is vital, so I could accept that the head is in a bad position for defence but it's in an excellent one to cool the animal.

I have never come across this hypothesis, but it does seem so perfect. I would still argue that keeping the weight down was the main purpose, but keeping the animal cool also works. Having a built in air-conditioner unit on your head does sound like something I would invest in. However, I have to point out that another use for African elephants ears are also to make the animal look larger (as if it needs it) when it feels threatened.

Although the frill would provide a certain amount of protection for the neck.

Yes, the frill would add protection to the back of the neck. However, ceratopcians would have had large cervical vertebra meaning any attack on the back of their neck would have been pointless anyways, just like in modern animals. The underside of the neck is the area that modern predators are most likely to attack and modern prey is lacking a frill.

It would be interesting if someone has done - does!? - a study on the volume of blood that passes through Stegasaurus' plates and how efficient they'd be as temperature control. This would give an idea of likely blood-loss before clotting occurs. As the plates have fossilised, this should be possible - it'd be more difficult with the Ceratopsids as the skin stretched between the frill's bone obviously hasn't survived.

Get on it Isotelus.

 

[Dragan Glas]

Greetings,

Although the frill would provide a certain amount of protection for the neck.

Yes, the frill would add protection to the back of the neck. However, ceratopcians would have had large cervical vertebra meaning any attack on the back of their neck would have been pointless anyways, just like in modern animals. The underside of the neck is the area that modern predators are most likely to attack and modern prey is lacking a frill.

Although the cervical vertebrae may appear to have been an unlikely target, predators with sufficient bite strength would be able to break the neck: consider hyenae, as well as cats - of all sizes - whose canine distance matches the first and seventh vertebrae distance of their major prey.

A more likely point of attack are the shoulders/hips to cause the prey animal to fall to the ground - or the spine.

It would be interesting if someone has done - does!? - a study on the volume of blood that passes through Stegasaurus' plates and how efficient they'd be as temperature control. This would give an idea of likely blood-loss before clotting occurs. As the plates have fossilised, this should be possible - it'd be more difficult with the Ceratopsids as the skin stretched between the frill's bone obviously hasn't survived.

Get on it Isotelus.

I've passed quite a few ideas her way in the OFNF thread for any of her students who're lost for ideas for their theses.

Kindest regards,

James

 

[he_who_is_nobody]

Yes, the frill would add protection to the back of the neck. However, ceratopsians would have had large cervical vertebra meaning any attack on the back of their neck would have been pointless anyways, just like in modern animals. The underside of the neck is the area that modern predators are most likely to attack and modern prey is lacking a frill.

Although the cervical vertebrae may appear to have been an unlikely target, predators with sufficient bite strength would be able to break the neck: consider hyenae, as well as cats - of all sizes - whose canine distance matches the first and seventh vertebrae distance of their major prey.

From what I understand, hyenas do not use their bite strength to break the necks of their prey. In addition, the big cats that have specialized canines are usually twice as big as their prey and they have specialized dentition. They hold their prey down so they can make a well placed bite. Theropods are lacking specialized dentition in the first place and none of them are big enough to be twice as big as a ceratopsian.

A more likely point of attack are the shoulders/hips to cause the prey animal to fall to the ground - or the spine.

Attacking the spine has all the same problems as attacking the back of the neck. Vertebras are large and thick bones. A predatory animal biting into a spine is going to lose many teeth and do little damage comparatively. There are easier places for predators to sink their jaws into, such as the shoulder/hip as you pointed out.

 

[Dragan Glas]

Greetings,

It'd be interesting if someone has done a study of bite strength in carnivorous dinosaurs.

I did see a report/study or documentary years ago where there was a bite on the back of a ceratopsid from either T. Rex or Allosaurus - whether this was post-mortem or not I can't remember.

Hyenae have sufficient bite strength to break a goat's neck - in fact, I did see a nature documentary where, in one part, a hyena snaps the neck of a young buffalo that was a bit bigger than it.

However, as you say, it's more likely for them to go for softer targets on the prey's body.

Kindest regards,

James

 

[he_who_is_nobody]

It'd be interesting if someone has done a study of bite strength in carnivorous dinosaurs.

I did see a report/study or documentary years ago where there was a bite on the back of a ceratopsid from either T. Rex or Allosaurus - whether this was post-mortem or not I can't remember.

First off, it would have to be T. rex, as Allosaurus existed in the Jurassic. Ceratopsians and tyrannosaurs both existed during the Cretaceous. I also believe I watched the same documentary and I have heard about other similar studies with different predatory dinosaurs. I know that measuring the depth of a puncture wound can tell you the amount of force it takes to create the mark. However, that would seem like a minimum measurement of the bite strength. A quick search on PubMed for "bite strength in dinosaurs" yields fifteen results, but some of them are not dealing with dinosaurs.
.

Hyenae have sufficient bite strength to break a goat's neck - in fact, I did see a nature documentary where, in one part, a hyena snaps the neck of a young buffalo that was a bit bigger than it.

That is awesome.

 

[he_who_is_nobody]

Answer!​