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back to article Dinosaurs on a diet shed tonnes

Dinosaurs were probably skinnier and lighter than previously imagined, according to a new paper in Biology Letters. Minimum convex hull mass estimations of complete mounted skeletons says “Volumetric methods are becoming more common as techniques for estimating the body masses of fossil vertebrates. However, they are often …

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Boffin

That's a very difficult area.

The fun part is that we don't have any living models for a bird or reptile anywhere near that size.

Mammals are clearly a bad model, and living things generally don't scale so birds and reptiles are of limited usefulness. For example, the size of the digestive tract varies immensely among animals of similar dimensions. (Compare horse to cow. Or even horse to hippo!)

All in all, it makes figuring out the likely physical build of a fossil creature incredibly difficult and often subject to bias - the Victorians went with 'slow and fat', hence the very high original weight estimates.

Smaller dinosaurs are much easier - birds are a close model, and we've even got a few skin impressions which helps immensely.

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Yes, but...

What is a suitable calibre for a charging 23 tonne dinosaur?

.60 nitro express suddenly seems inadequate.

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Re: Yes, but...

"Yes, but... What is a suitable calibre for a charging 23 tonne dinosaur?.60 nitro express suddenly seems inadequate."

Anti-tank gun. Flak 88, for example.

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Re: Yes, but...

Actually the .60 is perfectly adequate. Any elephant rifle will kill it, if you shoot it in the right place, the secret is to remember to dive to one side after firing to prevent yourself being squished by the dying carcass.

I've been told by someone who used to do it[1] that this is the drill for shooting Rhinocerous. The only place to shoot it is frontally in the head[2], the only way to get that shot is to get it to charge you[3] and it's absobloodylutely essential to dive sideways after firing.

[1] Many decades ago as a farm manager in Rhodesia.

[2] You can shoot it in other places, but all you'll do is piss it off. A lot.

[3] Fortunately quite simple. They'll happily do this without encouragement.

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Silver badge

Re: Yes, but...

I'm minded of the Hilaire Belloc poem about the Hippopotamus...

"I shoot the Hippopotamus with bullets made of platinum,

because if I use the leaden one his hide is sure to flatten em."

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Re: Yes, but...

The only problem with using a Rhino as an example is that relatively speaking, its brain volume is huge in comparison to most large sauropods. Hit a Rhino in the head and you've probably got a 30% chance of destroying something vital; hit a rampaging Argentinosaurus and its probably a 5-10% chance or less. So when I sign up for my time-travel safari I'll be packing a 30mm Bushmaster thanks, preferably in an armoured car.

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Coat

Re: Yes, but...

Isn't a 30mm Bushmaster some kind of adult product?

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Only 23 tonnes?

Suddenly I feel quite svelte...

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Coffee/keyboard

Hmmm

Will this new methodology soon be available in Bathroom Scales? I could do with losing a few pounds...

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Boffin

And in Reg Std Units?

1.5 double decker buses

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Re: And in Reg Std Units?

Yes, but how much is that in Football Fields, or Libraries of Congress?

-dZ.

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Headmaster

Re: And in Reg Std Units?

"Libraries of Congress"

Should be "Library of Congresses" as there is just the one library (and Congress almost never stops by to read anymore).

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Boffin

"He also points out that dinosaurs have been losing weight for years"

I would expect dinosaur weight loss to have stopped once their fossilisation process has completed. So, let's say 65 million years ago.

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Headmaster

Re: "He also points out that dinosaurs have been losing weight for years"

Fossils are minerals and therefore subject to erosion like any other rock.

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Coat

At least now we know...

...what killed of the dionsaurs.

It was them bloody boffins making them smaller and smaller until eventually they disappeared.

Coat please. The one with the microsaurian bottle zoo in the pocket.

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21% sounds too generalised...

...and a bit flawed overall.

In addition to questioning the validity of extrapolating the sizes of reptiles that lived in a higher oxygen content environment using figures derived from mammals living in a lower oxygen content environment (it was only because of the higher oxygen content in prehistoric times that those giant dragon flies and various other giant insects were able to evolve), I'd like to know a lot more about how they came up with that figure of 21%.

From the article it sounds like they ended up with an _average_ factor of 21% as a result of a rather diverse range of animals including, but probably not limited to, polar bears, giraffes and elephants and whilst it can be argued that they're all 'big' they have very different types of body. For example, I'd be very surprised to learn that both giraffes and elephants share that same 21% factor.

Furthermore, the healthy BMI of an animal can vary according to whether it's in captivity or not; polar bears in captivity tend to be leaner than wild polar bears, which have to live in more extreme conditions.

Any idea if they also included hippopotamuses or elephant seals in their data sample?

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Holmes

Remember pneumaticity

The other thing to remember with pretty much all dinosaurs was that they had bird-like breathing systems, involving air sacs. This meant that the volume of the animal that was air would have been far greater than it is on a comparably sized mammal, which further reduces the weight. Birds usually have hollow, air-filled bones and indeed evidence of air cavities in the bones of dinosaurs including sauropods has also been found, even extending to the spinal column as well as the major limb bones.

If you do the lung volume estimations, an air-sac based breathing system is the only way something the size of a sauropod could muster enough tidal volume to be able to breathe efficiently enough to survive, so they absolutely must have been using this system.

Finally, although sauropods had brain volumes right on the reptile brain to body size ratio, they were assuredly not "cold blooded". In fact, they probably had more problem keeping their body temperature down rather than keeping it up, as a herbivore that size would have several tonnes of fermenting plant material in its gut, which tends to generate a sizeable amount of heat. This BTW is why you very seldom see cows shivering; their gut fermentation processes generate more than enough heat to keep them warm. The gut fermentation is also why big bovids always keep on looking for food right through extremely cold winters; the animal its self isn't getting much nutrition off the forage, but it needs to keep on feeding the bacterial colonies throughout its gut to keep everything in good order.

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Re: Remember pneumaticity

More posts like this please. I can never ever get enough dinosaur trivia.

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Silver badge

I'm all for improving scientific analysis and exactitude

but I rather liked the idea of a lumbering Tyrannosaurus making the ground shake as it pursued its prey.

We already know that dinos were feathered and not like lizards, I do hope that we won't end up with a Barbiesaurus Rex daintily prancing through the prehistoric jungle in search of some man-sized appetizer to keep her weight down, taking special care not to disturb the shrubbery.

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21%

Confused by the 21% -- I understood 21% meat for 100% entire animal -- have I got it the wrong way round? When buyinig 1kg chicken, I expect to see more than 210g of meat I think, even if the head and feet are still on, giblets included. Even with an animal that's not optimized for being eaten 21% seems low.

Confused.

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Coat

Sweatin' to the Oldies

"He also points out that dinosaurs have been losing weight for years"

When I saw this line, I immediately had a vision of an overweight dinosaur wearing a glittery tank-top, shorts and headband 'Sweatin to the Oldies' with Richard Simmons.

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