Largest sauropods

[creature386]

Supercommunist This would be another problem, as they'd need a predator. There are no 15 m+ macro predatory theropods evidenced yet (a 15 m carnosaurs could easily reach weights of 12 t btw). 

[Fragillimus335]

May 26, 2013 22:20:56 GMT 5 creature386 said:

Supercommunist This would be another problem, as they'd need a predator. There are no 15 m+ macro predatory theropods evidenced yet (a 15 m carnosaurs could easily reach weights of 12 t btw). 

Nothing NEEDS a predator, eg. Humans, Elephants, Rhinos, Blue Whales. The adults of these species are almost never regularly hunted by other predators.

And don't forget that the juveniles would be fair game.

[creature386]

This is true, but the reason why herbivores get larger is usually the arms race. But if it is already won at 100 t, I don't see why they should become even larger. At a particular size, size can also become more of a disadvantage, than an advantage.

[theropod]

May 26, 2013 22:03:58 GMT 5 Grey said:

Like I said, I consider it an estimate, but not a reasonnable one for the reasons mentionned earlier.

I would quote again Matt Wedel about that.

Turning to A. fragillimus, the piece of vertebra that was preserved does not really tightly constrain the total size of the vertebra, and estimates of the vertebraÂ’s total height vary by something like 25%. CarpenterÂ’s (2006) estimates are all based on the upper end of the range. Also, the vert was extremely lightly built, much lighter than comparable vertebrae from Diplodocus. We know that vertebral pneumatization knocked down the volumetric mass of Diplodocus, and it does not seem unreasonable that A. fragillimus might have been lighter than a scaled-up Diplodocus would have been.

The third caveat is that the estimates of 120-160 metric tons for B. and A. are already based on long chains of ‘ifs’. To take those estimates as data, assume that they represent average individuals of their respective species, and then jump onward to imagine world-record individuals massing more than 200 tons is to pile uncertainty on top of uncertainty and speculation on top of speculation, while ignoring all the if/then decision points that led to the original estimates. People are welcome to do that, but no one is compelled to take it seriously.

The bottom line is that the evidence for whales weighing 190-200 metric tons is pretty darn good, and the evidence for sauropods weighing even 150 tons is frankly pathetic. So until much better evidence for the gigapods emerges, I’ll continue to award the “Heaviest Vertebrate Ever” prize to the blue whale.

Exactly, he's being cautious, something many scientists are. this is not a rebuttal, it is scepticism. I think we basically agree on this point. You can lower the density if you want, but take into account that 70m/200t is already based on a significantly lower density than the one carpenter assumed (0,7).
If you use a density of 0,6, it still reaches 170t.

If we are sceptical of this animals size, it should be because of uncertain phylogeny, scaling analogies or the doubt whether the fossil was really that large.

[theropod]

No animal is entirely invulnerable to predation, and juvies/subadults are always at risk. Being bigger holds advantages even at extreme sizes. Or why are Blue Whales that large? To them it should pose just as much trouble, considering the surface their mouth can cover gets proportionally smaller.
A. fragillimus and the other enigmatic giants may simply be old specimens. I think it is acknowledged that sauropods may have had extremely long lifespans, comparable to, if not exceeding, the lifespans of bowhead whales or giant turtles.

I have mentioned at times there actually are indications of truly gigantic Jurassic predators comfortably in the same league as cretaceous ones, and of all the really huge theropods, save for Tyrannosaurus and to a lesser extent (the mostly subadult) Mapusaurus (-group), we have only few specimens, leaving good possibilities of even larger individuals.
There could very well have been predators that would pose a thread to even the largest of "normal" sauropods. It is an armsrace, an escalation. Size doesn't necessarily stop increasing long before biomechanical limits are reached.

[theropod]

May 26, 2013 23:33:06 GMT 5 Grey said:

250 tons for A. fragillimus has NOT been hinted by scientists, the upper I've read was +150 tons by Armstrong. You're right about the rest.

Yes this topic is about meg size discussion.

I didn't say hinted, I said "not rejected".

and at least, not rejected for megalodon. That's not the case for A. fragillimus

Whether there be hints or not by specialists (and Armstrong, while apparently not a professional, did hint 200t+) or not, the calculations are hint enough

[Grey]

I need to see where Armstrong hints 200 tons and more. I've only seen he believes that weights in excess of 150 tons are possible, nothing about more than 200 tons.

Here is one of his posts :

IÂ’m not sure how Carpenter got such low mass estimates and length estimates, but going off of them is bound to produce massive errors, assuming I havenÂ’t missed something. So no matter what, as far as I can tell Amphicoelias massed way over 100 tonnes, probably over 150 tonnes even with the reduced height estimates.

And I'm fine with this.

[theropod]

If you are fine with "probably over 150t" I totally agree with you.

Fragillimus already cited the deviantart-journal-entry in question.

[Grey]

Yes I'm fine with this, just like as I'm fine with the lower 90 tons proposition. The margin of error is huge at this scale.

What I critic is that we see neither of these predictions in our discussions but all the time focusing on ridiculous and boring 250 tons claims.

[theropod]

"probably" or "possibly over 150t" would be my prediction actually.

[creature386]

May 26, 2013 23:37:44 GMT 5 theropod said:

Or why are Blue Whales that large? To them it should pose just as much trouble, considering the surface their mouth can cover gets proportionally smaller.

Well, blue whales weigh around of 100 t on average, what is close to the suggested maximum in Sauropods (Some freak specimen sauropods may indeed be able to reach sizes over 150 t).
From what I know, 200 t blue whales were pregnant ones or specimen who just ate a lot. So, I don't think there is a modern animal who can reach 200 t or more.

[Grey]

Have you a source for this creature386 ?

I've not read this, only that the individuals hat have approached and perhaps exceeded 200 tons were especially massive.

Anyway, even in the case of the blue whale, we can say thee have been exagerations or misinterpretations.

[theropod]

well, what I suggest is merely that a comparable maximum size is possible, not more.

[Supercommunist]

Supercommunist This would be another problem, as they'd need a predator. There are no 15 m+ macro predatory theropods evidenced yet (a 15 m carnosaurs could easily reach weights of 12 t btw).

How would a hypothetical twelve ton animal kill an eighty ton one?

No animal is entirely invulnerable to predation, and juvies/subadults are always at risk

Being a two hundred ton animal rather than a fifty ton one wouldn't radically increase the survival rate of their offspring if at all.

Being bigger holds advantages even at extreme sizes. Or why are Blue Whales that large? To them it should pose just as much trouble, considering the surface their mouth can cover gets proportionally smaller.

Perhaps because they often swim through chilly waters and a larger mass helps insulate them? Also it is arguably more vulnerable to orcas than sauropods to giant theropods, since not only would they be better coordinated then large theropodic predators (if they did indeed hunt in packs anyway), but also because they are underwater hunters and thus are able to attack other exposed areas of a whale that ground dwelling predators would never be able exploit on a sauropod. Directly above for example.

[gigadino96]

Amphicoelias could have had the vertebrae of impressive size, but it could also be part of the Dicraeosauridae or Rebbacchiosauridae, and you know that these animals have the vertebrae disproportionately high when compared to the body. I generally do not consider it, I think the biggest dinosaur is Puertasaurus.