Largest sauropods

[blaze]

Deviates even more? in two of the 3 measurements assuming 1500mm height deviates by twice the percentage than it does assuming 1050mm, though, on average both deviate about 16%. But what about assuming 1200mm? which only deviates by an average of less than 7% (only because of a single measurement, the others are less than 2% and 3% off)? in fact you were correct in that assuming 1050mm results in a reconstructed vertebral height of 1.6m, which is at odds with his claim of his reconstruction being 6ft (not that he hasn't failed this kind of conversions before) but so does assuming 1500mm which results in a vertebral height of 2.3m, almost 8ft, on the other hand assuming 1200m results in 1.9m, thus, 1200mm is consistent with the measurements, the reconstructed height both in text and illustration and is also what's suggested by the scale of the drawing given in the publication.

[Fragillimus335]

What's crazy is that the paper speculates that If Cope was right in his 1.5 meter measurement, then the entire vert was 2.8 meters tall, with a 90cm wide centrum! Along with a 4.76 meter long femur! They think Amphic… or should I say Diplodocus altus, was even bigger than Carpenter thought.

[theropod]

The sum (and consequently the average) of the three percentages is higher for 1050mm than it is for 1500mm, and the measurement coming closes is using the latter. Conclusion: no. Argument favouring the smalle4 figure, but if anything the larger one. And how do you get 1200 as a typo from that?

Cope wrote "probably more". That means more than 6 feet is viable, less is not.

[blaze]

Is higher by 0.3% and only because of a single measurement, the others are off by over 20%, either way all the measurements are wrong.

Cope also wrote no less than 6ft which yes, suggest his reconstruction can't be less than 6ft but why say 6ft if he actually ended up with one almost 8ft tall? you need to cut 3/4s of the centrum of his reconstruction to bring it down to that if 1500mm is the correct number, leaving only 32cm to complete the neural spine, neural arch and centrum, isn't that ridiculous? It simply isn't a realistic estimate at all so why suggest it? and why does the scale factor of the page also suggest something about 6ft for the whole reconstruction?

How to get 1200mm as a typo from 1500mm? it requires a typing a number 2 keys apart in the same position... yeah who knows, really. BTW, are we going to call it Diplodocus now?

[theropod]

Diplodocus? I think there are a number of clear distinctions between Amphicoelias and Diplodocus, what’s suggesting they are synonyms?

[Fragillimus335]

Dec 17, 2014 14:33:30 GMT 5 theropod said:

The sum (and consequently the average) of the three percentages is higher for 1050mm than it is for 1500mm, and the measurement coming closes is using the latter. Conclusion: no. Argument favouring the smalle4 figure, but if anything the larger one. And how do you get 1200 as a typo from that?

Cope wrote "probably more". That means more than 6 feet is viable, less is not.

The real problem is that we don't know exactly what landmarks Cope used in his measurements. I got numbers very close to his, 190mm, 585mm, using the 1500mm height just by using slightly different measures!

oi62.tinypic.com/29y1b9j.jpg

[theropod]

That’s the problem. Most likely, it’s simply the landmarks used in the paper that don’t come close enough to what Cope measured. Absolutely nothing compelling for the size issue.

[blaze]

Why didn't you try the other measurement? The neural arch and spine are very skinny though, they don't really look like those of Supersaurus or CM 84.

theropod

In the paper said that A. altus has no diagnostic characters to distinguish it from several Diplodocus specimens, that of course might not be obvious if we keep comparing it to CM 84 only. Amphicoelias isn't valid then.

This taxon is a pain in the ass, I've going to keep ignoring it.

[creature386]

What about A. fragilimus? If the type species (A. altus) is invalid, does this imply that the whole genus is invalid and can't be used for the other species?

[Fragillimus335]

Dec 18, 2014 18:31:12 GMT 5 creature386 said:

What about A. fragilimus? If the type species (A. altus) is invalid, does this imply that the whole genus is invalid and can't be used for the other species?

Yes, this paper sunk A. fragillimus into A. altus, then sunk A. altus into Diplodocus altus. There is no longer any Amphicoelias species according to this paper.

[blaze]

Edited
This post doesn't exactly deal with a contender to the largest sauropod but it has implications for one of them, the undescribed specimen of Mamenchisaurus sinocanadorum.

Some days ago I found out about Xinjiangtitan, which Wikipedia claimed at 30-32m and one of the largest sauropods, referencing Wu et al. (2013). The length estimate is real and is based on comparisons to Mamenchisaurus hochuanensis and Mamenchisaurus youngi. In the publication there are also comparisons to Omeisaurus (two species), Shunosaurus (two specimens) and Diplodocus CM84.

To get a grasp of how all of them compared in dimensions I turned to Paul (2010) and there were some intriguing things. Why does he estimate M. youngi at 7 tonnes when its limbs and dorsal column are comparable to the big Shunosaurus which he estimates at 3 tonnes? (Dorsal series 185cm vs 176cm, femur length 117cm vs 120cm) Why does he estimate M. hochuanensis at 14 tonnes when its clearly surpassed by CM 84 which he estimates at 12t (Dorsal series 345cm vs 269cm, tibia length ~106cm vs 86cm)? What was going on here? I decided to measure his skeletals and see how they differed from the actual measurements, to be sure I had them at the correct scale I recurred to Paul (2007).


M. hochuanensis is known from an skeleton that preserves the vertebral column from the first cervical to the 35th caudal and assorted other material, relevant measurements from Young and Zhao (1972) are (rounded) a neck of 9.5m, dorsal series of 2.69m, sacrum of 69cm, caudal series of 5.3m, ilium of 92cm, ischium 93cm long and tibia 86cm long. Paul's skeletal is 21m (both his claim and what I measured in GIMP) and he estimates it at 13.8 tonnes (Paul 2007,2010). Next I'll list the length of the aforementioned parts in Paul's skeletal and in parenthesis the percentage of this value compared to the actual measurement.

Neck: 9.3m (98%)
Dorsals: 3m (111%)
Sacrals: 0.8m (114%)
Caudals: 5.9m (111%) (up to 35th)
Ilium: 107cm (116%)
Ischium: 96cm (103%)
Tibia: 83cm (97%)

The limbs and neck are too short while the rest of the vertebral column is oversized by differing amounts, the torso, where inarguably most of the mass of a sauropod is, is so by ~12% correcting this translates to a volume reduction of 40%. So Paul's estimate goes down to ~9.9 tonnes.

M. youngi is also known from a remarkably complete skeleton, from the firt cervical to about half of the tail. Relevant measurements from Christian et al (2013), Wu et al. (2013) and Benson et al. (2014, supp) are a neck 5.96m long, a dorsal series 1.85m long, humerus 84cm, radius 55cm, femur 117cm long and tibia 67cm long. Paul's skeletal is 16.6m long (measured in Paul 2007, 17m claimed in Paul 2010) and he estimates the live individual at 6.7 tonnes. Repeating the process above.

Neck: 5.95m (117%)
Dorsals: 2.26m (122%)
Humerus: 85cm (102%)
Radius: 56cm (102%)
Femur: 118cm (101%)
Tibia: 60cm (90%)

With the exception of the tibia the limbs are perfectly scaled this time but once again the dorsal column is oversized, the torso being so by 22% which translates to a volume reduction of 82%, bringing down his estimate to ~3.7 tonnes.

In the DML various people raised questions about how even at 35m can an inverted Diplodocus like Mamenchisaurus be 50% heavier than the largest titanosaurs, to such criticism Paul responded that we should check out the femur length of Mamenchisaurus sinocanadorum, that the mounted skeleton was colossal and that Mamenchisaurus had "unusually short legs for their long and massive bodies" therefore such massive estimate was realistic, he also got irritated and said that unless we restore it ourselves we shouldn't be commenting on it.

I checked his publication in said Dinofest volume and he doesn't explain how he gets that they had unusually short legs, only outright states that they had the shortest legs to body mass of any sauropod, it seems this argument is based entirely on his own reconstructions and well, of course he is going to get that result when he consistently overestimates the size of the vertebral column, specially compared to the tibia.

So, are their legs short or not? According to Ye et al. (2001), in M. hochuanensis the tibia is 60% the length of the femur (based on a new more complete specimen) so we can estimate the femur length of the type specimen at 143cm thus a hind limb length of 229cm, 85% of the length of the dorsal series, in M. youngi this percentage is 99% and in Diplodocus it is ~75%, their legs are longer than in Diplodocus. But what about body mass to leg length? Lets take CM 84 as a base, scaling it down to the leg length of M. hochuanensis it'll weight 8.2t (compared to 9.9t) while scaling it down to M. youngi leg length it'll be 4.3t (compared to 3.7t), one is heavier by 21% the other lighter by 16%, on average the difference is minimal but more importantly, how does this compare to a titanosaur? the comparable leg length of Dreadnoughtus, which was at least 30 tonnes, is 311cm, scaling it down to that of M. hochuanensis resutls in a mass of 12 tonnes, 20% greater than the mamenchisaur.

In conclusion Mamenchisaurus is not short legged neither in proportion to their bodies nor their mass, Paul's reconstructions are not accurate (though, to his defense he probably didn't have access to some of these publications at the time he made them) and it is indeed similar in overall build to Diplodocus so a 35m individual just can't be 75 tonnes.

References:
Wu et al. (2013) A new gigantic sauropod dinosaur form the Middle Jurassic of Sahnshan, Xinjiang. Global Geology 32(3).
Paul (2010) The Princeton field guide to dinosaurs. Princeton University Press.
Paul (2007) Mamenchisaurus youngi, the dorky dinosaur. Prehistoric Times No. 83.
Young & Zho (1972) Mamenchisaurus. Institute of Vertebrate Paleontology and Paleoanthropology Monograph Series I, No. 8.
Christian et al. (2013) Biomechanical reconstructions and selective advantages of neck poses and feeding strategies of sauropods with the example of Mamenchisaurus youngi. PLoS ONE 8(10): e71172.
Benson et al. (2014) Rates of dinosaur body mass evolution indicate 170 million years of sustained ecological innovation on the avian stem linage. PLoS Biol 12(5): Supplemental.
Paul (1997) Dinosaur models: the good, the bad, and using them to estimate the mass of dinosaurs. Dinofest International.
Ye et al. (2001) New material of Mamenchisaurus hochuanensis from Zigong, Sichuan. Vertebrata PalAsiatica 39(4): 266-271.
Lacovara et al. (2014) A gigantic, exceptionally complete titanosaurian sauropod dinosaur from southern Patagonia, Argentina. Scientific Reports 4:6196.

[mysterymeat]

blaze
There are two numbers listed for the length of Xinjiangtitan's dorsal series, 3.72m and 3.32m. Not all the length dorsal vertebra were listed so I don't know which one is accurate. The length estimate is made using 3.72m. Xinjiangtitan's cervicals are extremely elongated, even for a Mamenchisaur. Its dorsal column is 201% of M. youngi's (both dinosaurs have 18 cervicals, 12 dorsals, and 5 sacrals), while the last two cervicals are 284%. So if it has similar proportions as M. youngi, it would have a 18.5m neck! That sounds quite unbelievable. It might be even longer than the 32m estimate.
As to the leg proportions, Xinjiangtitan does have very short legs compare to its total length, the femur is 1.65m long and the tibia is 0.98m. Femur+tibia length is only 70.7% of dorsal length, and that is lower than M. hochuanensis, M. youngi, and Diplodocus. The limb material from shishugou formation (SGP 2006/9 and SGP 2006/10)could be from a similar sized individual, if both has similar limb/body proportions.
Xijiangtitan could possibly contend for the title of the longest sauropod, and it is certainly one of the most bizarrely proportioned.

[creature386]

Hi mysterymeat, nice that you found us!

[blaze]

@misterymeat
Hi! it's been a while!

It is true that not all the individual centrum lengths of the dorsals were given but that is because for some reason they gave the articulated length of the D5-D8 series instead of giving the centrum length for each one, they add up to 3.72m, table 3 also agrees at 3.72m, from where is the 3.32m you mentioned?

The ratio of the hindlimb length to dorsal length is lower than in Diplodocus but not by a lot (71% vs 75%), it still doesn't really support Paul's claim of "shortest legs for their weight" but you are right that Xinjiangtitan very well could be among the longest sauropods.

[mysterymeat]

creature and blaze, good to see you guys too.
It's at the end of the first paragraph on page six. It says the total length of the dorsal series is 332cm, probably a typo.
I don't agree with the leg length vs. mass statement, but some Xijiangtitan shows that at least some Mamenchisaurs do have very short legs compare to body length.