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Saurophaganax maximus v Tyrannosaurus rex
Topic Started: Dec 15 2012, 10:02 PM (59,195 Views)
DinosaurMichael
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Saurophaganax maximus
Saurophaganax ("lizard-eating master") is a genus of allosaurid dinosaur from the Morrison Formation of Late Jurassic Oklahoma (latest Kimmeridgian age, about 151 million years ago). Some paleontologists consider it to be a species of Allosaurus (A. maximus). Saurophaganax represents a very large (13 metres (43 ft) long). Saurophaganax was one of the largest carnivores of Late Jurassic North America. Ray even gave an estimate of the body length of fifteen metres and Chure of fourteen, though later estimations have been lower. The fossils known of Saurophaganax (both the possible New Mexican material and the Oklahoma material) are known from the latest part of the Morrison formation, suggesting that they were either always uncommon or appeared rather late in the fossil record. Saurophaganax was large for an allosaurid, and bigger than both its contemporaries Torvosaurus tanneri and Allosaurus fragilis. Being much rarer than its contemporaries, making up one percent or less of the Morrison theropod fauna, not much about its behavior is known. Stovall in Oklahoma also unearthed a considerable number of Apatosaurus specimens, a possible prey for a large theropod.

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Tyrannosaurus rex
Tyrannosaurus is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex (rex meaning "king" in Latin), commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other tyrannosaurids. Fossils are found in a variety of rock formations dating to the Maastrichtian age of the upper Cretaceous Period, 67 to 65.5 million years ago.[1] It was among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction event. Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small, though unusually powerful for their size, and bore two clawed digits. Although other theropods rivaled or exceeded Tyrannosaurus rex in size, it was the largest known tyrannosaurid and one of the largest known land predators. By far the largest carnivore in its environment, Tyrannosaurus rex may have been an apex predator, preying upon hadrosaurs and ceratopsians, although some experts have suggested it was primarily a scavenger. The debate over Tyrannosaurus as apex predator or scavenger is among the longest running in paleontology. Tyrannosaurus rex was one of the largest land carnivores of all time; the largest complete specimen, FMNH PR2081 ("Sue"), measured 12.8 metres (42 ft) long, and was 4.0 metres (13.1 ft) tall at the hips. Mass estimates have varied widely over the years, from more than 7.2 metric tons (7.9 short tons), to less than 4.5 metric tons (5.0 short tons), with most modern estimates ranging between 5.4 and 6.8 metric tons (6.0 and 7.5 short tons). Packard et al. (2009) tested dinosaur mass estimation procedures on elephants and concluded that dinosaur estimations are flawed and produce over-estimations; thus, the weight of Tyrannosaurus could be much less than usually estimated. Other estimations have concluded that the largest known Tyrannosaurus specimens had a weight exceeding 9 tonnes.

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Edited by DinosaurMichael, Dec 15 2012, 10:02 PM.
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theropod
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I might know a way to figure this out, but we'd need data on the volumetrics of crocodilians (how much of its volume is in the torso, how much in its tail, neck, limbs etc., the same in T. rex shouldn't be that much of a problem, there are at least two studies that we can use)

Then we could assume that the percentage in the torso of the crocodile, supposedly ~8t, was roughly half to 2/3 that of the theropod (same width but not as deep), add the rest to both of them and finally adjust for the density, and we'd probably have a decent estimate.
Even better would be if I could manage to count the pixels in their respective torsos, assuming the width is constant that should be a relatively reliable way of figuring out their comparative volumes. Not 100%, as there are still some shape differences (croc torso is probably more rectangular, at least in the image, while that of the theropod ough to be an almost circular oval) but probably a good approximation. What do you think
Edited by theropod, Apr 23 2013, 03:03 AM.
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theropod
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seems to work using Histogram in gimp:
Croc's torso (lateral view) is 26,959px
T. rex torso is 41,046

The torso of T. rex seems 1,52 times as voluminous laterally. In top view it ought to be about the same. This is prone to slightly overestimating T. rex if anything, for said reasons in body cross-section.
Edited by theropod, Apr 23 2013, 03:11 AM.
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theropod
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The proportions of sue can be found in table 4&5 of A computional analysis of limb and body dimensions...

Now we only need a croc, preferably a large one with similar proportions to Sarcosuchus.
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blaze
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So doing a GDI of the croc? but with what end? so we can compare its volume with that of Sue, expecting Sue's to not be bigger enough for the difference in density to actually make Sue almost 25% lighter?

We don't really need to do that, it's easy to see that not only the skull of Sarcosuchus is probably not even half the weight of Sue's and that all its limbs are probably no more than just one of Sue's legs and that the tails are comparable. Then we have the issue that, do crocs really have a density equal to water? Colbert (1962) found out that the density of a young alligator was 0.9 kg/L, can that be extrapolated to an adult croc or to sarcosuchus? I don't know but do we have more measured densities of crocs?

Comparing "old vs new" Sue I can't see how one can apply the weight of the old version to the new one.
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Anyway, what is the attractiveness of the 6 tonne estimates? and I honestly don't understand why Hartman said 6 tonnes is a good midline, is only 5% more than the absolute lowest estimate for Sue there is, they are essentially the same, how is the lowest estimate there is a good midline?
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theropod
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The absolute lowest figure is 4,5t, from some femur lenght regression. 5,7t is from mortimer, 6,1t from Paul, various rather old studies all gave some values around 6t, 6,4t from Hartman, 6,7t from Brochu.

I don't want to make a GDI, just compare the trunk volume, because their torsos happen to be similar in all but one dimension. The torso ought to make up more than 60% of T. rex volume (Hutchinson 2011 study, table 4, it sais weight, so as the torso is probably more pneumatic than the rest its volume will account for an even bigger percentage).

What does the old and new version of Sue have to do with this? And why don't we just ask Hartman?
Edited by theropod, Apr 24 2013, 01:23 AM.
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MysteryMeat
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theropod
Apr 23 2013, 05:42 AM
The absolute lowest figure is 4,5m, from some femur lenght regression. 5,7t is from mortimer, 6,1t from Paul, various rather old studies all gave some values around 6t, 6,4t from Hartman, 6,7t from Brochu.

I don't want to make a GDI, just compare the trunk volume, because their torsos happen to be similar in all but one dimension. The torso ought to make up more than 60% of T. rex volume (Hutchinson 2011 study, table 4, it sais weight, so as the torso is probably more pneumatic than the rest its volume will account for an even bigger percentage).

What does the old and new version of Sue have to do with this? And why don't we just ask Hartman?
The torso was deemed by you to be too big due to incorrect orientation of the ribs, remember?
Perhaps it's only 50% of its total volume.
If Sarcosuchus has a torso only half the volume as sue, then it's total volume can't be more than 75% of sue, more likely like 60%-70%. If the croc is more dense, say 10% more, it's still only about 80% of Sue's weight.
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blaze
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The old vs new is more for broly, new one is clearly bulkier and if the old one is 6.4 tonnes the new one is clearly more though I'm not sure of how much of a role does the airsacks have in this.

And no, you are getting 4.5 tonnes from Brochu (1995) right? well, Brochu doesn't say which T. rex specimen he is talking about and Sue wasn't even fully described then, that femur regression equation (from Alexander 1985) gives 5.6 tonnes (not 5.7, my bad) for Sue, you can see that in The Tyrant King by Larson & Carpenter.

"various rather old studies" I think that's a problem, with the exception of a partial description in Larson (1994) all papers dealing with Sue's anatomy are more recent than 2000 and probably most don't mention how big it is until Brochu (2003). So probably all those old studies talk about the weight of the holotype.

Regarding T. rex and crocs volume, the tails in Hutchinson et al. (2011) for the minimum models were skinny, the real tails probably had twice the volume, changing the percentages. I still haven't found something on how much of the weight of a croc comes from the torso but I found how much does the tail accounts for in the American alligator, around 28% (Willey et al., 2004), the percentage that the torso of Sarcosuchus out of total body volume, assuming similar weight distribution to the American alligator is probably between 50-60%.
Edited by blaze, Apr 23 2013, 06:26 AM.
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7Alx
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Finally i made size comparison between T. rex specimen FMNH PR2081 and possible largest known S. maximus specimen OMNH 1935.
Note: The grey Saurophaganax is based on MOR 693 , while the smaller is based on UUVP 6000.
Link
Assuming that OMNH 1935 would be that as large as grey version here, Saurophaganax would have around 50 % chance. However if it was closer to size of this smaller one, it would lose other than not, only 25-30 % chance.

Edit: I feel that i overestimate large Saurophaganax's chance to winning. Around 50 % would be more reasonable. But if Saurophaganax was that large it would be still good deal.

Edited by 7Alx, Apr 24 2013, 05:44 AM.
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theropod
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MysteryMeat
Apr 23 2013, 06:07 AM
theropod
Apr 23 2013, 05:42 AM
The absolute lowest figure is 4,5m, from some femur lenght regression. 5,7t is from mortimer, 6,1t from Paul, various rather old studies all gave some values around 6t, 6,4t from Hartman, 6,7t from Brochu.

I don't want to make a GDI, just compare the trunk volume, because their torsos happen to be similar in all but one dimension. The torso ought to make up more than 60% of T. rex volume (Hutchinson 2011 study, table 4, it sais weight, so as the torso is probably more pneumatic than the rest its volume will account for an even bigger percentage).

What does the old and new version of Sue have to do with this? And why don't we just ask Hartman?
The torso was deemed by you to be too big due to incorrect orientation of the ribs, remember?
Perhaps it's only 50% of its total volume.
If Sarcosuchus has a torso only half the volume as sue, then it's total volume can't be more than 75% of sue, more likely like 60%-70%. If the croc is more dense, say 10% more, it's still only about 80% of Sue's weight.
Ok, that might balance out each other. It seems Sarcosuchus torso is about 2/3 that of sue, not half.

let's assume the rest is equal, that'd mean Sarcosuchus is:
(40%+(2/3*60%))*density

while T. rex is:
100%*density

This will probably change if we get proper figures on crocodilians tough.
Correct me if there's a mistake, I quickly get confused by too many numbers...

Blaze: Thanks for clearing this up. I tought I read the 4,5t in Chure, 1995, I didn't check what specimen it was for.

I personally didn't find anything in that study skinny, they modeled the tail muscles, why should they make them smaller than they are?
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blaze
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Look at the top view of the tail of the minimum model (the 9.5 tonne one) and then read this post or the paper in question if you have access to it. Seems like Hutchinson et al. (2011) underestimated the size of M. caudofemoralis.

Edit:the paper is free to access

@7Alx
Are the Saurophaganax both scaled to the humerus length of 545mm?
Edited by blaze, Apr 24 2013, 02:02 AM.
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7Alx
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Yes. Although i heard that the humerus would be 480 mm, however i am not sure about that. 480 mm humerus is for OMNH 1935?
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Jinfengopteryx
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According to Gecko's size scale, 1935's humerus is 545 mm long.

P.S. Where have you read that?
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theropod
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it's from the smith, 1998 study (Morphometric analysis of Allosaurus, available on JSTOR), it sais it includes Saurophaganax and lists the largest humerus at that lenght. I was not sure, because Mortimer lists the humerus at 55cm and sais the corresponding animal to be 13m (based on topotype i think) even tough she references that paper in her DML post on that subject. I have contacted Dan Chure, but so far I got no answer.
He might be busy, or the E-mail-adress is obsolete (found it in the paper on theropod orbita).
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blaze
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545mm is so far not published in any paper, however is more or less what you get measuring the humerus from the scalebar in figure 2(?) of Chure (1995). 488mm is from figure 18 of Smith (1998) as theropod said, it is not in written form but is what you get if you count the pixels in the plot.

btw Mortimer cites Smith (1998) after saying Saurophaganax was 13m long and 6 tonnes in weight, Smith (1998) is only cited for Saurophaganax falling in the growth curve of Allosaurus not for measurements.
Edited by blaze, Apr 24 2013, 04:14 AM.
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theropod
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Yes, but I guess she will have read the paper if she knows the growth curves...

When measuring figure 2 in Chure, 1995 the way shown in Smith, 1998, I get a lenght of 55cm. The bone in the scale would have to be oversized for about 13%, not impossible of course, but not necessarily true either.
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