Giganotosaurus carolinii

[DinoFan83]

As of late, it has come to my attention that there may be more mistakes underestimating Scott Hartman’s Giganotosaurus than just the shallowness of the chest from the incomplete pectoral girdle that earlier posts in this thread have went over.
Specifically, because he assumed the pectoral girdle was complete as preserved, the dorsal view for his Giganotosaurus is quite slender and has since been known well for being such, especially compared to T. rex. He talks of this on his website, and what he states may even lead some to believe his dorsal view isn't slender enough.

Quote:Tyrannosaurs have almost comically wide abdomens (and mine is not as broad as some other workers and some mounts show), while Giganotosaurus has the typical allosaur-grade torso.

Quote:I'm sure that some will claim that Giganotosaurus should have a wider torso or head, but the skull is already substantially wider than in Acrocanthosaurus and matches up with more recent reconstructions of the skull, like the one you see here. Also note that if anything the torso should be smaller up front due to the diminutive pectoral girdle.

Perhaps unsurprisingly to those that follow the thread, this is not in accord with the anatomy of more complete relatives.

How do I know this, you may ask? A combination of three factors: phylogenetic bracketing, the proportions of the animal used for this phylogenetic bracketing, and how Giganotosaurus' estimated complete pectoral girdle length would affect its proportions.

What is being used for the phylogenetic bracketing?

I will be using Acrocanthosaurus (specifically, NCSM 14345) as a means for the phylogenetic bracketing, as it preserves a complete pectoral girdle, complete ribs, has a publication and measurements for both, and is the most closely related animal to Giganotosaurus that has all of these preserved and/or published.

What are the proportions of this Acrocanthosaurus?

Currie & Carpenter (2000), on page 8 of their publication, give a length of 118 cm for the specimen's complete pectoral girdle. This together with its 130 cm wide ribcage gives us a ribcage width to pectoral girdle length disparity of about 10.2%.
Its femoral length is also probably about 120 cm as per the comments of here, which will come in handy for the next point.

Quote:Is it possible that the legs were shorter? I just noticed that the often mentioned femur lengths of both Fran and the holotype are estimates, with the later being criticized as too long by Harris (1998), that the femora are incomplete, I also just noticed in photos of the mount and the digital scans presented in several of Karl Bates publications that the femur is reconstructed there at ~120cm long, which is roughly what you'll get from isometric scaling comparing the circumference of Fran's femur with that of the only complete (sic) Acrocanthosaurus femur (SMU 74646).

How does Giganotosaurus' estimated complete pectoral girdle length affect its proportions based on this?

The change is bigger than some might think. As the link in the second point for ribcage width said, Scott Hartman's Giganotosaurus is 134 cm wide, and that would mean an estimated complete pectoral girdle of 121.6 cm assuming isometry with Acrocanthosaurus. 

Problem is, Giganotosaurus' complete pectoral girdle ends up longer than that based on Acrocanthosaurus. For instance, SpinoInWonderland has restored the pectoral girdle in his Giganotosaurus based almost entirely on Acrocanthosaurus as well as used its proportions to help do so.

Quote:The shoulder girdle is reconstructed based on Mapusaurus (which barely helped, but it's incorporated here anyway) and Acrocanthosaurus, with the length of the scapula based on the scapula:femur ratio found in Acrocanthosaurus.

Given the 136 cm femur length of the Giganotosaurus holotype from Carrano et al. (2012) that SpinoInWonderland used in his skeletal (as per the top of the comments section), this gives us a pectoral girdle length of 133.7 cm based on Acrocanthosaurus, and the ribcage would therefore be about 147.3 cm wide instead of 134 cm assuming isometry. 

The resulting ribcage is about 9.9% wider than what Scott Hartman restored, and while it's not barrel chested like a tyrannosaurid, neither is it the very slender animal some like to claim, instead being roughly intermediate between slender and barrel chested. 

In fact, directly to the contrary to what Scott Hartman's blogpost implies, known specimens of Giganotosaurus do not appear to have had ribcages any narrower than known T. rex individuals of the same size class (average, maximum, minimum). 

For one, the extrapolated width for MUCPv-95's ribcage of 162 cm (147.3x1.1) is right on par with or slightly greater than that of Sue (150 cm from Asier Larramendi to 160 cm from Scott Hartman, which I will be assuming the 155 cm mean of). That's not all - because the size difference between the estimates for Sue and MUCPv-95 (maximum vs maximum) is relatively less (8200 kg vs >11100 kg) than the size difference between the estimates for average vs average (6000 vs >9700 kg) or minimum vs minimum (<4000 kg vs >8320 kg), Giganotosaurus' ribcage would be decisively wider than that of T. rex when those size classes are compared.

What's more, Scott Hartman himself does not think my inflating the ribcage is unreasonable, as can be clearly seen in the post above this. So there really isn't any justification at this point that I'm aware of to be using the original version over the 9.9% wider version.

Of course, this fix to the ribcage would also bring all the Giganotosaurus size estimates in this thread and others up somewhat. Large as they already are compared to Scott Hartman's original estimates, they are based on that slender dorsal view, and I wasn't aware of the above issues with it at the time I made the estimates.

@GuateGojira 

I believe previously you have made points (->, ->) about how slender/lightly built these animals supposedly were.

Quote:These animals were long but relatively light in its composition. That is why even the hypotetical Giga of over 13 meter was just close to the 8 tons and not more.

Quote:The weights are always inflated, none Carcharodontosaurid weighed more than 7 maybe 8 tons, they were long but more slender than the T. rex. 

As such, you may find the information in this post useful if you still stand by the above. In fairness, just as you said and as stated above, they do not appear to be barrel chested like tyrannosaurids. However, they are almost certainly not as slender or lightly built as you might think. Reply