1a: I think the better way to put it would be "Giganotosaurus is in reliable T. rex size range" as we don’t really have much of a size range for the former (especially disregarding MUCPv-95), while we do for the latter. Adult T. rex specimens range in weight anywhere from 4-5 to 8-9 t. The Giganotosaurus holotype is probably most accurately estimated at 6-7 t (closer to the upper end of that range) as several recent volumetric analyses suggest something like this (Hartman, Franoys, scaling up from Acrocanthosaurus in Bates et al. 2009).
The average femur circumference in Larson’s dataset (n=16) of T. rex femora is 515 mm (89% of sue’s 580 mm), the average femur circumference in Person’s et al.’s dataset (n=12, including scotty) is 505 mm (87% of sue). The Giganotosaurus (and Tyrannotitan) holotype’s is 520 mm.
The respective reported femur lengths give very similar results, 90-93% the size of Sue on average.
As to how large the corresponding
T. rex would be:
This is a work in progress, currently based on a very limited sample, but still it should be more reliable than only scaling from a single individual, and thanks to the inclusion of two smaller specimens, the range of body sizes for which this relationship can be applied should also be larger, very important in this case.
data as follows:
tl fl fc
fmnhpr2081 1235 132.1 58
bhi3033 1178 128 50.5
cm9380 1188 126.9 53.4
lacm23845 821 90 NA
bmrp2002.4.1 645 79 25
mor555 1160 128 52
(taken from, in this order of priority, Franoys, Hartman, Persons et al. 2019, Hutchinson et al. 2011, and Larson 2008)
TL based on mean femur lengths from the Larson and Persons et al. tables is 10.9 m to 11.3 m, TL based on mean femur circumference is 11.3 to 11.5 m.
1b: The claim about speed is wrong. There has been an estimated speed for
Giganotosaurus that was higher than what is typically estimated for
T. rex (Blanco & Mazzetta 2001), but the methodology just isn’t comparable, and would have produced just as high a speed for
T. rex at the same size, as it calculated the maximum speed at which body equilibrium could be maintained during running. The 14ms⁻¹ are hence an estimate of maximum speed possible for a hypothetical 9 ton theropod, not specifically
Gigantosaurus.
Comparative analyses of the hind limbs suggest
T. rex to have been the more cursorial of the two (shorter femur, marginally longer tibia and pes, more gracile distal limb elements, larger knee flexors and extensors), even though the difference cannot have been much at similar body masses.
2: Intelligence. Well firstly, that
T. rex is supposed to have been as smart as a chimp is just plain old sensationalist BS, I don’t even need to explain why, but I think I’ll do it anyway:
T. rex’ overall brain volume is smaller than a chimps, despite the animal being 100 times larger, and more importantly, there is no comparable investment of brain mass in centres of higher cognitive function in
T. rex.
Secondly,
T. rex does have higher encephalization quotients than carcharodontosaurs, but not that much.
I’ve posted about this here:
theworldofanimals.proboards.com/post/34994/threadBased on crocodile brain/endocast ratios, it is 1.15-1.55 for the
Giganotosaurus holotype, 1.54-2.08 for sue (reptile EQs).
And before we go shouting "forebrain enlargement": as noted by Larsson et al. (2000), yes, the forebrains are proportionately larger in tyrannosaurid brains, but equating that to higher cognitive function is also erraneous, the olfactory bulbs are part of the forebrain as well. The big bulbous things in the front here:
Reconstructed endocast of FMNH PR 2081, Fig. 4A from Brochu (2000), dorsal view, volume 414 ml
For comparison, here’s the endocast of Giganotosaurus:
Endocast of MUCPv-Ch1, Fig 1B in Carabajal & Canale 2010, dorsal view, volume 275 ml
There’s a bit of a difference here, which doesn’t just explain the reason for the forebrain enlargement, but in fact also at least part of the reason for the slightly higher EQ of T. rex.
So let’s not overinterpret. What the encephalization quotient tells us is the difference of
overall brain size to that typical for an animal (in this case, reptile) of the same body size. Not what that difference was used for. Animals evolve larger brains for a variety of reasons other than higher cognition. Near the top of the list are sensory structures that require more neurons to process their information.
The whole narrative that T. rex was supremely intelligent compared to other later theropods is more sensationalism than anything else.
3: I sincerely hope nobody here needed a news article to remind them that Jurassic Park is not a reliable source of scientific information about T. rex, including its eyesight.
Bates, K.T., Manning, P.L., Hodgetts, D. and Sellers, W.I. 2009. Estimating mass properties of dinosaurs using laser imaging and 3D computer modelling. PloS one 4 (2): e4532.
Blanco, R.E. and Mazzetta, G.V. 2001. A new approach to evaluate the cursorial ability of the giant theropod Giganotosaurus carolinii. Acta Palaeontologica Polonica 46 (2).
Brochu, C.A. 2000. A digitally-rendered endocast for Tyrannosaurus rex. Journal of Vertebrate Paleontology 20 (1): 1–6.
Carabajal, A.P. and Canale, J.I. 2010. Cranial endocast of the carcharodontosaurid theropod Giganotosaurus carolinii Coria & Salgado, 1995. Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen 258 (2): 249–256.
Larsson, H.C., Sereno, P.C. and Wilson, J.A. 2000. Forebrain enlargement among nonavian theropod dinosaurs. Journal of Vertebrate Paleontology 20 (3): 615–618.
Persons IV, W.S., Currie, P.J. and Erickson, G.M. 2019. An older and exceptionally large adult specimen of Tyrannosaurus rex. The Anatomical Record.
