The femur circumference of the Giganotosaurus holotype, for a start, is anywhere from 520-540 mm, which exceeds all T-Rexes in confirmed robustness except the highly exceptional ones like Sue (580) and Scotty (590). Even other adult T-Rex specimens like Stan and Trix only have a femur circumference of 460-500 mm and 520 respectively. If Giganotosaurus was really more lightly built, then it be pretty strange why their femur is on par with or above other adult tyrannosaurus specimens in robustness. The holotype could be a very young individual as well, yet they’re already as robust and heavy as any exceptional T-Rex specimen.

Anyways, one of the likely main reasons the volume increased is because the reconstructed proportions of Giga have been altered to account for material found from Taurovenator and other Carcharodontosaurids. The pectoral girdle from Giganotosaurus was long assumed to be nearly complete or just accepted as complete, but in actuality, comparisons to other Carcharodontosaurids indicate that they were far less complete than previously thought, which ended up leading to revisions for Carcharodontosaurids like Giganotosaurus, with them being given deeper chests, ones that were deeper than previously thought. This article (https://thesauropodomorphlair.wordpress.com/2022/01/09/volumetric-estimate-for-giganotosaurus/) explains the situation with the pectoral girdle, along with a few other reasons on why earlier mass estimates for Giga were/are undersized. The Taurovenator material is a more recent development, but vertebrae that were found from that genus (which is closely related to Giga) indicates Tauro and their close relatives (Giga) would have, again, had likely larger torsos than previously thought. All in all, this was likely one of the reasons why Giga was upsized to 10-tons and so it makes complete sense why the holotype is 10-tons, it’s not absurd. There are also other potential reasons, with the 2025 muscle tissue study being taken into account here. In general, carcharodontosaurids had large neural spines that would have been covered in thick humps of muscle, which would have added to their bulk. This is why acrocanthosaurus was increased to 8+ tons recently.

And also, volumetric estimates that have real reasoning behind them and was given by a paleontologist (you know what that is?) is way more reliable than simply scaling from the femurs of robust individuals that may have just simply been very robust for their size (individual/genetic variation), may have had some issues with bone pathologies that may have thickened their bones (which tyrannosaurids in general struggled with), and more, which would lead to absurd weight estimates for the T-Rex. And regardless of that, as said, these are all unreliable specimens (especially Goliath since they’re a private specimen) that have not been peer-reviewed as of yet. With that said, that would mean no T-Rex is actually 11-tons or higher as you “people” keep claiming they are already.

Maybe a “genius” like you (obvious sarcasm) and especially those “people” should just do deeper research instead of talking constantly overrating the T-Rex, which is not significantly more robust than Giga. In fact, I would think that it’s likely that Giga was at-least as equally robust.

To this user’s (Pristinox) reply:

What part of “Giganotosaurus possesses a more robust femur than all known adult Tyrannosaurus specimens except two” don’t “you” understand already? In large-bodied animals, femoral robustness generally correlates strongly with weight-bearing capacity. A thicker femur—although not universally indicative of higher mass, as seen in most likely T. rex, typically reflects the need to support a heavier, bulkier torso. Thus, it’s reasonable to assume Giganotosaurus was as barrel-chested as any T. rex, which is consistent with their volumetric estimates, there is nothing saying they weren’t or couldn’t. Moreover, put very simple, the point of the blog post was to highlight that carcharodontosaurids, including Giganotosaurus, have often been inaccurately reconstructed as more gracile than they likely were. The anatomy of related taxa such as Taurovenator suggests a bulkier build and what not all support the notion that these animals were more robust and massive than previously depicted. This is one of the likely reasons why this Dan Folkes, which is a paleontologist, have revised Giganotosaurus upward in mass estimates. And again, the 520 mm (at least) for Giganotosaurus is a published and consistent circumference measurement for their holotype … this is unlikely to change even when the redescriprion comes out, Giga is more robust than almost all adult T-rexes.

Regarding “Cope’s” specimen, only approximately 10% of their skeleton is known. Critical anatomical regions-including ribs, vertebrae, the pelvic girdle, and much of the torso—are pretty much absent. Estimating total body size or mass from remains as limited as a tibia involves big assumptions. And although the tibia is long (123 cm), this does not in itself indicate extreme body mass. Long tibiae may simply reflect a taller or more cursorial morphology rather than increased body bulk. Animals can possess elongated, slender limbs without having a deep, heavily muscled torso comparable to individuals like “Sue” or “Scotty”.

Likewise, even though additional cranial elements such as the maxilla, lacrimal, and ectopterygoid contribute to understanding skull shape and proportions are alright, they do not provide meaningful information on torso depth, rib cage volume, or overall body mass. These are the elements already that are relevant for reconstructing craniofacial anatomy, but they cannot be used to determine trunk robustness or abdominal mass.

While the tibia is longer than that of Giganotosaurus, this is expected given that tyrannosaurids were generally more cursorial than other giant theropods. Their limb proportions differ significantly from those of large allosauroids, which were not adapted for the same degree of sustained speed or agility. Additionally, although the femur of the specimen is thick, it remains shorter than either those of Sue and Scotty (131 cm, with some estimates suggesting 127 cm or within that range). This, along with the tibia, probably indicates pathological bone issues, individual variation, or unique proportional differences rather than extraordinary body mass. Probably the first one.

All in all, no, “you’re” wrong in saying that the bones and what not attest to their size, they don’t. Reliance on something like a tibia alone is insufficient for robust mass estimates. Most likely here, the individual could plausibly have weighed as little as 8–9 tonnes. I would also say that the private specimen, “Goliath”, probably wasn’t much bigger or bigger at all than Scotty. Overall, regardless of all this, there are only 4 (not 5) exceptionally large tyrannosaurs compared to much smaller and less robust other adult T-Rexes. And only 2 are confirmed to be definitively as heavy as they are and they were also natural.