Size limit for bipedal animal

[Vladimír Socha]

Good day to all DMG members,

I'd like to follow up on the topic of the size limit of largest terrestrial animal (i. e. giant sauropods), but this time not quadrupedal, but bipedal (i. e. giant megatheropods). As the new discoveries show, there were once maybe 10 000 - 12 000 kg ginormous individuals of Tyrannosaurus rex present (BHI 6248 "E. D. Cope" and "Goliath" specimens), some other finds show similarly sized theropods can be found also in the families Carcharodontosaridae, Spinosauridae and maybe Abelisauridae (115 cm long footprint discovered in Bolivia back in 2016) as well. So my question is: What is, according to your opinion, reliable size (esp. weight) limit for any bipedal theropod? Could it be 15 tonnes, as Mallon and Hone posited last year for the hypothetical T. rex ultimate giant? Or even more in case of Spinosaurus aegyptiacus, walking opportunistically on all fours and living close to water all the time? Thank you for your thoughts! All best, VS.

References:

Calvo, J. O.; Coria, R. A. (1998). New specimen of Giganotosaurus carolinii (Coria & Salgado, 1995), supports it as the largest theropod ever found. Gaia. 15: 117–122.

Christiansen, P.; Fariña, R. A. (2004). Mass prediction in theropod dinosaurs. Historical Biology. 16 (2–4): 85–92.

dal Sasso, C.; Maganuco, S.; Buffetaut, E.; Mendez, M. A. (2005). New information on the skull of the enigmatic theropod Spinosaurus, with remarks on its sizes and affinities. Journal of Vertebrate Paleontology (Submitted manuscript). 25 (4): 888–896.

Therrien, F.; Henderson, D. M. (2007). My theropod is bigger than yours...or not: estimating body size from skull length in theropods. Journal of Vertebrate Paleontology. 27 (1): 108–115.

Hutchinson, J. R.; Bates, K. T.; Molnar, J.; Allen, V.; Makovicky, P. J. (2011). A Computational Analysis of Limb and Body Dimensions in Tyrannosaurus rex with Implications for Locomotion, Ontogeny, and Growth. PLOS ONE. 6 (10): e26037.

Persons, S. W.; Currie, P. J.; Erickson, G. M. (2019). An Older and Exceptionally Large Adult Specimen of Tyrannosaurus rex. The Anatomical Record. 303 (4): 656–672.

Campione, N. E.; Evans, D. C. (2020). The accuracy and precision of body mass estimation in non-avian dinosaurs. Biological Reviews. 95 (6): 1759–1797.

Mallon, Jordan C.; Hone, David W. E. (2024). Estimation of maximum body size in fossil species: A case study using Tyrannosaurus rex. Ecology and Evolution. 14 (7): 11658.

[Mike Taylor]

Let's not forget that even the biggest hadrosaurs (e,g. Shantungosaurus) were likely facultative bipeds. And I'm pretty confident the largest of those outweighed any theropod we have evidence for.

-- Mike.

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[Vladimír Socha]

True, but I highly doubt that 17 000 kg Shantungosaurus giganteus was still able to walk bipedally :-)

References:

Ji, Y., Wang, X., Liu, Y., and Ji, Q. (2011). Systematics, behavior and living environment of Shantungosaurus giganteus (Dinosauria: Hadrosauridae). Acta Geologica Sinica (English Edition). 85 (1): 58-65.

Benson, R. B. J.; Campione, N. E.; Carrano, M. T.; Mannion, P. D.; Sullivan, C.; Upchurch, P.; Evans, D. C. (2014). Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage. PLoS Biology. 12 (5): e1001853.

Benson, R. B.; Hunt, G.; Carrano, M. T.; Campione, N.; Mannion, P. (2018). Cope's rule and the adaptive landscape of dinosaur body size evolution. Palaeontology. 61: 13-48.

Dne středa 23. července 2025 v 12:16:22 UTC+2 uživatel Mike Taylor napsal:

[Darius Nau]

Has there ever been any followup on the giant basal sauropodomorph with
reduced forelimbs from the Lower Elliot Formation that Wedel and Yates
presented at SVPCA 2011?

The one from this abstract:
https://sauroposeidon.wordpress.com/wp-content/uploads/2010/04/wedel-and-yates-2011-wavp-a-diplodocus-sized-bipedal-basal-sauropodomorph-from-south-africa.pdf

According to this, the specimen would also be a contender for the
largest known biped, being roughly Diplodocus-sized. But I haven’t heard
anyone talk about it for ages.

- Darius

On 7/23/25 12:15, Mike Taylor wrote:
> Let's not forget that even the biggest hadrosaurs (e,g. Shantungosaurus)
> were likely facultative bipeds. And I'm pretty confident the largest of
> those outweighed any theropod we have evidence for.
>
> -- Mike.
>
>
> On Wed, 23 Jul 2025 at 10:22, Vladimír Socha
> <vladimir....@gmail.com <mailto:vladimir....@gmail.com>> wrote:
>
> Good day to all DMG members,
>
> I'd like to follow up on the topic of the size limit of largest
> terrestrial animal (i. e. giant sauropods), but this time not
> quadrupedal, but bipedal (i. e. giant megatheropods). As the new
> discoveries show, there were once maybe 10 000 - 12 000 kg ginormous

> individuals of /Tyrannosaurus rex/ present (BHI 6248 "E. D. Cope"
> and "Goliath" <https://dinosaurusblog.com/2025/07/02/nejvetsim-
> tyranosaurem-je-golias/> specimens), some other finds show similarly

> sized theropods can be found also in the families
> Carcharodontosaridae, Spinosauridae and maybe Abelisauridae (115 cm

> long footprint discovered in Bolivia back in 2016 <https://
> dinosaurusblog.com/2020/09/24/nejvetsi-znama-stopa-draveho-
> dinosaura/>) as well. So my question is: What is, according to your

> opinion, reliable size (esp. weight) limit for any bipedal theropod?
> Could it be 15 tonnes, as Mallon and Hone posited last year for the

> hypothetical /T. rex /ultimate giant? Or even more in case of /
> Spinosaurus aegyptiacus/, walking opportunistically on all fours and

> living close to water all the time? Thank you for your thoughts! All
> best, VS.
>

> *_References_*:
>
> Calvo, J. O.; Coria, R. A. (1998). New specimen of /Giganotosaurus
> carolinii/ (Coria & Salgado, 1995), supports it as the largest
> theropod ever found <https://www.researchgate.net/
> publication/40662857_New_specimen_of_Giganotosaurus_carolinii_Coria_Salgado_1995_supports_it_as_the_largest_theropod_ever_found>. /Gaia/. *15*: 117–122.

>
> Christiansen, P.; Fariña, R. A. (2004). Mass prediction in theropod

> dinosaurs <https://www.researchgate.net/
> publication/247494632_Mass_Prediction_in_Theropod_Dinosaurs>. /
> Historical Biology/. *16* (2–4): 85–92.

>
> dal Sasso, C.; Maganuco, S.; Buffetaut, E.; Mendez, M. A. (2005).

> New information on the skull of the enigmatic theropod /
> Spinosaurus/, with remarks on its sizes and affinities <https://
> www.researchgate.net/
> publication/281419012_New_information_on_the_skull_of_the_enigmatic_theropod_Spinosaurus_with_remarks_on_its_size_and_affinities>. /Journal of Vertebrate Paleontology/ (Submitted manuscript). *25* (4): 888–896.

>
> Therrien, F.; Henderson, D. M. (2007). My theropod is bigger than
> yours...or not: estimating body size from skull length in theropods

> <https://www.researchgate.net/
> publication/232687833_My_theropod_is_bigger_than_yoursor_not_Estimating_body_size_from_skull_length_in_theropods>. /Journal of Vertebrate Paleontology/. *27* (1): 108–115.

>
> Hutchinson, J. R.; Bates, K. T.; Molnar, J.; Allen, V.; Makovicky,
> P. J. (2011). A Computational Analysis of Limb and Body Dimensions
> in Tyrannosaurus rex with Implications for Locomotion, Ontogeny, and

> Growth <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3192160>. /PLOS
> ONE/. *6* (10): e26037.

>
> Persons, S. W.; Currie, P. J.; Erickson, G. M. (2019). An Older and

> Exceptionally Large Adult Specimen of /Tyrannosaurus rex/ <https://
> doi.org/10.1002%2Far.24118>. /The Anatomical Record/. *303* (4):

> 656–672.
>
> Campione, N. E.; Evans, D. C. (2020). The accuracy and precision of

> body mass estimation in non-avian dinosaurs. <https://
> onlinelibrary.wiley.com/doi/abs/10.1111/brv.12638> /Biological
> Reviews./ *95* (6): 1759–1797.

>
> Mallon, Jordan C.; Hone, David W. E. (2024). Estimation of maximum

> body size in fossil species: A case study using /Tyrannosaurus rex/
> <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11267449>. /Ecology
> and Evolution/. *14* (7): 11658.

[Mike Taylor]

Yes, that got written up by a completely different group, and Matt only found out about it some time later. I don't remember the details, though, sorry. It might be this one? https://www.sciencedirect.com/science/article/pii/S096098221830993X

-- Mike.

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[Mike Taylor]

Digging around my old emails I can confirm that Ledumahadi is indeed Yates and Wedel's (2011) giant prosauropod. Extracted from Matt's email:

That Sander and Lallensack thing from 2018 was a commentary on the description of the large-ish (~12-tonne) sauropodiform Ledumahadi by McPhee et al (2018). What I didn't know at the time, because I didn't look closely at the McPhee et al. paper, is that Ledumahadi IS the "Big Elliot Sauropodomorph" that I presented at SVPCA 2011 in Lyme Regis, with Adam Yates as coauthor. And apparently nobody clued in Sander and Lallensack, since they cite our abstract regarding an 'unpublished' animal that they thought was distinct from Ledumahadi, but was in fact the same critter.

Some due diligence was not done, it seems.

-- Mike.

[Stephen Poropat]

Vladimir Socha said, "True, but I highly doubt that 17 000 kg Shantungosaurus giganteus was still able to walk bipedally :-)"

Is its anatomy so different from that of other hadrosaurs? 

A cursory comparison between the postcrania of Shantungosaurus and Edmontosaurus suggests that the former has more robust humeri and taller sacral neural spines than the latter. Reinforced forelimbs presumably developed to support the increased mass of the animal during quadrupedal locomotion, but might the taller sacral neural spines indicate the need for reinforcement in that region during bipedal locomotion and rearing?

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--

Dr Stephen F. Poropat

Deputy Director

Western Australian Organic and Isotope Geochemistry Centre

School of Earth and Planetary Sciences

Curtin University

Bentley, Western Australia

Australia 6102

https://stephenporopat.weebly.com/

[Vladimír Socha]

Interesting, indeed. I just wonder how could a 17+ ton bipedal hadrosaurid walk on hind legs when recent studies - mainly on T. rex - showed that theropods of this size (i. e. half the mass of Shantungosaurus) would literally shatter their leg bones if running something like 29 kmph. Or more exactly, according to the study from 2017 a 7 tonne T. rex (about 2.5 times lighter than Shantungosaurus) would shatter its leg bones already when moving at speed of 18 kmph. I guess the pressure exerted by such a heavy body would be probably too much for any kind of bipedal dinosaur to handle. That's why I was asking if there is any study on the upper mass limit for being a biped and be able to move at the same time. All best, VS.

References:

Hutchinson, J. R.; Garcia, M. (2002). Tyrannosaurus was not a fast runner. Nature. 415 (6875): 1018–21.

Sellers, W. I.; Pond, S. B.; Brassey, C. A.; Manning, P. L.; Bates, K. T. (2017). Investigating the running abilities of Tyrannosaurus rex using stress-constrained multibody dynamic analysis. PeerJ. 5: e3420.

Hirt, M. R.; Jetz, W.; Rall, B. C.; Brose, U. (2017). A general scaling law reveals why the largest animals are not the fastest. Nature Ecology & Evolution. 1 (8): 1116–1122.

Dececchi, T. A.; Mloszewska, A. M.; Holtz, T. R. Jr.; Habib, M. B.; Larsson, H. C. E. (2020). The fast and the frugal: Divergent locomotory strategies drive limb lengthening in theropod dinosaurs. PLOS ONE. 15 (5): e0223698.

Dne středa 23. července 2025 v 16:30:47 UTC+2 uživatel Stephen Poropat napsal:

[The Dinosaur Heretic]

If a supposed 17t Shantungosaurus were to exist, it would likely be walking on its hind legs most of the time anyway (Moratalla et al., 1992). Reinforced neural spines over the sacrum facilitating this common locomotion makes sense. Sellers et al., 2009 suggests four-legged galloping would be more beneficial than two-legged running, but this places more strain on the forelimb. A robust humeri with massive muscle attachment points, as well as slightly pronated forelimbs whereby the first digit is parallel to the midline would create incredible propulsive force off a single point, and would logically support the immense mass of a 17t Shantungosaurus. Worth investigating more! It’d be neat seeing this modelled.

References

Moratalla, J. J., Sanz, J. L., Jiménez, S., & Lockley, M. G. (1992). A quadrupedal ornithopod trackway from the Lower Cretaceous of La Rioja (Spain): inferences on gait and hand structure. Journal of Vertebrate Paleontology, 12(2), 150-157.

Sellers, W. I., Manning, P. L., Lyson, T., Stevens, K., & Margetts, L. (2009). Virtual palaeontology: gait reconstruction of extinct vertebrates using high performance computing. Palaeontologia Electronica, 12(3), 11A.

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[Celestino Coutinho]

That 115 cm from bolivia as not actheropod origin but it is a sauropod pes print

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[Vladimír Socha]

That three-toed footprint on the photo? Was it somehow altered or damaged? Was it formally published? Thank you! VS.

Dne středa 23. července 2025 v 17:25:55 UTC+2 uživatel Celestino Coutinho napsal:

[Celestino Coutinho]

Meyer and ..... may be 2022 but surevit was Meyer

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[Jerry Harris]

Probably this paper:

Ch.A. Meyer, D. Marty, B. Thüring, S. Thüring, M. Belvedere. 2021. The Late Cretaceous dinosaur track record of Bolivia – Review and perspective. Journal of South American Earth Sciences 106: 102992. https://doi.org/10.1016/j.jsames.2020.102992.

[Celestino Coutinho]

Yes. This one. Thanks

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