Largest v. smallest non-avian dinosaur

[Vladimír Socha]

Good day!

I wonder which dinosaur species to use in this comparison - I'm using Argentinosaurus huinculensis with the highest relevant body mass estimate of 96 400 kg and the smallest known adult non-avian theropod Microraptor zhaoianus, estimated at 0.434 kg. Theropods like Parvicursor remotus, Zhongjianosaurus yangi, Anchiornis huxleyi and scansoriopterygids were much lighter, but the studied individuals were perhaps mostly juveniles or subadults. Hence the biggest known dinosaur was roughly 222 thousand times more massive than the currently smallest one known. If we include the smallest modern theropod Mellisuga helenae (average weight of 2.3 grams), the difference rises to some 4.2 million-fold. 

The largest (most massive) known theropod, Tyrannosaurus rex, was (based on the 8870 kg mass estimate for "Scotty" from 2020) about 20 500-times more massive than an adult Microraptor zhaoianus and 386 000-times more massive than bee hummingbird. Of course, there were even larger T. rex individuals, as the specimen "Goliath" clearly shows (and it possibly could grow to some 12 000 kg). Any thoughts? Thank you in advance! VS.

References:

Dalsgaard, B.; et al. (2009). Plant-hummingbird interactions in the West Indies: Floral specialisation gradients associated with environment and hummingbird size. Oecologia. 159 (4): 757–766.

González Riga, B. J.; et al. (2016). A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot. Scientific Reports. 6: 19165.

Benson, R. B.; et al. (2018). Cope’s rule and the adaptive landscape of dinosaur body size evolution. Palaeontology. 61: 13–48.

Persons, W. S.; Currie, P. J.; Erickson, G. M. (2020). An Older and Exceptionally Large Adult Specimen of Tyrannosaurus rex. The Anatomical Record. 303 (4): 656–672.

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

[Tim Williams]

Vladimír Socha <vladimir....@gmail.com> wrote:

> Theropods like Parvicursor remotus, Zhongjianosaurus yangi, Anchiornis huxleyi and scansoriopterygids were much lighter, but the studied individuals were perhaps mostly juveniles or subadults.

This might be splitting hairs (or feathers), but Xu and Qin (2017) are pretty convinced that _Zhongjianosaurus yangi_ was an adult individual, and provide reasons.  They give it an estimated mass of 0.31 kg, further stating "_Microraptor_ had a body mass more than four times that of _Z. yangi_."

_Ambopteryx_ is estimated to have weighed about the same (0.306 kg), although Wang et al. (2019) are unsure if the individual was subadult or adult.  If it was any bigger (and heavier), _Ambopteryx_ would be an even worse glider than it's already inferred to be; as it is, based on Dececchi et al. (2020), its wing loading is ridiculously high and its glide performance abysmal.