Deviation Actions
Description
I would not normally do a multi-view skeletal for such an incomplete taxon, but I did one anyways because I wanted to do a GDI mass estimate, since Argentinosaurus is normally listed as one of the larger dinosaurs. More on that technique here.
As restored here, Argentinosaurus is about 28.89 meters (94.75 ft) long with the neck raised or about 29.65 (97.25 ft) meters long with the neck straightened out. [Edit: I should point out that this is the projection of the length of the silhouette onto the ground, instead of the length that we usually think of in living animals, where they are measured along the back or belly. See comments by dracontes below] So it turns out to be a bit shorter than I have previously estimated (I thought it would come out at about 35 meters or so). The aforementioned GDI mass estimate gave a total volume of about 87.82 m3 and a resultant mass of 64.17 tonnes (70.5 US (short) tons). I used specific density estimates of 0.3 (300 kg/m3) for the neck, 0.8 (800 kg/m3) for the torso and tail and 1.0 (1000 kg/m3) for the limbs. This is considerably lighter than many previous mass estimates with often gave mass estimates in the 75-100 tonne range, although it is heavier than Greg Paul's most recent (2010) mass estimate of 55 tonnes.
My reconstruction conservatively restored the length of the torso and the densities I used may be considered on the low-end of the range of plausible densities, so it may be possible to add a few more tonnes. For example, increasing the density of the limbs to between 1.2 and 1.4 (which are equally plausible in my opinion) would lead to a mass estimate of between ~66 and ~69 tonnes. Also, the length of the missing dorsal vertebrae are restored with an average of the known dorsal vertebrae in size. This could lead to an underestimate because in at least some titanosaurs, the anterior dorsal vertebrae get longer as they get closer to the neck.
At any rate, with the available evidence, I think it looks like Alamosaurus probably got a bit larger than Argentinosaurus, although we have many more specimens of Alamosaurus so this could simply be sampling bias. Until recently, the largest available specimens of Alamosaurus were in the 15-20 meter range, with new discoveries potentially in the 25 meter range, so it may be that there were 35 meter, 110+ tonne Argentinosaurus specimens. We maybe just haven't found them yet. Until such specimens are found, I'm fairly comfortable with calling Alamosaurus larger.
Refs--
Bonaparte J, Coria R (1993). "Un nuevo y gigantesco sauropodo titanosaurio de la Formacion Rio Limay (Albiano-Cenomaniano) de la Provincia del Neuquen, Argentina". Ameghiniana 30 (3): 271–282.
Curry Rogers, K. A., 2005, "Titanosauria: A Phylogenetic Overview" in Curry Rogers and Wilson (eds), The Sauropods: Evolution and Paleobiology pp. 50–103
Paul, G.S."MASS ESTIMATE TABLE". 2010. [link]
Are you sure about the very low density?
I just GDI-ed your skeletal for fun, scaling it to 1px=1cm and taking one slice per pixel (so I think it should be pretty precise), and it came out at about 94 m³ overall, a bit higher than your result, but still comparable.
total axial 88586.796
head+neck 16453.036
thorax+sacrum 63875.716
tail 8258.044
forelimb 1263.264
hindlimb 1252.236
(volumes in litres)
Using your proposed densities I am getting 67.7t at an overall density of 0.723. However, when I give the neck segment a density of 0.6 rather than 0.3, the trunk a density of 0.8, the tail one of 0.95 and the limbs 1.0, the resulting overall mass estimate is 73.8 t. This still results in an overall density of 0.789, so this is still at the low end of SGs proposed in the literature, but would give a result very consistent with the usual 70-80t estimations for Argentinosaurus.
According to Larramendi et al.’s recent study on specific gravities, this might still be too "conservative". For Diplodocus, they propose a neck density of 0.844, a trunk density of 0.918 and tail, fore- and hindlimb densities of 1.01, 1.13 and 1.08 respectively, resulting in an overall 0.95.
Applying Larramendi et al.’s proposed segment densities to your Argentinosaurus would result in a mass of about 86.4 t and an overall density of 0.923.
While it is impossible to pinpoint the exact volume of pneumatic structures, and I’d be careful about proclaiming these as the "definite" densities to use (generally Larramendi et al.’s density estimates strike me as pretty high, and they certainly warrant further testing), I think it is fair to say that values far below 0.8 for the entire animal are probably too low (as of my knowledge, such low values have also never been achieved in any previous studies that attempted to use 3d modelling to quantify the size of air spaces for any non-avian dinosaur. The lowest I know of are both about 0.79, for Giraffatitan, estimated by Bates et al. 2015, and for Tyrannosaurus Sue, estimated in Hutchinson et al. 2011).
--refs:
Bates, K.T., Falkingham, P.L., Macaulay, S., Brassey, C. and Maidment, S.C. 2015. Downsizing a giant: re-evaluating Dreadnoughtus body mass. Biology letters 11 (6): 20150215.
Hutchinson, J.R., Bates, K.T., Molnar, J., Allen, V. and 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.
Larramendi, A., Paul, G.S. and Hsu, S. 2021. A review and reappraisal of the specific gravities of present and past multicellular organisms, with an emphasis on tetrapods. The Anatomical Record 304 (9): 1833–1888.