Spinosaurus News ~

[tigerluver]

(09-09-2020, 02:30 AM)DinoFan83 Wrote:

(09-09-2020, 12:43 AM)GuateGojira Wrote:

(06-13-2020, 04:37 PM)DinoFan83 Wrote: Here's a quote from SpinoInWonderland regarding the most recent information on Spinosaurus' size. It should also be noted that due to the tail change, Spinosaurus is a bit shorter than otherwise thought. Scaled 132% from the neotype in Ibrahim et al. 2020, MSNM v4047 is 14.4 meters instead of 15+ for instance. This also affects the other specimens:

"Ibrahim et al. (2020) has a volumetric estimate for the neotype, at 3864 litres. Using a mean density of 0.95 for Spinosaurus gives a mass estimate of ~3.67 tonnes. Scaling up to MSNM v4047 (32% greater dimensions as per Ibrahim et al. 2014) yields about ~8.44 tonnes. It has been argued that the chest of the new reconstruction is too deep, but then the scapulacoracoid is also placed too far back at the chest - these might cancel each other out. Henderson (2018) got a mass estimate too low as the chest they modellled for Spinosaurus was way too narrow than was indicated by the known material."

Now I think a density of 1 is probably more likely as the majority of aquatic animals tend to be neutrally buoyant (EG crocodiles, which converge a lot on Spinosaurus).
Assuming that density, we get:

~3.86 tonnes for the neotype (~10.9 meters)
~8.89 tonnes for MSNM v4047 (scaled up 32%, 14.4 meters)
~9.67 tonnes for NHMUK R-16421 (~14.81 meters), following the discrepancy between it and the neotype that SpinoInWonderland got (link)
~13.66 tonnes for NMC 41852 (~16.62 meters), following what SpinoInWonderland restored for the neotype (51 cm humerus) scaled to the restored size of NMC 41852 fit into the humerus of the Baryonyx holotype (77.7 cm in this image given a length of 46.3 cm for the humerus of the Baryonyx holotype).

Going by this, the average size of the 3 Spinosaurus adults we have seems to be ~15.37 meters and ~10.74 tonnes. That's definitely in pre-2014 Spinosaurus territory, so it looks to me as though Spinosaurus was never really downsized but just got a new look.

Interesting calculations, but the official values at this moment are up to 15-16 meters long and up to 7 tons in the biggest specimen, check these articles:

https://peerj.com/articles/5409/
https://www.nationalgeographic.com/scien...-swimming/

I am going with the official data for the moment. 

I think a few things should be noted regarding Donald Henderson's model:

-It had assumed that Spinosaurus was pneumatic when it was in fact not; Ibrahim et al. 2014 even stated the bones to be of very high density and with no pneumaticity whatsoever. So not only is the theory about Spinosaurus being highly terrestrial most likely bunk, the wrongly assumed pneumaticity underscores the mass of the animal quite unnecessarily.

-The ribcage on Henderson's model is apparently way too narrow given the known material. This is what SpinoInWonderland has told me, and given what the dorsal view from Ibrahim et al. 2020 looks like compared to Henderson's model I am inclined to agree with him. I apologize if the resolution on this is too low but here are the dorsal views compared from Ibrahim (2020) and Henderson (2018):

*This image is copyright of its original author

It should be beyond clear that judging from Ibrahim's model, Henderson's model is SUBSTANTIALLY too narrow - it's literally about 1/2 the width at the torso and this underscores the mass of the animal quite a bit.

-I would not consider Henderson's model to be as accurate as Ibrahim et al. 2020 in terms of its overall anatomy. In addition too the very narrow torso and the unnecessary pneumaticity, the torso on the model from Henderson is much shallower than the new model from Ibrahim, nor does it have the new tail added onto it. All of this is underscoring the model's mass. 
By the way, even if we take Henderson's estimation of 7 tonnes for MSNM v4047 at face value (which is a poor choice when Ibrahim's model is available considering what I went over above), it still does not factor in NHMUK R-16421 nor NMC 41852, both of which are most likely larger. Using the discrepancies in my above post on Spinosaurus' size, NHMUK would be about 8.12 tonnes, and NMC (although tentative until we find more Spinosaurus humeri) would be 10.55 tonnes.

As for that National Geographic article you linked, I am afraid that when I clicked on it the page said it no longer existed. However I suspect they are referring to the outdated model from Ibrahim (2014) that suggested 6 to 7 tonnes instead of the new model from the 2020 study in their article.
By the way, if you didn't already see this, there is something to consider:

*This image is copyright of its original author

Nizar Ibrahim himself supports masses of 10-12 tonnes for Spinosaurus in light of the new and more accurate model, and these sizes are easily replicated when scaling NHMUK R-16421 and NMC 41852. The old 6 to 7 tonne estimations are outdated.

So if you want to stick with the old 7 tonne estimations I suppose I can't stop you, but considering everything above the double digit tonnage is almost certainly more accurate.

I suppose the way to assess the accuracy of these models is the pubis vs skull measurement (I think it was a quadrate that is available?) on FSAC-KK 11888. The Henderson model has a much narrower pubis relative to the head than the Ibrahim et al. model.

On a tangent, there's supposedly a Spinpsaurus arm sitting in a lab now. Hoping this is true and we find out whether this animal was quadrupedal or bipedal, or both. Reply