Spinosaurus News ~

[DinoFan83]

Quote:The question is what value of mass is appropriate to use, it would seem the 3219kg would be, Spinosaurus aegypticus/Sigilmassasaurus (Smyth et al 2020 considers them to be same taxa based on dentition similarity) https://www.sciencedirect.com/science/a ... 7120302068) has been reported to have air sacs in the vertebra (FSAC-KK-7280 (pneumatic foramen and FSAC-KK-18122 known from posterior cervical vertebra with air spaces at the bottom), Lakin et al 2019

Using the improvement of Hendeson's spinosaurus, from the table, a density of 833kgm^3 density is most logical.

May I ask, why do you think those spinosaurid cervicals (that aren't even confirmed to be the same taxon, and if they are, are from an animal much further ontogenetically from the large adults than FSAC-KK 11888 is and therefore may not be a better model) are a better model for density than a reasonably complete skeleton which had its bones histologically analyzed and was found to be completely free of any pneumatization? I would prefer to trust the word of Nizar Ibrahim on Spinosaurus having completely solid bone (and therefore no air sacs with a density of 1 or so), given the difference between the specimens you and him are using to come to conclusions on pneumatization.
Not to mention, a density of 0.833 seems too excessively low for the following reasons:

-Even sauropods (some of the most pneumatic of all non-avian dinosaurs, with all species known so far having much more postcranial pneumaticity than Spinosaurus) would have been somewhat denser than that. Molina-Pérez & Larramendi (2020) suggest a density of 0.9 for them (page 10). Therefore, I find it difficult to believe that Spinosaurus (which may have had some airsacks in only its neck at most, and could just as well have had none at all) would have a density around 8% lower than animals with very extensive airsacks in both their necks and torsos.

-Most other theropods (which had significantly more airsacks than Spinosaurus did) do not seem to have been around the density of 0.833 either. For instance (although his conclusion on this blogpost was almost certainly incorrect for reasons I can explain if you so wish), Scott Hartman has come to a density figure of roughly 0.915 for Giganotosaurus when taking into account the (significantly greater) amount of airsacks in the head, neck, and torso. Molina-Pérez & Larramendi (2016) also support my viewpoint, suggesting an even higher figure of 0.95 (page 11) when taking into account the fact that all tissues save for fat are a good deal denser than water.

Therefore I do not see justification for such a low density in Spinosaurus, given its dense bones and the much higher densities of even theropods that had many more airsacks. As stated above, I find a density of 1 or so the most plausible, and that would result in 3,864 kilograms for the new model of the neotype. 

Quote:MSNM V4047 (largest specimen of spinosaurus)
Length: 12.566, despite the common misconception, there is a sort of myth of MSNM v4047's skull length, 1.75m is a overstatement, a revisited measurement indicates 1.5 metres.

*This image is copyright of its original author

Here is a direct quote from Therrien et al 2007,
''A note of caution concerns the dimension of the reconstructed Spino-
saurus skull. First, the proposed skull restoration (Dal Sasso et
al. 2005:fig. 5B) is a composite reconstruction with the front and
back halves being from different genera. Because skull shape
varies among spinosaurids (i.e., the shape of the rostrum, the
relative dimensions of the maxillae and premaxillae, and the
shape of posterior region of the skull differ among spinosaurids;
Fig. 3), there is potential for overestimating the length of a com-
posite spinosaur skull. Second, Dal Sasso and colleagues’
(2005:fig. 5) skull length estimate represents the distance be-
tween the premaxilla and the squamosal, which is greater than
the measurement (premaxilla-occipital condyle) used in our pre-
dictive equations. Therefore, the body length estimate derived
above (14.34 m) exceeds what must have been the total body
length of the animal. It only takes a skull length (premaxilla-
occipital condyle) of 1.50 m, that is, 0.25 m (14%) shorter than
originally suggested, to predict a substantially shorter (22% to
31%) total body length of 12.57 m''

I think you may be interested to know that by superimposing the rostrum on a privately owned complete skull of Spinosaurus, SpinoInWonderland has achieved a skull length of 1.86 meters for MSNM v4047. My assumption is that his reconstruction should hold at least as much as any other if not moreso, since it is bases solely on the complete and undistorted skull of a conspecific, so I don't know whether you have anything that suggests this to be wrong, but 175 cm or more does not seem to be an overestimate to me and in fact seems quite probable. There's also the skull reconstruction of 177 cm by theropod1, which is to my knowledge still accurate.

Quote:According to Ibrahim et al scaling the subadult neotype's skull (112 cm) to 32% larger gives a skull length for MSNV 4047 147.84cm.
https://d3qi0qp55mx5f5.cloudfront.net/p ... 1591805883
Hendrickx et al 2016 also agrees with this but slightly exaggerates the skull length to 160cm.
https://journals.plos.org/plosone/artic ... 695.ref022

Speaking of Lakin et al, the paper also favours a 12-15m long spinosaurus too.
https://www.sciencedirect.com/science/a ... 7118302052

Considering what I have outlined above, would you care to explain how 160 cm is an exaggeration?
Also, for what it's worth, the 112 cm skull length figure for FSAC-KK 11888 would result in MSNM v4047 being about 17.1 meters long using the 10.93 meter estimate from Ibrahim et al. 2020 as well as theropod1's skull reconstruction for it. 
One last thing: Comparing Therrien and Henderson (2007) to the models from Ibrahim is not apples to apples. The formula of the former is based on a much more compact animal (a short tailed tyrannosaurid) as a general basis, and therefore using it as the basis for Spinosaurus length estimates is generally problematic. I find 16 meters (Henderson 2018, corrected model outlined earlier in this thread) to 17.1 meters more likely given that they base on actual conspecifics instead of an unrelated theropod with a completely different lifestyle, etc.

Quote:With all of this in mind, using the formula from Therrien 2007, 
Body Length=1.03161 * 10 ^(0.85673*Log(1.5 metres)+0.93482)

This equates to 12.566 metres for a length.

Using the equation of square cube law

*This image is copyright of its original author

The new volume is 3.86434574m3 x(12.566m/10.37m)^3

6.87592090769 m3

Using Mass = Density 833kgm3 vs Volume (6.87592090769m3)
mass = 5727.64211611 kg

Can you explain how this would hold up compared to the higher estimates given how I have shown that it very likely does not?

Quote:Just to get a misconception out of the way, Henderson 2018 includes a pneumatic and non-pneumatic spinosaurus
https://peerj.com/articles/5409/

Quoting...
''As a test of how sensitive the buoyant Spinosaurus model was to the assumed presence of avian style air sacs and pneumatized bone, an alternate model lacking these features was tried. This model assigned a uniform axial density of 1,000 gm/l from the tip of the tail to the tip of the snout. The limb and sail densities were unchanged, and the same lung was retained. This alternate model can also be thought of as one with a denser skeleton. This model has higher mean density of 918 gm/l and is heavier, 7,160 kg,'

Still too pneumatic if my above sources are anything to go by. The corrected model of this (page 7) is more than 12 tonnes.

Quote:Some may wonder why Campione et al, using the circumference of the femur for Spinosaurus well according to Person's et al 2019 spinosaurus lacked a open medullary cavity that most over theropods have, increasing femora as a result,

https://anatomypubs.onlinelibrary.wiley ... 2/ar.24118

As I have told you before, femoral circumference is not reliable to estimate mass: https://thesauropodomorphlair.wordpress....timations/

Quote:(Therrien & Henderson, 2007) mass method overexaggerates theropod mass, in the case of other megatheropods.

The only available option is square cube law (isometric scaling) Lakin 2019 also confirms this.

''The disarticulated and fragmentary nature of this material makes it difficult to arrive at robust estimates of body length, and even more difficult to estimate mass given the lack of reliable indicators such as skull length (Therrien & Henderson, 2007), or limb bone dimensions (Campione and Evans, 2011, Benson et al., 2014). However, the proportions and shapes of the vertebrae are very similar to adult material described in previous work (Stromer, 1915, Dal Sasso et al., 2005, Ibrahim et al., 2014b), suggesting a broadly isometric growth pattern for Spinosaurus ''

https://www.sciencedirect.com/science/a ... 7118302052

But what if spinosaurus was 14.34 m (overexaggerated length - We know it's not bang on 15 metres because not only because Therrien et al's forumla but also Ibrahim et al 2014 scaling a ''supposed'' 11 metre individual an extra 32% which is 14.5m)?

Body Length=1.03161 * 10 ^(0.85673*Log(1.75 or 1.6 metres)+0.93482)

Volume =  3.86434574m3 (14.34m/10.37m) ^3 = 10.2185m3

Using Mass = Density 833kgm3 vs Volume 
1.75 skull length = 14.34m in length = 10.21 m3 volume = 8504 kg

1.6 skull length = 13.28m in length = 8.11m3 volume = 6760 kg

In conclusion the largest spinosaurus specimens were around 5.72 metric tonnes to 6.76 metric tonnes in mass, a 15 metre ong spinosaurus would still be less than 10 tonnes around 9.5.

What other reasons do you have for preferring such sizes over the new 10-12+ tonne estimates, considering everything I have outlined above? All things considered, I find the much higher length and mass estimates to be much more likely because they are 100% based on Spinosaurus material, assume what seems to be a proper density, and are solely volumetric. Reply