Spinosaurus News ~

[DrZapxX]

''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. ''

The latest studies would say otherwise, for starters Symth et al provides evidence that they are the same animal, the unique autapomorphies are supposed to be a result individual variation 
(Sigilmassasaurus and S. Aegypticus) are not only the same genus but the same species, actually, even FSAC-KK-7280 is referred to Spinosaurus Aegypticus (not Sigilmassasaurus), the reason why its the most appropriate is quite simple and not the 3864kg is because the 1000 kg/m3 to gain a 3.8 tonne mass is by far too dense and heavy, adult organisms with air sacs don't magically loose them either with growth.

In terms of presence/absence of air sacs, taphonomy cannot play into account like you suggest, because we have two separate individuals with the same pneumatised bone, it would be very coincidental that two separate specimens have pneumatised bone in the posterior cervical vertebra (exact same place!) it isn't even just Spinosaurus, it is a trait of other spinosaurids too.








The high bone compactness occurs from the material obtained from the legs only, specifically compactness in the femoral shaft in contrast to the foramen in FSAC-KK-7280 and FSAC-KK-18122 is from the dorsal vertebra there is a difference in position.



And the possibility of pneumatized bone density has directly came from Ibrahim et al 2020, ironically.





Even Ibrahim et al Wasn't completely not pneumatic, it had a cancellous bone with pores, the femur specifically contains fibrolamellar bone that becomes increasingly cancellous towards the middle.
Cancellous bone does have pores, so it's not completely solid bone like you claim by no air spaces in the 3800kg value.





I find it suddenly weird how your more willing to agree with Ibrahim et al 2014 on a non-pneumatic Spinosaurus but willing to contradict Ibrahim et al 2020 which considers the possibility of a pneumatic Spinosaurus too.







According to Lee et al 2014, Deinocherius rivalled the number of airsacs of sauropods, so other particular theropods could easily be exceptions to the general rule also Henderson 2003 actually has sauropod densities lower than the 833kg/m3 of Ibrahims pneumatic spinosaurus.(Apatosaurus's density 818 kg/m3, Diplodocus 814 kg/m3,Camarasaurus 791 kg/m3, Brachiosaurus 796 kg/m3) retrospectively...

*This image is copyright of its original author

''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.''

What you linked was a random image, that's not a source, MSNM V4047 is the largest specimen and even the max size of the skull is still smaller (175cm), SpinoInWonderland isn't a palaeontologist, nor is a image a reliable source and a link on how he got those measurements would be useful too.



As explained MSMN V4047 is a overestimated because Sasso 2005 used different taxon to determine it's length, it is in fact overexaggerated, Hendrickx et al 2016, Therrien et al 2007, Ibrahim et al 2014 also agrees by favouring 1.5-1.6 metre long skull.



''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.''




160cm is an exaggeration because (FSAC-KK 11888's skull is 112cm, basing this with a 32% increase for MSNM 4047 (Supplementary PDF for Ibrahim et al 2014) does not equate to 160cm but less than 160cm, (around 147cm) using Therriens length equation resolves much less than 17m around 12.5metres,  isometrically scaling 32% from 11m (how they got 11 metres is unknown and dubious) neotype also gives a result of 14.5m at max, the scaling increase of FSAC-KK 11888's skull shows a good consistently with Therrien et al 2007's skull length. Henderson 2018 states nothing more than 15 metres in length by the way.






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

No absolutely not pre ibrahim 2020 spinosaurus was not 12 tonnes if it had no air sacs/pneumatised bone, how is it pneumatic at all if it's LACKING airspaces and PNEUMATIISED bone?



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

If you actually read what I said, I mentioned why femoral circumfluence cannot be applied to Spinosaurus because of the unique marrow cavity affecting the accuracy of mass estimations (with Persons et al 2019 being referenced which your fully aware of challenging Campion et al's mass equations being applied to S. Aegypticus,and isometry is the only available option which I also quoted from Lakin et al 2019.






Speaking of Mickey Mortimer's criticism, at same scale, Tyrannosaurus (skeletal from Hartman) and Spinosaurus (skeletal from Ibrahim) have almost identical proportional tail lengths.

*This image is copyright of its original author

Reply