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Spinosaurus aegyptiacus skeletals (2014-2017)

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Description

NOTE: This reconstruction is defunct and outdated. Newer skeletal reconstruction can be found here.

Skeletal reconstructions of three specimens of S. aegyptiacus, the "water dragon" theropod that ruled the waters of North Africa during the Middle Cretaceous. Its name means "Egyptian spine reptile", for those that don't know for some reason. Its most distinctive feature are its tall spines.


This serves as a follow up from my journal entry: If you ask me about Spinosaurus...

I may have made mistakes on which parts are preserved(white) or inferred(grey), because the colour-coded 3d model has it's orange(inferred from holotype) and red(neotype) so similar in colour that at times I couldn't even tell them apart!

Seriously, Ibrahim and co. really should have used more contrasting colours.



The tail is based on the notion by Jaime Headden that none of the caudal vertebrae are further anteriorly than the D25.

"As it is, none of the caudal vertebrae seem to be anterior further anterior than about half of the tail’s length, assuming about 50 caudals."

Since neither the paper nor its supplement actually tries to prove it's placement of the holotype's tall, isolated posterior neural spine(it doesn't even actually mention it), I placed said spine as an anterior caudal. In addition, Cau makes an argument that the tall neural spine is likely an anterior caudal based on the spines' geometry.


The legs are displayed larger than in the Ibrahim et al. paper, due to the Ibrahim et al. model having splayed legs. A quadrupedal Spinosaurus is very unlikely, as Jaime Headden points out:

"First, the forelimbs, if they are anything like normal theropod forelimbs, are completely unsuited for weight-bearing. Rather than arranged vertically, the shoulder blades are aligned across the ribs in such a way that any quadrupedal stance would shove the shoulders deep into the neck and likely behead a Spinosaurus faster than Sean Bean in his next deat–film. Rather, they were suspended as in other theropods free from the ground, to dangle as they please.

Second, the authors even provide a furcula (recovered with the spinosaur Suchomimus tenerensis) for the shoulder, and this would have kept the shoulders from moving independently of one another, meaning it is unlikely the arms were permitted to walk in anything like a natural gait or a “typical” quadruped.

Third, the forelimbs while massive have not been described in sufficient detail and appear to possess characteristic typical of other spinosaurs. If they are anything like the forearms of Baryonyx walkeri, they’d lack almost any quadrupedal attributes, especially in the metacarpus, manus, and especially in the phalanges. The authors propose a semi-knuckle-walking locomotion style, but all extant knuckle-walkers have specific adaptations of the arm to permit this (and so it appears in extinct ones, even if you include chalicotheres which may not have been knuckle-walkers), including the presence of thickened, columnar first phalanges and strong curling joints for the other phalanges to bring them out-of-the-way, as well as thickened, solid wrists. Theropods, rather, have flexible wrists due to the semilunate carpal hinge and would likely have been unable to bear weight translating through the upper into the lower arm, much less straighten the limb passively enough to bear weight in such a fashion that a knuckle-walker would require."




I used a dark grey to represent the skin in the sail. Only the topmost 1/3 of the spine has the texture, which, along with sharp edges on the top, according to Ibrahim et al., suggested a sail.

"proximal one-third of dorsal neural spines textured externally by vertical striae"

So you have ~2/3 left for humps and ridges.

Using the chameleon analogue used in the Ibrahim et al. paper, the lowermost 1/3 would be embedded in muscle, likely buried in the back. My flesh silhouette doesn't differentiate between the back and the ridge.

The visible spine in life would be the upper ~2/3, with half of it as a sail and the lower half a transitional ridge.



FSAC-KK 11888, the neotype, is a juvenile specimen estimated at around ~15-19 years of age.

IPHG 1912, the holotype specimen destroyed in WW2, overlaps with FSAC-KK 11888, and seems to be quite small, probably a juvenile or a very small adult. I couldn't get Stromer's original description, luckily the plates are available in the interwebs. I expected this to be a ~15-m specimen or something, but it turned out much smaller.

MSNM v4047 is a bit trickier though, since it overlaps with neither IPHG 1912 nor FSAC-KK 11888. I had to pull out another scientific source for that one.


This also has huge implications on how we should reconstruct other spinosaurines, such as Oxalaia, Irritator, and Angaturama. Rather than the old Baryonyx/Suchomimus-like models assumed for them, they would very likely have been short-legged "water dragons".

__________

Measurements for IPHG 1912:

Hip height: ~1.75 m

Total height: ~3.2 m

Tip-to-tip total length: ~11.09 m

Axial length: ~11.68 m
__

Measurements for FSAC-KK 11888:

Hip height: ~1.81 m

Total height: ~3.38 m

Tip-to-tip total length: ~11.5 m

Axial length: ~12.12 m
__

Measurements for MSNM v4047:

Hip height: ~2.55 m

Total height: ~4.67 m

Tip-to-tip total length: ~16.19 m

Axial length: ~17.06 m

____

References/sources:

Ibrahim, 2014, "Semiaquatic adaptations for a giant predatory dinosaur" + supplementary materials
Dal Sasso, 2005, "New information on the skull of the enigmatic theropod Spinosaurus, with remarks on it's size and affinities"
Stromer, 1915, "Ergebnisse der Forschungsreisen Prof. E. Stromer in den Wüsten Ägyptens"
Headden, 2014, The Bite Stuff - The Outlaw Spinosaurus
Cau, 2016, Theropoda blog - Spinosaurus geometricus

__________

UPDATE(9/22/2014): Tweaked the scale of FSAC-KK 11888. Total length was increased from ~9 m to ~9.59 m as a result.

UPDATE(9/24/2014): Tweaked the dorsal vertebra of IPHG 1912 and the scale of FSAC-KK 11888. Also remeasured axial lengths.

UPDATE(10/24/2016): Remade the tail and tweaked some of the bones to match the Ibrahim et al. measurements. This time, I kept the same caudal count as the Ibrahim et al. model (55 from my count, although it's hard to count due to the terminal caudals being blurry). The tail is longer due to having to modify the anterior caudals to accommodate the neural spine. I also smoothed out the M-curve since it was actually unjustified, as Jaime Headden pointed out in the comment section.
Previous version for comparison

Measurements (axial lengths) for the previous version:
FSAC-KK 11888: ~9.34 m, IPHG 1912: ~10.93 m, MSNM v4047: ~16.48 m

UPDATE(10/20/2016): Fixed an issue with the feet and some minor scaling tweaks on the head size.
Previous version

Measurements (tip-to-tip standing lengths) for the previous version:
FSAC-KK 11888: ~9.92 m, IPHG 1912: ~11.54 m, MSNM v4047: ~17.33 m

UPDATE(12/19/2016): Rescaled body : [limb + hip] proportions after a conversation with :iconfranoys: prompted me to recheck and correct those.
Previous version

Apparently, the vertebrae of FSAC-KK 11888 were actually longer than those of IPHG 1912, and only had smaller measurement figures due to them not corresponding to the same measurement.

All together, these have the effect of blowing up FSAC-KK 11888's body size by a substantial amount and actually making it larger than IPHG 1912. The hip height stays the same since the legs were already correctly scaled based on the measurements, while the other specimens get reduced heights.

Measurements for the previous version:
FSAC-KK 11888: ~3.02 m total height, ~9.94 m standing length, ~10.09 m axial length
IPHG 1912: ~2.06 m hip height, ~3.44 m total height
MSNM v4047: ~3 m hip height, ~5.02 m total height

UPDATE(3/22/2017): Detailed the skull and fixed up the body-limb cross-scaling after triple-checking the measurements again. Remade the cervical ribs and adjusted the neck flesh envelope. Also fixed the randomly elongated atlas that I apparently gave IPHG 1912 and MSNM v4047 back in 2014 for some reason.
Previous version

Measurements for the previous version:
FSAC-KK 11888: ~3.45 m total height, ~12.6 m standing length, ~12.79 m axial length
IPHG 1912: ~1.62 m hip height, ~3.08 m total height, ~11.56 m standing length, ~11.73 m axial length
MSNM v4047: ~2.37 m hip height, ~4.52 m total height, ~16.87 m standing length, ~17.12 m axial length

UPDATE(4/9/2017): Reposed limbs to be more in line with my new standards for my skeletal reconstructions, and finally decided to give it the raised neck posture inferred from Sigilmassasaurus.
Previous version

Measurements for the previous version:
FSAC-KK 11888: ~1.78 m hip height, ~3.35 m total height, ~11.94 m standing length
IPHG 1912: ~1.72 m hip height, ~3.17 m total height, ~11.51 m standing length
MSNM v4047: ~2.5 m hip height, ~4.62 m total height, ~16.81 m standing length
Image size
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Thalassophoneus's avatar
Is it sure that those slim spines on Nizar Ibrahim's specimen are from the dorsal region? Couldn't they be from the base of the tail?