More on Spinosaurus' Posture

[Takama]

I think Spinosaurus may have been Bipedal.   But dont expect it to run after you, because it would be a slow mover

This Drawing by our very own Himmapaan was endorsed by Scott Hartman



To quote Scott Hartman

I think this is the best Spinosaurus rendition I've seen since the enshortening.

[Reptilia]

I've seen the documentary, but where I can find the paper? I've only read things about it but never had the chance to read the actual source.

[The Atroxious]

spinosaurus is too fragmentary for the census to be very big. Plus, it's just basic logic that a theropod couldn't be quadrupedal.

Correction: we don't have enough evidence for a solid argument that there was a quadrupedal theropod. That said, there are a few types of aquatic birds that aren't exactly bipedal either. There aren't a lot of them, but they do demonstrate that theropods can achieve unconventional locomotion, which is why I take the argument of bipedalism with the same grain of salt that I take the argument of quadrupedalism.

This is one of the very few illustrations of a bipedal Spinosaurus that looks plausible to me. I question it's accuracy, however, given how drastically the forelimbs have been reduced, and how the tallest neural spine appears to be joined into the sacrum, which is not seen in the known skeletal material. All plausible reconstructions of a bipedal Spinosaurus that I've seen have been the result of altering the shape, placement, and size of a number of the bones. It could be that these artists are right, and the proportions of the initial Ibrahim construction are wrong, but I don't feel we have enough information to go on yet to state absolutes about how the animal must have been.

[stargatedalek]

spinosaurus is too fragmentary for the census to be very big. Plus, it's just basic logic that a theropod couldn't be quadrupedal.

You forget all dinosaurs started out that way, it's inevitable such a transitional form would be awkward to witness, moreso if it was aquatic.

[Cloud the Dinosaur King]

spinosaurus is too fragmentary for the census to be very big. Plus, it's just basic logic that a theropod couldn't be quadrupedal.

Correction: we don't have enough evidence for a solid argument that there was a quadrupedal theropod. That said, there area few types of aquatic birds that aren't exactly bipedal either. There aren't a lot of them, but they do demonstrate that theropods can achieve unconventional locomotion, which is why I take the argument of bipedalism with the same grain of salt that I take the argument of quadrupedalism.

This is one of the very few illustrations of a bipedal Spinosaurus that looks plausible to me. I question it's accuracy, however, given how drastically the forelimbs have been reduced, and how the tallest neural spine appears to be joined into the sacrum, which is not seen in the known skeletal material. All plausible reconstructions of a bipedality Spinosaurus that I've seen have been the result of altering the shape, placement, and size of a number of the bones. It could be that these artists are right, and the proportions of the initial Ibrahim construction are wrong, but I don't feel we have enough information to go on yet to state absolutes about how the animal must have been.

I've heard some suggestions that Spinosaurus walked like a penguin, or even like Stromer portrayed it back in 1915.

[Cloud the Dinosaur King]

I think Spinosaurus may have been Bipedal.   But dont expect it to run after you, because it would be a slow mover

This Drawing by our very own Himmapaan was endorsed by Scott Hartman



To quote Scott Hartman

I think this is the best Spinosaurus rendition I've seen since the enshortening.

Wow, this is an incredible piece of artwork. Great job Himmapaan! My only nitpick is that Spinosaurus probably held its neck in an 'S' curve like that of a pelican. Also the feet should be flat, webbed, and the dew claw should be on the ground. Other than that, great job! I love the muscle contortion. It really brings out the movement in this animal.

[ZoPteryx]

I've seen the documentary, but where I can find the paper? I've only read things about it but never had the chance to read the actual source.

For those interested, here is the original source materials:

The original Ibrahim et al. paper that started it all:
https://www.researchgate.net/publication/265553416_Semiaquatic_adaptations_in_a_giant_predatory_dinosaur

and the Supplemental material:
http://science.sciencemag.org/content/suppl/2014/09/10/science.1258750.DC1/Ibrahim.SM.pdf

Notice how it's rather short, this is presumably because the authors were forced into a deadline due to their partnership with National Geographic and the Smithsonian.  The authors promised that a more detailed monograph was near completion and would verify all their claims.  Nearly three years later, we're still waiting.

tl;dr  The paper's main points:

a) all North African spinosaurine material can be lumped into Spinosaurus aegyptiacus
b) Stromer's photographed original Egyptian holotype (lower jaw and dorsal spines/verts) are not diagnostic
c) a neotype specimen of Spinosaurus is assigned composed of the pelvic girdle and mostly complete hindlimbs of a juvenile from Morocco, it compares favorably in basic proportions with Stromer's "Spinosaurs B"
d) this neotype was found in association and collected over the course of several years both by the authors and local fossil hunters
e) a composite Spinosaurus skeleton using scaled up specimens is created revealing the low slung and short legged profile
f) the far forward center of gravity, long forelimbs, long torso, and short hindlimbs suggest Spinosaurus moved quadrupedally
g) theropods can't pronate their hands, so Spinosaurus must have walked on its knuckles
h) the hindlimbs have very high bone density, a feature of aquatic animals that aids in stability
i) digit I of the neotype's foot is elongated and lowered.  This and features of the claws suggest the feet were webbed
j) all of these features combine to suggest Spinosaurus was heavily adapted to a specialized aquatic/semiaquatic lifestyle
k) features of the vertebral spines suggest they were only covered with a thin layer of skin and did not form a fatty hump

While a lot these sound good, many took issue with what hard evidence actually supported these theories.  Point for point, here's what many paleontologists and interested amateurs were concerned with upon reading the paper:

a) the Baharian fauna of Egypt and the Kem Kem fauna of Morocco are similar, but not identical.  In fact, they share no tetrapod species in common except for one or two unreliable tooth-taxa.  They also differ in age, with the Kem Kem spanning a much longer segment of time and is poorly constrained.  Why then should all spinosaurine material be assumed to be Spinosaurus aegyptiacus, especially when there is little overlapping material?  The following year, Evers et al. provided strong evidence the Sigilmassasaurs was valid based on a comparison of neck vertebrae from the Kem Kem.  They demostrated this environment contained at least two, possibly three, large spinosaurines.  AFAIK, this is the only peer-reviewed and published rebuttal to Ibrahim et al.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4614847/
Quadrate morphology also supports conclusion of multiple spinosaurines in the Kem Kem:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0144695
b) though destroyed, Stromer's original holotype survives through his excellent notes, sketches, and several photographs.  It is diagnosable and therefore valid.
c) the proposed neotype shares no overlapping features with the holotype to ensure it's the same taxon, this combined with the differences described in point a) preclude its use as a neotype for Spinosaurus.  Stromer, did not collect "Spinosaurus B" himself, and was not convinced it actually belonged to Spinosaurus.
d) remains from the Kem Kem are not usually found in association and local fossil hunters have been known to "jig-saw" together fossils found "in association" to form more complete looking specimens, throwing out whatever they think doesn't match from the bonebed.  Without more details regarding the collection of the specimen, its status is questionable.
e) even assuming all the specimens actually belong to Spinosaurus aegyptiacus, how do we know limb proportions wouldn't have changed with ontogeny, as they did in some other dinosaurs?  Also, the position of certain vertebrae was reassigned with little explanation, adding to the long-bodied look.
f) the proportions aren't totally out of range for certain bipeds, but yes, the resultant skeletal does look like it would be a quadruped.  Scott Hartman argued the hindlimbs hadn't been scaled properly based on the paper's own measurements.  The original authors responded that they had and the skeletal's legs were meant to be bowed slightly, hence they looked smaller.  Hartman corrected for the this and still got results that were slightly off.
g) Spinosaurus' knuckles are largely unknown and no theropod is known to have knuckle walking features.  Theropod forelimbs and pectoral girdles are not oriented properly to bare significant weight; the authors share no relevant features to indicate Spinosaurus was any different in this regard.  A good review of the topic and more:
https://qilong.wordpress.com/2014/09/12/the-outlaw-spino-saurus/
h) assuming these come from a single animal, this seems reasonable
i) assuming these come from a single animal, this seems reasonable
j) apart from the proposed quadrupedal gate, this seems reasonable for spinosaurines in general.  It's not a novel idea, it's been suggested several times.
k) this seems reasonable

I haven't bothered to link the many good blog articles on the topic.  The best ones are to be found at Skeletal Drawing.com, Mark Witton's Blog, the Bite the Stuff Blog, the Theropod Database Blog, the Theropoda Blog, and many more that I'm sure I've missed.

[Reptilia]

Thank you ZoPteryx.

[Halichoeres]

Nice review, Zopteryx, thanks for that

[ZoPteryx]

You're welcome. 

I should stress that, despite the critiques, there is a general feeling that Ibrahim et al. got close to the correct overall body shape for large spinosaurines.  Just the notion about it being a quadruped and perhaps the shape of the sail are off.

Also, relevant to the topic of this thread, there is apparently an undescribed theropod trackway from southeast Asia (Thailand, I think) that may be of interest.  I can't find the abstract I read it in to confirm, but as I recall, the tracks are said to have broad, four-toed feet... and a tail drag. 

[SBell]

You're welcome. 

I should stress that, despite the critiques, there is a general feeling that Ibrahim et al. got close to the correct overall body shape for large spinosaurines.  Just the notion about it being a quadruped and perhaps the shape of the sail are off.

Also, relevant to the topic of this thread, there is apparently an undescribed theropod trackway from southeast Asia (Thailand, I think) that may be of interest.  I can't find the abstract I read it in to confirm, but as I recall, the tracks are said to have broad, four-toed feet... and a tail drag. 

I think that was the biggest part of the Ibrahim et al. paper. That their review indicated a major change in how to view the body of Spinosaurus. There will very likely be revisions and updates--but it is such a surprising new framework, it is expected that a lot of confirmation work would be required! Major claims requiring major evidence and all!

[Cloud the Dinosaur King]

You're welcome. 

I should stress that, despite the critiques, there is a general feeling that Ibrahim et al. got close to the correct overall body shape for large spinosaurines.  Just the notion about it being a quadruped and perhaps the shape of the sail are off.

Also, relevant to the topic of this thread, there is apparently an undescribed theropod trackway from southeast Asia (Thailand, I think) that may be of interest.  I can't find the abstract I read it in to confirm, but as I recall, the tracks are said to have broad, four-toed feet... and a tail drag. 

These footprints are probably from a Siamosaurus.

[ZoPteryx]

You're welcome. 

I should stress that, despite the critiques, there is a general feeling that Ibrahim et al. got close to the correct overall body shape for large spinosaurines.  Just the notion about it being a quadruped and perhaps the shape of the sail are off.

Also, relevant to the topic of this thread, there is apparently an undescribed theropod trackway from southeast Asia (Thailand, I think) that may be of interest.  I can't find the abstract I read it in to confirm, but as I recall, the tracks are said to have broad, four-toed feet... and a tail drag. 

These footprints are probably from a Siamosaurus.

Possibly.  They could also be from Ichthyovenator.  But without knowing the exact age of the prints or foot material from either taxa, it's impossible to know for certain.

[Cloud the Dinosaur King]

You're welcome. 

I should stress that, despite the critiques, there is a general feeling that Ibrahim et al. got close to the correct overall body shape for large spinosaurines.  Just the notion about it being a quadruped and perhaps the shape of the sail are off.

Also, relevant to the topic of this thread, there is apparently an undescribed theropod trackway from southeast Asia (Thailand, I think) that may be of interest.  I can't find the abstract I read it in to confirm, but as I recall, the tracks are said to have broad, four-toed feet... and a tail drag. 

These footprints are probably from a Siamosaurus.

Possibly.  They could also be from Ichthyovenator.  But without knowing the exact age of the prints or foot material from either taxa, it's impossible to know for certain.

Ichthyovenator lived in what is now Laos, China so it probably wasn't an Ichthyovenator.