Quadruped Spino... GONE!

[War Bear 112]

Well, wasnt it something about the two not matching?

[albertonykus]

To reiterate what has already been said:

The main point of the paper is whether the vertebrae given the name Sigilmassasaurus are the same as Spinosaurus (as argued by the proponents of the new Spinosaurus model last year), not any issue regarding the legs.

However... the paper does discuss the possibility that the limb proportions of the new Spinosaurus are incorrect. It does not discuss any implications regarding stance and locomotion.

The focus of the paper is on vertebrae, but it does have some commentary on the legs:

The proportions of the new remains, specifically the disproportionally small pelvic and hindlimb remains, were used by Ibrahim et al. (2014a) to suggest very unusual leg proportions in Spinosaurus, noting that these unusual proportions are also found in the material of “Spinosaurus B,” thus allegedly supporting the association. As outlined below, however, there are significant anatomical differences between the appendicular remains of the ‘neotype’ of Spinosaurus aegyptiacus and the remains described as “Spinosaurus B,” so unless one assumes that these specimens represent closely related taxa with very similar proportions, but differences in limbbone morphology (for which there is no independent evidence), this coincidence in proportions is of doubtful value to prove association. As noted above, Stromer (1934) did not provide any evidence for original association of the remains described as “Spinosaurus B,” other than that they were found at the same spot (which would also be the case for non-associated materials resulting from a bone bed). However, it is striking that in both cases there is a set of matching vertebrae on the one hand, and a set of matching limb elements on the other hand.

While by no means falsifying Ibrahim et al.'s proposed limb proportions, these authors do take a somewhat skeptical view of them. Mark Witton has a blog post summarizing their main points, a good alternative to reading a one-hundred-page paper if one is short on time.

[Alijar]

Okay, so I know we're not talking about the legs here, but I think that the legs on the original presented model are from a younger spinosaurus than the rest of the skeleton is (unless someone can find me apart of an article that proves the age of the leg bones to be the same age as the rest of the skeleton).
But yeah, R.I.P quadruped spino. You set forth to be a new interesting idea, but was shot down immediately and then had your corpse prodded with a stick.

[Flishster]

It would be a weird coincidence for tiny legs being found with a Spinosaurus to happen twice.

[ShadeOfEclipse]

Even if it's not about the legs, I always thought something was.... not right about the skeletal reconstruction tbh. Idk why but I just had that feeling. XD

[Zillatamer]

Thanks Albertonykus, forgot to mention that bit.

Idk why but I just had that feeling. XD

God dammit.

[ExperiMUNt]

I understand that this artical about it being it's vertabre, but even then something still feels very unatural of how long it's torso is. If it were a biped, it's neck and tail would need to be incredibly long in order to balance things out properly, otherwise it'll just topple forward like an unbalanced table. I'm still thinking that it could still be a quadruped, but I guess we will still need to wait for a while until a complete skeleton is found. The Spinosaurus head is very similar shaped to that of a crocodile, and I was actually really happy when before they theorized that it was a quadruped. It just looked a lot more natural IMHO.

[Evan Chojnowski]

I was convinced quading was already out of the picture, but im still convinced it had legs to short to be useful for anything other than walking on land.



unless larger legs were found?

[ExperiMUNt]

It could have walked like a parasaurolophus. When it would run, it would stand up on its two hind legs and go, or when it was walking it would roam around on all fours. You can tell though how the spinosaurus would be more of a water-dwelling reptile compared to todays modern gators, crocs, and caimans.

[Zillatamer]

You all clearly don't actually know physics or biology; stop pretending that you understand the consequences of short legs in animals, or the distribution of mass in Spinosaurus.

Short legs don't alter the animal's balance; in theropods and humans the center of gravity (which doesn't actually have to be a position in or on an object) is placed above the feet for standing and slow walking, and for both groups the hips are typically placed above the feet (but not exactly so), while in quadrupeds the center of mass is between the limbs. In bipeds any mass below the hips is irrelevant to the distribution of weight in front of or behind the hips, which is what determines balance. Does a scale work differently if the center is higher? No, that would be silly.

The elongated body however does make a difference, but not nearly as much as you all seem so sure of for some reason. Firstly, take a look at these guys here. Note that more mass seems to be in front of the animal's hips in both cases. We don't think of T.rex, Giganotosaurus, chickens, or ducks as being front heavy like we do with the new Spinosaurus, but they're all just varying on the seeming extremeness of this sort of mass distribution. The other animal's don't fall over for several reasons, one of which being that the front isn't that much more massive than the back, and that the center of mass and distribution of gravitational forces can be altered by changing the angle(s) of the body, and the legs.

The chest cavity of a Rex or Spino would be partially hollow due to the lungs and air sacs, while the tail would be all bone and muscle, and would be much more dense as a result, so the weight differences of the torso and tail probably aren't as extreme as you'd think. It would also be wrong to assume much on the basis of mass distribution, since we don't have soft tissues or a good idea at all of the muscular composition of the animal or its thoracic cavity.

More importantly, the center of mass can be changed by altering the angle of the spine relative to the force of gravity, and by altering the angles of the leg bones; stance makes a difference. That's how people can assume crazy positions and movements without falling from more mass being in front of the hips.

http://cdn.phys.org/newman/gfx/news/...mputersimu.jpg

If the mass moves forward, the feet have to move forward, and birds do this by both crouching, and angling their front bits upward.

Best shown here, and here.

A Rex would fall over if it tried to keep its body perfectly horizontal with its feet right next to each other like this:



That's obvious, so why do people continually draw bipedal Spinosaurus in that same sort of position, when we know it's impossible? Drawing it that way reinforces the idea that it couldn't stand that way, sure, but the solution should then be to draw it in a way that does make sense. You could do that by drawing it as a quadruped, but the more parsimonious explanation would be to draw it as a biped with a modified stance from less elongated bipeds.

Bringing the body up, and the tail down by crouching would put its mass over the feet just fine as shown on these blog posts:

http://theropoda.blogspot.co.uk/2014...io-iv-una.html

http://prehistoricbeastoftheweek.blo...l-of-week.html

Once again there is not, nor was there before, any particularly good evidence to assume Spinosaurus was quadrupedal, and also no good reason for you all to doubt the leg proportions from a lack of understanding of biology of physics.


EDIT:


This image from Tomozasaurus shows the duck-like stance pretty well, with the an different sail that is still possible given the data we have.

[John Jurgo]

I really just wish a near complete fossil skeleton could be found, just so people would stop arguing about this.
And I want to know what it really looked like.

[Evan Chojnowski]

-accurate spino pic-

so its still very awkward and short legged.
meaning its still most likely an aquatic therapod yes?

about the sail though

(red bones are the ones that have been found)

are you sure it would still be a giant half oval?

[Zillatamer]

are you sure it would still be a giant half oval?

Did you not read? I wrote that it was speculative, as in we do not know enough to rule it out. The extent of the dip in the general population of Spinosaurus, from concave to essentially flat as shown in Tomo's picture, is unknown.

[Evan Chojnowski]

no need for the insult. i read... but with how the vertebra are (the ones shown) have been found, isn't that enough to show that it didn't have the type of sail shown in the lovely picture by Tomozasaurus? isn't it enough to disprove that speculation? or at the very least make it unlikely?

[Eriorguez]

We have a caudal spine. Ibrahim et al. just assumed it was the very first neural spine without any solid evidence.

In fact, Ibrahim et al. made plenty of bold statements without bringing matching bold evidence. I mean, quadrupedal theropod without knowing its forelimbs? Come on, it sells well, but you are being a piss poor scientist.

Compare and contrast the Deinocheirus paper from the same month, heavier on the science and evidence part at the cost of dry ice.