Giant theropods overview thread

[creature386]

Maybe the impact isn't so huge, but this is how I can explain that a lighter animal needs thicker legs. Even though, somebody could also say that Tyrannosaurus has only half as many weight-carrying legs, so I may need to retract this.

[blaze]

Titanoceratops, a 6m axial length ceratopsian also has leg bones as thick as those mammoths, me thinks mammoths (and proboscideans in general) just are not as athletic as similarly sized dinosaurs so they don't have the need for really robust limb bones.

[Godzillasaurus]

What exactly are you implying by "robust"? Longer but yet more gracile legs like we see in many maniraptorans, primitive theropods, small ornithopods, etc are actually the most ideal for speed and agility. Quadrupedal dinosaurs with robust limbs like triceratops would have more than likely used strength-related methods for defense as opposed to agility (take note of its skull, frill, and horns- common in many ceratopsians)

[blaze]

Longer lower legs you mean, long proximal segments of the leg (humerus and femur) are characteristic of slower moving graviportal animals, this configuration is necessary at great sizes but in dinosaurs we don't really see it expressed in an "elephant-like" fashion until we reach sauropod sizes, large theropods and ornithichians still retain digitigrady and are at least sub-cursorial in the proportions of their legs despite approaching or surpassing the size of the largest mammoths so IMO, it is no surprise that they posses more robust proximal limb bones than similarly sized fully graviportal animals like proboscideans whose bones were not subjected to the same amounts of stress.

Though I'm writing this for memory so I concede that I can be wrong.

[creature386]

Jul 16, 2014 0:38:42 GMT 5 Godzillasaurus said:

What exactly are you implying by "robust"? Longer but yet more gracile legs like we see in many maniraptorans, primitive theropods, small ornithopods, etc are actually the most ideal for speed and agility. Quadrupedal dinosaurs with robust limbs like triceratops would have more than likely used strength-related methods for defense as opposed to agility (take note of its skull, frill, and horns- common in many ceratopsians)

Athletic doesn't have to refer to speed or agility. Strength like you mean it can also be what blaze meant by athleticism.

[theropod]

The majority of mammal leg bones also has a medullary cavity that doesn’t contribute to weight-bearing, it is just filled with marrow, not air. There is certainly some degree of variation in the size of this cavity though, very likely related to both lifestyle and phylogeny.

The reason why T. rex’ femur is so thick by comparison is that its legs aren’t collumnar. In a collumnar leg, tickness is of less importance because the loads imposed on the bones are mostly compressional (i.e. it is important how much weight-bearing tissue there is, not how it is distributed). In a cursorial animal, the articulations are usually (and this is the case in theropods) somewhat bent by default, especially if it is a biped, and thus the bones have to be much more resistant to bending.

Either way, there are obvious problems associated with this if yoiu try to use it for estimating body masses. Perhaps bone crosssection (I mean the crosssectional area of the cortical bone of course) would be a more reliable metric, as in theory this should correct for part of the factors not directly correlated with weight, but I don’t think this was ever attempted.

[Dakotaraptor]

events.nationalgeographic.com/events/exhibits/2014/09/12/spinosaurus-lost-giant-cretaceous/

I am not only person that thinks the legs look very funny. I could expect that Spinosaurus may be not long-legged animal but not very short-legged like this, unless this is composition just like "Drouot Spinosaurus" (an 8 m juvenile one). I'm not surprised that many people in CF are disappointed because of reconstruction, which reminds the model from Milan. Hope there will be soon another details and informations about "new" Spinosaurus.

[theropod]

Especially because those legs aren’t only very short, but also very thin and yet have the built of relatively normal theropod hindlimbs: Those legs just don’t look as if they could support the body of that animal, and neither do they look as if they were adapted for swimming.
In the absence of better data I consider it most likely that this is a composite including the hips, hindlimbs, tail and perhaps also forelimbs of an individual that’s too small for the skull and torso.

Also the whole story doesn’t seem fixed on the science, it’s mainly sensationalistic about how it was discovered–remarkably without giving any details.

[Deleted]

It looks as if it's arms would do a better job as legs than those puny things. I seriously doubt the validity of the skeleton.

Anyway, here's Scott Hartman's thoughts on the mount:

"I know of it, but I haven't seen the details (e.g. whether it's a composite skeleton or not; for example the tail doesn't look like the centra are the same scale as the rest of the animal). I've rather assiduously not copied the data because it's never been officially shared with me, but I'm sure I'll have to make at least a few updates to my skeletal when it's published/revealed."

"And I agree, the hind limbs (and pelvis) look small. But again, we'll see "

Even he thinks the legs are too small.

[blaze]

lololol

I rearranged the legs so they are in a neutral standing posture.

[Infinity Blade]

^ROFLMAO!

[creature386]

LOL.

But not really surprising when looking at this picture:

There the forelimbs are already not far from the ground. But before mocking this, I will simply wait for a good explanation of the new Spinosaurus' lifestyle.

[Infinity Blade]

Luis V. Rey's reconstruction based on the mount.

luisvrey.wordpress.com/2014/08/13/that-was-then-this-is-now/

[Fragillimus335]

Even Rey's reconstructed legs are way bigger than in the skeleton! That thing has a femur ½ the length of its skull! THE THEROSNAKE RISES!!!

[creature386]

Is this just me or does the tibia appear surprisingly large compared to the femur? I know, the proportions are similar to Suchomimus, but wouldn't one, due to size allometry, suspect that a theropod as large as Spinosaurus would have a pretty long femur to carry the weight? Looks like this animal was really a lot more aquatic than we thought.