Giant theropods overview thread

[blaze]

	Head	Neck	Body	Tail	Forelimbs	Hindlimbs	Total
Bates et al. (2009)
Stan	679	334	3308	1106	24	2204	7655
MOR 555	651	442	1932	1079	20	1942	6066
Fran	398	306	2607	1149	25	1693	6178
Hutchinson et al. (2011)
CMN 9380	390	365	4271	858	13	1498	7395
Stan	383	190	3214	587	21	1539	5934
MOR 555	640	421	2039	1196	18	1463	5777

Here, a table of estimated weights of 3 T. rex specimens and one of Acrocanthosaurus. The 3 T. rex are pretty much identical in known measurements so being able to see where their estimated masses differ and why MOR 555 is that much lighter than Stan and one study and why both of them are of comparable weight and much lighter than CMN 9380 in another lead me to re-think my views on femur circumference in theropods and how it relates to mass, it seemed to me now, to be more predictable than I previously thought but then I remembered that I still don't understand why there are T. rex that have comparable femur circumference to those 3 but are, by all other measurements, much smaller in body size... So I don't know what to think.

[Dakotaraptor]

Hutchinson et al.'s paper has probably some big "glitches"
Stan's tail being over 2 times lighter than Wankel's one? Also i don't believe in Wankel having much heavier head, because it doesn't seem to be impressive by T. rex standart.

[blaze]

The heavier head is attributed to the low resolution of the scans. The tail of Stan, is not a glitch, it's just how the model ended up being fleshed out, the tail was left too skinny IMO.

Edit:

Some other interesting measurements, according to Currie and Carpenter (2000) the centrum of the 10th dorsal of Fran, the Acrocanthosaurus atokensis, is 135mm long and 138mm wide, while that of the T. rex MOR 555 is 145mm long and 180mm wide. Based on the photos and the vertebral height given in Brochu (2004) I got the measurements of 160mm long and 220mm wide for the same vertebra in Sue.

[theropod]

The Siats meekerorum description is now online: www.academia.edu/5224818/Neovenatorid_theropods_are_apex_predators_in_the_Late_Cretaceous_of_North_America
www.researchgate.net/publication/258829865_Neovenatorid_theropods_are_apex_predators_in_the_Late_Cretaceous_of_North_America

[thesporerex]

Jan 18, 2014 18:09:42 GMT 5 theropod said:

The Siats meekerorum description is now online: www.academia.edu/5224818/Neovenatorid_theropods_are_apex_predators_in_the_Late_Cretaceous_of_North_America
www.researchgate.net/publication/258829865_Neovenatorid_theropods_are_apex_predators_in_the_Late_Cretaceous_of_North_America

Finally some good data on siats

[theropod]

sources: theworldofanimals.proboards.com/post/10170

from top to bottom, left to right: Suchomimus tenerensis rostrum, Cristatusaurus lapparenti premaxillaries, Baryonyx walkeri dentary, Spinosaurus aegyptiacus rostrum, Spinosaurus aegyptiacus dentary (holotype)

some thoughts:
-strangely, Baryonyx’ dentary seems similarly-large to that of Suchomimus (in relation to the snout). There may be a scalebar error here.
-Suchomimus’ dentary is longer than  its rostrum, even though the latter is considerably more complete in terms of lenght (actually) than Spinosaurus’. There is no way the holotype denatry can fit MNHM’s rostrum
-does anyone here believe Spinosaurus was just the weight of Suchomimus/Cristatusaurus? I for my part have trouble believing that.

[theropod]

I revised my Spinosaurus aegyptiacus:


Its really hard to find a compromise between the posterior half of the skull of Irritator, the mandibular and rostral stuff of Spinosaurus and the remaining bits of baryonychines, but I did my best.

[blaze]

Looks pretty good but I think you should also consider scaling in other views.

Jaime Headden did it and this is one of his figures from his latest post.

They fit well without requiring any scaling, the dentary scaled 120% already looks much bigger than the milan rostrum, how will 136% look? I agree with Headden that the two mandibles don't represent the same taxon.

[theropod]

I’ll do that when I go about the dorsal (or perhaps ventral?) view. There’s a reason I haven’t done that yet, I first want to make sure I get everything right. I can still revise this one should it suggest something different.

You could try scaling that dentary 13% bigger if you want to see what it looks like. I’m not convinced it would be unreasonable. Until then, I an fairly skeptical of restoring the dentary as proportionally shorter than in Cristatusaurus, just because it is a more massive element. Its deep shape is imo consistent with its diet of really big fish that would need some considerably resistance, especially in the mandible (thus why it’s so deep).
Actually the thin posterior rim (and this suggests the dentary is not missing all that much) makes perfect sense, since for a scarf joint it is necessary for the individual ends to taper.

Also I think the narrower mandible shape is more likely, based on this: upload.wikimedia.org/wikipedia/commons/8/88/KDDM_Suchomimus_Skull.jpg

Concerning the taxonomy, I’m unsure. I’m usually more of a lumper than a splitter (surprise, surprise! ). Anyway, I think it is subjective whether one considers them distinct species based on the evidence at hand.

[blaze]

It is also subjective that it is the same, given the lack of overlapping material, also, thanks to a comment by Cau I realized that indeed Dal Sasso et l. don't attribute it to Spinosaurus aegyptiacus but rather Spinosaurus cf. S. aegyptiacus.

But the narrower mandible will have the teeth misaligned, have you read Headden's post in its enterity?

[theropod]

Yes, the problem is simply that teeth from different specimens don´t necessarily fit perfectly (not to mention we have some issues with the number of teeth actually preserved...2 1/2...). You´ll likely encounter the same problem if you try to align random human jaws to random human skulls.

[blaze]

Misaligned with themselves not with those of the rostrum.

[Dakotaraptor]

If the MSNM's rostrum and BSP's dentary fit well in width, but not in length. Then there is possible that MSNM v4047 may have proportionally longer snout, rather than being significantly bigger clone of holotype. I don't rule MSNM v4047 and other kem kem Spinosaurus specimens might belong to different taxon than BSP 1912 VIII 19.

Edit: On the other hand there might be other factors like age etc. 

[theropod]

References:
1) DAL SASSO, C., MAGANUCO, S., BUFFETAUT, E. and MENDEZ, M. A. 2005. New information on the skull of the enigmatic theropod Spinosaurus, with remarks on its size and af?nities.
Journal of Vertebrate Paleontology, 25, 888–896.
2) STROMER, E. 1915. Ergebnisse der Forschungsreisen Prof. E.Stromers in den Wustern Agyptens. II. Wirbeltier-Reste derBaharije-Stufe (unterstes Cenoman). 3. Das Original des Theropoden Spinosaurus aegyptiacus nov. gen., nov. spec.
Abhandlungen der Königlich Bayerischen Akademie der Wissenschaften, Mathematisch-Physikalische Klasse, 28, 1–32.

[theropod]

Volume comparison of T. rex FMNH PR 2081 and Spinosaurus (cf.) aegyptiacus:

Using the measurements from here→ and the scaling from here→ and here→.

IPHG 1912 VIII 19
lateral area minimum=34160px²
lateral area liberal=41053²
width ratio: 0.588

MSNM V4047 (136% length/185% area/251% volume)
lateral area minimum=63182 px²
lateral area liberal=75932 px²
width ratio: 0.800


FMNH PR 2081
lateral area minimum=28919
lateral area liberal=28919
width: 1.00

This is only a rough comparison, however by comparing the product of the
lateral area of a equivalent regions by their transverse width, onecan gauge their relative volumes:

volume ratio:
minimum: 0.695 | 1.748
liberal: 0.835 | 2.100

This is obviously a far faster (automated) mathod than GDI, at the expense of not giving us an absolute result. We don’t need one, since a GDI for one of them has already been done.

Result: Spinosaurus could very well be thinner than the largest Tyrannosaurus and still be considerably larger in terms of volume, and thus mass. Claiming that because its ribcage is narrower it cannot be heavier is a fallacy.

IMPORTANT NOTE: Spinosaurus is almost certainly less pneumatic than T. rex. It’s dorsal vertebrae are basically solid bone, those of rexy are hollow or trabeculated altogether.

UPDATE: In the light of recent revelations about previously unknown material, the underlying assumptions of this post do not hold true any more.