Giant theropods overview thread

[coherentsheaf]

Cau makes a new argument regarding the vertebrae comparison:

theropoda.blogspot.it/2014/01/coming-soon-tyrannotitan-reloaded.html

A few thoughts:

This is definitely some (though not overwhelming) evidence against a biomechanical explanation other than size.

However Cau claims this to be exceptional disparity when it comes to biomechanical properties vertebrae. I dont think this is the case, as eg. ceterhinus vertebrae are considerably less robust than carcharodon vertebrae at equal body mass.


He also claims: "Since I've never been hypothesized adaptations cursors in carcharodontosauridi, this hypothesis to the vertebrae of Tyrannosaurus is falsified."
That is not the case. It makes the hypothesis less likely, it does not falsify it outright. Just because high cursoriality was hitherto not postulated does not mean it is not there.

Also note that Tyrannotitan still has a substantially less massive centrum than T.rex and that the entrum looks like it is flattened.

[Grey]

What is your source about Cetorhinus ? This species has relatively slender vertebra and is relatively slender for its size, but I've not seen any comparison of vertebra size at equal body mass, especially since Cetorhinus body mass datas are mostly rough estimates.

[coherentsheaf]

Jan 9, 2014 2:27:51 GMT 5 Grey said:

What is your source about Cetorhinus ? This species has relatively slender vertebra and is relatively slender for its size, but I've not seen any comparison of vertebra size at equal body mass, especially since Cetorhinus body mass datas are mostly rough estimates.

I have no specific sourc, but whenever I see such vertebrae, vertebrae from athletic species like Carcharodon look massive. In any case there are differences in bone dimensions between athletic and non athletic species adjusted for body mass. I a not in amood for digging them up, but you can go to carnivora and find literally dozens of these exampes in the various threads about bone and muscle interactions.

[Grey]

theropoda.blogspot.fr/2014/01/coming-soon-tyrannotitan-reloaded.html#comment-form

Cau : Yes, both vertabrae size and femur dimension (both lenght and diameter) in Tyrannosaurus and Tyrannotitan are comparable. Thus, it's plausible they has comparable mass.

[blaze]

Canale et al. 2014 Osteology and phylogenetic relationships of Tyrannotitan chubutensis Novas et al 2005 (Theropoda: Carcharodontosauridae) from the Lower Cretaceous of Patagonia, Argentina.

Was just uploaded to the Taylor & Francis Online website some hours ago,

When's the osteology of Giganotosaurus coming? it's been 19 years.

[creature386]

Great!
I just posted it in the profile.
Canale's new paper seems to support the Giganotosaurini affinity of Tyrannotitan, so it looks like the Clarke and Eddy were the only ones, who don't believe that Tyrannotitan was closely related to Mapusaurus and Giganotosaurus.

[theropod]

That’s interesting. The description of Siats also supports this phylogenetic assignment. There are several works now that consider Tyrannotitan the closest relative of the Giganotosaurus+Mapusaurus-clade.
It would be very interesting to read that osteological description. We’re really in need for one, not just here but especially in Giganotosaurus.

I hope there’ll be an accessible document available soon.

However I’m pretty sceptical of the assertion that the Tyrannotitan paratype (comparable to MUCPv-Ch1 in terms of femur and skull dimensions) was as massive as the biggest T. rex, just because of femur and vertebral diameters.
Note that claim has been made earlier and with the same methodology about Giganotosaurus (albeit not necessarily with sue back then), and now it’s generally considered not just unlikely but downright laughable by the very people who hang on Cau’s every word.

Also, its cursoriality is totally unknown, one would expect Cau to acknowledge that since he doesn’t use inference from relatives elsewhere. A thick femur is a typical feature of cursorial animals.

[blaze]

A thicker femur but most of that thickness could be attributed to its relative shortness, assuming Carrano et al (2012) measurement for the length of the femur of MUCPv-Ch1 is correct, the paratype of Tyrannotitan has both the longest and thickest femur known of any Carcharodontosaurid, only surpassed by 4 T. rex specimens which is the best sampled giant theropod we have.

[theropod]

I meant thickness without an accompanying pneumatisation index or cortical thickness is not very relevant to the capacity of the bone in weight bearing, which is one of the reasons why we see similar-sized carcharodontosaurids having femora indicating a weight only a little more than half that of a Tyrannosaur.

T. rex tend to have thicker femora than presumably less cursorial carcharodontosaurs, even if the latter have femora that are significantly longer. The fact alone that Tyrannotitan is comparable in thickness to the very largest and thickest T. rex femur indicates it is quite robust, albeit also overally larger.

[blaze]

Well, that of the holotype has a circumference comparable to several T. rex that have femora of the same length mmm

anyway I don't think it weighted just as much as Sue, but Cau said comparable, which doesn't necessarily mean the same weight.

[creature386]

Not necessarily the same weight, but I don't think 100 or 200 kg difference will be very interesting for this discussion, but I don't know how Cau defines comparable.

[Fragillimus335]

Someone needs to chain up Scott Hartman until he does his Spinosaurus GDI, lol...

[creature386]

A Spinosaurus GDI would be a bit pointless, most of the skeleton is guesswork.

[gigadino96]

Still nothing about this? Pretty strange.

translate.google.com/translate?u=http%3A//theropoda.blogspot.it/2014/01/bio-ingegneria-di-un-gigante.html&hl=en&langpair=it|en&tbb=1&ie=UTF-8

Also, I think that this Cau's post will be the start of a big Tyrannotitan fanboysh.

[Dakotaraptor]

I am not suprised some people will say the cranium is too small compared to rostrum.