|
|
Post by Ceratodromeus on Jan 10, 2015 6:26:20 GMT 5
I find it somewhat pointless too, since those are rarely congruent with taxa actually diagnosed based on body fossils. Members of one ichnogenus are very unlikely to actually have been members of the same genus in life, so why bother calling it an ichnogenus based on nothing but rough morphology? Maybe that’s because in terms of genera, palaeontologists are splitters, but I think it makes more sense to try and establish as best was possible to what non-ichnotaxon an ichnite could be referred to. But what does that abstract say about size? it talks about the size classes these ichotaxon were assigned to, but only briefly. |
|
gigadino96
Junior Member
Vi ravviso, o luoghi ameni
Posts: 226 
|
Post by gigadino96 on Jan 10, 2015 23:51:45 GMT 5
|
|
|
|
Post by Infinity Blade on Jan 11, 2015 0:25:06 GMT 5
Very interesting indeed...
|
|
|
|
Post by Ceratodromeus on Jan 12, 2015 10:06:41 GMT 5
Does any one have info on "Edmarka" rex?
|
|
|
|
Post by spinodontosaurus on Jan 13, 2015 6:30:03 GMT 5
It's most likely synonymous with Torvosaurus tanneri, and is not any larger either. From a brief exchange me and Blaze had on Carnivora in June 2013: I think you made some mistakes, CPS 1002 is actually a scapulocorocoid and the 950mm figure is not only the scapula, basing it on Hartman's Torvosaurus (which is scaled to the size of the subadult holotype, apparently) it's only 20% bigger thus assuming isometry, it gives a 10m long individual, the jugual (CPS 1005) is only 5% bigger than the adult from dry mesa, which is in turn 18% bigger than the subadult individual (24% bigger in total) which gives us an estimate of 10.3m long, the first caudal is only 17% bigger from the ones from Dry Mesa, I don't know if they're supposed to come from the adult or the subadult, Hartman's Torvosaurus seems to follow it being from the subadult (since he incorporates unpublished material I think he would have a better idea of those things) thus it leads again to an individual around the 10m mark, slightly bigger than the Dry Mesa adult. (edited) Now, the pubic elements do give high estimates as they are 56% (CPS 1010) and 43% (TATE) bigger than the one in Hartman's Torvosaurus (so 12.9 and 11.9m as you got too) but that is if they grow isometrically with ontogeny, which seems to not be the case as they (at least CPS 1010) have a different shape than those known from Torvosaurus, so going by single measure doesn't seem reasonable. In fact CPS 1010 was originally identified as a sauropod pubis (and it looks a lot like a Barosaurus pubis to me) but Bakker et al gave some features of why its referable to a megalosaur and in turn to "Edmarka" but here's the catch based on its length and the breath of the iliac articulation they consider it to belong to the same individual as the scapulocorocoid, thus "Edmarka" being a Torvosaurus specimen around 10m long is most parsimonious, though whatever if it actually belongs to a megalosaur is another matter, Carrano et al. (2012) doesn't include it in the hypodigm of Torvosaurus, maybe it did belong to Barosaurus after all. |
|
|
|
Post by Ceratodromeus on Jan 13, 2015 21:44:03 GMT 5
Thanks for the info!
|
|
gigadino96
Junior Member
Vi ravviso, o luoghi ameni
Posts: 226
|
Post by gigadino96 on Feb 26, 2015 19:41:28 GMT 5
|
|
|
|
Post by theropod on Feb 26, 2015 19:56:49 GMT 5
|
|
|
|
Post by Grey on Apr 13, 2015 13:34:59 GMT 5
A Belgian biologist I'm in contact with (the one who had seen the megalodon backbone when kid) once showed that huge partial carcharodontosaurid dentary, probably Carcharodontosaurus, on a French forum (2006). He made a description of it because it was going into a private collection (sadly as ever) and could never be studied. It's from the Cenomanian in the Kem Kem Beds. He didn't know specifically the size of the piece but this pic might give an idea. I have the impression that this dentary seems even more massive than MUCPv-95 :    Yes, a supreme shame it is in private hands. |
|
|
|
Post by theropod on Apr 13, 2015 16:30:35 GMT 5
A Belgian biologist I'm in contact with (the one who had seen the megalodon backbone when kid) once showed that huge partial carcharodontosaurid dentary, probably Carcharodontosaurus, on a French forum (2006). He made a description of it because it was going into a private collection (sadly as ever) and could never be studied. It's from the Cenomanian in the Kem Kem Beds. He didn't know specifically the size of the piece but this pic might give an idea. I have the impression that this dentary seems even more massive than MUCPv-95 : Yes, a supreme shame it is in private hands. I think you once posted the same photos on Carnivora (actually after I had seen it, I corrected my Carcharodontosaurus skull to have the same deepened symphysis). It looks huge, but of course the pictures alone do not allow a conclusion. It certainly wouldn't be too surprising if that were true tough. It truly is aa shame, why aren't there any laws that prevent private collectors from snatching away such specimens, or at least allow access for scientific study? I also don't understand why fossil collectors are so unwilling to allow others to study and publish on their specimens, if I had a 20cm shark tooth or a giant carnosaur dentary, I'd want to share it with the world. Instead it seemms like those people purposefully lock their stuff away just so that others can't benefit from it! |
|
|
|
Post by Grey on May 5, 2015 13:56:49 GMT 5
|
|
|
|
Post by theropod on May 5, 2015 18:15:36 GMT 5
I only have the abstract, but if their model is really only 6t in mass but has a 1.6m skull, then it is severely shrinkwrapped (not totally surprising, not all modeling studies utilize accurate models and this becomes all the more unlikely when something has no currently known postcrania). No wonder then that the neck is so relatively weak and that the bite force estimate is only about a sixth of what would be expected (from multi-body dynamics simulations of related taxa), while the COM position turned out to be the least constraining factor.
If we use bite force estimates based on a consistent method (which correlate with head mass, and thus in some way also dorsiflexor strength) as a proxy, we'd expect a large Tyrannosaurus to be twice as strong a large carcharodontosaur. However, while it has a much stronger bite force, the COM position puts a natural limit on how much any animal with this body plan could lift (independently of bite force, if not less in an animal that already has a heavier head), hence excessively greater strength in the neck, beyond the amount needed to support the head may or may not have actually been useful and present.
So the question is if a realistic model (at least 2t heavier than estimated) would be more constrained in terms of its need to balance bipedally than by the jaw and neck muscles.
Neither can be expected to be able to support itself upright with an additional load of more than 3t in its jaws (and most likely less), which is close to the posterior bite force expected for SGM-DIN 1 (based on Bates & Falkingham 2012), hence the effective lifting strength difference may end up insignificant, regardless of the relative strength in the jaws and neck.
But then, obviously, at such forces Carcharodontosaurus' teeth would not be effective at gripping anything, they would likely slice off the sauropod's head. So in the end, yes, I suppose Tyrannosaurs would have greater lifting potential simply because their teeth were blunter.
An interesting simulation would be how much pulling force their respective teeth could excert before tearing through the flesh (or breaking).
Another question would be why a giant theropod would want to lift a large prey item. Energetically that would be costly very costly, an inefficient way of moving.
To answer your question, no, there were no equivalent studies. Hypothetically speaking, if there was a direct proportionality between bite force and dorsiflexor strength we’d expect it to be more powerful, but given the problems I mentioned the question would be whether it could use that without toppling.
---Reference:
Bates, Karl T.; Falkingham, Peter L.: Estimating maximum bite performance in Tyrannosaurus rex using multi-body dynamics. Biology Letters, Vol. 8 (2012); 4; pp. 660-664
|
|
|
|
Post by Grey on May 18, 2015 22:19:30 GMT 5
A Belgian biologist I'm in contact with is rather skeptical about Hartman depiction of the skull in Giganotosaurus and is still in the belief it could be 1.95m in the second specimen.
I love Scotty's work but I don't understand why Coria would have exaggerated at this point. Scott's reconstruction moderately convinces me because he does not take into account the increased length of the jugal branch. You just have to look at Eocarcharia which has a perfectly preserved maxilla. It's also notable in one of the Mapusaurus specimens. The reconstruction by Scott does not take into account this anatomical part and drastically shortens it. Or, Giga's holotype shows a preserved maxilla in two parts but the caudal part is missing. Now we can speculate on the length of the missing part.
|
|
|
|
Post by theropod on May 19, 2015 0:35:09 GMT 5
True, we can only speculate on the length of the missing part of the maxilla (I have demonstrated that in my digital reconstructions I think), but Hartman’s version is more in line with other carnosaurs with complete maxillae, while 1.95m seems hartly feasible. It might have based on a scalebar error in the holotype’s description in the first place, the reconstruction as shown there is not actually consistent with a 1.8m skull length as later claimed by Calvo & Coria, but it’s scalebar made it seem as if that was the case.
|
|
|
|
Post by Ceratodromeus on Jun 5, 2015 23:59:34 GMT 5
|
|
