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Post by Grey on Jan 5, 2014 1:57:30 GMT 5
Again, I do not compare McHenry's work to Siversson's, I'm well aware Siverson gives more conservative figures (as I noted in my post) in general. I'm simply comparing the weight for a 9m lamniform (based on several regression equations) to that estimated for a 10.5m Kronosaurus. I gave reasons why I think 5t are not a realistic weight figure for the latter. Yes, closer for average-sized specimens of Kronosaurus, but so will be smaller figures for Cardabiodon. Perhaps McHenry's estimate is a bit too massive, but based on Coherentsheaf's GDI of Rhomaleosaurus it would still have a weight advantage even then, and as he stated, Rhomaleosaurus is comparatively slender. It is true Forrest was even more conservative, but neither he nor Siversson gave any method supporting such low weight figures. blaze: Not sure what it was meant to represent. But 9m doesn't seem to be the average Cardabiodon. Sorry about the pachyderms  What I explain is that whatever Siversson's estimate for the shark, it appears to be stockier than Carcharodon at parity length. At 9 m, a stocky Cardabiodon is already in the weight range of the largest known Kronosaurus. Really as heavy or heavier is a matter of discussion. Siversson, without a doubt aware of McHenry works, suggests this shark was potentially heavier than Kronosaurus. I do not question McHenry estimate, but if his Kronosaurus is a bit too heavy and Siversson's 9 m Cardabiodon a bit too light, both are clearly in dispute weight wise. No need to start to discuss average size or so, Cardabiodon is known by few species, very few specimens, from different locations. And I don't count the average/smaller Kronosaurus specimens here. The best would be to get additionnal information from Siversson who's the actual guy specifically working on this species interaction. |
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Post by theropod on Jan 5, 2014 3:22:32 GMT 5
museum.wa.gov.au/explore/videos/rise-super-predatory-sharksSiversson seems to consider 5t (at ~10m TL) the upper bound for pliosaurs in this talk. Another quote from the Royal Tyrrell Museum talk (at 19:57): "TheyÂ’ve shrunk considerably. I think theyÂ’re down to 3, 4, 5, 6, 7 tons." It doesn't really sound as if he had estimated it using a rigorous method, it looks like this is a guesstimate, and it is evident from his phrasing that he does not consider it a certainty. By comparison, coherentsheafÂ’s Rhomaleosaurus would be 7.4t at that lenght, and McHenryÂ’s Kronosaurus (given it'd have to be scaled down and not just have a shorter tail or neck) 9.5t. 8t at 9m are stockier than a typical great white (around 1.3t at 5m yielding 7.6t at 9m was the average I got from elasmollet). 6-7t are not. Still, what exactly is it that suggests it was stockier (and, were does Siversson state it?)? According to Siversson, Cardabiodon was "up to 8-9m" (consistent with described fossils, which typically seem to be in large Carcharocles territory or slightly bigger, eg the holotype or the 125cm vertebra at 18:23 of the second talk) and ~7t. Lamniform lenght-weight regressions suggest a mean of 7.5t or a more liberal 8t at the upper end of this lenght range (Note that the upper end is assuming it had proportions similar to a great white, and in order to be bulkier it'd also have to be shorter). Kronosaurus could reach 10.5m, and volumetric models of pliosaurids by McHenry and Rhomaleosaurus suggest such an animal would be at least 8.5t. Note also that in the talks there's absolutely no notion of the shark being a "better predator" or a better fighter (not the same), and Siversson also did not imply that anywhere if I'm not mistaken.
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Post by Grey on Jan 5, 2014 3:57:31 GMT 5
His estimates for Kronosaurus are probably educated guess, but whatever the figure, he certainy considers Cardabiodon as a competitor in terms of body mass for Kronosaurus. This cannot be ruled out on the sole basis of McHenry's thesis.
Read my first comment from him in this thread :
The cardabiodontids were not only reaching a considerable adult total length (probably closer to 9 metres in the Albian) they were also most likely stocky in their build (indicated by the morphology of the vertebral centra), even more so than a white shark of comparable length(...)At that size they were probably well beyond the upper prey-size range of adult Kronosaurus. They may simply have been more efficient at catching the same prey and thereby contributing to the demise of the giant pliosaurs.
Siversson primarily suggests in his research and talks that these sharks won the battle for supremacy against the pliosaurs and, in the mail, that they may have been better at capture preys.
Then he suggests, in his talk, that large cardabiodontids were potentially heavier than Kronosaurus.
I recall that Siversson's main field is the Cretaceous marine environments (just looking at his publicatons) and being from Australia and a direct colleague of McHenry, we cannot assume he's not aware of McHenry's thesis. At this time it is pointless to discuss more of this as the main factor to know for this match is to know how can be compared in size Cardabiodon and Kronosaurus.
McHenry gives a weight of 11 tonnes for Kronosaurus (or perhaps a bit less) but he did not work on Cardabiodon.
Siversson gives rather lower figures for Kronosaurus for some reasons but he's clearly suggesting that Cardabiodon was a direct rival in size to Kronosaurus. The best would be to get more clues from Siversson and not try to reach a premature conclusion without more details. Asking him why does he give to Kronosaurus such low figures, what about his colleague estimate, and then were really the cardabiodontids rivaling with the pliosaur.
Note that I've not concluded anything, only hinting of Mike Siversson specific research which is the most directly related to this thread and thus cannot be ignored and only using McHenry's. So no need to argue more until we get something new. I'm positive with Kronosaurus at 11 tonnes so being in the absolute the bigger predator but I ask to know more about Siversson claims, why Kronosaurus was potentially outsized by this shark.
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Post by creature386 on Jan 5, 2014 14:20:47 GMT 5
Wow, there seems to be quite a variation within estimates. When scaling McHenry's estimate for a five meter Liopleurodon to ten meters, I get roughly eight metric tons, which is more than twice as high as his lower limit. Even Sue didn't have such a great variation (4.5-9.5 t). I personally prefer McHenry's estimates, because they rigorously measured the volume of the animal. |
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Post by theropod on Jan 5, 2014 15:53:54 GMT 5
Grey: I'm not ruling it out solely on the basis of McHenry. As you saw I also consider Siverssons estimate for the shark too low. But comparison of rigorous estimates makes it seem unlikely that the shark would rival Kronosaurus, based on an alleged total lenght of 8-9m (rather 8 if it was considerably bulkier than a great white, since 9 bases on the exact same vertebral diameter/body lenght proportions. Anyway, I used 9t to make sure it didn't get too low). Asking to know more before concluding things is good (I think it should be clear that a conclusion at any given point can only be based on the available data, and can change any day), but if you ask me, it's simply because SiverssonÂ’s educated guesses (less massive than crocodilians at lenght parity) on Pliosaurid body mass are relatively and absolutely too low. creature386: That's likely because itÂ’s a guesstimate spanning over a range of 3 to 7t...
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Post by Grey on Jan 5, 2014 16:01:33 GMT 5
I don't keep in mind Siversson estimates here. I simply see a shark bulkier than a white shark reaching 9 m, so reastically in excess of 8 tonnes or so.
I never had any problem with McHenry estimate of 11 tonnes for Kronosaurus, even if it is possibe this one is a bit too massive.
Beside weights figures, Siversson proposes Cardabiodon as a potential rival in size for Kronosaurus. There we need to know why he thinks the shark was a rival if Kronosaurus really reached 11 tonnes.
I think you too much focus on this estimate from Siversson. I ignore it, keep in mind McHenry's data but also wonder about how can be properly compared in size Cardabiodon and Kronosaurus. If you can contact him...
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Post by theropod on Jan 5, 2014 16:28:21 GMT 5
At 9m it has the exact same proportions as a white shark. Keep in mind this figure bases on vertebral diameter. Since the bulkiness does too, it will be stockier only if it is shorter relative to its vertebral diameter (which, I think, is the reason Siversson doesn't say "8.7m" based on that 145mm centrum, but rather "8-9m"). IÂ’m agreed that at 8m it would be more robust, since it'd have a stouter vertebral collumn, but at 9m it wouldnÂ’t (itÂ’d actually be more elongate based on the data from the talk, but I suspect those are rough figures). Now according to Newbrey et al. , Cardabiodon has short vertebrae for a shark in general, but is just intermediate for a lamniform. It's centra are comparable (0.51 lenght/width ratio) to a bit shorter (up to 0.3) than those of C. carcharias (relatively speaking of course). At 9m, 8t is bulkier than a typical great white. If you want it precise, use 8.7m, which is the lenght estimate yielded by the largest centrum and direct comparison to C. carcharias. If you assume it shorter and bulkier, scale down linearly (not cubically since it will only be smaller in one dimension) from that figure. I think we have a reasonably good idea of CardabiodonÂ’s size. Siversson didn't acknowledge Kronosaurus reached 11t, that's probably why he stated the shark rivaled it. PS: The paper is here: www.app.pan.pl/archive/published/app58/app20120047_acc.pdf |
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Post by Grey on Jan 5, 2014 16:50:03 GMT 5
No offense but I don't think your expertise here is relevant. Simply said, Cardabiodon was more heavily built than a white shark. White shark weight varies but there are various specimens which would be easily 8 tonnes at 9 m.
I don't know if or how Siversson acknowledges Kronosaurus body mass. But I know that given his research field (Early Cretaceous marine environments from Australia), he certainly knows very well the beast and I assume he perfectly knows the rigorous estimate from McHenry. Now if he's not agreed with that figure, that's another discussion again. Thanks for the pdf (even if I had already linked it on the forum). P.S. I've used the formula you've posted with the data about lower jaw perimeter in Cardabiodon, it seems to perfectly fit).
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Post by theropod on Jan 5, 2014 18:23:16 GMT 5
Yes, that was the formula used in the paper (which is actually the way I found it).
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Post by theropod on Jan 5, 2014 19:16:33 GMT 5
What then, is the morphological feature that suggests that at equal vertebral diameter Cardabiodon was bulkier than Carcharodon? Also with "stockier than a great white" what he meant was likely not "stockier than even the stockiest great whites" but rather "stockier than typical great whites". A typical great white would yield 7.6t at 9m TL A relatively bulky one could be around 8t The mean of lamniform regression equations is 7.5t, the biggest is pretty much exactly 8t (Casey & Kohler, note that it bases on Mako sharks) Considering the largest known Cardabiodon (and that assuming geometric similarity to Carcharodon!) is 8.7m long (for which figures would be 6.8, 7.2 and 6.7 [max. 7.2t] respectively), it remains unlikely any known specimen would be in excess of 8t. Its body mass is fairly well constrained at 6.7-7.2±a few hundred kilos, depending on its exact lenght (which to know, in turn, we'd need a complete vertebral count for). Its not my expertise that yields such results, those are all based on scientific measurements and methods. I'm attempting the same thing you are trying too, to find the most conclusive relative sizes, but I don't want to rely on guesses. As far as the animal’s robusticity is concerned, you may attribute that to my own reasoning, but I also want to remind you that its better to wonder why and in which cases it would be bulkier than to guess and attribute the disparity between an estimated 7 or 8t animal and an estimated 11t animal solely to the former's alledgedly underestimated bulk. For the very reason that the point is unclear, I tried to be as "cautious" as possible in this regard, meaning the above estimates, as demonstrated, reflect a considerably stockier built than would be normal for Carcharodon. |
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Post by Grey on Jan 6, 2014 3:48:55 GMT 5
The best would to ask more to him. (Failed to join McHenry by the way).
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Post by Deleted on Apr 9, 2018 1:09:01 GMT 5
Krono has the edge here with its superior weaponry.
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Post by dinosauria101 on Feb 6, 2019 18:09:53 GMT 5
Kronosaurus wins, it has the better bite and is larger
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