|
|
Post by Grey on Jun 19, 2013 22:00:56 GMT 5
Note that pliosaur tooth morphology is very varied and the dentary occlusion of Livyatan would suggest similar ecology to orcas. You are right, but the point that some scientists compare the morphology of non-cetacean animals to that of orcas is still valid. McHenry longly did it in his doctorial thesis, also with crocodiles. |
|
|
|
Post by theropod on Jun 19, 2013 22:06:28 GMT 5
I think there are worse analogies. Despite tremendous differences between Orcinus and Pliosaurs or crocodiles, both have certain features of the dentition that are analogous (deep roots, robust coronae and at least partly or nearly conical teeth...). If you can compare C. megalodon to T. rex this is no problem. Analogies always have to be seen in context of what they are for.
|
|
|
|
Post by coherentsheaf on Jun 19, 2013 22:12:33 GMT 5
Note that pliosaur tooth morphology is very varied and the dentary occlusion of Livyatan would suggest similar ecology to orcas. You are right, but the point that some scientists compare the morphology of non-cetacean animals to that of orcas is still valid. sure |
|
|
|
Post by Grey on Jun 19, 2013 22:17:27 GMT 5
|
|
|
|
Post by theropod on Jun 19, 2013 22:51:45 GMT 5
^Is that were the comparison originated? I think I understand a bit better how it was meant now.
|
|
|
|
Post by Grey on Jun 19, 2013 22:56:59 GMT 5
There are also photographic comparisons about the similarity between T. rex and meg teeth in Renz book (2002), but it is not available anymore in google books. I remember that Life had posted these comparisons in the old carnivora forum (2008-2009), I don't know if he still owns these. BTW, Mark Renz book, though outdated on some points now, is still regarded as a reference about megalodon information. |
|
|
|
Post by coherentsheaf on Jun 20, 2013 1:43:26 GMT 5
Note that pliosaur tooth morphology is very varied and the dentary occlusion of Livyatan would suggest similar ecology to orcas. It's been a while since you did not express on this coherentsheaf. I know you're very rationnal, more than I am, and that the uncertainties disturb you to have a definitive opinion but I would be interested by your thoughts ! I do not really know enough to have well developed ideas in this direction. |
|
|
|
Post by Grey on Jun 20, 2013 3:25:56 GMT 5
By the way, does anyone know the skull length of Acrophyseter? It looks like ~80 cm (I added a bit, as I didn't measure it along the curve). in that image:  www.provincia.livorno.it/attivita/museo/pubblicazioni/23/lambert.pdfIf the length estimates are correct, it would yield over 15 m for Livyatan, but it isn't more complete than Livyatan, so this is pointless. I had missed that post. So very basically, Acrophyseter as basis would yield somehting like 14,3-15,8 metres... Roughly 15 m, something within the size range between the two others propositions for Livyatan. I don't want to speculate but I really think the 15 m mark is a good guess for the beast... Still, I don't reject 16,2 and 17,5 m based on Zygophyseter... |
|
|
|
Post by creature386 on Jun 20, 2013 13:11:01 GMT 5
As I said, this is quite pointless, because Acrophyseter is as complete as Livyatan. It is like using Irritator for Spinosaurus. But yeah, 15 m sounds quite realistic.
|
|
|
|
Post by theropod on Jun 20, 2013 15:09:19 GMT 5
Yeah, no point in using it, its own estimate is not based on any postcranial remains either.
I whish we had at least part of it, since the cranium seems pretty similar in shape to L. melvillei. The most similar out of all yet discovered stem-physeteroids, due to the compressed built and curved jawlines. However we also have to regard its small size, which may nullify these perks or not. Due to the very similar skull shape however I´m inclined the overall morphology would be similar too. If the overall proportions were greatly different, one may also expect a different skull.
Sadly we cannot derive an estimate based on it.
|
|
|
|
Post by creature386 on Jun 20, 2013 15:25:59 GMT 5
It seems like they didn't used a large sample of whales for estimating the size range of Acrophyseter, as the range is a lot smaller than in Livyatan (3,9-4,3 m vs 13,5 m-17,5 m).
|
|
|
|
Post by theropod on Jun 20, 2013 15:29:39 GMT 5
I wonder which ones they used...
The mean looks like Brygmophyseter, even tough its (possibly incomplete) skeleton would indicate a far smaller size. But how come there´s a size range?
|
|
|
|
Post by creature386 on Jun 20, 2013 15:34:18 GMT 5
Maybe size estimate range would have been the better word
|
|
|
|
Post by Grey on Jun 20, 2013 15:56:07 GMT 5
This match is really a damn headache...
I usually tend to follow Mike Siversson's suggestion as he's the only one to have paid attention, as much as possible given the limited fossil data, on the rivalries between giants marine extinct predators and his assumption of Carcharocles approaching 20 meters TL.
But as unbiased as I am, I question myself and still wonder...
It seems that no one is really able to give a definitive answer on it.
Was Livyatan really 17,5 m (some lists 18 m) and if so, how built would it be ?
The fleshed comparison by the team displays a skull and head less massive that I would thought, but perhaps this is misleading. In their official artistic depiction with the scuba diver, it sounds a bit larger.
The volume potency of the jaws compared to meg's is a headache to determine. At the first glance, some meg jaws seem way bigger, litteraly, but I'd like to found more pics of Livyatan's jaws and determine the size of the chunks it would take each bite.
The fact that it survived probably not as long as megalodon is disturbing too (Siversson). Was it an unsuccessfull attempt to compete with the shark, or was it a real competitor since it was able to evolve after all but was destroyed by another cause. In that case, why the cause did not destroy megalodon which occupied a similar niche ? Especially since large apex predators sharks have not a very good reproduction rate level ?
Also De Muizon stating the physeteroid couldn't have tackled a modern large whale, whereas Compagno says the giant shark could...
That's a damn headache.
|
|
|
|
Post by creature386 on Jun 20, 2013 16:04:46 GMT 5
Where was 18 m for Livyatan listed?
|
|
