Megalodon vs. Livyatan melvillei

[theropod]

I merely hinted I think delphinid proportions were more likely than credited for, not that they should be used, and that we may as well take them as an analogy of what raptorial cetaceans can also look like and why basing everything solely on Physeter instead of raptorial relatives is not wise. Occasional reference and comparison to the Orca in other regards is fully justified, the authors of L. melvillei's paper did so themselves.
What I did indeed state and still do is that I do not believe it had the body shape of extant Physeter macrocephalus (head is more or less the deepest point of the animal), at all, something not indicated by other stem physeteroids either (quite the contrary when looking at the deep chest of Brygmophyseter).

[Grey]

Physeter is more logical than delphinids for two reasons :

- phylogenetically
- size proportions above 10 m range

I tend to more likely favor raptorial analogous than Physeter, but Physeter is beter than...dolphins.

The reference to orca in the paper are about the toothy raptorial behavior. In the same sense, orcas are referred as such in publications talking about pliosaurs feeding apparatus.

Lambert et al. have worked during two years on L. melvillei before publishing it, still they did not suggested any physical relationship with any delphinids.

Definitely a loosy suggestion.

[theropod]

It would be closer to large raptorial delphinids in terms of:
-ecology
-morphology

Also phylogeny without regards to the above points is an even more loosy predictor of proportions. Since I do not suggest to use either delphinids or Physeter, no need from my side to argue about this. The reference to the Orca (ecology was of course what I referred to primarily) is very common for Livyatan. Eg. the head-comparison you showed also compares it to an orca, so does the scale from the paper. The orca is an analogy commonly used for Livyatan's ecology and gross morphology.
That orcas today, as top predators of the sea, have a somewhat similar niche to pliosaurs in their time is out of the question, but by the same logic one can compare C. megalodon to one, which is not commonly done. There are clear parallels between Livyatan and the Orca, and these have been stated by the team describing it.

[creature386]

Pliosaurs are not only compared to O. orca because they are apex predators, it is also done because of their morphology (in this case tooth morphology):
Massare reviewed the tooth morphology of the Oxford Clay pliosaurs and demonstrated similarities between Liopleurodon and a modern apex marine predator, the killer whale Orcinus (Massare 1987).
From: McHenry, Colin Richard (2009) Devourer of Gods: the palaeoecology of the Cretaceous pliosaur Kronosaurus queenslandicus p. 33

[Grey]

Ecology does not make an exactly similar body plan in all apex predators or all predators in the evolution would have the exactly same body and skull ratio.
Morphology ? You must be kidding.

Orca skull :




Livyatan skull :



Their only link is the raptorial apparatus (large teeth, robust structure). The jaws of the orca are much wider, the mandible is not tightened in one block like in the PHYSETEROID, and it lacks the spermaceti organ.

There is no freakin reason to think they had the same body plan. You just suggest that because it makes Livyatan even bigger than in what is described as upper end proposition in the paper work.

Again you misinterpret what you read and make Livyatan an orca in its official depiction. You're very good at that.

And you again challenge any the works at suggesting that delphinids are nearer in morphology than Physeter, when you don't have studied the phylogeny of Livyatan, nor analyzed the skull.

Basically I favor Lambert et al. works over theropod enthusiastics suggestions.

[creature386]

His point was that an orca is closer to Livyatan in terms of morphology than a sperm whale is, not close (the raptorial apparatus already has more similarities with an orca than with a sperm whale).

Jun 19, 2013 17:29:52 GMT 5 theropod said:

It would be closer to large raptorial delphinids in terms of:

[theropod]

Oh, for godness sake. I DO NOT SUGGEST THAT!
The only person who misinterprets something here is you, misinterpreting my post, maybe willingly, into me suggesting it had the proportions of an orca, which I frankly did not.

Yes Livyatan has a longer symphysis. Content now? That must mean it is on any regard much closer to a suction feeder, suction feeders are generally very good models for raptorial predators as regards body shape.
On a more serious note, the morphology is not that different. Try for a moment to look past the symphysis and the jaw width. You see two animals with a very similar basic structure. At least, morphologically, it is much closer than physeter. I suggest to use neither of these as a model, just please stick to stem physeteroids and stop claiming Physeter was a better model! I think you want to believe this because it makes it smaller and more gracile...

[Grey]

I believe it because it is closer phylogenetically than delphinids.

Because it is closer morphologically, as it remains a sperm whale skull. It has orcas like traits because of the raptorial apparatus that's all.

I believe it because it has been proposed as an extrapolation, even though I personnally believe that others stem physeteroids are probably better proxy.

I believe it more than delphinids because delphinids have not been used in two years of works on it.

This is you who are all the time recalling your suggestion. I know how you function, slowly but surely, you bring this as a suggestion if nobody argues against you.

I don't prefer it smaller (more gracile ? at parity, I see it bulkier than at 17,5 m, with the same skull or at least not more gracile. Is Zygophyseter bulkier than Physeter ? I doubt so), I prefer the truth. The truth is probably not in the paper, but the likelihood is.

I have no bias against Livyatan, far from it, certainly less than you toward Carcharocles, which sounds unimpressive in all departments except for its great size.

[theropod]

That's just paranoid, no offense. You pick some post from another forum, misinterpreting it. I then clarify what I wrote, thinking you have then understood it, but in everything I write you see some suggestion you do not like. It is as if you prophylactically argued about this matter in case I could ever think about bringing it up.

To clarify: I think both Orcinus and Physeter are equally bad analogies, both with their pros and cons. I cannot see any supposed morphological similarity between Physeter and Livyatan, but feel free to point it out. The skull of Livyatan has a less laterally expanded rostrum than Orcinus, but is much stockier than the skull of Physeter. It has a long symphysis, but if you think this:

would be any closer than Orcinus, I fear I cannot help you.

This is about morphology, not small anatomical characteristics supporting Livyatan as a closer relative of Physeter than Orcinus. it is gross morphology that is important for proportions, at least more so than the lenght of the symphysis or how much exactly there is of a step between the rostrum and posterior cranium.

[Grey]

Like I said, feel free to discuss between Zygophyseter, any other stem physeteroids or Physeter. But do not bring orca in it.

Yes, I prefer Physeter than orca as proxy. Yes the skull of Livyatan still displays obvious similarities with Physeter.

Why Physeter can be in some instance favored ?

It is, in my opinion, more appropriate to use a closely related taxon of similar size (in this case Physeter macrocephalus) as template when you estimated total length. At the end of the day we are all guessing.

Mike Siversson.

I prefer Zygophyseter and potentially others stem physeteroids overPhyseter, but I do not reject Physeter at all. I reject orca which has nothing to do here, except if we discuss the ecological question.

[theropod]

I reject both. The skull of Livyatan is at least as similar to Orcinus as to Physeter.
The size argument is the only one that has reasonable validity imo. You must not take opinions as gospel, especially if they are clearly expressed as an educated guess.

[Grey]

It is no gospel, it is educated guess. Just like yours. Like he says we are all guessing.

And generally, when opinions come, I simply prefer, without seing them written in the rock, specialists opinions than forumers opinions.

In your case, sorry if I feel a bit paranoid but my history with you on some questions let me think your overenthusiasm lead you to favor any optimistic predictions, as well as "the newer, the better". I'm perhaps too much suspicious but rest my case for now, I admit you've improved yourself though.

If you wishe, I suggest to discuss our feelings in the Members Café.

[coherentsheaf]

Jun 19, 2013 18:12:15 GMT 5 creature386 said:

Pliosaurs are not only compared to O. orca because they are apex predators, it is also done because of their morphology (in this case tooth morphology):
Massare reviewed the tooth morphology of the Oxford Clay pliosaurs and demonstrated similarities between Liopleurodon and a modern apex marine predator, the killer whale Orcinus (Massare 1987).
From: McHenry, Colin Richard (2009) Devourer of Gods: the palaeoecology of the Cretaceous pliosaur Kronosaurus queenslandicus p. 33

Note that pliosaur tooth morphology is very varied and the dentary occlusion of Livyatan would suggest similar ecology to orcas.

[Grey]

Jun 19, 2013 19:48:41 GMT 5 coherentsheaf said:

Jun 19, 2013 18:12:15 GMT 5 creature386 said:

Pliosaurs are not only compared to O. orca because they are apex predators, it is also done because of their morphology (in this case tooth morphology):
Massare reviewed the tooth morphology of the Oxford Clay pliosaurs and demonstrated similarities between Liopleurodon and a modern apex marine predator, the killer whale Orcinus (Massare 1987).
From: McHenry, Colin Richard (2009) Devourer of Gods: the palaeoecology of the Cretaceous pliosaur Kronosaurus queenslandicus p. 33

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 !

[creature386]

Jun 19, 2013 19:48:41 GMT 5 coherentsheaf said:

Jun 19, 2013 18:12:15 GMT 5 creature386 said:

Pliosaurs are not only compared to O. orca because they are apex predators, it is also done because of their morphology (in this case tooth morphology):
Massare reviewed the tooth morphology of the Oxford Clay pliosaurs and demonstrated similarities between Liopleurodon and a modern apex marine predator, the killer whale Orcinus (Massare 1987).
From: McHenry, Colin Richard (2009) Devourer of Gods: the palaeoecology of the Cretaceous pliosaur Kronosaurus queenslandicus p. 33

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.