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tatehntr

Question on Megalodon/Ang/Ric Evolution

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tatehntr

Hi everyone,

 

I was just seeking a little information on the relationship between the Megalodon, Angustidens, Auriculatus, and modern Great White sharks. Clearly the modern Great Whites are the most recent subspecies, but what about before them? Was Megalodon first with each shark decreasing in size until today's Great Whites? Did Angustidens come before or after Auriculatus? Any kind of clarification would be appreciated!!

 

Thanks :) 

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Tidgy's Dad
Just now, tatehntr said:

@Tidgy's Dad Perfect thank you so much!

Not sure it's perfect, half of these names are probably out of date by now! ;)

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WhodamanHD
1 hour ago, Tidgy's Dad said:

Not sure it's perfect, half of these names are probably out of date by now! ;)

Only some, all in the hastilis group are Carcharodon or cosmopotodus, though planus is for some reason still revered to as Isurus, and the Carcharodon sp is Carcharodon hubbelli. And Carcharocles should be Otodus of course.

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tatehntr

@WhodamanHD so this is something I’ve been curious about. What is the difference between Otodus and Carcharocles? Is Otodus the same thing/ new name? Would really appreciate clarification on this! 

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WhodamanHD
1 hour ago, tatehntr said:

@WhodamanHD so this is something I’ve been curious about. What is the difference between Otodus and Carcharocles? Is Otodus the same thing/ new name? Would really appreciate clarification on this! 

Carcharocles was the name for megatoothed sharks, Otodus was thought to be their predecessor (and still is). A recent revision found that All Carcharocles species should in fact be put in the genus Otodus. Now this could change, as taxonomy is a very fluid science but it seems it will hold for a while to me. So instead of Carcharocles megalodon it is now Otodus megalodon.

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Macrophyseter

The entire relationship between all these sharks all starts with Cretolamna appendiculata, which is practically the godfather of a huge portion of the Lamniformes order. 

 

Megalodon/Angustidens/Auriculatus/Otodus lineage

Cretolamna appendiculata -> Cretolamna bryanti -> Otodus obliquus -> Otodus aksuaticus -> Carcharocles auriculatus -> Carcharocles sokolovi -> Carcharocles angusteidens -> Carcharocles chubutensis -> Carcharocles megalodon

 

Great White lineage according to Garcia-Alix et al. (2014) and Cione et al. (2012)

Cretolamna appendiculata -> Cretoxyrhina dendiculata -> Cretoxyrhina mantelli -> Isurus schoutedenti -> Isurus praecursor -> Isurus desori -> Cosmopolitodus hastalis -> Carcharodon plicatilis -> Carcharodon hubbelli -> Carcharodon carcharias

 

As for what @WhodamanHD stated about the status of Otodus and Carcharocles, it's kind of complicated. Traditionally, the Otodus lineage ends as it evolves into C. auriculatus. However, in 2015, there was a discovery of a shark named Megalolamna paradoxodon. Phylogenic research of the shark showed that it was the sister group of Otodus. A sister group is basically any two or more groups that evolved together directly from the same ancestor. With however this conclusion, this causes a paraphyly in the Otodus genus, with the genus Carcharocles as the cause. While paraphylys are a common thing (The best example would be the class Reptilia), for some reason these scientists find it uncomfortable to have it exist. But if all members of Carcharocles is moved into the Otodus genus, then the paraphyly would magically disappear. Although this change is widely voiced out in the media, many scientists still use Carcharocles.

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doushantuo

alhhliftekkhhrnakristlanthc.jpg

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WhodamanHD

A few points of clarification, by no means a refutation:

1) It’s angustidens

 2) I believe that genera are meant to be monophyletic whereas broader groups don’t have to be (maybe @doushantuoknows more)

3) The Otodus placement of Megalodon is fairly widely used now. No subsequent paper has denied the findings to my knowledge. I suspect it will be even more prevalent in the near future. 

4) Cretalamna is the correct spelling (though it’s not used as often as it should be)

 

Now things i’d like to learn about:

@Macrophyseter do you have a link to the GW papers, there are some species in there I haven’t heard of (particularly plicatalis) and I would like to see the justification for the Ginsu-> Mako idea (one I had not heard previous)? Thanks!

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Macrophyseter
1 hour ago, WhodamanHD said:

@Macrophyseter do you have a link to the GW papers, there are some species in there I haven’t heard of (particularly plicatalis) and I would like to see the justification for the Ginsu-> Mako idea (one I had not heard previous)? Thanks!

Here is the link to the paper on the Ginsu->Mako theory

https://www.hindawi.com/journals/paleontology/2014/934235/

What's interesting in this article is that the authors believe that Cretoxyrhina should be an invalid genus and be replaced with Isurus.

 

The other article regarding Carcharodon plicatalis is not an open paper, so I'll have to PM you to show it.

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WhodamanHD
22 hours ago, Macrophyseter said:

Here is the link to the paper on the Ginsu->Mako theory

https://www.hindawi.com/journals/paleontology/2014/934235/

What's interesting in this article is that the authors believe that Cretoxyrhina should be an invalid genus and be replaced with Isurus.

Huh, I guess that makes quite a bit of sense. More than the Isurolamna->Isurus route. I don’t know about the Isurus subsumption, seems like a stretch, but maybe. 

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Macrophyseter
2 hours ago, WhodamanHD said:

Huh, I guess that makes quite a bit of sense. More than the Isurolamna->Isurus route. I don’t know about the Isurus subsumption, seems like a stretch, but maybe. 

Yeah. Apparently, they decided that the evolutionary trend mapped out makes Cretoxyrhina congeneric with Isurus and so according to ICZN rules, Cretoxyrhina would then be discarded as Isurus was coined first in 1810. However, I don't think this is going to be commonly accepted and all, and that everyone's still going to continue to use Cretoxyrhina. Another confusing thing is the mention of the species Isurus appendiculatus, and it's placement in Isurus. The paper is kind of rambling on the history of the species' taxon, and I'm not sure if it says that Otodus appendiculatus is a synonym of Isurus appendiculatus or Cretoxyrhina/Isurus dendiculata. What was the previous genus assigned to that shark? If it indeed was Otodus, then we've got a lot of weird stuff. If we accept the taxon Isurus appendiculatus, then the stretch you mention will be very real. If it is in Otodus, then there goes another paraphyly and the utter annihilation of the Lamnidae family.

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MikaelS
On 6/6/2018 at 10:28 AM, WhodamanHD said:

Huh, I guess that makes quite a bit of sense. More than the Isurolamna->Isurus route. I don’t know about the Isurus subsumption, seems like a stretch, but maybe. 

Just about all of my colleagues are highly critical of that publication. Basically we all disagree with his classification and instead regard Cretoxyrhina as a perfectly valid taxon (and a dead-end lineage). Regarding Carcharocles vs Otodus I use the former for serrated species of the lineage (eg in my 2015 revision of Cretalamna). There is no agreement among current workers in the field (eg David Ward, Charlie Underwood and Henri Cappetta use Otodus for megalodon whereas I and eg Bretton Kent use Carcharocles). Although I do not support the use of polyphyletic taxa I am less concerned about the usage of paraphyletic taxa in palaeontology.

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WhodamanHD
3 hours ago, MikaelS said:

Just about all of my colleagues are highly critical of that publication. Basically we all disagree with his classification and instead regard Cretoxyrhina as a perfectly valid taxon (and a dead-end lineage).

Seemed a little fishy (no pun Intended)

So are we at Isurolamna inflata as the best candidate for the ancestor to Isurus praecursor?

3 hours ago, MikaelS said:

Regarding Carcharocles vs Otodus I use the former for serrated species of the lineage (eg in my 2015 revision of Cretalamna). There is no agreement among current workers in the field (eg David Ward, Charlie Underwood and Henri Cappetta use Otodus for megalodon whereas I and eg Bretton Kent use Carcharocles).

Has Kent published any shark tooth related paper since the recent revision into Otodus? He has switched his preferences before, as with retroflexus (which I believe is an alopiiad now). By the way, I skimmed the paper, quite well done and comprehensive.

 

3 hours ago, MikaelS said:

Although I do not support the use of polyphyletic taxa I am less concerned about the usage of paraphyletic taxa in palaeontology.

And why is this? I understand the species concepts are different, but shall we not at least endeavor to make them Monophyletic? 

 

Understand, I am no scientist (yet) and I am  just trying to get a grasp of the different positions here.

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Macrophyseter
On 6/10/2018 at 11:55 PM, MikaelS said:

Just about all of my colleagues are highly critical of that publication. Basically we all disagree with his classification and instead regard Cretoxyrhina as a perfectly valid taxon (and a dead-end lineage).

I've read your paper regarding Isurus denticulatus (Mid-Cretaceous Cretoxyrhina (Elasmobranchii) from Mangyshlak, Kazakhstan and Texas, USA 2013), but what do you think regarding the genus validity for 'Isurus'  in I. denticulatus? Unless there is an Isurus lineage theory that I'm not aware of that includes I. denticulatus and not C. mantelli, wouldn't that mean 'Isurus' would be invalid for that species? Would it just be a species of Cretoxyrhina?

 

Also, what of the species 'Isurus' appendiculatus (as said in Garcia-Alix et al. (2014))? Would it revert back to 'Otodus appendiculatus' if Garcia-Alix et al. (2014)'s claims for it is indeed wrong?

 

On 6/11/2018 at 3:36 AM, WhodamanHD said:

as with retroflexus (which I believe is an alopiiad now)

Can you show me any papers regarding the change? I've always been used to 'Isurus' retroflexus being the direct ancestor of the modern longfin mako (Isurus pacus).

 

On 6/11/2018 at 3:36 AM, WhodamanHD said:

So are we at Isurolamna inflata as the best candidate for the ancestor to Isurus praecursor?

I've always wanted to ask regarding I. praecursor's ancestry, but what is of the species Isurus schoutedeni? I have found zero papers analyzing the species and yet some sources seem to accept that as the praecursor ancestor.

 

 

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MarcoSr
On 5/22/2018 at 2:03 PM, Tidgy's Dad said:

Evolutionary lineages of Carcharodon carcharias and Carcharocles megalodon

Half the names are in flux, but this should give a reasonable idea, i think. 

 

Nice job putting this together.  I agree with most of it.

 

I agree that a number of the names are in flux.  For the megalodon lineage more and more researchers are now using Otodus instead of Carcharocles for the genus throughout.

 

For the Isurus lineage you might consider the following:  Adding in Carcharodon hubbelli  (‬Ehret et al 2012‭) a transitional tooth form between the  broad toothed mako sharks of the Isurus genus and and the white shark Carcharodon carcharias for 6).  A bigger problem is retroflexus.   Cappetta (2012) and other researchers now use Anotodus as the genus for retroflexus.  In 1979 Herman reclassified the genus as a giant Alopidae.   If retroflexus is a giant thresher it wouldn't be a direct ancestor of I. paucus.

 

The lineage of I. planus is still in doubt but until I. planus is extensively studied and new fossil evidence emerges I agree with where you have placed it.

 

Marco Sr.

 

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Tidgy's Dad
16 minutes ago, MarcoSr said:

 

Nice job putting this together.  I agree with most of it.

 

I agree that a number of the names are in flux.  For the megalodon lineage more and more researchers are now using Otodus instead of Carcharocles for the genus throughout.

 

For the Isurus lineage you might consider the following:  Adding in Carcharodon hubbelli  (‬Ehret et al 2012‭) a transitional tooth form between the  broad toothed mako sharks of the Isurus genus and and the white shark Carcharodon carcharias for 6).  A bigger problem is retroflexus.   Cappetta (2012) and other researchers now use Anotodus as the genus for retroflexus.  In 1979 Herman reclassified the genus as a giant Alopidae.   If retroflexus is a giant thresher it wouldn't be a direct ancestor of I. paucus.

 

The lineage of I. planus is still in doubt but until I. planus is extensively studied and new fossil evidence emerges I agree with where you have placed it.

 

Marco Sr.

 

Erm, I'm rather afraid I pinched it from the web. 

Sorry, should have said. 

I can just about recognize a Meg and possibly Otodus obliquus , but my knowledge of shark teeth and evolution ends about there. :(

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WhodamanHD
7 hours ago, Macrophyseter said:

Can you show me any papers regarding the change? I've always been used to 'Isurus' retroflexus being the direct ancestor of the modern longfin mako (Isurus pacus).

See what he said:

54 minutes ago, MarcoSr said:

bigger problem is retroflexus.   Cappetta (2012) and other researchers now use Anotodus as the genus for retroflexus.  In 1979 Herman reclassified the genus as a giant Alopidae.   If retroflexus is a giant thresher it wouldn't be a direct ancestor of I. paucus.

 

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MarcoSr
On 7/11/2018 at 8:41 AM, WhodamanHD said:

See what he said:

 

 

A bigger problem is retroflexus.   Cappetta (2012) and other researchers now use Anotodus as the genus for retroflexus.  In 1979 Herman reclassified the genus as a giant Alopidae.   If retroflexus is a giant thresher it wouldn't be a direct ancestor of I. paucus.

 

 

 

On 7/11/2018 at 12:50 AM, Macrophyseter said:

 

Can you show me any papers regarding the change? I've always been used to 'Isurus' retroflexus being the direct ancestor of the modern longfin mako (Isurus pacus).

 

 

The below text and figure is from Cappetta 2012.

 

5b4753fe037da_AnotodusCappetta2012.thumb.jpg.4e08acc2234b15a28790b0393b5c327e.jpg

 

5b47543525db4_AnotodusCappetta2012a.jpg.1e783cdba81576532902e94491a97a07.jpg

 

5b4753f997a2c_AnotodusCappetta2012b.thumb.jpg.6ff0a9c1d2d34e9e261b22a46d1beb3b.jpg

 

 

Marco Sr.

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Macrophyseter
4 hours ago, MarcoSr said:

The below text and figure is from Cappetta 2012.

 

5b4753fe037da_AnotodusCappetta2012.thumb.jpg.4e08acc2234b15a28790b0393b5c327e.jpg

 

5b47543525db4_AnotodusCappetta2012a.jpg.1e783cdba81576532902e94491a97a07.jpg

 

5b4753f997a2c_AnotodusCappetta2012b.thumb.jpg.6ff0a9c1d2d34e9e261b22a46d1beb3b.jpg

Thanks!

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