Carcharodon megalodon?? Kiev. Ukraine.

[Phitoplancton]

Hi! I found this tooth in sand where I collected striatolamia, otodus and other shark tooth fossil. But this separated I never found before. This is carcharodon megalodon?? Thank!) 

[Macrophyseter]

Actually, its not Carcharodon megalodon, but Carcharocles megalodon. It used to be that way, but now we know that megs aren't related enough to be in the same genus. 

 

As for the tooth, there is no (or just a extremely thin) bourrett, which is a carcharocles signature trait. The serrations also look extremely big for a tooth, which is something that a great white has, but of course the serrations are too worn down to tell exactly. And the bottom of the crown and root are very robust compared to the top the crown.

 

I think its one half of a rear posterior great white tooth. 

[Phitoplancton]

9 minutes ago, Macrophyseter said:

Actually, its not Carcharodon megalodon, but Carcharocles megalodon. It used to be that way, but now we know that megs aren't related enough to be in the same genus. 

 

As for the tooth, there is no (or just a extremely thin) bourrett, which is a carcharocles signature trait. The serrations also look extremely big for a tooth, which is something that a great white has, but of course the serrations are too worn down to tell exactly. And the bottom of the crown and root are very robust compared to the top the crown.

 

I think its one half of a rear posterior great white tooth. 

Thanks! 

[FossilDAWG]

Just a point of clarification, the most recent revision has the name as Otodus megalodon.

 

Don

[Troodon]

If you collected it where you found a striatolamia or otodus it cannot be a Megalodon since they did not exist in the Eocene.   It can be another megatoothed shark 

[Macrophyseter]

16 minutes ago, Troodon said:

If you collected it where you found a striatolamia or otodus it cannot be a Megalodon since they did not exist in the Eocene.   It can be another megatoothed shark 

That makes it a tad bit harder. Because the morphology to me is very much like that of a great white, but of course they didnt appear untill the miocene. And I dont know any premiocene cenozoic sharks without cusps . Perhaps its possible that you just found it in a nearby but different formation?

 

Also, I read somewhere that Striatolamna and Otodus persisted untill the miocene and possible furthur. If thats true, then a great white id wouldnt be that farfetched.

[Miocene_Mason]

While otodus may have survived till the Eocene, I think they would be rare. The lack of bourlette steers me away from megs as well. Perhaps it is a worn paleocarcharodon?

[Miocene_Mason]

Also a quick look online reveals mostly Eocene fossils from the area.

[Fossildude19]

44 minutes ago, Macrophyseter said:

 

Also, I read somewhere that Striatolamna and Otodus persisted untill the miocene and possible furthur. If thats true, then a great white id wouldnt be that farfetched.

53 minutes ago, Macrophyseter said:

But that name is not official yet as we yet to still have more evidence to make that way. Untill then, the official name is still Carcharocles megalodon

 

 (my opinion, Im against the otodus placement)

It's always best to try to back up what you are saying with evidence.   

Citations are helpful, in this respect. 

[Phitoplancton]

This tooths I found on the same place..

[FossilDAWG]

Plea

1 hour ago, Macrophyseter said:

But that name is not official yet as we yet to still have more evidence to make that way. Untill then, the official name is still Carcharocles megalodon

 

 (my opinion, Im against the otodus placement)

Please, do enlighten me as to the entity that designates "official names".  After nearly 50 years of fossil collecting, and 35 years as a professional biologist, I have somehow escaped encountering this entity.  I was under the impression that it is experts who actually work on the systematics of the organisms under consideration (sharks in this case) who decide on the most valid names, based on data and rigorous analysis.  For example, here is a link to a recent study by Kensu Shimada, David Ward, and other fossil shark experts who show (using actual data and phylogenetic analysis) that including Carcharocles produces a biologically invalid paraphyletic phylogenetic tree for the megatoothed sharks.  

Also see the post by Piranha in this thread, and the posts by Al Dente and Boesse here for discussion of the issue.  A search of the forum will yield several more discussions of the topic.

 

I am curious to hear your counter argument in favor of retaining Carcharocles.  I assume you have an even more convincing phylogenetic analysis.  Will you be publishing this any time soon?

 

Don

[PaleoRon]

The root seems too robust to be either Great White or Paleocarcharodon. Neither Otodus nor Striatolamia survived until the Miocene, although reworked specimens occasionally occur in Miocene sediments. I have found Otodus, Striatolamia, and Squalicorax in a Miocene exposure near Fort Washington, Maryland. It is probable that it is a piece of an early Carcharocles tooth. One of the sites I dive produces Striatolamia, Otodus, partially serrated Otodus, and coarsely serrated early Carcharocles teeth, all from the same formation. The Woodstock Fm. exposed at Popes Creek, Maryland produces the same mix of species.

[Miocene_Mason]

24 minutes ago, PaleoRon said:

The root seems too robust to be either Great White or Paleocarcharodon. Neither Otodus nor Striatolamia survived until the Miocene, although reworked specimens occasionally occur in Miocene sediments. I have found Otodus, Striatolamia, and Squalicorax in a Miocene exposure near Fort Washington, Maryland. It is probable that it is a piece of an early Carcharocles tooth. One of the sites I dive produces Striatolamia, Otodus, partially serrated Otodus, and coarsely serrated early Carcharocles teeth, all from the same formation. The Woodstock Fm. exposed at Popes Creek, Maryland produces the same mix of species.

Interesting, would this be along the lines of C. auriculatus ? 

[PaleoRon]

The fully serrated forms are.

[Macrophyseter]

1 hour ago, PaleoRon said:

The root seems too robust to be either Great White or Paleocarcharodon. Neither Otodus nor Striatolamia survived until the Miocene, although reworked specimens occasionally occur in Miocene sediments. I have found Otodus, Striatolamia, and Squalicorax in a Miocene exposure near Fort Washington, Maryland. It is probable that it is a piece of an early Carcharocles tooth. One of the sites I dive produces Striatolamia, Otodus, partially serrated Otodus, and coarsely serrated early Carcharocles teeth, all from the same formation. The Woodstock Fm. exposed at Popes Creek, Maryland produces the same mix of species.

Intresting, but the one thing that hits me all the time is the lack of cusps, but is it possible that pre-meg Carcharocles could have cuspless rear posterior teeth? Seeing pre-meg serrated and cuspless Carchaorcles tooth would be a first time for me. (That is, if the left root isnt broken, which to me is still whole)

 

[ynot]

1 hour ago, Macrophyseter said:

the lack of cusps,

Both sides look broke to Me. I would say that the cusps have been removed from this piece.

[Macrophyseter]

16 minutes ago, ynot said:

Both sides look broke to Me. I would say that the cusps have been removed from this piece.

Alight, I guess then I'd lean towards ron's auriculatus ID, my first guess was based on the assumption that the left root wasnt broken off  but his explaination makes more sense now.

[Anomotodon]

Yes, this is Otodus auriculatus or O. sokolowi lateroposterior tooth. Teeth on the group photo are mainly Striatolamia, Hypotodus and Borealotodus.

[jdp]

20 hours ago, FossilDAWG said:

Plea

Please, do enlighten me as to the entity that designates "official names".  After nearly 50 years of fossil collecting, and 35 years as a professional biologist, I have somehow escaped encountering this entity.  I was under the impression that it is experts who actually work on the systematics of the organisms under consideration (sharks in this case) who decide on the most valid names, based on data and rigorous analysis.  For example, here is a link to a recent study by Kensu Shimada, David Ward, and other fossil shark experts who show (using actual data and phylogenetic analysis) that including Carcharocles produces a biologically invalid paraphyletic phylogenetic tree for the megatoothed sharks.  

Also see the post by Piranha in this thread, and the posts by Al Dente and Boesse here for discussion of the issue.  A search of the forum will yield several more discussions of the topic.

 

I am curious to hear your counter argument in favor of retaining Carcharocles.  I assume you have an even more convincing phylogenetic analysis.  Will you be publishing this any time soon?

 

Don

Nomenclature is a little complicated and recommended synonymies are not always accepted. The name Carcharocles is still in wide use and probably will remain so for a while. There are a few reasons for that.

 

1. Stability is preferred when possible.

2. With fossils as common as shark teeth, the criterion that Shimada & colleagues are trying to stick to (monophyly) is not a reasonable expectation for any fossil shark genus or species.

3. We don't even know if the results reported by Shimada & colleagues will remain stable.

 

As a result, the solution they recommend is not actually useful and is likely to make the nomenclatural situation worse. So yeah, the idea is out there, but it's not wrong to keep using Carcharocles for the time being until the paleontological community decides how to deal with this problem. In other words, you're both right.

[FossilDAWG]

2 hours ago, jdp said:

Nomenclature is a little complicated and recommended synonymies are not always accepted. The name Carcharocles is still in wide use and probably will remain so for a while. There are a few reasons for that.

 

1. Stability is preferred when possible.

2. With fossils as common as shark teeth, the criterion that Shimada & colleagues are trying to stick to (monophyly) is not a reasonable expectation for any fossil shark genus or species.

3. We don't even know if the results reported by Shimada & colleagues will remain stable.

 

As a result, the solution they recommend is not actually useful and is likely to make the nomenclatural situation worse. So yeah, the idea is out there, but it's not wrong to keep using Carcharocles for the time being until the paleontological community decides how to deal with this problem. In other words, you're both right.

Certainly if you choose to continue to use Carcharocles megalodon people will understand what species you intend, as the name has been in use for quite a while.  In that sense the name fulfils one of the functions of a classification system, which is to assign a unique name to each species so we can discuss and publish about that species and everyone will know what we are talking/writing about.

However another and equally important function of a classification system is to accurately reflect the phylogeny (i.e. the relationship) of the named taxa.  In that role, paraphyly is a "cardinal sin" because it results in a phylogeny that is not based on the biological relationships of species.  Your statement that "trying to stick to (monophyly) is not a reasonable expectation for any fossil shark genus or species" is a statement that we should just throw in the towel and not try to determine the actual relationships of fossil sharks, just give them a label and be done with it.  That might be OK if the goal is just to stick labels on things, but it isn't (or should not be) acceptable to anyone trying to understand evolution and biological relationships.

Of course in systematics names are ultimately labels for hypotheses about relationships between organisms.  People will propose new names, or synonymize old names, based on their analysis of data they have been able to collect, and the community of experts will look at that analysis and decide if they agree or not.  Ideally if they disagree they will do their own analysis, hopefully adding new observations and data.  At one time, taxonomic names were based solely on the opinion of experts that "this fossil looks different from that fossil".  Today we hope to see statistical analysis of multiple characters measured on large samples of specimens (though that is still not always the case).  As sample sizes increase and the sophistication of the analysis improves, we can hope that the proposed phylogenies will get closer and closer to the actual evolutionary history of the organisms under study, and so the names will change less often.

So you are correct to say time will tell if people (by which I mean researchers who actually study fossil sharks) will agree that the analysis proposed by Shimada et al is the best fit for the phylogeny of the megatoothed sharks.  I would just say that "I don't like change", or "it's a pain to relabel my collections", or "Carcharocles is the name I have always used" are not valid reasons to reject Shimada's conclusions.  Also bear in mind that Shimada's work is building on analysis by Russian shark experts going back to the 1960's, and rejection of their analysis in favor of using Carcharocles seems to include an element of ignorance of work that was done outside of the Western countries.  If Carcharocles is biologically "real" and distinct from Otodus, there should be some character or combination of characters that allow them to be separated into distinct non-paraphyletic branches in a phylogenetic analysis.  That would be the appropriate scientific basis for retaining Carcharocles.

 

Don

[MarcoSr]

When people come over to my house and look at my collection one comment I always get is why I don't use any labels with genus/species etc. to id my specimens in my displays.  I did use labels years ago but I truly got tired of changing them over the years with the large number of name changes.  Plus I know what everything is.  I tend to use the nomenclature being used by the researchers that I follow and respect like Cappetta.,

 

Marco Sr.

[jdp]

20 hours ago, FossilDAWG said:

However another and equally important function of a classification system is to accurately reflect the phylogeny (i.e. the relationship) of the named taxa.  In that role, paraphyly is a "cardinal sin" because it results in a phylogeny that is not based on the biological relationships of species.  Your statement that "trying to stick to (monophyly) is not a reasonable expectation for any fossil shark genus or species" is a statement that we should just throw in the towel and not try to determine the actual relationships of fossil sharks, just give them a label and be done with it.  That might be OK if the goal is just to stick labels on things, but it isn't (or should not be) acceptable to anyone trying to understand evolution and biological relationships.

So this gets into somewhat more technical territory. If I go too fast, let me know.

 

Most phylogenetics that we do in paleontology is essentially just cladistics. We assume that no species is ancestral to any other species and we assume this before we do any analyses. By definition, a cladistic analysis cannot find ancestor-descendant relationships and by definition a cladistic analysis assumes that every species you put into the analysis went extinct without leaving observed descendants.

 

With some fossils (say, soft-bodied Mazon Creek fossils) there's a good chance this assumption is correct, or close enough to correct that it won't dramatically affect your results. 

you can trust that the branches in the tree represent true splits between lineages.

 

With fossil sharks specifically, this is not a safe assumption because we have literally tens of thousands to hundreds of thousands of teeth from all around the world for any given species, and many of these species (particularly large lamnids) have global distributions (like white sharks today). We have a pretty good sense that, if a shark was alive at a given time, we've probably sampled it in the record and have a pretty good sense of when it did and didn't live. In fact, this is the perfect sort of system in which to look for ancestor-descendant relationships, which cladistic by definition cannot recover. The splits between lineages, then, do not represent true splits, but rather an artifact of the analyses used.

 

There are methods that can combine cladistics-type systematic assessment of character evolution with the ability to find ancestor-descendant relationships (e.g. stratocladistics, stratolikelihood, etc) but Shimada and colleagues did not use these methods. As soon as we accept that ancestor-descendant pairs may exist, we are necessarily accepting that the species we have input into our analysis (which we've assumed a priori) are themselves not monophyletic. This is honestly fine, so long as we understand where on the phylogeny we're drawing the lines. 

 

So this is less "I don't want to change my labels" and more a technical point about the limits of the analytical tools that we use in determining relationships between fossil organisms.