Carcharodon Plicatilis?

[BellamyBlake]

I have here a tooth from Charleston, SC, a river find.

 

 

I've narrowed it down to a white shark, and based on this guide I'm torn between Carcharodon Plicatilis and Carcharodon Carcharias. I'm leaning towards the former. Could anyone please provide confirmation?

 

[Huntonia]

Hmm I'm seeing clear serrations on yours which doesn't seem to match plicatilis. I could be wrong however.

@Praefectus

[Praefectus]

The serrations on the tooth indicate that it is Carcharodon carcharias (great white shark). Carcharodon plicatilis is the proposed name for the Pliocene version of Carcharodon hastalis. It is debatable if Carcharodon plicatilis represents a new species or if it should be lumped together with Carcharodon hastalis. Regardless, your tooth is serrated and Carcharodon plicatilis/hastalis is unserrated. 

[Huntonia]

Praefectus knows his teeth! 

Nice find

[Al Dente]

It’s not Carcharodon. The burlette indicates something along the Otodus (Carcharocles) lineage.

[Miocene_Mason]

I agree with Carcharocles. In that area, could be C. angustidens or C. megalodon. Hard to say which with corners knocked off.

[Praefectus]

Aw, shoot. This is probably the 2nd or 3rd one that I have IDed as great white when it is actually a meg. @Al Dente @WhodamanHD what is the rule on bourlettes? Do white sharks have them or not? I've seen a lot of close calls. 

[Miocene_Mason]

9 minutes ago, Praefectus said:

Aw, shoot. This is probably the 2nd or 3rd one that I have IDed as great white when it is actually a meg. @Al Dente @WhodamanHD what is the rule on bourlettes? Do white sharks have them or not? I've seen a lot of close calls. 

Great whites don’t have them. The problem is that it wears off on megs sometimes so it can’t be the only feature relied upon.

[Boesse]

Given the location, it's possible that it's C. angustidens rather than C. megalodon, which are quite a bit more common around here.

 

Also, of note: hastalis, xiphodon, and plicatilis are all the same thing, and I'm extremely skeptical when anyone claims they can tell the difference. Not a single statistical analysis has ever even been conducted demonstrating anatomical differences between these proposed 'species'.

[BellamyBlake]

Color me surprised! Thank you, everyone for the exciting discussion - definitely I thought I had ruled out Megalodon and others from its lineage. It certainly is harder to tell with the corners broken off. Choosing between C. Megalodon and C. Angustidens, though, I would go with Angustidens for the reason that this looks closer to that than any Megalodon tooth I've handled. It also seems Angustidens is the consensus!

[Notidanodon]

Yes the otodus lineage has a more v shaped bourlette than carcharadon which is much flatter 

[Macrophyseter]

On 7/6/2020 at 8:23 AM, Boesse said:

Given the location, it's possible that it's C. angustidens rather than C. megalodon, which are quite a bit more common around here.

 

Also, of note: hastalis, xiphodon, and plicatilis are all the same thing, and I'm extremely skeptical when anyone claims they can tell the difference. Not a single statistical analysis has ever even been conducted demonstrating anatomical differences between these proposed 'species'.

Do you think Whitenack & Gottfried (2010) is inadequate of a study to prove the differentiation between hastalis and xiphodon/plicatilis?

[Boesse]

I had actually completely forgotten about that paper. I briefly re-read parts of it - one issue is that it depends upon the sample that's analyzed. Whitenack and Gottfried didn;t show us what these teeth look like in photos - if they're cherry picked end members of variation - without specimens of intermediate shape included - it will bias the result of the analysis towards two different species. Another issue is that the narrower teeth are probably geologically older, and there's a geochronological component as well (ancestral hastalis teeth from the Oligocene look a lot like gigantic, straight crowned oxyrhinchus with more rectangular root lobes).

[Macrophyseter]

Ah, but fortunately they did list all of the specimens they used, so someone could try verifying the samples for bias if they really wanted to. But regarding the geochronological components, wouldn't the pattern of some unserrated Carcharodon teeth becoming broader and more triangle-like over time be interpretable as a chronospecies-like or offshoot lineage containing multiple (two) species with defined distinctions like that established with the megatoothed lineage? Of course, there's the problem with identifying the distinction if we were to do so, though I believe that Kent (2018) proposed that C. plicatilis be differentiated from C. hastalis by the shape of the root and interestingly implies the geochronological trend of unserrated Carcharodon teeth is possible evidence against a conspecific relationship.

 

On a segway on classification, is there a problem with designating a direct ancestral and descendant species that continue to coexist for millions of years under the same genus? Given that Ebersole et al. (2017) and one of its cited papes reported C. hastalis (identified as having a "xiphodon" morphology; they seem to follow Ehret et al. (2012)'s definition) teeth of Early Pleistocene age, the former paper claims that keeping C. hastalis within Carcharodon might not float given that the coexistence of the two (or three) species after the rise of C. carcharias in Plio-Pleistocene deposits indicates the possibility that the latter is more of an offshoot than a final culmination of a chronospecies. But given such evolutionary relationship, is there a reason for some scientists to find lumping them all under one genus problematic, even if it may mean an unnecessary Cosmopolitodus paraphyly?