Indonesia megalodon from same location but different layer

[Jerrychang]

A few days ago I arranged some megalodon tooth fossils in my collection in a row according to their size.
I found two black teeth that were noticeably different in shape from the other brown ones, their long sides and thickness were almost equal, but the short sides were noticeably more curved and the crowns were more slender.

I'm wondering if it's because they are belong to individuals of different genders?  
Or maybe the black teeth belonged to a different species, because according to photos of the excavation site, the black formation was below the brown formation.

Besides, the bigger black one has a very small remaining cusps.

[siteseer]

It looks like the preservation is about the same but they're maybe from different sites not that far apart.  As for the shapes, the larger, taller teeth are anteriors (teeth from the front of the jaw) and the smaller, lower-crowned teeth are from the farther back in the jaw.  It's not the same but similar to how our incisors are a different shape from our canines, premolars, and molars.

 

I've collected at an area of California (Bakersfield) where one quarry yields teeth that are off-white in color but another quarry exposing the same layer but farther to the north has mostly different-colored teeth - some blue and some more gray.

[Jerrychang]

@siteseer

How about these two teeth? Which one is more back in the jaw?

They have almost the same length, width and thickness, but why the crown shape is obviously different?

Or is it because they belong to the upper and lower jaw teeth individually?

[Coco]

Hi,

 

I think the rearmost tooth in the jaw is the one on the right. The same size for a different position surely depends on the size of the shark...

 

Coco

[Meganeura]

For comparison - these 4 Meg teeth are all from the same site, but the white one is from a different layer than the other 3. And the smallest is a posterior Meg - you can see from the shape and also the size, so it came from the back of the mouth of a juvenile Meg.

[Gareth_]

You've got an impressive collection! 
I'm a bit late to the party here, haven't been on this forum for quite some time - a baby will do that though!

It's worth noting, this shark was around for about 20 million years, I haven't come across any information about the evolution of Meg teeth over those 20 million years, or if there were isolated populations that evolved slightly different teeth to suit their specific local needs. There is no evidence for sexual dimorphism, although there is in Carcharodon carcharias - a very distant relative (I think the lineages split around 60 million years ago).

In saying that, tooth shape is strictly down to the individual tooths position in the mouth. But because of what I mentioned above, a tooths position in the jaw can be more difficult to figure out than others. I've had Meg teeth that really didn't "fit" the model, with that it comes down to what individual characteristics does the tooth have - which will help place it in its likely jaw position.

I'll post a link below, it's been the most helpful so far in my hunt for information.

At the top right, click the drop down menu and select Megalodon

At its simplest level.... lower anterior teeth are like daggers, quite thin. As they go more lateral, about 1/3 the way up the crown the crown starts to pinch. They stay fairly symmetrical all the way to the posterior position.
Upper jaw anterior are obviously different, the blades aren't a straight edge going to the tip like a lower anterior, the crown stays wider until about 2/3 to the tip where the blades curve in to the tip. As they go lateral the crown develops a hook and the tooth goes more asymmetrical.
 

 

 

elasmo.com: Reconstructed Tooth-sets

 

[Meganeura]

1 hour ago, Gareth_ said:

It's worth noting, this shark was around for about 20 million years, I haven't come across any information about the evolution of Meg teeth over those 20 million years, or if there were isolated populations that evolved slightly different teeth to suit their specific local needs. There is no evidence for sexual dimorphism, although there is in Carcharodon carcharias - a very distant relative (I think the lineages split around 60 million years ago).

So since Megalodon has been renamed from Carcharodon to Otodus, has Carcharias also been renamed to Otodus? If not, does that imply that they're not relatives, or just that they're so distant that the genus is different? Also I know this is off-topic but considering the topic at hand I figured it would be okay.

[Gareth_]

20 hours ago, Meganeura said:

 or just that they're so distant that the genus is different? .

This

I'm not overly familiar with my shark family tree that far back in time, that was a little bit of info I came across sometime.... 

If you look at the taxonomic rank, Otodus and Carcharodon are both in the Order Lamniformes - along with a few other extant species

[Meganeura]

6 minutes ago, Gareth_ said:

This

I'm not overly familiar with my shark family tree that far back in time, that was a little bit of info I came across sometime.... 

If you look at the taxonomic rank, Otodus and Carcharodon are both in the Order Lamniformes - along with a few other extant species

Ahh that makes a lot of sense! Do we know what the difference specifically between Otodus and Carcharodon are?

[Gareth_]

1 hour ago, Meganeura said:

Ahh that makes a lot of sense! Do we know what the difference specifically between Otodus and Carcharodon are?

A prominent bourlette is specific to Otodus, through all species.
Species in Otodus have typically regular serrations, Carcharodon carcharias has irregular serrations. 
The root is deeper and more a U or V shape in Otodus, Carcharodon typically has a flatter root

All species in Otodus have cusplets, with the exception of O. megalodon. 

O. megalodon was a small shark at one point in its life.... which the adult sized shark teeth are usually fairly obvious what genus they belong in (fossil C. carcharias touched on a 3" slant high where O. megalodon teeth can reach over 7") the small teeth can be hard to place in a genus is the preservation is poor.

 

Here is one in my collection, the shape says Carcharodon but the bourlette and regular serrations don't lie! It's a juvenile O. megalodon tooth 
 

[Meganeura]

6 minutes ago, Gareth_ said:

A prominent bourlette is specific to Otodus, through all species.
Species in Otodus have typically regular serrations, Carcharodon carcharias has irregular serrations. 
The root is deeper and more a U or V shape in Otodus, Carcharodon typically has a flatter root

All species in Otodus have cusplets, with the exception of O. megalodon. 

O. megalodon was a small shark at one point in its life.... which the adult sized shark teeth are usually fairly obvious what genus they belong in (fossil C. carcharias touched on a 3" slant high where O. megalodon teeth can reach over 7") the small teeth can be hard to place in a genus is the preservation is poor.

 

Here is one in my collection, the shape says Carcharodon but the bourlette and regular serrations don't lie! It's a juvenile O. megalodon tooth 
 

I appreciate this a lot - but I was more referring to the specific difference between the genus of Otodus versus the genus of Carcharadon - as in, why did they make the switch from C. Megalodon to O. Megalodon?

As a side note though, that's a really nice juvenile Meg! If not for the bourlette I wouldn't have thought it was a Meg from the root size!

[Gareth_]

1 minute ago, Meganeura said:

I appreciate this a lot - but I was more referring to the specific difference between the genus of Otodus versus the genus of Carcharadon - as in, why did they make the switch from C. Megalodon to O. Megalodon?

As a side note though, that's a really nice juvenile Meg! If not for the bourlette I wouldn't have thought it was a Meg from the root size!

Haha dang I typed all that for nothing. I hope it comes up in a search and someone uses the info in the future!
I believe there was enough evidence to show the 2 separate lineages, Otodus can be traced back to about 60 million years with the species O. obliquus, there is good evidence to suggest O. obliquus evolved from Cretalamna. Carcharodon doesn't go back nearly that far in time (less than 10 million years as a round figure, I can't remember exactly how far)

It gets complicated on the Carcharodon side too.... which I'm not 100% caught up on but some teeth that were placed in Isurus (Mako) aren't all from Isurus (for eg Cosmopolitodus Hastalis). They've now been assigned the genus Cosmopolitodus, the precursor genus to Carcharodon. Some are arguing they belong in the same genus, Carcharodon. But hey, that is best left to the scientists to fight out the classification! 

[Meganeura]

30 minutes ago, Gareth_ said:

Haha dang I typed all that for nothing. I hope it comes up in a search and someone uses the info in the future!
I believe there was enough evidence to show the 2 separate lineages, Otodus can be traced back to about 60 million years with the species O. obliquus, there is good evidence to suggest O. obliquus evolved from Cretalamna. Carcharodon doesn't go back nearly that far in time (less than 10 million years as a round figure, I can't remember exactly how far)

It gets complicated on the Carcharodon side too.... which I'm not 100% caught up on but some teeth that were placed in Isurus (Mako) aren't all from Isurus (for eg Cosmopolitodus Hastalis). They've now been assigned the genus Cosmopolitodus, the precursor genus to Carcharodon. Some are arguing they belong in the same genus, Carcharodon. But hey, that is best left to the scientists to fight out the classification! 

Ahhh that makes sense. It’s super fascinating to me that despite finding these fossils for years, we’re still learning and changing. Also that we can figure out so much about a shark based on some teeth and vertebrae!

[Top Trilo]

I had a similar question about the different names as I had seen three.

Carcharodon megalodon

Carcharocles megalodon

Otodus megalodon

The answer I got was Carcharodon is completely incorrect and was only used when it was thought that megalodon was a close relative to the white shark. Otodus is more correct as O. obliquus is thought to be a direct ancestor to megalodon. Carcharocles is a synonym for Otodus.

Here is the thread I was referring to.