A Bent Shark Tooth- Or?

[Al Dente]

Hello all,

Sorry for the not so great quality of the pics below. Not easy to get those small ones photographed (scanner is busted). The tooth in the pictures below is the one Bob Ernst found that's suspected to be Megachasma. Based on partial cutting edges, D-shaped X section, root orientation, volume and apparent histology (in so far as it is visible), acute crown angle, overall size, crown bump/"cusp", this looks like Megachasma to me.

The tooth is a little over 3/8" across the root base.

I think isurus90064's tooth has more in common with a Physogaleus symphyseal than with Megachasma. Here are some previous threads on similar teeth.

http://www.thefossilforum.com/index.php?/topic/27943-lee-creek-megachasma/

http://www.thefossilforum.com/index.php?/topic/51333-megamouth-shark-tooth-from-calvert-cliffs/

[Troodon]

ynot have you tried looking at the crown under a microscope to see any telltale signs of serrations?

[ynot]

Hello Tony,

I think there is a good chance you'll never know for sure. Going by individual tooth characters and eliminate respective candidates, especially when comparing symphyseals to "garden variety" examples, is at best very difficult. I guess all I am saying is that there is a chance it's Megachasma :-).

I think the lack of crown expansion onto the shoulder could be due to the fact that your tooth may indeed come from a place close to the symphysis. Not just that, the entire tooth is laterally compressed as if it had to fit in the limited space available.

Regarding curvature, the crown curvature is non-existent on your tooth, however the crown to root angle is similar on both teeth (acute, with a flat area on the labial side).

Hey-hi issurus,

I am just a "have to know" kinda fool! -- Although I do realize that I can not know everything.

After taking a closer look at My tooth (for the 100th time ) I can see that the "curve" is indeed in the crown / root junction.

I am in total compliance with it being a symphyseal (or close to one).

Does Megachasma have a symphyseal?

Could You please explain what is wrong with the idea of it being a Hexanchus andersoni symphyseal?

ynot have you tried looking at the crown under a microscope to see any telltale signs of serrations?

Hey Troodon,

Yes, and the cutting edge is smooth , except for the small chip .

Thanks for taking the time to answer an old fool like Me!!!

Tony

PS I am a novice at trying to identify My fossiles (beyond class). My collecting goes way back, but I did not have the resource to identify until I found this wonderful site!!!

[isurus90064]

Hey ynot and Al Dente,

Thanks Al Dente for the links, I think I remember reading those back when.

ynot, I do think that Al Dente may be correctemundo. While it doesn't give you an ID, the links he re-posted illustrate how it's far less likely to be Megachasma. I also dug up my Megachasma examples last night and while my STH example has no serrations, it simply makes it equally unlikely for it to be a G. contortus as it does a Megachasma.

[ynot]

So at this point We have determined that it is most likely NOT a Hexanchus, Hemipristis, Megachasma or C. contortus. (I hope that I am making a correct interpretation of the comments in this string.)

This brings it back to #@$&%%^ and I still do not know.

Does anyone know of a site that shows a Megachasma dentition set?

Thanks for all the help!!!

Tony

[siteseer]

Hi Tony,

The modern megamouth, Megachasma pelagios, does not have symphyseal. In its original description (Taylor et al,. 1983) the species does not have well-differentiated teeth - no distinct anteriors nor laterals nor even any teeth where the symphyseals would be. That doesn't mean the teeth are uniform in shape. The article does not provide multiple figures of teeth. However, just because the modern form doesn't have them, or at least the relatively few specimens available do not bear them, that doesn't mean its ancestors didn't have them and it's possible that the Miocene forms could have been in the process of losing them to the point that the file(s) only occasionally occurred (as appears to be the case with Eocene-Miocene? Carcharocles megalodon).

With that said I doubt your tooth is a Megachasma symphyseal because it seems too large for what I would expect of a reduced tooth (size and morphology) of what appears to be a small to medium-sized shark.

I'm not sure there is a figure of a Megachasma dentition anywhere. You have to realize that ichthyologists are examining the whole body. The teeth got only a few paragraphs in the original description with no real detail given. Several specimens have been collected, however. At some point someone might extract a functional row of an upper and lower quadrant so that could be studied in more detail especially if that person also studies extinct sharks.

Hexanchus doesn't have an upper symphyseal but it does have upper parasymphyseals. It sounds like I'm splitting hairs but the upper parasymphyseals have more flared-out roots and the lower symphyseal looks nothing like your tooth, being broader and more compressed. If the first upper parasymphseal were damaged as it was developing early in a sharks life and it got squeezed between teeth a little further along in their development (or somehow wedged between foreign objects that punctured that area), it's possible it could look like your tooth. Pathologic Hexanchus teeth, modern or fossil, are extremely rare and the ones I've seen have been laterals. However, I would expect the root to look weirder than yours does. It's hard to say.

Not every tooth is going to get a quick-and-easy ID. Sometimes, you have to wait years-decades before your weird tooth and others like it get under a paleontologist's skin to the point that it generates paperwork. Those Pyramid Hill megamouth teeth have been collected and pondered since at least the early 1960's. Collectors wanted a name back then, but sometimes, it helps to wait and see if anything similar pops up in the tree of life. In this case a living relative actually came to light.

Jess

Taylor, L. R., L.J.V. Compagno, and P. J. Struhsaker. 1983.

Megamouth — a New Species, Genus, and family of lamnoid Shark (Megachasma pelagios, Family Megachasmidae) from the Hawaiian Islands. Proc. Calif. Acad. Sci., 43(8): 87-110.

Hey-hi issurus,

I am just a "have to know" kinda fool! -- Although I do realize that I can not know everything.

After taking a closer look at My tooth (for the 100th time ) I can see that the "curve" is indeed in the crown / root junction.

I am in total compliance with it being a symphyseal (or close to one).

Does Megachasma have a symphyseal?

Could You please explain what is wrong with the idea of it being a Hexanchus andersoni symphyseal?

[siteseer]

Tony,

I'll try to get a photo of it next week.

Jess

Hey-hi Jess,

I would like to see a photo of the tooth that You have that Is the same as mine, could You please post one.

Thanks Y'All!!

Tony

[ynot]

Tony,

I'll try to get a photo of it next week.

Jess

Thank You Jess.

I really do learn from Your explanations, would be even more lost without them!!!

Do You think that isurus's tooth is the same?

Tony

[siteseer]

Al Dente,

I see what you're saying. The thing about Physogaleus symphyseals is that there is some variation among them but I think isurus90064's tooth differs not only in its lack of serrations but also in that the heels do not extend as far down the lobe as I would expect in a Physogaleus tooth. His tooth also bears a crown curves back over the root without a twist near the apex. Physogaleus teeth tend to have at least a slight twist while Megachasma (in this case M. applegatei of the Early Miocene of California) may have the twist or not. The lack of serrations and lack of a twist indicates that it is not a Physogaleus tooth. It's impossible to be certain as I have seen maybe only 5-6 of these Physogaleus symphyseals.

I don't know what it is but it does resemble what a megamouth tooth might look like several million years after the time of M. applegatei, a species with teeth that usually bear lateral cusplets but seemed to be in the process of losing them (some teeth lack them; some have just one while others have just what appear to be unworn bumps of enameloid). It might be a related form otherwise unknown to science.

Jess

I think isurus90064's tooth has more in common with a Physogaleus symphyseal than with Megachasma. Here are some previous threads on similar teeth.

http://www.thefossilforum.com/index.php?/topic/27943-lee-creek-megachasma/

http://www.thefossilforum.com/index.php?/topic/51333-megamouth-shark-tooth-from-calvert-cliffs/

[siteseer]

Tony,

I don't really know. I think it is a different form. We're dealing with incredibly rare tooth forms. I have never seen a tooth that resembles the one isurus90064 is showing. Elasmo.com has a frequency breakdown that I like. Put simply, there are teeth that are so common that you can expect to find several examples on every collecting trip. There are teeth that you might find only one or two of every trip and there are those you might find only one per many trips. I think there should also be a category for once-in-a-lifetime teeth like isurus90064's and yours.

I'm going to show the photos to another friend who was collecting the bonebed before I was born and see what he says.

Jess

Thank You Jess.

I really do learn from Your explanations, would be even more lost without them!!!

Do You think that isurus's tooth is the same?

Tony

[ynot]

Tony,

I don't really know. I think it is a different form. We're dealing with incredibly rare tooth forms. I have never seen a tooth that resembles the one isurus90064 is showing. Elasmo.com has a frequency breakdown that I like. Put simply, there are teeth that are so common that you can expect to find several examples on every collecting trip. There are teeth that you might find only one or two of every trip and there are those you might find only one per many trips. I think there should also be a category for once-in-a-lifetime teeth like isurus90064's and yours.

I'm going to show the photos to another friend who was collecting the bonebed before I was born and see what he says.

Jess

Thank You Jess, I am very curious what as to what Your friend will have to say about it!!

Tony

[Mike from North Queensland]

I am not an expert on shark teeth but could the item in question be a clasper from the tail.

Attached photo are some I have collected

Mike

[ynot]

I am not an expert on shark teeth but could the item in question be a clasper from the tail.

Attached photo are some I have collected

Mike

Hey-lo Mike,

That is an intriguing possibility! Can You provide photos from different angles?

Tony

[Al Dente]

Al Dente,

I see what you're saying. The thing about Physogaleus symphyseals is that there is some variation among them but I think isurus90064's tooth differs not only in its lack of serrations but also in that the heels do not extend as far down the lobe as I would expect in a Physogaleus tooth. His tooth also bears a crown curves back over the root without a twist near the apex. Physogaleus teeth tend to have at least a slight twist while Megachasma (in this case M. applegatei of the Early Miocene of California) may have the twist or not. The lack of serrations and lack of a twist indicates that it is not a Physogaleus tooth. It's impossible to be certain as I have seen maybe only 5-6 of these Physogaleus symphyseals.

Not all Physogaleus symphyseals have serrations. The three in front on this photo lack any hint of serrations and several that I have that are fairly pristine only have a few serrations tucked away in the corner. As you can see they come in a great variety of shapes and sizes. There are about 40 or 50 in this photo, all found within the Lee Creek mine.

Bob Purdy misidentified these as Megachasma in the Geology and Paleontology of the Lee Creek Mine, NC, vol. 3. Here is a picture of Pungo River teeth. I would assume these all lack serrations.

[ynot]

Hey all ,

I just wanted to bring this one back to see if We could come to a consensus about it.

The possible ID of this tooth seem to be...

1. Physogaleus symphyseals

2. a clasper from the tail

3. still do not know

Thanks for looking again! (and again, and again....)

Tony

[ynot]

To Anyone that cares,

I asked Marco sr. to take a look at this tooth and He forwarded the request to a well know shark expert.

Here is the reply...

"Tony

This is what the well known shark expert answered when I asked if he had an opinion on the identification of your tooth.

"The tooth photos look a lot like a hexanchid symphyseal. I suppose it might be an abnormal Galeocerdo but I think the former is more likely."

I agree that it looks like a symphyseal and most likely a hexanchid.

Marco Sr."

Thanks to all that helped with this puzzle!

Tony

[ynot]

Al Dente,

I don't think it's deformed because I happen to have a tooth just like it.

Jess

I guess We know what they are now!

Thanks for all of You help, here and on My other strings!

Tony

Edited September 15, 2015 by ynot

[siteseer]

On September 14, 2015 at 6:15 PM, ynot said:

I guess We know what they are now!

Thanks for all of You help, here and on My other strings!

Tony

 

Hi Tony,

 

I went to the Tucson show last February but only during the past week was I able to get some of the specimens photographed (trip outlined in another thread posted today).

 

This tooth was one of a small group available as a lot.  When I saw it, I realized I had to buy it because it reminded me of your tooth in question.  The tooth is from the Moroccan phosphates and measures about 7/8 inches measured along the apparent root height the top of which is just below the level of the crown tip.  A view not shown is the opposite side of Image 3.  That shows the apparent base of the root with an apparent nutrient groove or crack.

 

This specimen is not a dead-ringer for yours as the root seems more irregular though the overall form of the tooth is similar.  As I left the dealer room, I was thinking about who to show it to at the other venues but then saw someone in the hallway who would undoubtedly have an expert opinion on it.  David Ward.  He has been researching fossil sharks and rays (and selachians in general) since the 70's and is among the foremost experts on them with a lot of experience with European and North African fossils.  He's also a very modest and down-to-earth guy who will talk shop with longtime collectors as well as converse with the kid who just bought his first shark tooth.  He looked at this tooth and instantly recognized it as a pathologic Otodus.  He said he had seen numerous similar specimens - each the result of having been crushed while in the process of developing.  The crown was pushed into the root while both were still rather soft.  He added that he had seen more recent fossil mako teeth of that form as well.

 

I'm not saying that is what your tooth is but thought this tooth and the story behind it would be interesting to you and others that have read this thread.

 

Jess

[ynot]

3 hours ago, siteseer said:

'm not saying that is what your tooth is but thought this tooth and the story behind it would be interesting to you and others that have read this thread.

 

Jess

Hey hi Jess,

Thanks for the update and further information. 

I can see it being a pathological Cosmopolitodus (Isurus) hastalis 

 

Tony