Found a contortus today.

[Fin Lover]

I find quite a few contortus here and they vary like Al Dente's picture.  Off the top of my head, I would say I find more like the one on the right, but that is just a guess.

  

[digit]

On 6/10/2023 at 5:58 PM, ThePhysicist said:

I lean towards G. cuvier. I note that it has complex serrations, does anyone have a clear example of Physogaleus with complex serrations? If not, they could be a useful distinguishing feature between later species of Galeocerdo (e.g. G. cuvier, G. aduncus) and Physogaleus.

We could use a good close-up image of the tooth in question where we can see if the serrations are indeed simple or compound. One of my shark tooth experts looked at the images and considered the serrations to be simple. That, along with a narrow twisted crown tip, lead him to lean toward P. contortus.

 

 

Cheers.

 

-Ken

[Shellseeker]

2 hours ago, digit said:

We could use a good close-up image of the tooth in question where we can see if the serrations are indeed simple or compound. One of my shark tooth experts looked at the images and considered the serrations to be simple. That, along with a narrow twisted crown tip, lead him to lean toward P. contortus.

Cheers.

-Ken

Ken, 

If "tooth is question'  is my original tooth you can just just click on it above   until it maximizes size and you see this:

My knowledge is not very deep on P. contortus or "Complex Serrations".. Do all "shark experts"  have the same definition of "Complex Serrations"  and if so, Do they agree that what we have below is "Complex Serrations"? What is the definition of Complex Serrations ?

Many (Most ?) G. cuvier teeth below 1 inch do not seem to have these Complex Serrartions..

 

If the tooth in question is the Example that @Al Dente provides (on the left side),  then he would have to provide a close_up of that image.

Thanks for trying to sort this out....   Jack

 

 

[digit]

On 6/10/2023 at 10:03 PM, Shellseeker said:

 

Your highlight of this image clearly shows serrations on serrations which should be the definition of compound serrations.

 

50 minutes ago, Shellseeker said:

 

 

 

The areas you highlighted on this tooth seem to show tight single serrations on the shoulder (left circle) and possibly some serrations on serrations on the primary serration that is between the two circles. All of the other serrations seem to be simple and don't seem to show a second order set of smaller serrations. I tend to find a recurring pattern when I try to diagnose any but the most obvious shark teeth taxa--the more I drill down into the details the less sure I become of any shark tooth ID skills. With only limited knowledge many lower carcharhinid teeth are often mistaken for Negaprion (lemon shark) teeth. The devil is often in the details (and in many cases those details are serrations).

 

I enjoy these diagnoses by discussion as it often brings to the surface methods for distinguishing various confusingly similar taxa. I'm still in the head-scratching stage trying to identify the upper teeth of the Bonnethead Shark (Sphyrna tiburo) from those of Rhizoprionodon which they appear maddeningly similar. I have lower anterior and lower lateral teeth from this smallest of the hammerhead sharks from a particular site. I know there must be a few uppers but they are camouflaged among the numerous Rhizoprionodons.

 

 

Cheers.

 

-Ken

[Shellseeker]

12 minutes ago, digit said:

Your highlight of this image clearly shows serrations on serrations which should be the definition of compound serrations.

Ken,  I am trying to keep my eye on the prize... We (you and I) have a definition that we can both agree to and defend. No one else involved , yet.  Let me paraphrase to make sure.  Uniform serrations on serrations (for larger teeth >25 mm or not?) means you have G. cuvier.  If no Uniform serrations on serrations, then you have something other than G. cuvier.  We have to figure whether specificity counts, whether general agreement counts.

[Meganeura]

6 hours ago, Shellseeker said:

Ken,  I am trying to keep my eye on the prize... We (you and I) have a definition that we can both agree to and defend. No one else involved , yet.  Let me paraphrase to make sure.  Uniform serrations on serrations (for larger teeth >25 mm or not?) means you have G. cuvier.  If no Uniform serrations on serrations, then you have something other than G. cuvier.  We have to figure whether specificity counts, whether general agreement counts.

I don’t think uniformity is the key factor here so much as the presence of complex serrations as a whole. If you have “serrations” on serrations in some spots and not others - perhaps they’re not complex serrations, but little feeding damage spots. Or, perhaps they are complex serrations, but they’ve just been worn down over time in other spots.

[Al Dente]

10 hours ago, digit said:

One of my shark tooth experts looked at the images and considered the serrations to be simple. That, along with a narrow twisted crown tip, lead him to lean toward P. contortus.

 

6 hours ago, Shellseeker said:

Uniform serrations on serrations (for larger teeth >25 mm or not?) means you have G. cuvier.  If no Uniform serrations on serrations, then you have something other than G. cuvier.  We have to figure whether specificity counts, whether general agreement counts.

Many of my contortus teeth have complex serrations. Difficult to photograph with just my phone, but here is a Pungo River tooth showing complex serrations.

 

 

[Family Fun]

Love this thread, maybe my favorite of all time.  But I’m confused, which isn’t difficult for me.  
 

So uniform, complex and compound are all the same?  In Al Dentes last post, his contortus have these, which is opposite of what I read at the beginning of the thread.  As I said this is my favorite thread of all time, so interesting 

 

 

Rick

[Shellseeker]

1 hour ago, Family Fun said:

Love this thread, maybe my favorite of all time.  But I’m confused, which isn’t difficult for me.  
 

So uniform, complex and compound are all the same?  In Al Dentes last post, his contortus have these, which is opposite of what I read at the beginning of the thread.  As I said this is my favorite thread of all time, so interesting 

Rick

Rick,

We are working it... working it... This is the sausage making process... What are the facts and what are the opinions ? I , like everyone else, have lots of opinions and definitions,  but if faced with a fact that negates one of my strongly held beliefs,  what do I do ? Drop the belief like a hot potato and get out with as much dignity as I can muster. After all, I am not a politician. 

 

We need a common definition of "Complex Serrations"  that 70% of us can agree on.. We need to discover who coined the term "Complex Serrations".

 

@Al Dente has thrown a new fact into the mix.  A tooth, of which he has many, that otherwise would be identified as Contortus,

has "Complex serrations"  as we have defined them so far.. In my mind, that means , Complex serrations can not be used as a differentiator between Cuvier and Contortus.   Comments/ ?

 

 

[Meganeura]

1 minute ago, Shellseeker said:

Rick,

We are working it... working it... This is the sausage making process... What are the facts and what are the opinions ? I , like everyone else, have lots of opinions and definitions,  but if faced with a fact that negates one of my strongly held beliefs,  what do I do ? Drop the belief like a hot potato and get out with as much dignity as I can muster. After all, I am not a politician. 

 

We need a common definition of "Complex Serrations"  that 70% of us can agree on.. We need to discover who coined the term "Complex Serrations".

 

@Al Dente has thrown a new fact into the mix.  A tooth, of which he has many, that otherwise would be identified as Contortus,

has "Complex serrations"  as we have defined them so far.. In my mind, that means , Complex serrations can not be used as a differentiator between Cuvier and Contortus.   Comments/ ?

 

 

I do believe complex serrations has been the scientific term with a specific definition - at the very least, I’ve seen it on Elasmo a few times, to mean serrations on serrations. Serrated serrations. I don’t think that should necessarily be in question - I do think that we can now say that P. Contortus cannot be distinguished from G. Cuvier based on simple vs complex serrations alone though. 

[Fin Lover]

Agree with @Meganeura.  I have always distinguished between the two based on the longer, twisted crown.  The book I have also points out that contortus has a centrally raised root.

[Fin Lover]

Here's a quick picture of that raised root on a contortus:

[digit]

1 hour ago, Family Fun said:

Love this thread, maybe my favorite of all time.  But I’m confused, which isn’t difficult for me.  

You and me both. Topics like this that drill down into the specifics and are supported by so many members with useful imagery evolve into wonderful little nuggets of learning.

 

The two images above from @Al Dente wonderfully show the presence of undeniable compound serrations on the large shoulder serrations of a tooth that has the classic shape of a P. contortus. Now, to dig deeper it would be interesting to locate some literature to see what features have caused researchers to separate out this taxon from the rest of Galeocerdo. If the primary reason for calling this a tiger-like shark of a different genus has anything to do with compound serrations then that is surely in question. I believe a large part might be due to the elongated twisted nature of the cusp. I've read that this is more a grasping tooth than the cutting tooth of the tigers. While it is true that modern day Tiger Sharks can use the extremely distally pointed cusps and the complex serrations to saw through tougher prey. Sea turtles are a common prey item and vigorous side-to-side head shakes allow large tigers to easily saw through bone and shell. The more elongate and pointy teeth would be much more useful in grasping smaller slippery prey items like fish.

 

I'm starting to put more interest in the camp that believes the contortous-type teeth may just be the lower teeth of a heterodont species of tiger shark. Consider our other favorite Florida shark taxon with serrated teeth--Hemipristis serra. The lower teeth on this species are more pointed and awl-like for grasping/piercing and the uppers are similar to Galeocerdo in their curvature and distinct serrations. I don't recall ever seeing very large contortous-type teeth and this could be explained either by that species not getting very large or it could be an ontological change where a species of tiger shark feeds more on smaller fishes when young and then graduates up to larger prey as an adult. If this were the case there may be some signs that the modern Tiger Shark might vary its tooth shape throughout its lifetime. Now I need to engage my extant shark expert to see if this might be the case.

 

Till further corrected or clarified I will personally ignore simple/compound serrations and focus on the narrow twisted tip of the cusp as the primary feature in distinguishing P. contortus from the tigers.

 

 

Cheers.

 

-Ken

[Shellseeker]

35 minutes ago, Meganeura said:

I do believe complex serrations has been the scientific term with a specific definition - at the very least, I’ve seen it on Elasmo a few times, to mean serrations on serrations. Serrated serrations. I don’t think that should necessarily be in question - I do think that we can now say that P. Contortus cannot be distinguished from G. Cuvier based on simple vs complex serrations alone though. 

Daniel,

Here is the concern I have. We have 100s ? 1000s of TFF members, many of which know a lot about shark teeth ( and lots of other fossil related topics.

How would we get 70% of them to agree on anything ?

You and @ThePhysicist used a term that I had not previous analyzed "Complex Serrations" (Ken used the words "Compound serrations" . and wondered if you would provided me with a Reference / a Research paper written by someone who is a "recognized shark tooth identification expert" unlikely to be questioned.

Someone like:

Quote

Dr. Gordon Hubbell has perhaps the largest and best preserved collection of rare shark jaws and rare fossil shark teeth, and associated teeth, in the world. Dr. Hubbell is considered by many to be one of the world's foremost experts in shark paleontology, and yet he doesn't even have a degree in paleontology. Dr. Hubbell is a trained veterinarian and therefore, technically, an "amateur ..

Had you pointed me to Gordon, and his statement (if he has one) about "Complex Serrations",  I could have easily complied and gone forward supporting his definition to everyone else.  I know his bono fides and would be happy to based my conviction on his reputation.

 

I think that Complex,  Compound,  etc needs to be defined in order to avoid have different experts use different interpretations, thus adding confusion. 

[digit]

25 minutes ago, Fin Lover said:

The book I have also points out that contortus has a centrally raised root.

My fossil shark tooth expert also mentioned the very prominent central nutrient groove that is apparently found on unworn contortous-type teeth but not so much the other tigers.

 

https://www.floridamuseum.ufl.edu/panama-pire/blog/fossil-friday-121815-an-extinct-carcharhiniform-shark/

 

The conversation about these teeth is long standing as @Al Dente has already been discussing these teeth for the last dozen years (or more).

 

http://www.thefossilforum.com/index.php?/topic/20447-galeocerdo-or-physogaleus-aduncus/

 

 

Cheers.

 

-Ken

[Shellseeker]

29 minutes ago, digit said:

You and me both. Topics like this that drill down into the specifics and are supported by so many members with useful imagery evolve into wonderful little nuggets of learning.

 

The two images above from @Al Dente wonderfully show the presence of undeniable compound serrations on the large shoulder serrations of a tooth that has the classic shape of a P. contortus. Now, to dig deeper it would be interesting to locate some literature to see what features have caused researchers to separate out this taxon from the rest of Galeocerdo. If the primary reason for calling this a tiger-like shark of a different genus has anything to do with compound serrations then that is surely in question. I believe a large part might be due to the elongated twisted nature of the cusp. I've read that this is more a grasping tooth than the cutting tooth of the tigers. While it is true that modern day Tiger Sharks can use the extremely distally pointed cusps and the complex serrations to saw through tougher prey. Sea turtles are a common prey item and vigorous side-to-side head shakes allow large tigers to easily saw through bone and shell. The more elongate and pointy teeth would be much more useful in grasping smaller slippery prey items like fish.

 

I'm starting to put more interest in the camp that believes the contortous-type teeth may just be the lower teeth of a heterodont species of tiger shark. Consider our other favorite Florida shark taxon with serrated teeth--Hemipristis serra. The lower teeth on this species are more pointed and awl-like for grasping/piercing and the uppers are similar to Galeocerdo in their curvature and distinct serrations. I don't recall ever seeing very large contortous-type teeth and this could be explained either by that species not getting very large or it could be an ontological change where a species of tiger shark feeds more on smaller fishes when young and then graduates up to larger prey as an adult. If this were the case there may be some signs that the modern Tiger Shark might vary its tooth shape throughout its lifetime. Now I need to engage my extant shark expert to see if this might be the case.

 

Till further corrected or clarified I will personally ignore simple/compound serrations and focus on the narrow twisted tip of the cusp as the primary feature in distinguishing P. contortus from the tigers.

Cheers.-Ken

Well thought out , Ken This is a great thread because it because it probes at the distinctions between the different Tiger Sharks Genus and Species over the ages.

I note that I am likely retracing discussions threads that discussed these points when I was not paying attention. I depend on you for your steadying influence to my random thoughts.  I think we have moved the ball on this topic forward a little and we should capture consensus to the extent that it exists.

[digit]

2 minutes ago, Shellseeker said:

I depend on you for your steadying influence to my random thoughts.

Wait, what!?

 

I though I was depending on you.

 

I spotted the link to the earlier conversation while doing image searches. TFF has been around long enough to have many ancient layers of conversations that can be excavated and brought back into the light. This conversation too may one day be resurrected when this topic of these shark teeth piques someone's interest in the future.

 

 

Cheers.

 

-Ken

[Family Fun]

Just when you think the thread was beyond excellent it continues to get even better.  Thank you all for your knowledge, expertise and time.  This is awesome!

[digit]

My fossil shark tooth expert has weighed in on the theory of Galeocerdo aduncus and Physogaleus contortus being the heterodont dentition of a single taxon. He remembers reading a European study where they had some localities where they would only find G. aduncus and other localities where they would only find P. contortus which would seem to be a strike against simultaneous heterodonty. In my mind it does leave open the possibility of something like a taxon with homodont contortous-like dentition growing up into aduncus-like dentition and one site representing a nursery site and the other the primary range of the species. The complete absence of aduncus-like teeth at a nursery site is a bit difficult to justify though as the adult would have had to travel to a nursery setting (even temporarily) to give live birth.

 

I did turn up an interesting paper online that talks about the change in the shape of modern Tiger Shark teeth over an individual's lifetime (ontogenetic changes). Some of the subadult teeth (Figure 6 b-c) really do have kind of a contortus-like shape to them.

 

 

 

I've attached a couple of links to interesting papers that I'm going to enjoy reading through and hopefully will provide some useful background. I haven't digested them yet but they look to be useful to this conversation.

 

https://www.researchgate.net/publication/350343303_Evolution_diversity_and_disparity_of_the_tiger_shark_lineage_Galeocerdo_in_deep_time

 

https://www.researchgate.net/publication/359992493_Heterodonty_and_ontogenetic_shift_dynamics_in_the_dentition_of_the_tiger_shark_Galeocerdo_cuvier_Chondrichthyes_Galeocerdidae

 

Cheers.

 

-Ken

 

 

[Meganeura]

1 hour ago, digit said:

My fossil shark tooth expert has weighed in on the theory of Galeocerdo aduncus and Physogaleus contortus being the heterodont dentition of a single taxon. He remembers reading a European study where they had some localities where they would only find G. aduncus and other localities where they would only find P. contortus which would seem to be a strike against simultaneous heterodonty. In my mind it does leave open the possibility of something like a taxon with homodont contortous-like dentition growing up into aduncus-like dentition and one site representing a nursery site and the other the primary range of the species. The complete absence of aduncus-like teeth at a nursery site is a bit difficult to justify though as the adult would have had to travel to a nursery setting (even temporarily) to give live birth.

 

I did turn up an interesting paper online that talks about the change in the shape of modern Tiger Shark teeth over an individual's lifetime (ontogenetic changes). Some of the subadult teeth (Figure 6 b-c) really do have kind of a contortus-like shape to them.

 

 

 

I've attached a couple of links to interesting papers that I'm going to enjoy reading through and hopefully will provide some useful background. I haven't digested them yet but they look to be useful to this conversation.

 

https://www.researchgate.net/publication/350343303_Evolution_diversity_and_disparity_of_the_tiger_shark_lineage_Galeocerdo_in_deep_time

 

https://www.researchgate.net/publication/359992493_Heterodonty_and_ontogenetic_shift_dynamics_in_the_dentition_of_the_tiger_shark_Galeocerdo_cuvier_Chondrichthyes_Galeocerdidae

 

Cheers.

 

-Ken

 

 

Hmm - if the Contortus teeth belonged to juveniles, why would there be plenty of aduncus teeth that are smaller than other Contortus teeth? And vice versa?

[Al Dente]

1 hour ago, digit said:

He remembers reading a European study where they had some localities where they would only find G. aduncus and other localities where they would only find P. contortus which would seem to be a strike against simultaneous heterodonty

I think some European researchers have always lumped the contortus type in with Galeocerdo aduncus and just accept that the G. aduncus lowers are contorted. Here's Pieter De Shutter's website-https://www.somniosus.be/Homepage_set.htm

On his Miocene section, if you look at his G. aduncus, you will see a classic contortus tooth (third one down) even though many collectors claim contortus aren't found at the site.

 

 

[digit]

5 minutes ago, Al Dente said:

On his Miocene section, if you look at his G. aduncus, you will see a classic contortus tooth (third one down) even though many collectors claim contortus aren't found at the site.

That certainly confuses things when we cannot even call a contortus a contortus.

 

 

Cheers.

 

-Ken

[ThePhysicist]

Glad for renewed discussion on Galeocerdo/Physeogaleus, it's something I've only looked at in passing. Thank you especially to @Al Dente for the possible counterexample of Physogaleus with complex serrations, it prompted further thought. 

10 hours ago, digit said:

I've attached a couple of links to interesting papers that I'm going to enjoy reading through and hopefully will provide some useful background. I haven't digested them yet but they look to be useful to this conversation.

Thank you, the first was one I was aware of and had downloaded. A conclusion from this recent (2021) evaluation was that Physogaleus was well-separated morphologically from Galeocerdo. They also included an interesting figure:

^Türtscher et al. (2021)

What we previously called "variation" in morphology within P. contortus, the authors claim is actually different species - a "narrow form" of G. aduncus, and true P. contortus. While they are frustratingly similar in having a narrow crown, G. aduncus has a strongly serrated distal heel (area distal to the notch) with complex/compound serrations, while P. contortus has simple, fine serrations. The three morphologies presented here were also recognized earlier in "The Geology and vertebrate paleontology of Calvert Cliffs, Maryland" (2018) pg. 108-111; ISSN: 1943-6688. The same publication also notes distinction between the narrow G. aduncus and P. contortus in part by the presence of compound serrations on the former, but not the latter:

 

"A number of characters in this species [P. contortus] are at variance with most other Galeocerdo species: (1) a slender, finely serrate crown, (2) the absence of large, compound serrations on the distal heel, (3) the absence of a distinct notch separating the distal cutting edge from the distal heel, and (4) a thicker, more prominent lingual protuberance. As already discussed (see above), the crown resembles the narrow tooth form of G. aduncus, but the other three characters are sufficient to separate the two."

 

Türtscher et al. (2021): "The dataset of †G. aduncus in the present study contained teeth with broad and narrow morphologies, both clustering together. However, both types of teeth together showed distinct differences to teeth unambiguously representing †P. contortus (Fig. 8). This demonstrates the presence of a heterodont dentition in †G. aduncus, with broad and narrow teeth, which nevertheless are clearly different from †P. contortus, and therefore the validity of both taxa. Although a certain heterodonty, either dignathic or gynandric, seemingly exists in †G. aduncus, it is not to the extent previously proposed (i.e., including †P. contortus–type teeth)."

Edited June 14, 2023 by ThePhysicist

[digit]

Wonderful! I didn't have time last night to get into the papers but I'll make time tonight. Thanks for the CliffsNotes summary.

 

I love the image above--it is at one time a good example of the distinctive features discussed in the text and yet at a brief glance maddeningly similar if viewed briefly. It really hits home that these three forms can be easily confused if the time is not taken to learn the distinctions and to carefully assess a tooth for ID.

 

The example tooth from @Al Dente with the complex/compound serrations on the distal heel would then be the "narrow form" of G. aduncus. The "comparison" photo from the earlier discussion on this topic would also then show the "normal" form of G. aduncus on the top and the "narrow form" of G. aduncus on the bottom.

 

 

As these teeth are approximately the same size, it might appear that this heterodonty are either the result of jaw position (upper/lower) or possibly a male/female dimorphism as mentioned in the paper. I might question the last distinction "(4) a thicker, more prominent lingual protuberance" as that seems to be shown in the lower tooth above--unless others agree that the lower tooth above fits into the P. contortus bin.

 

Getting back to what started this wonderful exposition, it would appear that Jack's tooth does not display a thicker lingual protuberance and has faint complex/compound serration that would put it into the "narrow form" of G. aduncus rather than P. contortus. Have I assessed that correctly or do others have differing opinions?

 

 

Cheers.

 

-Ken

[Meganeura]

12 minutes ago, digit said:

Wonderful! I didn't have time last night to get into the papers but I'll make time tonight. Thanks for the CliffsNotes summary.

 

I love the image above--it is at one time a good example of the distinctive features discussed in the text and yet at a brief glance maddeningly similar if viewed briefly. It really hits home that these three forms can be easily confused if the time is not taken to learn the distinctions and to carefully assess a tooth for ID.

 

The example tooth from @Al Dente with the complex/compound serrations on the distal heel would then be the "narrow form" of G. aduncus. The "comparison" photo from the earlier discussion on this topic would also then show the "normal" form of G. aduncus on the top and the "narrow form" of G. aduncus on the bottom.

 

 

As these teeth are approximately the same size, it might appear that this heterodonty are either the result of jaw position (upper/lower) or possibly a male/female dimorphism as mentioned in the paper. I might question the last distinction "(4) a thicker, more prominent lingual protuberance" as that seems to be shown in the lower tooth above--unless others agree that the lower tooth above fits into the P. contortus bin.

 

Getting back to what started this wonderful exposition, it would appear that Jack's tooth does not display a thicker lingual protuberance and has faint complex/compound serration that would put it into the "narrow form" of G. aduncus rather than P. contortus. Have I assessed that correctly or do others have differing opinions?

 

 

Cheers.

 

-Ken

Would @Al Dente’s teeth be narrow G. aduncus as well then, instead of P. Contortus?