Galeocerdo Or Physogaleus Aduncus

[Al Dente]

I am curious to hear other opinions on this subject.

In Ward and Bonavia's 2001 paper on the shark teeth of Malta, they determined G. contortus and G. aduncus were the same species and attributed both to Physogaleus calling them Physogaleus aduncus . The elasmo.com website accepted that G. contortus belongs to Physogaleus but rejected G. aduncus as the same species and kept it as Galeocerdo. I've noticed that many collectors have followed elasmo.com's example.

Ward and Bonavia's idea isn't new. Applegate (1978) shows an artificial tooth set of G. aduncus in which he used the contortus type teeth as lowers. He wrote: "The difference of anterior edge shape in the lower teeth of G. aduncus has caused past workers to split the species to two, a point that was not justified in the opinion of Leriche (1926)." Unfortunately I don't have Leriche's paper and only have the abstract to Ward and Bonavia's paper.

I have a hard time believing aduncus teeth aren't Galeocerdo when I compare them to juvenile G. cuvier teeth. They are almost identical. But there are several arguments that I can think of for contortus and aduncus teeth being from the same shark. Contortus teeth are clutching type teeth and aduncus are cutting. Many carcharinids have lower jaws with clutching teeth and upper jaws with cutting type teeth. It would seem odd to have the twisted contortus teeth as upper and lower, anterior and lateral teeth in the same jaw. Aduncus teeth are thin and contortus teeth thick and bulbous. Many sharks have thicker teeth in the lower jaws.

[Auspex]

I think that, until someone finds an associated dentition, they are "form species" anyway, with no solid way to establish genetic relationships. (Not that I mind the various speculations, which are informative in their own right).

[Northern Sharks]

I had never heard that theory before, and it does make logical sense, but only to a certain degree. I agree that Galeocerdo aduncus and cuvier are quite similar, and I would have a tough time teeling them apart on visual inspection alone. What I can say is that in a modern G. cuvier jaw, the upper and lower teeth are pretty much identical, and other than size, there isn't much difference between anterior and lateral teeth either. Maybe the angle of the blade changes the further back you get in the jaw, but not too drastically. If this is true of modern tiger sharks, I have no reason to believe a fossil version, with nearly identical upper teeth, would have such a different set of lower teeth. Just my opinion

[cowsharks]

I hope to have an answer or at least more information on this very subject within the next few months. I recently began a study, using approximately 15,000 "Contortus" teeth, collected from Calvert Cliffs, MD. I sorted through them to pick out only perfect teeth, yielding somewhere around 5,000 teeth. I am making a variety of measurements and observations about each tooth, then placing each in its own tiny zip-loc bag and number. Doing this I can clearly see certain tooth positions already. I have come across some teeth that almost appear to be a cross between an Aduncus and Contortus. These teeth look just like an Aduncus, however, the crowns exhibit a similar characteristic in that they have a slight twist (recurved) in them, similar to Contortus. I'm putting them aside for now since I need to study them more to determine what bucket they go into. When I'm done with the Contortus teeth, I have about 10,000 "Aduncus" teeth to repeat this process on. I also have a couple of modern Cuvier jaws for study, but they are fairly small. I need to purchase a larger Cuvier jaw, preferrably one male and one female, to see if there are any sexual dimorphisms in the teeth.

Needless to say, it has been very time consuming, but the data looks neat so far.

Daryl S.

[Al Dente]

I think that, until someone finds an associated dentition, they are "form species" anyway, with no solid way to establish genetic relationships. (Not that I mind the various speculations, which are informative in their own right).

I think this is a good way to think of them. By the way, there has been a published report of an associated dentition. I have never read it, but I am told it is just a partial jaw. Maybe someone who has the article can comment on it.

GOTTFRIED, M.D. (1993)

An associated tiger shark dentition from the Miocene of Maryland. Mosasaur, 5: 59-61

[cowsharks]

I think this is a good way to think of them. By the way, there has been a published report of an associated dentition. I have never read it, but I am told it is just a partial jaw. Maybe someone who has the article can comment on it.

GOTTFRIED, M.D. (1993)

An associated tiger shark dentition from the Miocene of Maryland. Mosasaur, 5: 59-61

Al, I have a copy of that Mosasaur publication and have seen the partial jaw piece. It's a very small piece of jaw (~1") with about 3 or 4 teeth clumped together. With such a small piece and few teeth, it doesn't help answer whether they are lowers or uppers, etc.

Daryl S.

[Hieronymus]

Here are some scans from Leriche, 1926 on Galeocerdo.

Due to the (very;)) limited uploadable filesize I will need multiple messages...

[Hieronymus]

Second scan

[Hieronymus]

Third and fourth

[Hieronymus]

The final ones.

I hope this helps!

[cowsharks]

Thanks H. I wish it was in English! I think I can figure out some of the words though.

Daryl S.

[Al Dente]

Al, I have a copy of that Mosasaur publication and have seen the partial jaw piece. It's a very small piece of jaw (~1") with about 3 or 4 teeth clumped together. With such a small piece and few teeth, it doesn't help answer whether they are lowers or uppers, etc.

Daryl S.

Daryl:

Thanks for the information on the Mosasaur publication article and good luck with your sorting of teeth. I don't know how many contortus and aduncus teeth I have but it certainly is not as many as you. The majority of mine are Lee Creek and I find about 1 aduncus for every four contortus but it could be due to some sort of collector bias.

[Al Dente]

The final ones.

I hope this helps!

Hieronymus:

Thanks for posting this. I'll read through it this weekend when I have a little more time.

[siteseer]

Al Dente,

You bring up a sticky subject. I'm on my way to dinner so this post is less an explanation and more a collection of notes.

Ward and Bonavia saw a distinction between teeth widely recognized as Galeocerdo aduncus (but what they see as "Galeocerdo cuvier-lineage" or early Galeocerdo cuvier) and what they recognize as Physogaleus aduncus upper teeth. To them P. aduncus upper teeth are separable "by their more rounded, less stocky and angular roots, more arcuate, less angular root lobe separation." Such fine distinctions between genera and going by only teeth leaves some room for skepticism.

Leriche (1942) considered G. contortus a race (a rank even below subspecies) within aduncus in his text showing contortus-type teeth as lowers and aduncus as uppers in his Plate 7. White (1956) questioned this conclusion and deemed contortus as a valid species.

Yes, it is understandable that aduncus are the upper teeth and contortus are the lower teeth of the same shark species since lowers tend to be thicker labiolingually (and narrower mesiodistally) than uppers in many sharks. However, some paleontologists (Kent, 1994; Purdy et al., 2001) have said that fine measurements of a large sample of contortus allow for uppers and lowers to be distinguished within that tooth type. Also, Purdy et al. (2001) found twice as many contortus as aduncus in a sample from the Pungo River Formation of the Lee Creek Mine, NC. Lower teeth are generally less common than upper teeth so that doesn't fit well with the idea.

There is a different inconsistency when you look at Miocene finds in Europe. The aduncus-type tooth is known from several sites but contortus is not even considered uncommon. It's rare - so rare that some paleontologists (e.g. Cappetta, 1987) have stated that the teeth do not occur in Europe.

To explain its wildly inconsistent frequencies at various sites around the world it would seem more logical that contortus is a separate species rather than just a lower tooth form within a dentition.

So what are we left with? We have reason to accept either conflicting explanation but only one can be true. Ward and Bonavia is a good article. You should track that down. It commented on several points made by Purdy et al. (2001).

I am curious to hear other opinions on this subject.

In Ward and Bonavia's 2001 paper on the shark teeth of Malta, they determined G. contortus and G. aduncus were the same species and attributed both to Physogaleus calling them Physogaleus aduncus . The elasmo.com website accepted that G. contortus belongs to Physogaleus but rejected G. aduncus as the same species and kept it as Galeocerdo. I've noticed that many collectors have followed elasmo.com's example.

Ward and Bonavia's idea isn't new. Applegate (1978) shows an artificial tooth set of G. aduncus in which he used the contortus type teeth as lowers. He wrote: "The difference of anterior edge shape in the lower teeth of G. aduncus has caused past workers to split the species to two, a point that was not justified in the opinion of Leriche (1926)." Unfortunately I don't have Leriche's paper and only have the abstract to Ward and Bonavia's paper.

I have a hard time believing aduncus teeth aren't Galeocerdo when I compare them to juvenile G. cuvier teeth. They are almost identical. But there are several arguments that I can think of for contortus and aduncus teeth being from the same shark. Contortus teeth are clutching type teeth and aduncus are cutting. Many carcharinids have lower jaws with clutching teeth and upper jaws with cutting type teeth. It would seem odd to have the twisted contortus teeth as upper and lower, anterior and lateral teeth in the same jaw. Aduncus teeth are thin and contortus teeth thick and bulbous. Many sharks have thicker teeth in the lower jaws.

[Al Dente]

Siteseer:

Thank you for your insight into this subject. It would be interesting to see exactly what frequencies aduncus and contortus occur in all the formations they are found.

I'm glad you brought up the rarity of contortus teeth in Europe. I have been told by more than one European collector that contortus is very rare in Europe. I have also read a discussion about whether they even occur in Europe on one of the European fossil forums. With this in mind, about a year ago I saw a group of aduncus teeth from Antwerp for sale. In the group I saw one that appeared to be a contortus tooth so I purchased the group. When I received this group of 12 teeth, I found that 5 had the typical twisted blade that I associate with contortus teeth. It made me realize that the criteria that I use to differentiate aduncus and contortus is different than what some other collectors use. Below is a photo of some of the teeth from Antwerp. The top 3 have twisted blades and the one on the bottom is a typical aduncus type tooth. The inset picture shows the twisted blade of two of the teeth. One thing I noticed is the roots are not as thick as roots on typical North American contortus teeth which is probably the reason they are identified as aduncus.

[siteseer]

Yes, that would be interesting. In my own collecting in the Sharktooth Hill Bonebed on my last two trips, I found the following:

1/4 day of collecting (approx. 2 hours)

3 aduncus

3 contortus

1/2 day of collecting (approx. 4 hours)

4 aduncus

7 contortus

In both cases I found at least as many contortus as aduncus which is at least one indicator arguing against them being lowers and uppers of the same species if we accept that lower teeth are at least generally less common than upper teeth of the same species.

Also, even when you allow for contortus having a more upright crown than aduncus, the STH contortus crown slant height range is higher than that of aduncus. Having higher-crowned lower teeth than upper teeth would be extremely unusual, if not unique, among the carcharhinids (and would be unusual among sharks in general). It's just one collector's observation but upper teeth are generally less upright than lowers yet have at least as great a slant height as the lowers.

I'd like know if other collectors (STH and other areas) are seeing the same things.

I have to go now - meant to give the full reference info for the articles I cited in my previous post but maybe you know those already.

Jess

Siteseer:

Thank you for your insight into this subject. It would be interesting to see exactly what frequencies aduncus and contortus occur in all the formations they are found.

I'm glad you brought up the rarity of contortus teeth in Europe. I have been told by more than one European collector that contortus is very rare in Europe. I have also read a discussion about whether they even occur in Europe on one of the European fossil forums. With this in mind, about a year ago I saw a group of aduncus teeth from Antwerp for sale. In the group I saw one that appeared to be a contortus tooth so I purchased the group. When I received this group of 12 teeth, I found that 5 had the typical twisted blade that I associate with contortus teeth. It made me realize that the criteria that I use to differentiate aduncus and contortus is different than what some other collectors use. Below is a photo of some of the teeth from Antwerp. The top 3 have twisted blades and the one on the bottom is a typical aduncus type tooth. The inset picture shows the twisted blade of two of the teeth. One thing I noticed is the roots are not as thick as roots on typical North American contortus teeth which is probably the reason they are identified as aduncus.

[FossilFreak]

Here is what I believe to be a symphyseal aduncus from Lee Creek.

You pose an interesting question and have had several good responses.

This is an indirect observation, but it goes to Auspex point. I believe scientists have a vested interest in "finding" new species.

Also, sounds like Daryl has quite a project a head of him. Good luck.

Edited May 2, 2011 by FossilFreak

[BSE]

I hope to have an answer or at least more information on this very subject within the next few months. I recently began a study, using approximately 15,000 "Contortus" teeth, collected from Calvert Cliffs, MD. I sorted through them to pick out only perfect teeth, yielding somewhere around 5,000 teeth. I am making a variety of measurements and observations about each tooth, then placing each in its own tiny zip-loc bag and number. Doing this I can clearly see certain tooth positions already. I have come across some teeth that almost appear to be a cross between an Aduncus and Contortus. These teeth look just like an Aduncus, however, the crowns exhibit a similar characteristic in that they have a slight twist (recurved) in them, similar to Contortus. I'm putting them aside for now since I need to study them more to determine what bucket they go into. When I'm done with the Contortus teeth, I have about 10,000 "Aduncus" teeth to repeat this process on. I also have a couple of modern Cuvier jaws for study, but they are fairly small. I need to purchase a larger Cuvier jaw, preferrably one male and one female, to see if there are any sexual dimorphisms in the teeth.

Needless to say, it has been very time consuming, but the data looks neat so far.

Daryl S.

Hi Daryl,

while researching the web for informations about Physogaleus latus I found that post. What's about your project distinguishing and comparing aduncus and contortus teeth? It has been some years ago you started it - I'm just interested in the final conclusion...

By the way, I'm looking for the dentition of Physogaleus latus from the Oligocene, just to identify the positions in the jaw of the pieces I found in the Mainz basin, Germany. Has anybody some Images?

See ya,

Bernd

[Al Dente]

By the way, I'm looking for the dentition of Physogaleus latus from the Oligocene, just to identify the positions in the jaw of the pieces I found in the Mainz basin, Germany. Has anybody some Images?

See ya,

Bernd

Bernd

There was an articulated Physogaleus latus found in a clay pit in Germany. Do you have the paper that describes it? I have the paper somewhere. There is a photo of its teeth in the paper.

[BSE]

Hi Al,

Unfortunately not... Could you look for it and give me the title? Or maybe you're so kind to post a scan of the photo.

Best regards,

Bernd

[Al Dente]

The paper that has the articulated P. latus is titled "A review of the chondrichthyan fauna of Grube Unterfeld (Frauenweiler) clay pit" by Hovestadt, Hovestadt-Euler and Micklich.

This thread was started quite a while ago. Since then I've looked at a lot of Physogaleus teeth and I'm more convinced that G. aduncas is the upper teeth of P. contortus but right now I don't have time to go into why. Here is a photo from the Grube paper. I think the upper P. latus teeth have a similar outline (when using some imagination) to G. aduncas and the lowers look similar to P. contortus.

[BSE]

Hi Al,

Thanks for posting the pic, now I'm able to determine my Physos.

You're right, there are some similarities between upper teeth of P. latus and G. aduncus, but I think much more between lower teeth and P. contortus. Both we could recognize in our samples. Some teeth are very similar shaped like contortus, but not twisted.

In the Mainz Basin (Upper Rupelium, Lower Oligocene) Physogaleus latus is usual - okay, less usual than C. cuspidata and C. acutissimus, but more than Notorynchus and the rare Carcharhinus elongatus, Galeorhinus sp. and Isurolamna gracilis.

Physogaleus contortus is also reported in this area. But no picture is added so that I can't decide if they are really some or just contortus-like shaped P. latus.

G. aduncus are reported too, especially when they prepared the ground several years ago for building up new houses. They are definitely Galeocerdos.

Unfortunately the location of the contortus isn't named, so I couldn't say if contortus and anduncus are found at the same locations or at different places. I will ask some of the local collecters.

Best regards,

Bernd

[Gneave]

I am an amateur collector and I have been collecting in south carolina and maryland's calvert cliffs for about 8 years. I have probably hundreds of specimens from both species (yes i believe they are different too). I gathered as many as i could find in order to gain evidence of any frequency inconsistencies, and i found something interesting. In SC almost all the tiger shark teeth were contortus (9.5 out of 10), with only a couple being aduncus. However, of the dozens i found in maryland, I didnt find a single contortus. These wide gaps in frequency seem very evident( especially with relatively large sample sizes) of the fact that, although they can be found together at times, they are 2 different species. I have found G. aduncus specimens that appear to have more characteristics of lowers but are still definitely aduncus, as have i for contortus uppers vs. lowers. Now, these discrepencies i find quite evenly throughout each species(with about half being suspected lowers and half suspected uppers per species). This all leads me to strongly believe in the two being separate species. I hope my logic and explanation made sense and can be used as further evidence of this idea.

[Al Dente]

In SC almost all the tiger shark teeth were contortus (9.5 out of 10), with only a couple being aduncus. However, of the dozens i found in maryland, I didnt find a single contortus.

This is a good demonstration of collector bias. My collection of South Carolina teeth yields only slightly more contortus type than aduncus type. While you found dozens of aduncas in Maryland but no contortus, a paper describing shark tooth frequencies found 132 aduncas and 137 contortus teeth at Calverts cliffs in Maryland (Variation in Composition and Abundance of Miocene Shark Teeth from Calvert Cliffs, Maryland, 2010). Their study has them close to equal in frequency while yours has dozens of one but none of the other.

Sometimes when comparing teeth from different localities it can be like comparing apples to oranges. Some collectors favor lag deposits because of the abundance of teeth that can be found but most lag deposits are size and density sorted. Aduncas teeth are flat while contortus have more three dimensional shape and have a large pulp cavity affecting their density. Current sorting would affect them differently. Comparing ratios from Lee Creek with ratios from Shark Tooth Hill might not be appropriate because of different depositional environments.

There is also a problem with how different collectors would sort these teeth. Is one collector calling a tooth aduncas while a different calls it contortus?

[non-remanié]

In the basal Kirkwood fm of NJ (earliest Miocene), contortus-type greatly outnumber aduncus-type. I wish I had access to my collection right now to do a quick check, but I would say its something like 5:1 and I have a large sample, easily 1k+. However, the fossils originate from a basal very high energy transgressive lag deposit. Size sorting could definitely be playing a role in that.

This is a good demonstration of collector bias. My collection of South Carolina teeth yields only slightly more contortus type than aduncus type. While you found dozens of aduncas in Maryland but no contortus, a paper describing shark tooth frequencies found 132 aduncas and 137 contortus teeth at Calverts cliffs in Maryland (Variation in Composition and Abundance of Miocene Shark Teeth from Calvert Cliffs, Maryland, 2010). Their study has them close to equal in frequency while yours has dozens of one but none of the other.

Sometimes when comparing teeth from different localities it can be like comparing apples to oranges. Some collectors favor lag deposits because of the abundance of teeth that can be found but most lag deposits are size and density sorted. Aduncas teeth are flat while contortus have more three dimensional shape and have a large pulp cavity affecting their density. Current sorting would affect them differently. Comparing ratios from Lee Creek with ratios from Shark Tooth Hill might not be appropriate because of different depositional environments.

There is also a problem with how different collectors would sort these teeth. Is one collector calling a tooth aduncas while a different calls it contortus?

Edited June 5, 2015 by non-remanié