Jump to content

Shark Vert Size Ratio To Body?


Recommended Posts

fossilized6s

I just bought a large shark vert. It's from a Otodus obliquus. It measures 3 3/8" at the widest point. I was wondering if a true size of this shark can be determined from the measurements of the vertebra? I know the vertebrae differs throughout the shark's body. But let's just say this was the largest vert.

post-14584-0-60038600-1427175205_thumb.jpg

Any help is appreciated.

Thanks!

My uneducated guess: about 25'-30'.

Link to post
Share on other sites
fossilized6s

So i found that the Otodus obliquus only grew to about 30'. And people have recovered vertebra as large as 5".

So 5" vert= 30'

Every inch would be 6', give or take. So mine would have been around 21'.

This is just a very basic attempt of understanding. If anyone has any references, even with modern shark ratios, that would help.

Now correct me if im wrong, but wouldn't this ratio mean that Megalodon verts would have to be around 9"-10" at their largest in diameter? I've never heard of such verts being found.....

Link to post
Share on other sites

It's all pretty speculative; a 'guestimate' of a size range is about all that can be done (unless someone catches a live one!).

Still, investing our imagination is what keeps our sense of wonder chugging along! To paraphrase Aldo Leupold: "What a dull world if we knew all about sharks".

Link to post
Share on other sites
fossilized6s

I agree it's just guessing. But i would think from all of the almost complete sharks (teeth, jaws, cartilage and verts) that have been found that some kind of ratio is out there. I have found so many conflicting opinions on shark vert rings determining age, tooth length determining shark size, Megalodons grew to 70'+, so on and so forth. Quite exhausting. I don't know who to believe...... :l

Link to post
Share on other sites

It depends if the vertebra was the largest present in the column.

If that's the case, in lamnids the total size of the shark correspond to 55-60 times the width of the largest vertebra. So assuming this piece was the largest in the shark, the range is 4.7 m (15.4 feet) to 5.15 m (~17 feet).

Link to post
Share on other sites

I don't know who could have made that determination unless that person had a time machine. Otodus died out about 50 million years ago and it has no modern descendants and none of its post-Eocene descendants are known from even one complete skeleton. People use the one inch of tooth per ten feet of shark so a 3-inch tooth equals about a 30-foot shark. That doesn't work often enough to be helpful because a 20 foot modern great white can have 2 1/2-inch teeth so it should be considered only a ballpark equation for multi-inch teeth. Great whites don't grow continuous in length slowing in that dimension during adulthood and they start getting bulkier. Because we have no Otodus nor Otodus descendants, we don't know what the body proportions were for them at any point in their lives. A paleontologist once half-jokingly proposed that C. megalodon could have been more eel-like in body form and that would really mess up any attempt to gauge its size using a modern shark as a model. Some scientists tried using a modern great white to estimate megalodon size at a time when some thought the two sharks were closely related. It turns out they aren't closely related (different families with their common ancestor at least as old as the Paleocene) so the basis for their numbers had no basis.

I think the best that could be done at this point is find out the size of the largest Otodus vertebra known and then see how it measures up to the larger whale shark or basking shark vertebrae (genera known to exceed 30 feet) known and those associated with a complete skeleton. That might give you some indication of maximum size still leaving you only justified to say that it could have been the same length or somewhat shorter or somewhat longer.

So i found that the Otodus obliquus only grew to about 30'. And people have recovered vertebra as large as 5".

So 5" vert= 30'

Every inch would be 6', give or take. So mine would have been around 21'.

This is just a very basic attempt of understanding. If anyone has any references, even with modern shark ratios, that would help.

Now correct me if im wrong, but wouldn't this ratio mean that Megalodon verts would have to be around 9"-10" at their largest in diameter? I've never heard of such verts being found.....

Link to post
Share on other sites
fossilized6s

Thanks guys.

Siteseer, now you see my dilemma. For everything i read, there's a contradicting opinion or theory.

Aren't there any papers with a rough idea of size pertaining to whole shark skeletons that were found?

Link to post
Share on other sites

I don't know who could have made that determination unless that person had a time machine. Otodus died out about 50 million years ago and it has no modern descendants and none of its post-Eocene descendants are known from even one complete skeleton. People use the one inch of tooth per ten feet of shark so a 3-inch tooth equals about a 30-foot shark. That doesn't work often enough to be helpful because a 20 foot modern great white can have 2 1/2-inch teeth so it should be considered only a ballpark equation for multi-inch teeth. Great whites don't grow continuous in length slowing in that dimension during adulthood and they start getting bulkier. Because we have no Otodus nor Otodus descendants, we don't know what the body proportions were for them at any point in their lives. A paleontologist once half-jokingly proposed that C. megalodon could have been more eel-like in body form and that would really mess up any attempt to gauge its size using a modern shark as a model. Some scientists tried using a modern great white to estimate megalodon size at a time when some thought the two sharks were closely related. It turns out they aren't closely related (different families with their common ancestor at least as old as the Paleocene) so the basis for their numbers had no basis.

I think the best that could be done at this point is find out the size of the largest Otodus vertebra known and then see how it measures up to the larger whale shark or basking shark vertebrae (genera known to exceed 30 feet) known and those associated with a complete skeleton. That might give you some indication of maximum size still leaving you only justified to say that it could have been the same length or somewhat shorter or somewhat longer.

Well, the fact otodontids and lamnids are not that related does not mean any size estimate can't be made. We do have complete sets of teeth from otodontids and a number of vertebra, which are still very similar to those in Carcharodon and allow comparisons. Body size and shape is determined by environmental constraints and given their equivalent lifestyle, it is unlikely that otodontids would have been extraordinarily different than lamnids. The Late Cretaceous Ginsu shark is even more distant than the white shark still its overall body plan (we have complete skeletons from it) is quite similar.

Also, I don't understand why people are still using the 1 inch/1 foot method whereas several really scientific methods have been made and are still used in litterature as of now.

Link to post
Share on other sites
Harry Pristis

Well, the fact otodontids and lamnids are not that related does not mean any size estimate can't be made. We do have complete sets of teeth from otodontids and a number of vertebra, which are still very similar to those in Carcharodon and allow comparisons. Body size and shape is determined by environmental constraints and given their equivalent lifestyle, it is unlikely that otodontids would have been extraordinarily different than lamnids. The Late Cretaceous Ginsu shark is even more distant than the white shark still its overall body plan (we have complete skeletons from it) is quite similar.

Also, I don't understand why people are still using the 1 inch/1 foot method whereas several really scientific methods have been made and are still used in litterature as of now.

That's interesting, Gabe. What are the several scientific methods used instead of the "1 inch/1 foot" [sic] rule of thumb for estimating the length of megalodon sharks. Can you direct us to the literature?

I think that siteseer might argue that, even if we did have a scientifical way to estimate the length of megalodon individuals, such a technique may not be reliable for estimating the length of progenitor Otodus individuals. Estimating body length from isolated, or small groups of Otodus vertebrae is a leap into the unknown.

Having said that, I have my own theory: I think that Otodus was a stubby, Jabba-the-Hut sort of ambush predator. I think Otodus preyed primarily on protowhales, which were making the transition from artiodactyl to cetacean at the time. I think Otodus rested in shallow water, pumping water over its gills, waiting to ambush protowhales (which, after all, were just not yet streamlined swimmers).

Otodus likely never exceeded 4 meters in length, but they were all mouth -- shaped like a teardrop or like a wide-bodied wobbegong. Here's my reconstruction:

post-42-0-09435000-1427311065_thumb.jpg

Edited by Harry Pristis
Link to post
Share on other sites
fossilized6s

Interesting theory Harry. I like it.

Isn't it (1 inch of tooth=10 feet body length). I've read that is theory is outdated, but there isn't any evidence to dismiss it either. Just assumptions. No room in science for assumptions.

I guess i just "assumed" that there were more fossilized shark skeletons recovered and studied. And all of this was scientific common knowledge. My bad.

Link to post
Share on other sites

That's interesting, Gabe. What are the several scientific methods used instead of the "1 inch/1 foot" [sic] rule of thumb for estimating the length of megalodon sharks. Can you direct us to the literature?

I think that siteseer might argue that, even if we did have a scientifical way to estimate the length of megalodon individuals, such a technique may not be reliable for estimating the length of progenitor Otodus individuals. Estimating body length from isolated, or small groups of Otodus vertebrae is a leap into the unknown.

Having said that, I have my own theory: I think that Otodus was a stubby, Jabba-the-Hut sort of ambush predator. I think Otodus preyed primarily on protowhales, which were making the transition from artiodactyl to cetacean at the time. I think Otodus rested in shallow water, pumping water over its gills, waiting to ambush protowhales (which, after all, were just not yet streamlined swimmers).

Otodus likely never exceeded 4 meters in length, but they were all mouth -- shaped like a teardrop or like a wide-bodied wobbegong. Here's my reconstruction:

attachicon.gifwobbegong.JPG

Hello, the various methods in litterature are :

- vertical height of the second upper anterior tooth (Gottfried, M.D., L.J.V. Compagno, and S.C. Bowman. 1996. Size and skeletal anatomy of the giant “megatooth” shark Carcharodon megalodon.)

- vertical crown height accounting tooth position (The relationship between the tooth size and total body length in the white shark, Carcharodon carcharias (Lamniformes: Lamnidae) - Journal of Fossil Research (Japan) 35 (2): 28–33. - Kenshu Shimada - 2002.).

- tooth width (In Renz, 2002, Megalodon : Hunting the Hunter)

- dentition and jaw perimeter, similar to the tooth width method and variously used by some authors (Bretton W. Kent: Speculations on the Size and Morphology of the Extinct Lamnoid Shark, Parotodus bend (le Hon). In: The Mosasaur. 6, 1999, p. 11-15) (Vertebral morphology, dentition, age, growth, and ecology of the large lamniform shark Cardabiodon ricki MICHAEL G. NEWBREY, MIKAEL SIVERSON, TODD D. COOK, ALLISON M. FOTHERINGHAM, and REBECCA L. SANCHEZ)

I don't know from where exactly comes the 1 inch/1 foot, I'm not aware of any qualitative study using it.

Your idea about Otodus is interesting but I think it's wrong, the shape of its centra simply does not suggest this kind of body plan.

At the very least, we do know thanks to the structure of their vertebra that Otodus (and its lineage) were sharks with a robust fusiform body.

Link to post
Share on other sites
Harry Pristis

Hello, the various methods in litterature are :

- vertical height of the second upper anterior tooth (Gottfried, M.D., L.J.V. Compagno, and S.C. Bowman. 1996. Size and skeletal anatomy of the giant “megatooth” shark Carcharodon megalodon.)

- vertical crown height accounting tooth position (The relationship between the tooth size and total body length in the white shark, Carcharodon carcharias (Lamniformes: Lamnidae) - Journal of Fossil Research (Japan) 35 (2): 28–33. - Kenshu Shimada - 2002.).

- tooth width (In Renz, 2002, Megalodon : Hunting the Hunter)

- dentition and jaw perimeter, similar to the tooth width method and variously used by some authors (Bretton W. Kent: Speculations on the Size and Morphology of the Extinct Lamnoid Shark, Parotodus bend (le Hon). In: The Mosasaur. 6, 1999, p. 11-15) (Vertebral morphology, dentition, age, growth, and ecology of the large lamniform shark Cardabiodon ricki MICHAEL G. NEWBREY, MIKAEL SIVERSON, TODD D. COOK, ALLISON M. FOTHERINGHAM, and REBECCA L. SANCHEZ)

I don't know from where exactly comes the 1 inch/1 foot, I'm not aware of any qualitative study using it.

Your idea about Otodus is interesting but I think it's wrong, the shape of its centra simply does not suggest this kind of body plan.

At the very least, we do know thanks to the structure of their vertebra that Otodus (and its lineage) were sharks with a robust fusiform body.

Thank you, Gabe . . . I can see that you've put some effort into constructing a response.

As siteseer pointed out earlier, there is a non-scientific formula of 1" of tooth/10' of body length that is used in speculation about megalodon length. There is no "1 inch/1 foot" formula.

Considering that we're speculating on the size of Otodus, the speculation on the size of megalodon is not germane. Not germane, that is, unless you believe that Otodus has an identical body plan and habitus, and that is what is in question.

The shape of the Otodus centra doesn't suggest a fusiform body form as you assert . . . as far as I can determine, there is no complete Otodus vertebral column on which to base that assertion. What we do have is intuition, a feeling that Otodus MUST HAVE looked like megalodon or carcharias regardless of the 40 Ma separating them.

Estimating body length, much less body form, from isolated, or small groups of Otodus vertebrae is a leap into the unknown.

I've offered a different idea -- counterintuitive as it may be -- of the body form and habitus of Otodus. In my view, large vertebrae (~5 inches) are found in the thorasic region and the size tapers almost abruptly in the caudal region. This arrangement reflects the habitus of this 4-meter, ambush predator in which a powerful tail is not required for pursuit or cruising. Prove this conception wrong without relying on references to megalodon, if you can.

post-42-0-81104200-1427524116_thumb.jpg

Link to post
Share on other sites

In speculation, heuristic techniques are a useful tool, as long as the results are not interpreted as scientific fact.

Rules of thumb have a tendency to become regarded as more meaningful than they are when repeated often enough.

Link to post
Share on other sites

Harry, yes of course I meant 1 inch/10 feet.

You don't need to have a whole column for Otodus, isolated centra at least suggest the body plan and I'm highly, inherently skeptical regarding a Wobbegong like shape.

A number of papers and studies have been made about Otodus, such a possible body plan would have been hinted since a long by fossil sharks researchers. Though I agree it's an interesting question to discuss further. There is a paleontologist shark expert on the forum, MikaelS, who could give a more extensive comment on the matter.

Link to post
Share on other sites

...I'm highly, inherently skeptical regarding a Wobbegong like shape...

I think Harry's whole point is that, without physical prima facie evidence, all is conjecture; no one can prove his thesis wrong.

Conjecture, even when informed, is still conjecture.

Link to post
Share on other sites
Harry Pristis

I think Harry's whole point is that, without physical prima facie evidence, all is conjecture; no one can prove his thesis wrong.

Conjecture, even when informed, is still conjecture.

Yes, it was a point I was trying to make, triggered by the unfounded speculation earlier in this thread. But, Gabe's reluctance to question his convictions about Otodus illustrates the need for a broader caution:

Question everything, particularly your own beliefs. What is the evidence for what you believe . . . about sharks or about anything else significant to you at the moment? Keep an open mind for better, stronger evidence.

post-42-0-21740600-1427668804_thumb.jpg

Harry, yes of course I meant 1 inch/10 feet.

You don't need to have a whole column for Otodus, isolated centra at least suggest the body plan and I'm highly, inherently skeptical regarding a Wobbegong like shape.

A number of papers and studies have been made about Otodus, such a possible body plan would have been hinted since a long by fossil sharks researchers. Though I agree it's an interesting question to discuss further. There is a paleontologist shark expert on the forum, MikaelS, who could give a more extensive comment on the matter.

  • I found this Informative 1
Link to post
Share on other sites

Gabe,

You brought up "the ginsu shark," a somewhat popular name for Cretoxyrhina (and perhaps specifically C. mantelli). Cretoxyrhina mantelli is known from a couple of near-complete vertebral columns with numerous teeth some preserved cartilage of the cranium, jaws (plus fin elements in one; perhaps two feet missing from the the tail in both) plus a few specimens with several associated teeth and vertebral centra (the vertebrae=verts). No one knows how many vertebrae made up a column even in this shark - one of the best known Cretaceous sharks and certainly the best-known of the larger forms. Without that knowledge it's hard to compare it to the great white which has a known range in its vertebral count (170-187).

Also, the dentition of C. mantelli is not a good tooth-to-tooth match for C. carcharias because the former has been shown to have had more tooth files (and at least one more rowgroup type - symphyseals) than the latter with the largest teeth in the jaw being smaller than the largest teeth in a C. carcharias jaw. A very large Cretoxyrhina tooth would be 2 inches in slant height while that is more medium-to-large in a great white with a very large tooth being 3 inches in slant height. Yet, these two sharks appear to have shared about the same total length range, adults being 15-20 feet in length). If the near-complete Cretoxyrhina skeletons had not been found, and the genus were known only from isolated teeth, I would say that estimates of its size would range smaller because comparisons with a modern predatory shark would have led to that.

The C. mantelli dentition is the tearing-type like a mako while the great white is the cutting-type. The tearing-type is optimal for slicing into soft-bodied, thin-boned prey like bony fishes. It is not as efficient for chopping through thicker bones of marine reptiles, so despite the flashy artwork we've seen of the "ginsu shark" taking on a mosasaur, it might not reflect an interaction as common as Cretoxyrhina attacking the large bony fish of its time.

Paraphrasing Mikael Siverson, the giant shark vertebrae (4-5 inches in maximum width) found in the Early Cretaceous (Late Albian) of Texas probably belong to Cardaboidon even though that genus does not have teeth as large as Leptostyrax, the shark that appears to have had the largest teeth of that time. This may mean that Cardabiodon had more tooth files than Leptostyrax or at least a different formula within the rowgroups (anteriors, laterals, posteriors, etc.) that left it with a larger jaw perimeter which would indicate a larger body size (more massive and perhaps longer).

It's interesting that the 4-5 inch shark vertebrae of the Late Albian of Texas are in the same size range as the largest Otodus vertebrae but Otodus has been seen to have teeth reaching four inches in slant height which is about twice the size of most of the largest shark teeth of the Cretaceous.

Jess

Well, the fact otodontids and lamnids are not that related does not mean any size estimate can't be made. We do have complete sets of teeth from otodontids and a number of vertebra, which are still very similar to those in Carcharodon and allow comparisons. Body size and shape is determined by environmental constraints and given their equivalent lifestyle, it is unlikely that otodontids would have been extraordinarily different than lamnids. The Late Cretaceous Ginsu shark is even more distant than the white shark still its overall body plan (we have complete skeletons from it) is quite similar.

Also, I don't understand why people are still using the 1 inch/1 foot method whereas several really scientific methods have been made and are still used in litterature as of now.

  • I found this Informative 1
Link to post
Share on other sites

Siteseer, I agree with that. My point is that Otodus vertebra are well known and reported in litterature and their shape actually suggests the overall structure of the body. To my knowledge, Otodus vertebra do not suggest an extremely short and stocky body.

I even think that Dr. Mikael Siverson thinks (because of their vertebral structure) that otodontids were (slightly) more slender for their length than a lamnid such as Carcharodon. Maybe we should ask him, I think he's present on the forum.

Edited by Gabe
Link to post
Share on other sites

Gabe,

I would have to agree that Bretton Kent would be a go-to researcher when trying to answer the question of how to calculate the total length of Otodus as he specializes in realistically reconstructing a variety of extinct animals from whatever remains he has to work with (a modern-day Cuvier). If you could confidently reconstruct at least most of a Parotodus dentition, you would have some idea of the jaw perimeter and you could extrapolate from that to some extent. However, even he used the word "speculations" in the title of his article. Yes, good scientists try to use conservative language even when they're reasonably certain they're on the right track, but as an anatomist, he likely didn't want to go to far out on a limb either. He's probably hoping for some miracle deposit where someone can find at least a near-complete Parotodus (or closely-related Carcharocles) vertebral column with some associated teeth so he can see how his math worked out.

I have seen Otodus categorized as having a cutting-type dentition and I see that but it would also be an atypical example because its teeth are more robust, more thick-crowned than a genus I see as more typical like Carcharodon. Otodus had a mouth full of spikes rather than a set of saws like the great white. I think it was more of a shark that ate its prey whole rather than chopping out chunks but then it didn't have an opportunity to attack or scavenge larger animals. It was at least among the largest fishes, if not the largest marine vertebrate, of its time.

Carcharodon does have the classic cutting dentition and with serrated tooth edges it could kill a variety of marine mammals that were well-established or as recently-evolved as it was at the beginning of the Pliocene. Carcharodon could also scavenge the giant whales that were probably too large for it to prey upon when alive and healthy.

I'm not saying that these sharks were totally dissimilar but they do seem different enough in their teeth and apparent body size that they did not have the same lifestyle. Otodus evolved when life in the ocean was still recovering from the K/T extinctions (a time of warm seas), and within five million years, it pulled away from the pack as apex predator. It has been said that Otodus didn't die out. It's just that humans decided to give it a different name just because it developed fully serrated-edged teeth by the Middle Eocene and we also labelled each apparent stage of increasing serratedness as a separate species. In reality it was the same shark changing through time though the Early Eocene form likely looked noticeably different by the Early Pliocene just as its teeth reduced in number, increased in size, and flattened somewhat relative to its size.

Carcharodon appeared at a time of transition as well though with a longterm cooling trend nearing its own apex - the ice ages. It was a smaller, more energy-efficient, cool water-adapted marine mammal hunter at a time when being a gigantic, warm-temperate predator (Carcharocles) was no longer a winning combination.

Jess

Hello, the various methods in litterature are :

- vertical height of the second upper anterior tooth (Gottfried, M.D., L.J.V. Compagno, and S.C. Bowman. 1996. Size and skeletal anatomy of the giant “megatooth” shark Carcharodon megalodon.)

- vertical crown height accounting tooth position (The relationship between the tooth size and total body length in the white shark, Carcharodon carcharias (Lamniformes: Lamnidae) - Journal of Fossil Research (Japan) 35 (2): 28–33. - Kenshu Shimada - 2002.).

- tooth width (In Renz, 2002, Megalodon : Hunting the Hunter)

- dentition and jaw perimeter, similar to the tooth width method and variously used by some authors (Bretton W. Kent: Speculations on the Size and Morphology of the Extinct Lamnoid Shark, Parotodus bend (le Hon). In: The Mosasaur. 6, 1999, p. 11-15) (Vertebral morphology, dentition, age, growth, and ecology of the large lamniform shark Cardabiodon ricki MICHAEL G. NEWBREY, MIKAEL SIVERSON, TODD D. COOK, ALLISON M. FOTHERINGHAM, and REBECCA L. SANCHEZ)

I don't know from where exactly comes the 1 inch/1 foot, I'm not aware of any qualitative study using it.

Your idea about Otodus is interesting but I think it's wrong, the shape of its centra simply does not suggest this kind of body plan.

At the very least, we do know thanks to the structure of their vertebra that Otodus (and its lineage) were sharks with a robust fusiform body.

  • I found this Informative 1
Link to post
Share on other sites

Gabe,

In what articles are Otodus vertebrae discussed? I have MacFadden et al. (2004) but that is more of a study of the growth of the animal.

While I was reading up on this general topic, I learned that even in the vertebral column of an individual shark, a relatively thin vertebra can be next to a noticeably-thicker one and bigger ones can be next to smaller ones or they can all be around the same size from head to tail. It's like the rest of nature. Things don't move in a perfect circle, and sometimes, a cat eats popcorn.

Jess

MacFadden, B.J., J. Labs-Hochstein, I. Quitmyer, and D.S. Jones. 2004.

Incremental growth and diagenesis of skeletal parts of the lamnoid shark Otodus obliquus from the early Eocene (Ypresian) of Morocco. Palaeogeography, Palaeoclimatology, Palaeoecology. 206: 179-192.

Siteseer, I agree with that. My point is that Otodus vertebra are well known and reported in litterature and their shape actually suggests the overall structure of the body. To my knowledge, Otodus vertebra do not suggest an extremely short and stocky body.

I even think that Dr. Mikael Siverson thinks (because of their vertebral structure) that otodontids were (slightly) more slender for their length than a lamnid such as Carcharodon. Maybe we should ask him, I think he's present on the forum.

Link to post
Share on other sites

Siteseer, I certainly agree that Otodus was not an exact equivalent of Carcharodon in ecology and lifestyle, not the same lineage, the same teeth functions nor the same marine environemental context.

I know that Kent proposed an educated size estimate for Parotodus (favoring the upper jaw perimenter rather than the enamel height) but I don't think he proposed any body size estimate for Otodus.

The only mentions for Otodus size I know of are in Mark Renz book (9 m), in which we can see in picture a 7.5 m life size Otodus model made by Clifford Jeremiah, and a mention of a max size about 12 m from Hubbell's museum.

It is quite clear to me that Otodus, beyond its feeding apparatus and ecological evolution, was probably somewhat larger than the largest modern Carcharodon individuals.

I'm not an anatomist expert either but I don't think the various centra we found from Otodus suggest something shaped like a Wobbegong. Nor its pelagic lifestyle would suggest that.

Link to post
Share on other sites

Gabe,

In what articles are Otodus vertebrae discussed? I have MacFadden et al. (2004) but that is more of a study of the growth of the animal.

While I was reading up on this general topic, I learned that even in the vertebral column of an individual shark, a relatively thin vertebra can be next to a noticeably-thicker one and bigger ones can be next to smaller ones or they can all be around the same size from head to tail. It's like the rest of nature. Things don't move in a perfect circle, and sometimes, a cat eats popcorn.

Jess

MacFadden, B.J., J. Labs-Hochstein, I. Quitmyer, and D.S. Jones. 2004.

Incremental growth and diagenesis of skeletal parts of the lamnoid shark Otodus obliquus from the early Eocene (Ypresian) of Morocco. Palaeogeography, Palaeoclimatology, Palaeoecology. 206: 179-192.

This paper is pretty much one of the main I know where Otodus material is discussed with this one :

Paleobiology and taxonomy of extinct lamnid and otodontid sharks (Chondrichthyes, Elasmobranchii, Lamniformes) by Ehret, Dana Joseph, Ph.D., UNIVERSITY OF FLORIDA, 2010, 166 pages; 3496230

But I had the opportunity to read and discuss with several fossil selacians experts, nowhere I've seen the suggestion that O. obliquus could be a very short, stody shark with a disproportionnally wide mouth.

Edited by Gabe
Link to post
Share on other sites
Harry Pristis

Siteseer, I certainly agree that Otodus was not an exact equivalent of Carcharodon in ecology and lifestyle, not the same lineage, the same teeth functions nor the same marine environemental context.

I know that Kent proposed an educated size estimate for Parotodus (favoring the upper jaw perimenter rather than the enamel height) but I don't think he proposed any body size estimate for Otodus.

The only mentions for Otodus size I know of are in Mark Renz book (9 m), in which we can see in picture a 7.5 m life size Otodus model made by Clifford Jeremiah, and a mention of a max size about 12 m from Hubbell's museum.

It is quite clear to me that Otodus, beyond its feeding apparatus and ecological evolution, was probably somewhat larger than the largest modern Carcharodon individuals.

I'm not an anatomist expert either but I don't think the various centra we found from Otodus suggest something shaped like a Wobbegong. Nor its pelagic lifestyle would suggest that.

Now we're getting to the source of Gabe's convictions: Mark Renz's book. I helped Mark edit his book for science content, so I'm familiar with it. But, Mark didn't limit himself to the science, and that makes it fun reading for the average reader. Mark will tell you that he is no shark expert. Cliff Jeremiah is a dentist who entertains his office patients with composite reproductions of shark jaws and the illustrated fantasy Otodus in fiberglass. Gordon Hubbell will tell you Otodus size and form is speculation. All of this speculation is based on the unsupported assumption that Otodus had a body plan similar to megalodon or carcharias.

It is quite clear to me that Otodus, beyond its feeding apparatus and ecological evolution, was probably somewhat larger than the largest modern Carcharodon individuals.

What seems quite clear, Gabe, is that you are arguing from the 'illusion of knowledge.' What do you suppose is the "ecological evolution" of Otodus -- what does that even mean? You assert that Otodus had a pelagic lifestyle, but I don't think there's evidence for that. Based on where the fossils are found, it might be more accurate to call Otodus a near-shore predator.

You admit that you're no "anatomist expert," yet you assert that the shape of Otodus vertebral centra suggests something about the Otodus body plan. What specific features are you talking about? What characteristics of the Otodus centra suggest a fusiform body rather than a wobbegong body?

But I had the opportunity to read and discuss with several fossil selacians experts, nowhere I've seen the suggestion that O. obliquus could be a very short, stody shark with a disproportionnally wide mouth.

Here's the thing, Gabe: The fact that an idea has not occurred to you, or been mentioned to you by others, is not an argument against the new idea. That sort of thinking is illogical . . . a roadblock to progress . . . it is anti-scientific.

Edited by Harry Pristis
Link to post
Share on other sites

I've not used Mark Renz as an authority (I fairly know he's not an expert himself) and despite the speculative status of Jeremiah's reconstruction, I've not seen any fossil shark expert complaining about it.

I base mainly my assumption of this body shape in Otodus because of the similarities of its centra with those of C. megalodon. To my knowledge there are no important differences in their respective morphology and for reading Gottfried, Kent and others, C. megalodon centra are definitely consistent with a robust fusiform body. So are O. obliquus and C. megalodon centra that different ?

You then accuse me of being anti-scientific, well I'd just ask a scientific analysis and observations suggesting by A + B that the various vertebral centra of O. obliquus are indicating of a very stocky, disproportionnally wide-jawed shark, I have nothing against the idea as long as it is based on some data, possibly tested.

Baseless speculations are actually anti-scientific.

Edited by Gabe
Link to post
Share on other sites

Lot's of questions here. Maximum vertebral diameter relative to body length is quite variable in lamniform sharks. Cetorhinus, for example, has a slender vertebral column whereas some anacoracids had large-diameter centra relative to body length.

The Otodus vertebra (if we assume it was the largest within the vertebral column) probably originates from a shark 4-10m in length based on vertebral data alone (using modern and fossil lamniforms as templates). However, upper jaw combined tooth-width would most likely give a much better estimate as jaw circumference/body length does not vary that much in apex predatory sharks. There are a couple of notable exceptions though. Cretodus crassidens had a pretty wide mouth relative to body length (undescribed skeleton).

Leptostyrax teeth reached a greater height than did late Albian cardabiodontid teeth but this is quite irrelevant as the latter are wider. Tooth-width is more indicative of jaw circumference than is tooth height at a given tooth-file count.

Did Otodus reach a greater total length than the largest modern white sharks? Most likely yes based on upper jaw circumference (several associated, seemingly complete dentitions in the GH collection) [however see example above regarding C. crassidens]. Vertebral data, although considerably less reliable, indicate, if anything, that O. obliquus reached a larger maximum size. Was O. obliquus built like a wobbegong? Probably not based on the vertebral centrum morphology and the fact that there are no modern examples of dorsoventrally flattened sharks with a dentition of Otodus type. The latter may however have looked like a giant sand tiger shark. We simply don't know at this stage. Ambush predatory sharks with a flat body seem to converge dentally towards the Squatina dentition bauplan. For example Wobbegongs are more closely related to the white shark than to angel sharks but a white shark dentition probably does not work that well for a dorsoventrally compressed suction feeder.

In cardabiodontids there is a general trend (late Albian to middle Turonian) of slowly increasing maximum tooth size coupled with a slowly decreasing maximum vertebral diameter. Combined this indicates a relatively rapid reduction in tooth-files over time (as there are no clear indications of a steepening of the tooth-size gradient). An alternative interpretation would be of a progressively more slender vertebral column, perhaps not the most likely scenario.

  • I found this Informative 4
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...