Shark Vert Size Ratio To Body?

[MikaelS]

Do you have a reference for that statement?

or they can all be around the same size from head to tail. It's like the rest of nature.

[MikaelS]

One of the syntypes of C. mantelli is huge and would have been closer to 80mm in height originally (not slant height but vertical height).

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.

[MikaelS]

This conclusion seems to be based on specimens from the WIS whereas the admittedly scant evidence at hand suggest that the truly gigantic individuals of C. mantelli spent their twilight years in fully open marine environments (which the WIS was not).

Yet, these two sharks appear to have shared about the same total length range, adults being 15-20 feet in length).

[MikaelS]

A couple of comments. Unpublished data on a very diverse otodontid assemblage from the Danian type region includes a proper Otodus dentally close to Thanetian O. obliquus but a bit smaller. Its tooth-crowns are all in pristine condition with hardly any wear at the tips so perhaps they did swallow their prey whole, at least the earliest forms. A giant co-occurring Cretalamna species on the other hand have heavily worn tooth crowns indicating abrasive prey.

I would however caution against making general statement about tooth form and feeding habits. Large individuals of Cretodus crassidens for example did not really have a cutting dentition but that did not really matter as its massive roots secured the robust teeth well enough for it to eat large turtles like we eat a sandwich, literally.

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.

[MikaelS]

You can't really be that specific as that would indicate a maximum body length around 5 metres in Cetorhinus for example. The basking shark is most likely more closely related to lamnids (assuming you mean Lamnidae) than it is to O. obliquus.

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).

Edited March 31, 2015 by MikaelS

[fossilized6s]

I'm glad to see my ignorance has spurred such an informative and thought provoking discussion.

I'll be the first one to say that my knowledge of sharks may classify as "moronic". Haha!

Being an artist, i study pictures and recreations in great detail, and then log them to memory. So if i want to draw something i can without referencing to a picture. So when i continuously saw recreations of O. obliquus looking similar to a scaled up version of a GW, (in my ignorance) i had assumed that a body plan was established. I had also assumed that since "people" kept representing Otodus as a giant GW that a "we" could determine such things as length from a vert size by comparing the two and doing simple math. Reading all of this makes me realize that we can't. And every picture i google isn't accurate. It seems as though it very well maybe a case of "he said, she said" until a complete and perfect specimen is recovered. But that is one thing that i love about paleontology, it's one of the last frontiers of discovery left in this World.

If it's not for ignorant, curious, dumbass' like my self asking impossible questions, we wouldn't have the educated school us with knowledge. Allowing the cycle of knowledge to continue.

Thanks guys!

[Harry Pristis]

Thank you, MikaelS . . . Thank you for couching your opinions in probabilities. Speculation should have some flexibility, leaving room for the improbable.

I erected the wobbegong-like Otodus as a foil for the absolutes in the speculation in this thread. There is nothing like a counterintuitive argument to get people to examine evidence and to pare opinions down to a fact base . . . usually, it works like that. Not completely, in this case.

But, I see that fossilized6s has figured it out, and I'm happy with that.

[MikaelS]

I did realise the wobbegong example was, above all, an attempt to stimulate critical thinking. As you say we should definitely not flat out rule out the improbable. I know of Cretaceous shark tooth morphotypes than no-one would have guessed functioned they way they did (i.e. taxa based on isolated teeth but represented by undescribed skeletons).

[Gabe]

I pretty much agree that improbable explanations can't be ruled out, I was more claiming for the most probable suggestion given by the morphology of the centra in Otodus and as MikaelS confirmed, a wobbegong-like body is not the most likely for O. obliquus. That's all what I reported.

Of course there are previous examples where improbable body shape became true (a recent example would be the small-legged, maybe partly quadrupedal Spinosaurus).

Critical thinking to stimulate research is a good thing to do, I believe that's what Jack Horner did while arguing that T. rex was a scavenger, his claims, though unpublished, stimulated new research regarding T. rex ecology, allowing to know more in details the lifestyle of the animal.

MikaelS, I have failed to find any published size estimate for O. obliquus, I've just seen this indication for Hubbell's private Museum, : http://files.tellmewhereonearth.com/Photos%20Sharks/gordon82a.JPG

Is it tenable ?

I agree that jaw circumference is a good method but in the particular case of C. megalodon, couldn't be possible that the shark had a wider mouth compared to its body length ? I have the clear impression that, compared to the white shark, the summed tooth width in C. megalodon is much wider at the same maximum tooth height. I think that the reconstruction of about 16 m suggested by Gottfried et al. 1996 indeed suggests a stocky, wide-jawed shark.

If that's the case for C. megalodon, would that be the same in O. obliquus ?

Edited April 1, 2015 by Gabe

[siteseer]

Hi MikaelS,

Thank you for joining the conversation. It was something Gordon Hubbell once said informally and probably not about a large shark. I was paraphrasing him from memory so my statement may have strayed from the actual quote.

Jess

Do you have a reference for that statement?

[siteseer]

I'd like to see that tooth. It makes me wonder how old that individual was.

One of the syntypes of C. mantelli is huge and would have been closer to 80mm in height originally (not slant height but vertical height).

[siteseer]

Yes, the largest C. mantelli teeth I've seen have come from Kansas and Texas. Where has the evidence of gigantic individuals been found?

This conclusion seems to be based on specimens from the WIS whereas the admittedly scant evidence at hand suggest that the truly gigantic individuals of C. mantelli spent their twilight years in fully open marine environments (which the WIS was not).

[MikaelS]

The giant syntype (along with all but one syntype) of C .mantelli is from an unknown chalk quarry (there are many) near Lewes, England. Its possible age is somewhere within the Cenomanian to early Coniacian interval (i.e.pre-Smoky Hill Chalk age). Charlie Underwood sent me a picture of it so I shall upload it here when I get to work tomorrow. Its a cusp, about 60% taller than the tallest cusp in the dentition of VP-2187, a specimen with an estimated TL of 4.5m or thereabouts (Shimada 1997) to just under 5.5 m (Newbrey et al. in press APP). Some of the other syntypes are also very large, much larger than C. mantelli teeth of pre-Smoky Hill Chalk age in the WIS.

As shown by Shimada there is a general increase in tooth size in this species in the WIS with the largest being found in the Smoky Hill Chalk which makes the size of the UK specimens even more remarkable.

[siteseer]

That is interesting - Otodus confirmed in the Danian. I don't think I've heard of a Danian-age Otodus tooth from Morocco. I haven't seen many teeth of that age at all - some from at least one site in New Jersey and the biggest teeth were Cretalamna.

Otodus feeding on prey it could swallow whole fits with the idea that it was like a large sand shark. With all these Otodus dentitions floating around when are we going to see an article on at least one of the more complete ones?

I understand that general statements about tooth form and feeding habits are going to have exceptions. It's just that Otodus teeth don't seem to show a lot of wear - animals that ate a lot of fish.

A couple of comments. Unpublished data on a very diverse otodontid assemblage from the Danian type region includes a proper Otodus dentally close to Thanetian O. obliquus but a bit smaller. Its tooth-crowns are all in pristine condition with hardly any wear at the tips so perhaps they did swallow their prey whole, at least the earliest forms. A giant co-occurring Cretalamna species on the other hand have heavily worn tooth crowns indicating abrasive prey.

I would however caution against making general statement about tooth form and feeding habits. Large individuals of Cretodus crassidens for example did not really have a cutting dentition but that did not really matter as its massive roots secured the robust teeth well enough for it to eat large turtles like we eat a sandwich, literally.

[MikaelS]

The Danian Otodus (NP3) is from the Limhamn quarry in Southern Sweden. All rocks exposed are of Danian age.

https://c1.staticflickr.com/9/8309/8051249618_9c313e44b8.jpg

I think DW and JB intended to describe these (the Moroccan Otodus dentitions) but nothing has materialised. Neither of them are in the 'publish or perish' rat race.

Edited April 1, 2015 by MikaelS

[Gabe]

Do we know where exactly in the Danian ?I'm half surprised that otodontids had enough time to evolve, after all the Danian represents quite a time lapse.

MikaelS, do you think it is plausible to envision a particularly wide-jawed C. megalodon, not as much as Harry Pristis suggested for Otodus, but simply quite bigger-headed than most lamnids ?

The dentition of the white shark seems shorter by comparison to the preserved sets of C. megalodon, meaning that the tooth height decreases quicker in Carcharodon than in Carcharocles.

Meaning either that Carcharocles had more massive jaws/head or that it was comparatively even larger at maximum size than calculations solely based on tooth height usually suggest (16-17 m) ?

Edited April 2, 2015 by Gabe

[siteseer]

Gabe,

The Danian covers about five million years. There was a radiation of sharks and rays during that time - not just new species of Cretaceous survivors (Cretalamna, Sphenodus, Dasyatis, etc.) but new genera like Palaeocarcharodon and Archaeomanta. It's interesting that there was a "giant Cretalamna" in the Danian. It gives an idea of the rather crowded rush to take the apex predator niche once the mosasaurs, plesiosaurs, and most of the large sharks were gone. It seems like a lot more is being learned about the Paleocene these days.

Jess

Do we know where exactly in the Danian ?I'm half surprised that otodontids had enough time to evolve, after all the Danian represents quite a time lapse.

MikaelS, do you think it is plausible to envision a particularly wide-jawed C. megalodon, not as much as Harry Pristis suggested for Otodus, but simply quite bigger-headed than most lamnids ?

The dentition of the white shark seems shorter by comparison to the preserved sets of C. megalodon, meaning that the tooth height decreases quicker in Carcharodon than in Carcharocles.

Meaning either that Carcharocles had more massive jaws/head or that it was comparatively even larger at maximum size than calculations solely based on tooth height usually suggest (16-17 m) ?

[MikaelS]

Could not find that photograph on my computer atm so I simply have to refer to Agassiz 1843, pl. 33, fig 9. The labially curved cusp in profile view in this specimen as well as in the tooth in fig. 8 is something I have seen on larger teeth from the late Cenomanian and early Turonian but not in specimens of Smoky Hill Chalk age (supporting the age deduced from the local stratigraphy in the Lewes area). The isolated cusp in fig. 9 is taller than the largest complete anterior tooth in VP-2187. Add to that the missing root and you get a very, very large Cretoxyrhina tooth.

Yes, the largest C. mantelli teeth I've seen have come from Kansas and Texas. Where has the evidence of gigantic individuals been found?

Edited April 5, 2015 by MikaelS

[MikaelS]

Well the age was given in the previous post (NP3).

Do we know where exactly in the Danian ?I'm half surprised that otodontids had enough time to evolve, after all the Danian represents quite a time lapse.

[siteseer]

For those unfamiliar with the term, "NP3" refers to a zone within a series of zones used to break up the Cenozoic Era into smaller time units. This series, or zonation, is based on the presence of particular calcareous nannofossils found in marine deposits. The Paleocene is divided into nine NP zones with NP9 overlapping the Paleocene-Eocene boundary. NP1 is the first zone covering the first half-million years of the Paleocene. NP3 roughly covers from about 64 to almost 62 million years ago which is about the middle-third of the Danian age.

[MikaelS]

That is possible. I have noticed a (perceived) discrepancy between my calculated jaw circumference in large C. megalodon and the actual size of the vertebrae of this taxon. Jaw circumference (using the associated dentition illustrated by JB on elasmo.com as a base) indicate a maximum length of roughly 18 metres but 30 cm diameter centra seem to be absent (assuming a centrum diameter/TL ratio comparable to the white shark) or at least I have not seen any. However as explained in an earlier post centrum diameter/body length ratios varies considerably in lamniforms.

MikaelS, do you think it is plausible to envision a particularly wide-jawed C. megalodon, not as much as Harry Pristis suggested for Otodus, but simply quite bigger-headed than most lamnids ?

[Gabe]

That is possible. I have noticed a (perceived) discrepancy between my calculated jaw circumference in large C. megalodon and the actual size of the vertebrae of this taxon. Jaw circumference (using the associated dentition illustrated by JB on elasmo.com as a base) indicate a maximum length of roughly 18 metres but 30 cm diameter centra seem to be absent (assuming a centrum diameter/TL ratio comparable to the white shark) or at least I have not seen any. However as explained in an earlier post centrum diameter/body length ratios varies considerably in lamniforms.

That's intriguing.

Or maybe the absence of very large corresponding centra is simply because of sampling bias ? Really large teeth from really large dentition are already rare, I could assume megalodon centra should be even more uncommon ? The largest centra I've heard about is one of these reported in this paper http://2dgf.dk/xpdf/bull32-01-02-1-32.pdf at 23 cm in diameter. Not sure if we can assume it was definitely the largest in that shark ? Interestingly there is an associated big tooth with it that they estimate the original length at 16 cm.

Or that could mean megalodon was really large but slightly less deep than a typical lamnid, though would that be an appropriate body shape for a shark of that lifestyle ?

What is the jaw circumference you've calculated for this species ? I've never found a proper data in the scientific litterature despite that several fairly complete associated dentitions are known (the one from Saitama).

I find interesting that you find a maximum size of 18 m, looks like these authors found a similar size using a different method among various teeth specimens in this article (the last one in the table) :

Sharks and Rays (Chondrichthyes, Elasmobranchii) from the Late Miocene Gatun Formation of Panama Catalina Pimiento, Gerardo González-Barba, Dana J. Ehret, Austin J. W. Hendy, Bruce J. MacFadden, and Carlos Jaramillo

Are we going toward a consensus regarding the maximum size of C. megalodon ? (I was thinking the max would level off at 15-16 m).

Edited April 7, 2015 by Gabe

[Auspex]

Or maybe the absence of very large corresponding centra is simply because of sampling bias ? Really large teeth from really large dentition are already rare, I could assume megalodon centra should be even more uncommon ?...

Certainly a factor. Sharks go through hundreds of teeth in a lifetime, but have only one spinal column. Still, one could graph either by size/abundance and see a useful correlation.

[Still_human]

Oh well, I found this thread cause I had the exact same question. Ive been doing a little research on shark size/max very size, but so far the info has been very limited. So far I only have 3 or 4 examples of size/max very size of great whites, so I'm still far from having any thorough results.

 

Also, worry not everyone, I CAN solve the otodus shape/size issue, as I have actually found a picture of it, believe it or not!

http://www.prehistoric-wildlife.com/species/o/otodus.html

As you can see, it also proves that they're either still alive, or that humans have actually been around for much longer than we thought!