Megalodon size

[Grey]

Is the study anticipating introducing other associated tooth sets in the official publication? That would be great.

Yes, including a Chilean large dentition.

I'm still uncertain why some type of interdental spacing wasn't used. I understand they can't predict how much space was between the teeth, but we know such space existed between the teeth. The poster states the sum of the teeth provides stable estimates of jaw size. But without accounting for interdental spacing, doesn't it slightly reduce the size of jaws? Perhaps a calculation that includes very conservative calculation of spacing would yield more accurate findings.

No, the spacing is simply disregarded in both (living sharks and extinct sharks) since there is no data about. That would be complexifying the method for the same result. The spasing, being disregarded, is assumed as similar. That's like with their regression to estimate Livyatan size based on skull width, Lambert et al. would have tried to include the amount of thickness of muscles, flesh and blubber around the skull.

[Grey]

Here's a comparison of body sizes estimates based on vertical height, tooth width and crown height compared with the summed dentition width based estimates. The base group are great white sharks specimens from Mollet et al. 1996 (when the corresponding measurement is available) at all ontogenetic stages (from the smallest/youngest to the largest/oldest).

Otodus megalodon tooth specimen PF 1168, vertical height 168 mm; width/crown width 125 mm; enamel/crown height approx. 125 mm

Body size estimates based on vertical height :

14.01 m
14.27 m
14.71 m
14.52 m
16.1 m
15.52 m
21 m
14.2 m
15.18 m
16.15 m
19.3 m
15.15 m
15.54 m
16.42 m
14.44 m
18.79 m
15.5 m
15.51 m
17.22 m
15.85 m
15.87-16.25 m
17.35 m
18.86 m
21.22 m (7 m GWS ?)

The range of body size for the Otodus megalodon with this particular tooth, based on tooth vertical height, is 14-21 m, with an average about 16.3 m from 24 white sharks UA1 height, relatively close to the value proposed by Gottfried et al. using an even larger sample. (I’ve included the problematic 7 m specimen from the chart, the exact body size is disputed but there is consensus it was remarkably large). Based on all ontogenetic stages.
There is no recorded size for the UA1 vertical height of the Yorktown dentition but derived from PF 1168, its vertical height would be about 146 mm, which would indicate a range about 12-18.4 m with an average size about 14.1 m. Whilst the summed width of the Yoktown upper dentition suggests a range about 15-22 m at all ontogenetic stages, 17-20 m at adult stage for an average about 18 m.

Body sizes estimates for Otodus megalodon based on the 125 mm width of the PF 1168 tooth:

20.41 m
20.09 m
17.79 m
14.4 m
15.86 m
15.09 m
13.5 m
15.25 m
12.65 m
18.22 m
19.39 m
15.79 m
18.71 m
14.38 m
16.8 m
15.58 m
18.64 m
14.175-15 m
22.81 m (7 m GWS ?)

The range of body size based on the UA width for the O. megalodon with a tooth width about 125 mm is 13-23 m at all ontogenetic stages for an average about 16.7 m. Taking the UA1 width of the Yorktown dentition should result in a range of 11-20 m for an average about 14.5 m, whilst the body size estimate from Leder 2016 based on white shark summed upper dentition is 15-22 m, and 17-20 m based on adults only.


The average body size estimates for an Otodus megalodon based with the125 mm crown/enamel height of the PF 1168 tooth as an UA1 should be approx. 14.1 m. (Shimada 2003), the UA1 from the Yorktown dentition using the same method should be 12.4 m, whilst the average size based on summed upper dentition width in adult white sharks indicates 18 m.



Regarding the estimates, it is notable there is no need of the "discutable" GWS specimens in order to obtain sizes around 20 m or more using isolated tooth measurements for megatooth. This is a matter of variation, not selection of specimens.
These estimates are usually considered conservative since in larger specimens the teeth have stopped their growth.
There is demonstration that summed upper dentition width is more stable than the previous methods used to extrapolate O. megalodon size and results in significantly higher estimates.
Even the smaller UA1 tooth from the Yorktown dentition results in larger sizes estimates than the larger PF 1168 specimen using vertical, width and crown height related methods.
Of course, additional data from white sharks/makos and megatoothed dentitions need to be added to definitely confirm this. Also, it appears that Pimiento & Balk 2015 datas about megalodon size trends are mostly erroneous. Shimada's method is definitely not appropriate for this genus.

Site note : if the latest method is proven more tenable, I suspect the classic rule of thumb used by meg teeth collections "1 inch=10 feet" for the slant length of an anterior tooth will coincidentally correspond to the results of the summed dentition width...

[elosha11]

Thanks for that summary Grey. Very informative. I know there is a bigger Chilean Meg set being analyzed. Any idea just how much bigger the Chilean front tooth row set is compared to the Yorktown set? Has your research team found other complete short fin mako and GWS tooth sets? One source who might be able to point you to some complete sets for both GW and Mako is Henry Mollet. I've communicated with him several times over the years about his great white and other shark profile pages at elasmollet.com.

I'm trying to remember what Pimiento and Balk said about Meg size trends in their 2015 research. My recollections is that they just stated that max BL seemed fairly stable throughout Meg's existence, but that there may have been a greater number of maximum sized sharks closer to the end of its existence. I'll have to look it up again to see if I'm remembering their findings correctly. If that's the case, how does your current research disprove that?

Did they also make specific BL predictions, my recollection is that they followed the current consensus that the shark's maximum length as probably 18+ meters, which your research may certainly cast into doubt. I guess that your research may also cast doubt on their use of lateral teeth to make size predictions, is that what you were referring to?

[Grey]

No idea how bigger but apparently definitely bigger.

I think they're clearly looking at a bigger sample from both species.
With access to Hubbell's house and various collections I think they'll have enough at hand.

The current research demonstrates that Shimada's method is adapted to Carcharodon but not Otodus/Carcharocles because of the extreme variabilities of the size estimates between each tooth position in a complete dentition.

There is already some variation when applied to Carcharodon. C. hubbelli estimates from each tooth position varies already varies between 3 and 7 meters.

But applied to a meg dentition gives even more enormous variation, from 12 to 45 meters on the Yorktown dentition.

From this it is clear that Pimiento 2015 estimates are problematic given the unreliability of the method with meg teeth. And if you try to adjust Pimiento teeth measurements with the meg individual teeth from the on-going study and derive some sizes estimates from the ones in the poster, you'll note a total dissimilarity with Pimiento's estimates.

[Grey]

It's been a long since this thread and subject have been discussed. Making a point :

Meg size estimates in the scientific lit :

C. megalodon (or Otodus(Megaselachus) megalodon) was estimated at 24-30 m, even as much as 39 m (Leriche 1926), in pre-WWII by scientists, based on erroneous anatomical reconstructions of sharks jaws and dentitions, mainly the famous Bashford Dean 1909 reconstruction.

Since, Randall (1970) published an estimated length of about 13 m TL based on crown heights of 115-117 mm using a sample of white shark specimens as basis. Ellis & McCosker (1991) challenged this conclusion, arguing that crown height does not increase necessarily with the animal total length.

Using the total tooth height of of a 168 mm high UA2 from the Chicago Museum, Gottfried et al. (1996) suggested a conservative maximum length of 15.9 m. Conservative because, as expressed in their abstract, not in their main paper but in Mollet (1996) from the same book, modern very large great white sharks continue growing after their teeth have reached maximum size.

Moreover, 15.9 m is a mean size estimate derived from their regression. Based on the same tooth, depending the modern great white specimen, sizes estimates from this tooth vary as low as less than 14 m to as much as 21 m. Further, Gottfried et al. suggested a possible maxima in excess of 20 m based on the 168 mm tooth using a very large, somewhat problematic great white shark specimen. Using a large (largest?) confirmed specimen, they got a total length of about 17 m. However, because of individual variability, even somewhat average sized individuals can result in remarkably low or large sizes extrapolations for megalodon.

Shimada (2002) using his method based on crown height from each tooth position, proposes a somewhat lower 14.5-15.1 m for the same individual tooth.
However, Pimiento (2010), determining sizes estimates from teeth found in the Gatun Formation, figures a specimen at 16.8 m. In 2013, using new specimens from the same location, an estimate of about 18 m is proposed for one specimen. Interestingly the calculation for this tooth specimen appears to be wrong itself and the corrected result is 19.6 m. In 2015, Pimiento & Balk suggest a mean average size of about 10.5 m for the species using the same method and a sample of 544 teeth.

The implication of the latest sizes estimates for megalodon :

18 m is currently considered a consensus among fossil sharks specialists for C. megalodon. It is important to recall that 18 m is an extroardinary length for any aquatic macropredator, especially a shark. Simply put, no other shark in history, except maybe for some whale sharks specimens, approach such a length. Among apex predatory tetrapods, only the modern sperm whale reaches or exceed this length, but preying on animals less than 1 % its own body mass, with no apparent use of its teeth, its status as a macropredator is questionable. The largest true macropredator comparable to megalodon in modern days are the orca (up to 9 m) and the white shark (up to more than 6 m). In the fossil records, despite numerous exaggerations and poorly rigorous reports, the biggest Mesozoic pliosaurs all level off at 12-13 m based on the most modern data (McHenry 2009; Knutsen 2012; Benson 2013). The giant archaeocete Basilosaurus was an incredibly large macropredator, as large as 16-18 m (Gingerich et al. 1990) and perhaps as much as 23 m but its body plan probably made it a much lighter animal at the same length than a fusiform lamniform shark. Some mosasaurs perhaps exceeded 17 m (Lingham-Soliar 1998) but this has come under some criticism. The largest complete mosasaurs skeletons measure actually almost 14 m (Bruce and the Bunker Tylosaurus). All in all, the only fossil macropredator that rivals megalodon size estimates is the physeteroid Livyatan melvillei. Interestingly, this genus occures at the same time as megalodon (it is also notable that along with megalodon, some of the largest macropredatory sharks in the history appeared during the Neogene). Livyatan would have measured about 14 m long comparing its skull width with modern sperm whales. Using a specimen of its relative Zygophyseter, a possible lenght of 16.2-17.5 m. So it is quite important to report how megalodon may have been a spectacular and truly unique organism in the history of life.

But how solid are the methods in use and is 18 m a maximum size ?


There are some issues with the methods involved in the published works about meg size.

As Gottfried et al. reported, teeth stop growing in some white sharks individuals, which limit the relevance of the data.
Shimada's method, although widely in use for this genus, is even more problematic.
At first, a criticism of this method could be that it is based on a small sample of only 12 C. carcharias specimens.
Second, the finding of complete C. megalodon associated dentitions show (but this was never really described) proportional differences in the dentition proportions with the modern white shark dentition. Basically, megalodon teeth decrease in size much more slowly from anterior to posterior, both in height and width, than in white sharks. For the same anterior tooth size, the megalodon dentition size extends sensibly wider than in the white shark.
Third, all Pimiento's estimates for individual teeth are themselves mean estimates from several possible positions. Also, Pimiento willingly ignored the problematic (and potential) UA3 position in all her datas.
This results in any estimates based on Shimada prone to vast errors. It should be added that attempts to extrapolate a precise average size for this species are even more difficult because of sampling bias, specimens removal, geographical restrictions (large adult individuals were rarer in most of the sites available to findings, which were mainly shallow water areas) and indications that immature sharks shed their teeth more frequently than adults.


In 2002, Renz reports in his book a method, proposed by Cliff Jeremiah, using sole anterior tooth width in comparison with a white sharks tooth from the same position. Although no true maximum size was proposed in this book, a size of at least 18 m was proposed for an adult of this species. This method implies that for each cm in tooth width, there is 1.37 m of shark. Using this, the largest upper anterior tooth in Hubbell collection suggests a megalodon of a bit more than 19 m. However, its exact details being not published, it is difficult to discuss further the relevance of this method in statistic. Nevertheless, a calculation using the average size estimate from this post of me (http://theworldofanimals.proboards.com/post/29099) suggests it to be credible.
Also, although Hubbell's large tooth is really huge, there are at least a handfull of teeth from similar positions that appear wider.
Plus, some smaller teeth but extremely large for their likely position, indicate the existence of similar-sized or even larger upper anterior teeth specimens.

In various lecture talks from the 2010's, Mikael Siversson explained he prefered to use the total width of known entire dentitions of megalodon and compare it with the most related or morphologically comparable modern sharks species. Using the Bone Valley dentition found by fossil collector Larry Martin, considered as coming from a juvenile individual, later sold to Gordon Hubbell, he estimated the shark behind it at 11-12 m long. Using large isolated teeth and adjusting them to the same position in the Bone Valley dentition, Siversson reported max lengths of almost 20 m. However this estimate was based on a sole, somewhat small-sized individual. Individual whole sets teeth from larger individuals have been found elsewhere, but not always available to the scientific community. Leder et al. (2016) using Siversson suggestion, tested this method on a large dentition from the Yorktown Formation, which resulted in a 18 m total length estimate of average mean size based on a sample of adult white sharks specimens (for a range of 17-20 m). Interestingly, the teeth in this dentition are not among the largest ever found, which would suggest the larger specimens of this species were significantly larger than the specimen from which this dentition came. Other sets of teeth will be tested by the authors of this study. One of the main advantages of this method is that it is based on the largest available, quantifiable material we have from this species, the entire summed width of the associated dentition. In biology, on theoretical grounds, body size estimates based on uncomplete remains are likely to be more stable and reliable as the material used as basis composes a larger part of the body.


So, based on this method, it appears that megalodon could quite plausibly and not so uncommonly exceed 18 m as at the very least least one of the very few individuals known from associated dentitions would be already that large. However, more work on this method need to be done.
Another interesting point from Leder et al. is to use specimens from the same ontogenic status. Using this factor even with the other, possibly less stable methods, based on isolated teeth height or width would be interesting.

The alternative, that megalodon did not exceed 18 m, would necessarily imply the largest individuals (or the species as a whole) to have proportionally much wider dentition/mouth/skull and possibly overall a much wider and thicker body plan, which would raise the question of how such a proportioned shark with active lifestyle and mobile prey items would operate. Actually this would make the animal even thick bodied than the reconstruction proposed by Gottfried et al.
The Bone Valley dentition, using the method from Leder et al. 2016, suggests a body length between 20 and 30 % larger than while using Shimada's method applied to the anterior teeth of the same dentition.

At the very least, what can be said is that the Bone Valley juvenile megalodon upper dentition summed width corresponds to the summed upper dentition width of a hypothetical 12 m white shark, while the crown height of its upper anterior teeth corresponds to a hypothetical 9.3-9.4 m white shark.
The discrepancy between the two methods seems even wider with the Yorktown specimen.



It is possible as well the reality lies between both methods, although this still would suggest both a remarkably large and thickly-shaped shark. Finally, the main purpose nonetheless being to more appreciate the actual plausible size range of this species.

All the methods suggest this species reached at least up to 17-18 m, and this is constrained by the availability of large teeth to the paleontologists. Almost all the largest megalodon teeth reported are from private collections, and almost always measured in diagonal length, a data not directly used in the papers and methods involded. Plus, rumors, more or less credible, of even larger teeth persist to this day... Gottfried et al. used a 168 mm or their data, indicate a mean conservative size of 16 m and a max of 20 m, but the Black Hills Institute possesses a tooth 5 mm higher. This tooth is also 4 mm wider than Gordon Hubbell tooth...

The current conclusion is that C. megalodon indeed reached 18 m and plausibly exceeded it by a sensitive margin. If not, it may have been a particularly large-jawed, thickly-built shark, certainly a good deal heavier at the same length than the current white shark.

[Grey]

The preserved C. chubutensis jaw from Ica is under description. We'll know soon about the actual structure of the jaw and if the estimates of size based on dentition with lamnids as template are really realistic.

Strangely I've heard from one of the students that the fossil seems to suggest that "Carcharocles were rather small". Unless the dentition has a totally unexpected structure making the whole mouth overall smaller than one would expect while based on Carcharodon, I don't understand how this would indicate the genus being overall "smaller", especially since that specimen doesn't seem to be particularly large even for chubutensis, the teeth in it are reported being about 8-9 cm. Still the few pictures of the mold seem to indicate a quite massive piece.
My personnal comparison of the Yorktown C. megalodon associated set of teeth from the Yorktown formation compared with the dentition of Carcharodon hubbelli (total length estimated at approx. 5 m based on dentition and vertebral measurements, Ehret. 2009) shows the C. megalodon tooth row being more than 3.5 times larger than in C. hubbelli.

I discussed this with Bill Heim who suspects that Carcharocles possessed an imbricated or partially imbricated dentition, which would reduce body size estimates based on dentition, but even then he still predicts a good-sized C. megalodon dentition would look like this, both in aspect and size :



So I'm rather curious to know more about this new material and see its actual structure.

[elosha11]

Thanks Grey! Great info.

Is Bill Heim working on the C. Chub or any other pending research? I've heard him opine before that Megalodon might be smaller than commonly depicted because some fossil whale bones seem to show bite marks with teeth imprints closer together than what you'd see in a great white. See his comments here. www.elasmo.com/frameMe.html?file=heim/bh-cm1.html&menu=bin/menu_topics-alt.html. But there are other bite marks attributed to Megalodon, which arguably show wider spacing in the teeth, such as the juvenile Meg that presumably that bit into the rorqual whale rib found at the Calvert Cliffs. Seen here.



So I'm not sure if Heim is on the right track or not. I've never heard of any lamnid shark with overlapping, inbricated teeth.

Do you have any pictures you could post of the C. Chubs mold? I agree that it's strange that the student would describe C. Chubs as possibly being "quite small" when the largest known teeth are far larger than the assoiciated teeth in the jaw. Was the student referring to both C. Megalodon and C. Chubutensis or just the latter?

[elosha11]

Also Grey, I like your observation that your "personnal comparison of the Yorktown C. megalodon associated set of teeth from the Yorktown formation compared with the dentition of Carcharodon hubbelli (total length estimated at approx. 5 m based on dentition and vertebral measurements, Ehret. 2009) shows the C. megalodon tooth row being more than 3.5 times larger than in C. hubbelli."

If the Yorktown jaw tooth row (perimeter?) is more than 3.5 times the size of the tooth row in the 5 meter C. hubbelli, that would roughly correspond to the conclusion that the Yorktown specimen represents about an 18 meter shark, and would also suggest Meg could well exceed 18 meters. Still too early to tell, but this seems to be pointing the right direction of you and your collaborators' conclusions based on complete dentition sets.

[elosha11]

Aug 27, 2017 0:39:07 GMT 5 Grey said:

The preserved C. chubutensis jaw from Ica is under description. We'll know soon about the actual structure of the jaw and if the estimates of size based on dentition with lamnids as template are really realistic.

Strangely I've heard from one of the students that the fossil seems to suggest that "Carcharocles were rather small". Unless the dentition has a totally unexpected structure making the whole mouth overall smaller than one would expect while based on Carcharodon, I don't understand how this would indicate the genus being overall "smaller", especially since that specimen doesn't seem to be particularly large even for chubutensis, the teeth in it are reported being about 8-9 cm. Still the few pictures of the mold seem to indicate a quite massive piece.
My personnal comparison of the Yorktown C. megalodon associated set of teeth from the Yorktown formation compared with the dentition of Carcharodon hubbelli (total length estimated at approx. 5 m based on dentition and vertebral measurements, Ehret. 2009) shows the C. megalodon tooth row being more than 3.5 times larger than in C. hubbelli.

I discussed this with Bill Heim who suspects that Carcharocles possessed an imbricated or partially imbricated dentition, which would reduce body size estimates based on dentition, but even then he still predicts a good-sized C. megalodon dentition would look like this, both in aspect and size :



So I'm rather curious to know more about this new material and see its actual structure.

Grey,

I just visited for the first time Theropod's listed website (listed under his name in WoA profile), and in 2015 he posted a very good summary of Purdy's 2001 analysis of C. Sub (older/analogous name for C. Chub, I'll continue to refer to it as C. Chub for ease of reference) size based on tooth row for two C. Chub complete tooth rows. Theropod believes they were adult specimens of around 8.2 and 9.5 meters long respectively. However, he notes that Purdy cites a far larger single lower lateral tooth belonging to C. Chub, which may support length-estimates of C. Chub EXCEEDING 14 meters.

Theropod, with your permission, I'm going to post your entire summary analysis from your linked website. And a number of us miss your commentary and insights. I haven't seen you post in quite awhile, so I hope you will start doing so again.

Here's Theropod's summary analysis:

Carcharocles subauriculatus–bigger yet smaller than we think?
Well first of all, C. subauriculatus is actually the older, and hence the valid name, not the inexplicably more popular C. chubutensis (PalaeoDB ONLINE).

This shark species is not nearly as well known, or indeed as common (at least based on ocurrence in museum displays) as its bigger relative, C. megalodon, but it, too, is among the largest chondrichthyans in earth’s history.

The size figure one sees cited commonly is a little over 12m, based on the regression between tooth height and total length in Gottfried et al. (1996) and the largest teeth, which reportedly approach 13cm in diagonal, or slant length. However, this is fallacious on more than one level, because the method was not supposed to be used with the diagonally measured length, but with vertical tooth height, and because it assumes the same proportions within the dentition as in Great White Sharks, which do not actually appear to be present in C. subauriculatus.

So, how large was this taxon really?
Purdy et al. 2001 figured, described and listed measurements for two sets of associated teeth, each representing the partial dentition of a single animal.
Better still, the fact that the lateral cusplets (a paedomorphic feature) are absent or very weakly developed is a strong indication that the specimens were adults at the time of death.
The smaller of the two, USNM 411881, has one upper quadrant almost completely preserved. Based on the relative widths of the overlapping teeth, the second one, USNM 299832, is 15.8% bigger.
Completing the dentition by extrapolating the missing anteriormost tooth from the larger specimen (and the diminuitive posteriormost tooth, which is not preserved in either specimen, from C. megalodon), the result is an estimated summed tooth width of ~600m, resulting in a total of ~1200mm in both sides of the upper jaw. Adding 15% of interdental spacing (admittedly a little liberal), this results in the overall length of the upper toothrow being ~1380mm, that of the larger individual is thus an estimated 1598mm long.

How does this help us? Much it turns out, since estimating the size of a shark from a complete or nearly complete dentition is much more reliable than using a single tooth. Lowry et al. 2009 examined the relationship between the length of the tooth row (or bite circumference) and the total length of the shark, and found a strong correlation. Since the best overall analogue in terms of size, ecology and morphology is probably the Great White, the formula relevant here is that for C. carcharias, which we can transform and solve for total length:

LOG(tooth row length)=1.007*LOG(total length)-0.8
LOG(tooth row length)=LOG(10^-0.8*total length^1.007)
tooth row length=10^-0.8*total length^1.007
(tooth row length/10^-0.8)^(1/1.007)=total length
Length estimates based on Lowry et al. 2009
So these specimens were ~8.2 and ~9.5m long, and based on published length-weight-regressions (Casey & Pratt 1985, Kohler et al. 1995) for C. carcharias they probably massed ~5.0-6.0 and ~7.8-9.4t respectively.
But that is not the end of the story. Purdy et al. mention a first lower lateral tooth that is 9.5cm tall, which is 79% and 56% bigger than the equivalent teeth in the aforementioned dentitions, suggesting a tooth-row length of ~2474-2489mm and a total length of 14.5-14.7m. [Elosha added emphasis]
To put this into perspective, that is well within the territory of C. megalodon, and actually above its average size (which, for adults, is about 14m based on data from Pimiento & Balk 2015).
Obviously every estimate that just bases on a single tooth is prone to huge margins of error, so this should be taken with a grain of salt. All this shows is that what is popularized about this species’ size is not founded on facts all that firmly.

–––References:
Casey, John G.; Pratt, Harold L. (1985) Distribution of the White Shark, Carcharodon carcharias, in the Western North Atlantic. Memoirs of the Southern California Academy of Sciences, 9 (Biology of the White Shark, a Symposium.) pp. 2-14
Kohler, Nancy E.; Casey, John G.; Turner, Patricia A. (1995): Length-Length and Length-Weight Relationships for 13 Shark Species from the Western North Atlantic. Fishery Bulletin, 93 pp. 412-418
Lowry, Dayv; Castro, Andrey L. F. de; Mara, Kyle; Whitenack, Lisa B.; Delius, Bryan; Burgess, George H.; Motta, Philip: (2009): Determining shark size from forensic analysis of bite damage. Marine Biology, 156 pp. 2483-2492
Pimiento, Catalina; Balk, Meghan A. (2015): Body-size trends of the extinct giant shark Carcharocles megalodon: a deep-time perspective on marine apex predators. Paleobiology, 41 (3) pp. 479-490
Purdy, Robert W.; Schneider, Vincent P.; Applegate, Shelton P.; McLellan, Jack H.; Meyer, Robert L.; Slaughter, Bob H. (2001): The Neogene Sharks, Rays, and Bony Fishes from Lee Creek Mine, Aurora, North Carolina. In: Ray, Clayton E.; Bohaska, David J.: Geology and Paleontology, of the Lee Creek Mine, North Carolina, III. Smithsonian Contributions to Paleobiology, 90 pp. 71-202
PaleoDB: Fossilworks: Carcharodon subauriculatus. fossilworks.org/bridge.pl?a=taxonInfo&taxon_no=83172 (accessed 21 July 2015)

---posted 1911, 22/07/2015

[Grey]

I had read it.

Because I don't rely so much on the artificial 15 % of interdental spacing.

That's the point behind Leder et al. 2016 poster, we only compare fossil associated dentitions with extant one.

If this "chub" has a dentition length on one side of 600 mm, it might be just around 9-10 m long, comparing with the poster.

But I think looking at some very large chub teeth that sensibly larger sizes are probable.

[Grey]

A new paper on Megalodon (#Otodus megalodon), the biggest predatory shark that ever lived.

Many thanks to Ferrón Humberto Jiménez for this new open access paper and the permission to use the amazing image of the paleoillustrator Hugo Saláis (HS scientific illustration).

In this work it is demonstrated that Megalodon was a "warm-blooded" (regional endothermic) shark and several aspects of this finding with multidisciplinary interest are discussed in detail.

In the image of Hugo Saláis (HS scientific illustration), that was made specifically for this work, there is a #Megalodon ambushing a group of #Cetotherium whales, in a similar way than the great white sharks do today.



Humberto Ferrón Jiménez (2017) Regional endothermy as a trigger for gigantism in some extinct macropredatory sharks. PLoS ONE 12(9): e0185185

Link: journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0185185&type=printable

[Grey]

Sept 14, 2017 3:29:03 GMT 5 elosha11 said:

Thanks Grey! Great info.

Is Bill Heim working on the C. Chub or any other pending research? I've heard him opine before that Megalodon might be smaller than commonly depicted because some fossil whale bones seem to show bite marks with teeth imprints closer together than what you'd see in a great white. See his comments here. www.elasmo.com/frameMe.html?file=heim/bh-cm1.html&menu=bin/menu_topics-alt.html. But there are other bite marks attributed to Megalodon, which arguably show wider spacing in the teeth, such as the juvenile Meg that presumably that bit into the rorqual whale rib found at the Calvert Cliffs. Seen here.



So I'm not sure if Heim is on the right track or not. I've never heard of any lamnid shark with overlapping, inbricated teeth.

Do you have any pictures you could post of the C. Chubs mold? I agree that it's strange that the student would describe C. Chubs as possibly being "quite small" when the largest known teeth are far larger than the assoiciated teeth in the jaw. Was the student referring to both C. Megalodon and C. Chubutensis or just the latter?

You make a good point. The Kallal et al. case doesn't seem to indicate an imbricated dentition. Bill himself admits his suggestion is wild ass guess and that the bone he described could just have broken.

The student on the chub jaws added that they presumably based this on some vertebra associated with the jaws. But here again, other otodontids dentitions have been described in association with vertebra and the authors never suggested a smaller size based on them.

[elosha11]

^ Grey in reference to your comment above, did the students working on the C. Chub jaw mention the size of the associated vertebrae and how many they have recovered? For instance we know the size of certain Meg vertebrae possibly associated with teeth, like the 1983 Denmark fossil with 20 vertebrae, with the centra ranging from 100 millimeters (3.9 in) to 230 millimeters (9.1 in) in diameter. The tooth arguably associated with it (looked like an UA to me) was quite large, estimated 16 cms diagonal height and 12 cms wide. However, Meg probably had around 200 vertebral centra. Given that only about 10 percent of the centra were found and they were all of varying sizes (suggesting widely different places in the vertebral column), the chances are that there were centra larger than the 230 cm that were never recovered. So it's hard to make really any conclusions on size from on that evidence. Here's the study on linked to the Denmark Meg remains.

2dgf.dk/xpdf/bull32-01-02-1-32.pdf

Similarly I'm wondering how much evidence the students above can draw from the C. Chub fossil? If they only have a few centra, it would make little sense to say they must certainly have the largest in the vertebral column of a shark that probably had around 200. So I'm curious as to how many centra they have, as well as how large the centra are.

[Grey]

It's not the first time a megatoothed shark is found with teeth associated to vertebra.
The 'angustidens' described by Gottfried & Fordyce has an almost complete dentition along with about 35 vertebra. The authors didn't suggest a downsizing looking at those vertebra. So I'm inherantly skeptical at what the student said.

I don't know the measurements of those vertebra nor their number. I don't know how they could conclude that if this specimen has ecen less centra than the Gottfried and Fordyce specimen.

[elosha11]

Agreed. I guess we will just have to wait for the C. Chub. description to be published. Any idea just how soon that will be?