Megalodon

[elosha11]

Here's a new paper published yesterday on Peer new possible earliest known link to the mega-toothed sharks, including C. Megalodon. The approximately 4.5 meter shark is known as Cretalamna bryanti, or the "Bryant Shark." Obviously this new species could have its own thread, but since it's likely related to all the megatoothed line, I thought I'd reference it here. The references below are from Live Science article summarizing the research and and then the Peer research article. Here's the links to the live scientist article and the full Peer paper. The live science article is quoted below.

peerj.com/articles/4229/
www.livescience.com/61360-fossil-shark-megalodon-ancestor.html





Figure 5: Cretalamna bryanti sp. nov. anterior teeth.
(A–E) ALMNH 3322, paratype, upper right anterior tooth in (A) oral, (B) basal, (C) mesial, (D) lingual, and (E) labial views. (F–J) ALMNH 3566, upper right anterior tooth in (F) lingual, (G) labial, (H) mesial, (I) oral, and (J) basal views. (K–O) ALMNH 3935, upper left anterior tooth, large morphology, in (K) oral, (L) basal, (M) mesial, (N) lingual, and (O) labial views. (P–T) ALMNH 9724, lower right anterior tooth in (P) lingual, (Q) labial, (R) mesial, (S) oral, and (T) basal views. Scale bars equal 1.0 cm.


Megalodon Ancestor: Fossil Teeth Link Beast to Earth’s Largest Shark
The Bryant Shark's teeth are about 1 inch tall, while the great white shark (represented by the jaw) has teeth approaching 3 inches.
Credit: McWane Science Center
It took nearly 40 years, but researchers have finally collected enough fossil teeth in Alabama to properly identify a previously unknown species of ancient shark — one that was a possible ancestor of megalodon, the largest shark to ever exist.

The newly identified mega-toothed shark lived about 83 million years ago, during the dinosaur age. Its largest tooth discovered so far measures about 1 inch (2.7 centimeters) long, which is substantially smaller than the 7-inch-long (17.7 cm) teeth sported by megalodon (Carcharocles megalodon), the researchers said in a new study.

"Over time, the sharks in the megalodon line acquire [tooth] serrations, lose their cusplets (the little 'fangs' on the sides of the main cusp) and grow to enormous sizes," said study lead researcher Jun Ebersole, director of collections at the McWane Science Center in Birmingham, Alabama. The newfound shark is an early member of this family, so its teeth are small and unserrated, with up to two pairs of cusplets, he said. [Aahhhhh! 5 Scary Shark Myths Busted]


Researchers found 33 teeth from the Cretaceous period shark from nine different sites in central Alabama over a period of 38 years, Ebersole said. He and his colleague named the species Cretalamna bryanti, or the "Bryant Shark" for short, in honor of the late University of Alabama football coach Paul "Bear" Bryant and his family.


The Bryant Shark teeth are tiny compared to a giant megalodon tooth.
The Bryant Shark teeth are tiny compared to a giant megalodon tooth.
Credit: McWane Science Center

It's incredible that until now, C. bryanti was "overlooked, not recognized or misidentified by previous scientists as other shark species," Ebersole said in a statement. The discovery shows that mega-toothed sharks had more diversity than previously realized during the dinosaur age, he noted.

The Bryant Shark's family, the otodontids, evolved more than 100 million years ago, but are now extinct. The family's largest member, the 60-foot-long (18 meters) megalodon, lived during the Miocene and Pliocene, epochs that lasted from 23 million to 2.6 million years ago, Ebersole said.

Given that C. bryanti's teeth had similar chompers to other mega-toothed sharks that survived the nonavian dinosaur extinction 66 million years ago, it's possible that C. bryanti was part of the lineage that led to megalodon, Ebersole said.

The Bryant Shark teeth are different sizes, but the largest one is 1 inch (2.7 centimeters) tall. Notice the small cusplets on the sides of the teeth.
The Bryant Shark teeth are different sizes, but the largest one is 1 inch (2.7 centimeters) tall. Notice the small cusplets on the sides of the teeth.
Credit: McWane Science Center
He added that it's difficult to calculate the length of C. bryanti based on its teeth alone. However, the shark's crown teeth are similar to a those of a mako shark, even though the two species are not related. "Thus, using recent makos as a modern analogue, the Bryant Shark may have reached lengths of up to 15 feet [4.5 m]," Ebersole told Live Science.

The public will soon be able to see a handful of C. bryanti's teeth on display in the fossil hall at McWane Science Center. The study was published online today (Jan. 8) in the journal PeerJ.

[Grey]

The SVP abstract book is out.

BODY LENGTH ESTIMATES OF FOSSIL LAMNIFORM SHARKS DERIVED
FROM SUMMED WIDTH OF ASSOCIATED DENTITIONS
PEREZ, Victor, University of Florida, Gainesville, FL, United States of America; LEDER,
Ronny, Naturkundemuseum Leipzig, Leipzig, Germany; BADAUT, Teddy, Thoirette,
France

Carcharocles megalodon is often regarded as the largest shark that ever lived, yet current estimates have been highly variable, ranging from 40 to 148 ft for a single individual.
Among the various metrics for estimating body length, the linear relationship between tooth crown height and total body length for each tooth position of the Great White, Carcharodon carcharias, is most frequently applied to isolated teeth of C. megalodon.
While there are numerous issues with this approach, one that stands out is the need to identify tooth position. Carcharocles megalodon exhibits both monognathic and dignathic heterodonty; however, the shape changes from the anterior to posterior and between the upper and lower jaws are subtle, making it exceedingly difficult to confidently and accurately identify tooth position.
To resolve this issue, a novel method for estimating body length in lamniform sharks is proposed based solely on associated dentitions. The proposed method uses a simple mathematical concept referred to as the rule of three and essentially assumes direct proportionality between the ratio of summed crown width to body length in fossil and modern taxa. Summed crown width is used as a proxy for jaw size and, for the most part, eliminates the necessity of identifying teeth to their original position. This method is
applied to 10 fossildentitionsrepresenting five lamniformtaxa:Carcharocles chubutensis,
C. megalodon, Carcharodon hastalis, Carcharodon hubbellii, and C. carcharias. A total of 19 modern dentitions representing three lamniform taxa (C. carcharias, Isurus oxyrinchus, and Isurus paucus) are used as analogs. Summed crown width for each of these dentitions was segmented into four regions: upper left, upper right, lower left, and lower right. The rationale for segmenting the summed width into these four regions is due to the partial preservation of many of the fossildentitions.
Our results found that estimates based on the lower jaw tend to be higher than the upper jaw, likely due to differences in the dental formula between fossil and modern taxa.
Unsurprisingly, estimates derived from Mako sharks, Isurus, were always greater than those derived from modern Great Whites, which can likely be attributed to different feeding ecologies and corresponding narrower teeth of Mako sharks. Our best estimate for an average adult C. megalodon, based solely on Great Whites and after removing outliers, is 16.68 m (54.7 ft).
Grant Information
National Science Foundation Graduate Research Fellowship Grant No. DGE-1315138

[elosha11]

Very interesting new research on Megalodon's possible extinction. This isotopic analysis of Megalodon's teeth suggests it maintained a substantially higher body temperature than would have been expected, (even for a quasi-endothermic/ectothermic animal), which would imply it had a greater than expected metabolism and had to eat more often than lamnid sharks of today such as great whites or makos. It's estimated their body temperature ran from 95 to 104 degrees F, which is very comparable to mammals and birds. When whales migrated to colder climates, this put even more pressure on Megalodon than had been surmised, given their higher than expected caloric needs their warm bodes required. If this research pans out, it may mean Meg may have to be moved up in the various metabolism/activity charts that have gone around comparing various marine fauna.

The Extinction of Iconic Megatoothed Shark Otodus megalodon: Preliminary Evidence from 'Clumped' Isotope Thermometry

Authors: Neumann, A. N.; Clarke, C. A.; Griffiths, M. L.; Becker, M. A.; Kim, S.; Maisch, H. M., IV; Eagle, R.; Pedersen, D. T.; Nixon, T. J. A.; Mautz, C. F.; Shimada, K.

ABSTRACT

The largest and most iconic extinct shark to have ever lived is Otodus megalodon (Lamniformes). Fossil teeth and vertebrae indicate this highly successful apex predator achieved lengths up to nearly 20 m, weights exceeding 20,000 kg, and global distribution throughout the Miocene and Pliocene (23-2.5 MYA). A general consensus indicates that the ability to thermoregulate in O. megalodon acted as a key driver for the evolution of gigantism that impacted its ecological role and success in surviving environmental changes. There is little agreement as to the primary cause for O. megalodon's disappearance but models suggest predator-prey dynamics or environmental change influenced its extinction. To address these uncertainties, we propose to constrain body temperatures of both living and extinct marine vertebrates across the mid-Miocene and Pliocene using 'clumped' isotope thermometry (CIT) in mid-latitude carcharhiniform and lamniform shark teeth from the Pacific and Atlantic Oceans. Preliminary results from several clumped isotope measurements conducted on aquarium-reared and wild-caught shark teeth provide encouraging results that do not deviate from previously published calibrations of bioapatite. Applying these same calibration equations to the fossil record provides encouraging results. Indeed, comparison of extant Carcharodon carcharias (white shark) with O. megalodon from Pliocene deposits of Japan, reveal that the much larger O. megalodon maintained a higher body temperature compared with its modern lamniform equivalent, C. carcharias, owing to its much larger body size. While still preliminary, these results may provide clues as to what may have led to the demise of O. megalodon during the Pliocene. For example, one hypothesis is that O. megalodon consumed large quantities of prey in order to maintain such a high body temperature. However, cooling of ocean temperatures during the Pliocene would have constrained the species to lower latitudes where ocean temperatures were warmer, whilst its preferred prey (e.g., whales) evolved traits to adapt to cooler temperatures of the higher latitudes. Therefore, large climatic shifts combined with evolutionary limitations may provide the "smoking gun" for the extinction of the largest shark species to ever roam the planet.

Publication in: American Geophysical Union, Fall Meeting 2018, abstract #PP13F-1405

Publication Date: 12/2018

Link: adsabs.harvard.edu/abs/2018AGUFMPP13F1405N

Citation: Neumann, A. N., Clarke, C. A., Griffiths, M. L., Becker, M. A., Kim, S., Maisch IV, H. M., ... & Shimada, K. (2018, December). The Extinction of Iconic Megatoothed Shark Otodus megalodon: Preliminary Evidence from'Clumped'Isotope Thermometry. In AGU Fall Meeting Abstracts.

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Related content below.

Dec. 11, 2018 WASHINGTON — Why did the monster shark megalodon go extinct? New research has answers, and the shark's high body temperature may have played a part.

Megalodon was a mega-shark, an enormous, prehistoric "Big Bad" that still fuels nightmares and fascinates scientists today. This massive fish could grow to up to 60 feet (18 meters) long, and it took down prey with a terrifying mouthful of teeth, each of which measured as long as 7 inches (18 centimeters) — longer than a human hand. [Top 10 Deadliest Animals (Photos)]

Fearsome though this giant predator was, it disappeared from the oceans about 2.6 million years ago. And new research looked to the body temperature of Otodus megalodon to offer an explanation for what may have caused it to die out.

Like some other sharks alive today, such as great white and mako sharks, megalodon is thought to have been able to thermoregulate, or adjust its body temperature in response to cooler or warmer water. This would have enabled it to hunt in a broader range of habitats than other sharks, according to research presented today (Dec. 10) at the annual meeting of the American Geophysical Union (AGU).

But was megalodon's body temperature similar to that of modern sharks? To find out, scientists used geochemistry to examine rare carbon and oxygen isotopes in megalodon teeth and in teeth of modern sharks. (Isotopes are versions of molecules with different numbers of neutrons.) These isotopes form different bonds depending on the animal's temperature when teeth form, researcher Michael Griffiths, an associate professor in the Department of Environmental Science at William Paterson University in New Jersey, told Live Science.

With this method, scientists could estimate what the ancient beast's average body temperature may have been and thereby find clues that might explain how megalodon's biology or habits doomed it to extinction, the researchers said.

Their preliminary results suggested that megalodon was "quite warm" for a shark, Griffiths said. Ancestors of today's makos and great white sharks that swam alongside megalodon millions of years ago likely had body temperatures of about 68 to 86 degrees Fahrenheit (20 to 30 degrees Celsius).

By comparison, megalodon may have been running a body temperature as high as 95 to 104 degrees F (35 to 40 degrees C), which is the body temperature of whales, Griffiths said.

With such a high body temperature, megalodon must have had a very active metabolism that required frequent feeding, Griffiths said. Then, the climate warmed, and megalodon's prey moved to cooler waters at higher latitudes. Food scarcity and competition from new predator species such as killer whales may then have been the fatal combination that drove megalodon to extinction, Griffiths explained.

"Large climatic shifts combined with evolutionary limitations may provide the 'smoking gun' for the extinction of the largest shark species to ever roam the planet," the scientists said.

Link: www.livescience.com/64274-megalodon-shark-body-temperature.html

The sharks that roam today’s oceans can be fearsome, but they don’t really compare to some of the species that dominated the seas millions of years ago. The Megalodon — a massive shark that is thought to have died out around 2.6 million years ago — has left plenty of fossils behind for researchers to find, but determining what exactly killed the species off has proven a big challenge.

As LiveScience reports, new research was presented recently at the annual American Geophysical Union conference that suggests the shark could regulate its body temperatures similar to some species of modern sharks. However, the ancient shark’s much higher body temperature may have been its downfall.

Determining the body temperature of an animal that hasn’t existed for millions of years is tough but not impossible. Clues to the shark’s body temperature were found in its teeth. Isotope bonds form differently depending on the temperature, and the teeth of the megalodon suggest its body temperature was very high.

The shark’s size was the key to its dominance, but it was so large that its body temperature may have rivaled that of whales. If the creature was keeping its body temperature as high as 104 degrees Fahrenheit its metabolism would likely have demanded that it consume a huge amount, and as global temperatures change, it’s likely that the sharks just couldn’t keep up.

As the shark’s prey moved to new, cooler areas, the massive predators would have felt a serious pinch. It’s also likely that new predators began to out-hunt the large sharks, putting even more strain on the species

Link: bgr.com/2018/12/11/megalodon-extinction-teeth-body-temperature/

[Life]

Did a supernova kill off the megalodon?


A shower of particles may have spelled curtains for the megalodon, a school-bus-sized shark, 2.6 million years ago. Image via Wikipedia/University of Kansas.

A new study suggests that a tsunami of cosmic energy from a supernova killed off large ocean animals – including the huge megalodon shark – 2.6 million years ago.

About 2.6 million years ago, an oddly bright light arrived in the prehistoric sky and lingered there for weeks or months. It was a supernova some 150 light-years away from Earth. A new study suggests that, within a few hundred years, well after the supernova had faded from Earth’s sky, a tsunami of cosmic energy from that star explosion reached our planet. The rain of particles pummeled the atmosphere, the researchers say, touching off climate change and triggering mass extinctions of large ocean animals, including the megalodon, a shark species that was the size of a school bus.

The effects of such a supernova — and possibly more than one — on large ocean life are detailed in the study published November 27, 2018, in the journal Astrobiology. Adrian Melott is a professor emeritus of physics and astronomy at the University of Kansas and lead author of the study. Melott said that recent papers revealing ancient seabed deposits of iron-60 isotopes provided the “slam-dunk” evidence of the timing and distance of supernovae. He said:

"As far back as the mid-1990s, people said, ‘Hey, look for iron-60. It’s a telltale because there’s no other way for it to get to Earth but from a supernova.’ Because iron-60 is radioactive, if it was formed with the Earth it would be long gone by now. So, it had to have been rained down on us. There’s some debate about whether there was only one supernova really nearby or a whole chain of them. I kind of favor a combo of the two — a big chain with one that was unusually powerful and close. If you look at iron-60 residue, there’s a huge spike 2.6 million years ago, but there’s excess scattered clear back 10 million years."

Artist’s concept of a supernova. Image via University of Kansas/NASA.

Whether or not there was one supernova or a series of them, the supernova energy that spread layers of iron-60 all over the world also caused penetrating particles called muons to shower Earth, causing cancers and mutations — especially to larger animals. Melott said:

"The best description of a muon would be a very heavy electron — but a muon is a couple hundred times more massive than an electron. They’re very penetrating. Even normally, there are lots of them passing through us. Nearly all of them pass through harmlessly, yet about one-fifth of our radiation dose comes by muons. But when this wave of cosmic rays hits, multiply those muons by a few hundred. Only a small faction of them will interact in any way, but when the number is so large and their energy so high, you get increased mutations and cancer — these would be the main biological effects. We estimated the cancer rate would go up about 50 percent for something the size of a human — and the bigger you are, the worse it is. For an elephant or a whale, the radiation dose goes way up."

According to the researchers, the supernova 2.6 million years ago may be related to a marine extinction – known as the marine megafauna extinction – where an estimated 36 percent of the largest marine animals like sharks, whales, sea birds and sea turtles disappeared. The extinction was concentrated in coastal waters, where larger organisms would have caught a greater radiation dose from the muons. The researchers say damage from muons would extend down hundreds of yards (meters) into ocean waters, becoming less severe at greater depths. They wrote:

"High energy muons can reach deeper in the oceans being the more relevant agent of biological damage as depth increases."

Indeed, a famously large and fierce marine animal inhabiting shallower waters may have been doomed by the supernova radiation. Melott said:

"One of the extinctions that happened 2.6 million years ago was megalodon. Imagine the great white shark in Jaws, which was enormous — and that’s megalodon, but it was about the size of a school bus. They just disappeared about that time. So, we can speculate it might have something to do with the muons. Basically, the bigger the creature is the bigger the increase in radiation would have been."

He added:

"There really hasn’t been any good explanation for the marine megafaunal extinction. This could be one."

Bottom line: A new study suggests that particles from a supernova raining onto Earth 2.6 million years ago killed off large ocean animals – including the huge megalodon shark.

Source: earthsky.org/earth/supernovae-killed-off-megalodon-large-ocean-animals-extinction-pleistocene

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Muon Radiation Dose and Marine Megafaunal Extinction at the end-Pliocene Supernova

ABSTRACT

Considerable data and analysis support the detection of one or more supernovae at a distance of about 50 pc, ~2.6 million years ago. This is possibly related to the extinction event around that time and is a member of a series of explosions which formed the Local Bubble in the interstellar medium. We build on previous work, and propagate the muon flux from supernova-initiated cosmic rays from the surface to the depths of the ocean. We find that the radiation dose from the muons will exceed the total present surface dose from all sources at depths up to a kilometer and will persist for at least the lifetime of marine megafauna. It is reasonable to hypothesize that this increase in radiation load may have contributed to a newly documented marine megafaunal extinction at that time.

Link: arxiv.org/abs/1712.09367

[elosha11]

So some heavy hitters as far as Meg researchers just published a new article re the evolution of Megalodon's teeth from C. chubutensis all the way to the teeth we know today. It features Brentton Kent, Stephen Godfrey, and lead author, Victor Perez, who teamed up with Grey from WoA over the last couple years to also write what could become a transformative article as to how to measure Megalodon size by associated dentition.

Here's the abstract of this March 2019 paper, you can also go to this website to see the pictures and footnotes and you can also download it as a pdf.

www.tandfonline.com/doi/full/10.1080/02724634.2018.1546732


ABSTRACT—The teeth of two megatooth macro-predatory shark species (Carcharocles chubutensis and Carcharocles
megalodon; Otodontidae, Chondrichthyes) occur within the Miocene Chesapeake Group of Maryland, U.S.A. Definitive
separation between all the teeth of Carcharocles chubutensis and Carcharocles megalodon is impossible because a complex
mosaic evolutionary continuum characterizes this transformation, particularly in the loss of lateral cusplets. The cuspleted
and uncuspleted teeth of Carcharocles spp. are designated as chronomorphs because there is wide overlap between them
both morphologically and chronologically. In the lower Miocene Beds (Shattuck Zones) 2–9 of the Calvert Formation
(representing approximately 3.2 million years, 20.2–17 Ma, Burdigalian) both cuspleted and uncuspleted teeth are present,
but cuspleted teeth predominate, constituting approximately 87% of the Carcharocles spp. teeth represented in our sample.
However, in the middle Miocene Beds 10–16A of the Calvert Formation (representing approximately 2.4 million years,
16.4–14 Ma, Langhian), there is a steady increase in the proportion of uncuspleted Carcharocles teeth. In the upper
Miocene Beds 21–24 of the St. Marys Formation (representing approximately 2.8 million years, 10.4–7.6 Ma, Tortonian),
lateral cusplets are nearly absent in Carcharocles teeth from our study area, with only a single specimen bearing lateral
cusplets. The dental transition between Carcharocles chubutensis and Carcharocles megalodon occurs within the Miocene
Chesapeake Group. Although this study helps to elucidate the timing of lateral cusplet loss in Carcharocles locally, the
rationale for this prolonged evolutionary transition remains unclear.

[theropod]

www.deviantart.com/theropod1/journal/How-bulky-was-Megalodon-795970644

[sam1]

May 1, 2019 19:40:00 GMT 5 theropod said:

www.deviantart.com/theropod1/journal/How-bulky-was-Megalodon-795970644

Well done..obviously the more massive one being closer to the real thing imo.

[elosha11]

Theropod, really nice drawings. Couple questions. I take it the 5 meter GWS is the proxy for determining the weight of the 16.8 meter Megalodon? First, I definitely agree with the length comparison. A 5 meter GWS is a large, above average GWS, but still not yet approaching maximum size, particularly for females. Whereas most research, including the recent publication by Perez, Ledder, and Grey, would indicate that 16.8 meters would be a large, and probably a bit above average size adult Megalodon (most pertinently the females) but not yet approaching maximum size. So I think the length comparison is very apt.

Where I may have some further question is the weight estimate of 1195 kg average for a 5 meter GWS. Knowing you, I would assume such a figure is backed by research or at least some rational inferences. However, I note that on elasmomollet.org's GWS size page, there are 15 GWS sharks with weights calculated/estimated from between 4.67 meters (obviously shorter than the proxy model) up to 5 meters. Out of those 15 sharks, 10 of the 15 GWS have higher weights than 1195 kgs, including some of them well below 5 meters. A number of them significantly exceed such weight such as 1400 or 1500 kgs. Two of the 5 below 1195 are well below, something like 800 or 700 kgs, but as I said, the median average (and quite possibly the mean, I haven't yet checked) would seem to indicate a larger overall weight than your proxy model. These 15 sharks were weighted from all different parts of the world and over many different years, so it more likely represents a more typical size representation for such individuals. I know that 15 sharks in this context, isn't a huge comparison sample, but it's not small either, particularly when taking into account both geography and time differentials.

I suspect that GWS historically have averaged a bit heavier weight than 1195 Kgs at 5 meters. How much, I don't know. But it seems rather common for 5 meter animals (and even those below 5 meters) to exceed 1195 kgs in weight. I suspect that something like 1300 kgs might be a little closer to the truth. Which in turn, would result in a modest increase in bulkiness of your Meg model. Maybe something like 54,000 for the mean model and closer to 60,000 kgs for max size estimates.

BTW, what would your current model predict for the weight of an 18 meter Megalodon, which is a fairly commonly cited estimate for max size Megalodons? Personally, I think the largest specimens probably exceeded 18 meters, but I'm comfortable using 18 meters as a baseline for max size.

I'm going to post this same comment in the Meg v. Livyatan thread, since we have the same discussion there. But I note that such conversations should likely be transferred, or at least copied, to the very comprehensive Megalodon size thread, since that is probably the most pertinent thread for it. Obviously, the size of the shark matters in the question of interspecific conflicts with Livyatan, so I do acknowledge the info can also readily be posted in that interspecific thread.

[theropod]

It’s all there in the post I linked. I and will respond more in depth on the other thread.

In short, no, that 5m Great White is not relevant at all for determining the weight or bulkiness of megalodon, though both are based on the same equations.
Firstly, you probably wouldn’t even see a difference between a 1.3 and a 1.2 ton great white. Secondly, the megalodon is not scaled isometrically from that 5m shark, and even if (which I don’t think would be correct) you assumed the 5m shark would have to be 100kg heavier than the equations predict, that would not automatically translate to the megalodon also becoming heavier.

I thought I’d explained what I did properly, but it seems it requires some further clarification. The model was made based on the estimated mass, from six published regression equations, basing on a total of over 1000 sharks. I modeled a great white shark first, measured its volume, and adjusted the body depth and width in proportion to make the model match the predicted mass. So the model you see there is specifically scaled to be as bulky as implied by the regression equations. I purposefully provided both the mean of all six (52t model), and the upper bound in terms of bulk (the highest estimate at 16.8m is 57t, based on Gottfried et al.). Of course a shark could conceivably be bulkier, just as it could be less bulky, than implied by the regression equations; these methods provide mean estimates. But surely that would be a speculative assumption, which is why such regressions exist to provide more accurate and representative mass estimates.

As requested, here are the masses predicted by the mean of those six methods over a range from 3 to 20 m:


TL (m) MASS (kg)
3 244.4
3.5 394.6
4 597.6
4.5 861.7
5 1195.4
5.5 1607.3
6 2106.2
6.5 2700.6
7 3399.5
7.5 4211.8
8 5146.4
8.5 6212.6
9 7419.2
9.5 8775.5
10 10290.7
10.5 11974.1
11 13835
11.5 15882.7
12 18126.7
12.5 20576.5
13 23241.4
13.5 26131.1
14 29255.2
14.5 32623.3
15 36244.9
15.5 40129.9
16 44287.9
16.5 48728.7
17 53462.1
17.5 58497.9
18 63846
18.5 69516.2
19 75518.5
19.5 81862.8
20 88559.2


Here is the full table including results of all the individual equations (too wide to paste here in the same manner as above):

masses.dat (2.02 KB)

As you can see, there is some variation between the results different authors got. Depending on the equation, a 5m shark could just as well be 1083kg as 1294kg. 1300kg for a 5m shark is certainly not that uncommon, as it is quite close to the prediction made by at least one of these, which I took into account in that these equations were all incorporated into the mean value I illustrated. I also illustrated the highest estimate for the megalodon; I didn’t consider doing so for the great white necessary, since, as I mentioned, you probably wouldn’t even be able to tell the difference, and also because this is about megalodon, not the white shark. I also didn’t illustrate the minimum value, since it would be just an isometrically scaled great white.

On average, the predicted value at 5m is closer to 1200 than 1300 kg. Again, this is based on hundreds of sharks, not just 15, and six regression equations, not just one. This would certainly appear to be far more trustworthy than a handful of accounts compiled on a website, most of them being suspicious in some way, overly vague, lacking important methodological information, explicitely described as guesses, or at least of questionable reliability.

Here is the R-code for replication:

c(seq(3,20,0.5))->a
data.frame(3.29*10^-6*(100*a)^3.174,
7.5763*10^-6*(0.9442*(100*a)-5.7441)^3.0848,
4.80376*10^-6*(100*a)^3.09497,
7.914*a^3.096,
3.8*10^-6*(100*a)^3.15,
10^0.99*a^3.00)->masses
round(masses, 1)->masses
colnames(masses)<-c("Gottfriedetal","Kohleretal", "CaseyPratt","MolletCailliet", "TricasMcCosker", "McClainetal")
c(seq(3,20,0.5))->rownames(masses)
round(rowMeans(masses[,1:6]),1)->masses$mean

And here is an ods table you can use if you want to estimate masses for other lengths than the ones listed in the table: masses.ods (30.24 KB)

References (as already given in the linked post→):

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.
Gottfried, Michael D.; Compagno, Leonard J.V.; Bowman, S. Curtis. 1996. Size and Skeletal Anatomy of the Giant “Megatooth” Shark Carcharodon megalodon. In: Klimley, Peter A.; Ainley, David G.: Great White Sharks: the biology of Carcharodon carcharias. San Diego, pp. 55-66.
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.
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Mollet, Henry F.; Cailliet, Gregor M. 1996. Using Allometry to Predict Body Mass from Linear Measurements of the White Shark. In: Klimley, Peter A.; Ainley, David G.: Great White Sharks: the biology of Carcharodon carcharias. San Diego, pp. 81-89.
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[Grey]

The 52 ft updated model.

www.smithsonianmag.com/smithsonian-institution/reimagining-megalodon-worlds-most-terrifying-sea-creature-180972193/

[Grey]

Hans Sues says 48 tonnes, the original point estimate for a 52 ft meg is still plausible though on the high end.
I d wait for more pictures for theropod to be able to make a volumetric model. I expect something in the 40's.

[elosha11]

Well a better angle of the more completed model show eye placement that isn't quite such a disparity as the earlier angles Sam1 posted. But the model's eye placement still undisputedly looks different and further set back than modern day lamnid GW's and makos. I hope Grey can get some further insight on this.




Not entirely sure what I think about they theory that Megalodon was more streamlined and mako shaped, as the model proposes, or a very mako shaped head. That wouldn't seem to account for the sharks overall more robust head and larger dentition (in comparison to the GWS and even more so to the more gracile mako), but perhaps that shape does better conform to the active lifestyle of such a large predator. But mako sharks, while possessing a very formidable bite as adults, have a relatively narrow head and jaws which doesn't seem to line up with what we know about Meg teeth, and the associated dentitions, which show a relatively wide and deep jaw perimeter. Likewise, it seems to me the model's jaws are a bit small for a 52 foot shark, (granted its mouth as posed may not quite be fully extended).

[Grey]

From the main paleo-artist Gary Staab :

"Teddy, Sorry for my slow reply. The model is 52ft at its greatest length on it's midline and is 34 feet around at its greatest circumference. 11'5" from Belly to base of Dorsal fin. I used the set of teeth from the Hubbard collection and scaled them up to match body size. I hope this helps?"

"I figured the surface area of the body for the manufacturing process but not the volume. The body surface calculations came out to be 951 Sq. Ft. For the body. 210 Sq.ft. For the fins. 216 square ft for the mouth interior.Teeth are 4.5 inches."

[Grey]

www.tandfonline.com/doi/full/10.1080/08912963.2019.1666840

This paper is going to be a bit debatted given the unreliability of crown height method in the dentition of this genus.

[Grey]

That is to be expected since a long, this method always gives maximum size in that range using the larger anterior crowns.

Though I m pretty sure that there are way larger lower and upper anterior teeth than the one he used here. He mentions the existence of larger upper anterior in the paper.

The only way with crown height method to get larger sizes than this is to use lateral and posterior teeth crown height.

Our initial poster already pointed to the issues with this method.

www.google.com/url?sa=t&source=web&rct=j&url=https://www.researchgate.net/publication/308891065_SIMPLIFYING_THE_METHODS_-_BODY_LENGTH_ESTIMATES_FOR_CARCHAROCLES_MEGALODON_USING_ASSOCIATED_TOOTH_SETS_AND_JAW_WIDTH_RELATED_DATA_FROM_GREAT_WHITE_SHARKS_AND_MAKOS&ved=2ahUKEwjG07GqtfrkAhUNrxoKHQPVCIgQFjAAegQIAxAB&usg=AOvVaw0s_XUqBgXgRTLmgV8usyC8