Megalodon
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Name: O.
megalodon
(Big tooth).
Phonetic: Meg-ah-low-don.
Named By: Louis Agassiz - 1843.
Synonyms: Procarcharodon megalodon,
Megaselachus megalodon.
Classification: Chordata, Chondrichthyes,
Elasmobranchii, Lamniformes.
Species: Otodus megalodon,
Carcharocles megalodon, Procarcharodon
megalodon or even Otodus megalodon refer
to text for full
explanation.
Diet: Carnivore.
Size: Many estimates exist but usually between 15
and 17 meters long.
Known locations: Worldwide.
Time period: Late Oligocene to
Early Pleistocene.
Fossil representation: Mostly teeth, but some
vertebrae are also known.
Teeth and vertebra - The
fossils of
megalodon
The
teeth are by far the most common remains of C. megalodon
with the larger
teeth approaching 18 centimetres in height. It is uncertain for
how long people have been collecting C. megalodon
teeth, but it was not
until 1667 that science recognised them as shark teeth. Before
this time people generally and honestly thought that C.
megalodon teeth
were actually the tongues of dragons that had been petrified (turned
to stone). The truth about them came about when the Danish
naturalist Nicolas Steno correctly identified one of these 'dragon
tongues' and mentioned it in his book The Head of a Shark
Dissected.
C.
megalodon
teeth are usually compared with those of the great white shark because
of their superficial similarities of being triangular and serrated.
Because of this similarity, particularly with the serrations, it
is thought that C. megalodon had the same biting
style
as the great white
shark. This would involve biting down upon its prey and then shaking
its head from side to side so that the teeth serrations sawed through
the flesh.
There
have even been what are close to being complete sets of C.
megalodon
teeth
from the same individual found together. These reveal that C.
megalodon
was like other sharks in that the largest teeth were at the front of
the mouth. Also the further towards the front the teeth were, the
more evenly triangular they became. The more sideward the teeth went
towards the rear of the jaws, the more inwardly curved they became.
These teeth would hook into the flesh of the prey making it harder for
it to escape while the front teeth did the cutting.
One
of the most common myths most often told about C. megalodon
is that it is
only known from teeth. In reality the teeth are by far the most
common fossils of C. megalodon, but a small and
growing number of
vertebras have also been recovered. In shark biology in general,
the skeleton is always made up of 'soft' cartilage, but the
vertebrate are made up of harder calcified cartilage. This means that
while the vertebra can and often do decompose, they can survive for
longer increasing the chance of them getting fossilised.
Size -Estimating the upper size
of megalodon
Ever
since the teeth of C. megalodon were realised to be
the teeth of sharks
most people immediately asked, 'but how big was the shark?'. The
honest answer is that we don't exactly know for certain because there
is no complete specimen that someone can take a tape measure to. So
instead palaeontologists and ichthyologists have to work with what they
have, in this case the teeth. They have been many studies into
estimating the length of a shark based upon analysing teeth, the four
most commonly referred to being here.
One
method once used to gauge the length of C. megalodon
was from measuring
the height of the tooth enamel. This method was developed by John E.
Randall in 1973 and resulted in an estimate of 13 meters.
However the method is not considered accurate by the wider scientific
community as the method was first originated by comparing the teeth of
the great white shark, and although these teeth appear similar at a
glance, they are actually quite different from the teeth of
C. megalodon. Also the amount of enamel on a tooth
can vary even amongst
teeth of the same species through wear and poor preservation.
Another
method of estimation developed in 1996 by Michael D. Gottfried,
Leonard J. V. Compagno and S. Curtis Bowman works on the basis
of establishing a correlation between the slant height of a tooth and
the length of the shark. Slant height is not the total height but the
length of the tooth tip to the lateral edge, and is the actual
cutting length of the tooth. Again this study was based upon the
study of great white teeth, and this yielded an estimate of 15.9
meters. However even if this method is reliable, it can only
give estimates from the given teeth, and not necessarily the species.
In
2002 Dr. Clifford Jeremiah established another method based upon
the width of a tooth root, the bit below the crown that is covered by
flesh. This is a simple principle that the width of the tooth crown
can be used to figure out the width of the jaw, which in turn can be
used to work out the length of the shark. In the simplest terms it
works on the basis that there is 1 centimetre of tooth root for
roughly every 129 centimetres of body length. This resulted in a
15.5 meter length estimate for a tooth which had around 12
centimetres of root.
Also
in 2002, Dr. Kenshu Shimada developed another more complex method
based upon the proportions of the tooth crown. When this method was
used upon the tooth that had been used by Gottfried et al. in
1996, the estimated length came back as 15.1 meters. The
maximum estimate ever yielded from this method was obtained from a
particularly large tooth from Panama which gave a body length of
16.8 meters.
Going
with an estimated body length in the range of 15-16 meters is
considered quite safe for C. megalodon, with
higher
estimates
approaching 17 meters being considered realistically possible.
Larger estimates do exist with claims that C. megalodon
could approach
and even exceed lengths of 20 meters, however most of these
estimates are considered to be only possibilities and do not reflect
any current fossil evidence. Still, even at a more modest 15
meters, C. megalodon would still have dwarfed any
other shark either
alive or extinct with even a Great White shark paling in comparison to
its gigantic size.
How
much C. megalodon weighed is another matter of
study,
although its one
than can produce an even wider range of estimates. Current estimates
are once again based upon comparison to the great white shark, with
an estimate for a 15.9 meter C. megalodon being
gauged at 47
metric tons. Larger estimates include 59 metric tons for a 17
meter C. megalodon and 103 metric tons for a
20.3 meter
C. megalodon. As you may have noticed, the
weight
of a C. megalodon does
not increase by a constant amount with length, which is why a 20.3
meter shark is roughly a third longer than a 15.9 meter shark,
yet weighs more than double the slightly smaller specimen. This is
because you have to realise that the shark is not just longer, it is
also proportionately thicker and bulkier with increased muscle mass to
move the larger frame. This also means that an animal, be it a shark or
any other kind, will always reach a size from which it can grow no
further because of what its habitat can support in terms of food, a
natural fact based upon the logic that a bigger body needs a greater
intake of food for energy to fuel it.
Possibly Biology - The inner
workings of megalodon
Because
of its large body size C. megalodon is thought to
have
almost certainly
have lived with the effects of gigantothermy. This is where a
creature is so massive that its body holds onto heat with the outer
layers of muscle and flesh actually insulating the internal organs from
the environment. This causes an increase in metabolism which in turn
makes the creature more active. C.
megalodon
may have taken the process of gigantothermy even further by directing
the flow of warmer blood into its head and snout like the great white
shark is known to do. This would have the effect of making the brain
and sensory organs of C. megalodon such as smell,
sight and
electroreceptive ampullae operate at warm blooded metabolism levels.
The
fact that C. megalodon teeth are known from every
continent is proof that
it had a cosmopolitan distribution like many other successful marine
predators. However the distribution of C. megalodon
seems to have become
reduced as the oceans cooled, especially towards the end of the
Pliocene.
The
overall appearance of C. megalodon would most
likely
have been very
similar to the lamniform sharks that are swimming in the ocean today,
although its large size and inherent power means that it was probably
quite stocky in comparison to modern sharks. Also the cartilaginous
skeleton would have likely been more robust to deal with the greater
stresses of larger muscles and more powerful prey items.
C.
megalodon
probably had a movable upper jaw that not only moved up and down, but
could be projected forwards independently from the rest of the body.
This kind of jaw can be seen in modern sharks today and is why a shark
that is about to bite down on something looks very different from a
shark
that is just cruising. When the upper jaw is projected forward, the
upper teeth and jaw actually become visible, whereas they are
normally hidden by the mouth. With a jaw that moves in this way,
C. megalodon would latch onto its prey with its
lower
jaw holding it in
place and then shake its head from side to side so that the teeth
serrations sliced off a chunk of flesh. The upper jaw is then
retracted which has the effect of pulling the chunk of flesh into its
mouth. The shark then repeats this process until it has eaten its
fill.
An
area of study immediately associated with the discovery of the teeth is
the estimation of the bite force that C. megalodon
was
capable of. This
is an important thing to know as how strongly an animal can bite down
upon something can lead to clues to what kind of prey an animal ate to
how it ate them. In 2008 a biomechanical computer model was
created to estimate the bite force of great white sharks. When this
model was applied to C. megalodon it was revealed
that
a 15.9 meter
C. megalodon, a large average, was capable of
exerting a bite force
of 108, 514 newtons, just over 11 metric tons. When the
bite force for a 20.3 meter C. megalodon, the
upper end of the
estimated potential C. megalodon size scale, was
estimated the result
was 182, 201 newtons, over 18.5 metric tons. This means
that even the lower estimates for C. megalodon
still
give it a much higher
bite force than the ferocious placoderm
Dunkleosteus,
and even higher
than the mighty Tyrannosaurus
rex. Another thing to be considered is
the fact that C. megalodon probably did shake its
head
from side to side
like other sharks with a similar dentition. This meant that the
actual forces subjected to the unfortunate prey of C.
megalodon
were
likely even greater.
Whereas
most of the study for C. megalodon centres on the
teeth, one area that
is often overlooked are the vertebrae. Because of the small number of
known vertebrae not everyone is able to study them like they can the
teeth, but one thing that the vertebra clearly show are concentric
rings. These concentric rings are essentially the same as the growth
rings that you can see in a tree stump, and they are also visible in
other modern sharks that are swimming the oceans today. Counting
these concentric rings has yielded estimates of 25 to 40 years
of age for the C. megalodon known from fossils,
with
palaeontologists
suggesting that C. megalodon may have been able to
live for even longer
than this.
Young megalodon
- Pups and
Nursery grounds
Given
their large size and pelagic lifestyles, C. megalodon
are thought to
have given birth to live young. Exactly how C. megalodon
did this though
is still open to debate as sharks have two methods of doing this. The
first is termed viviparity, and this is where the pup, which is
what a baby shark is called, grows inside the mother until it is
ready to be born. Shark pups born in this method are fed nutrients
via an umbilical cord, and once the pup is born, the placenta is
usually ejected straight afterwards.
The
second method is ovoviviparity, and this is where the pup develops
inside an egg. However in sharks that display ovoviviparity the egg
is not laid but retained inside the mother shark. Pups of these
sharks are not attached to their mother by an umbilical cord, but
instead use up the egg yolk in the course of their development. In
both types of development the pups are conscious and able to swim under
their own power when they pass out of their mother’s body. C.
megalodon
pups are usually depicted as coming out tail first and while this is
deemed the usual method, some shark species today are actually born
head first.
Also
like we see in sharks today, C. megalodon
probably
didn't give birth
to their pups just anywhere, but instead chose what are called
nursery areas. A nursery area is where a young shark can live and
hunt while being safe from other larger predators. Sharks in nursery
areas are considered generalists that attack and eat all manner of
creatures including fish, cephalopods (like octopus and
cuttlefish), turtles, and pretty much anything else they can
catch.
To
identify potential nursery areas palaeontologist look for
concentrations of smaller C. megalodon teeth. One
area that seems to be
plentiful in these teeth is central America and the most Southern areas
of the United States. Going back towards the Oligocene, Panama did
not exist because the higher ocean levels of the time submerged much of
the area. This area was known as the Central American Seaway, and
formed an oceanic pass between the Pacific and Atlantic oceans. The
area likely had a huge expanse of shallow waters that were simply not
deep enough for larger predators to operate in, making them
relatively safe for the much smaller C. megalodon
pups.
 |
| Fossil evidence strongly suggests that during the Miocene the shallow waters between North and South America had a very high population of juvenile C. megalodon, while the larger adults roamed the deeper waters of the open ocean (red). Fossil deposits also indicate that early cetaceans such as whales (purple) used what was then known as the Central American Seaway as a passage between Pacific and Atlantic waters. High volcanic activity as well as falling sea levels closed this passage off resulting in a reduction of available prey as well as a dramatic shift in ocean currents. Above right is Central America as we know it today, with the warm water ocean currents. |
Study of the smaller teeth indicates that the C. megalodon in the nursery areas were as small as 2 to 3 meters long. However this does not mean that they were this large when they were first born, just that the teeth came from juvenile individuals that were active in the area. As the young C. megalodon grew older they would also grow bigger, and as such they would eventually have to leave the shallows for open ocean life. This would begin the second stage of their lives where they would have to specialise in attacking large ocean going creatures.
Prey items - What did
megalodon eat?
One
thing that needs to be immediately cleared up is that C.
megalodon
did not
eat dinosaurs. This is a myth spread around in popular culture,
particularly in films and novels where the C. megalodon
'villian'
gets built up to be more dramatic. C. megalodon
does not enter the
fossil record until the late Oligocene, about 36 million years
after the dinosaurs went extinct at the end of the Cretaceous making it
impossible for C. megalodon to have eaten
dinosaurs
(for a shark that
really could have fed upon dinosaurs and large marine reptiles look up
Cretoxyrhina).
The
preferred food for C. megalodon seems to have been
cetaceans
and
particularly small to medium sized whales. There is also evidence
that C.
megalodon
attacked
and ate large sea turtles which were presumably too slow to escape with
even their shells not providing protection against the colossal bite
force of C. megalodon. However what C.
megalodon
hunted depended upon the
age of the individual with smaller C. megalodon
hunting animals like
dugong, and larger older C. megalodon hunting the
larger whales.
The
attack strategy of C. megalodon was not exactly
refined, but it was
effective at taking down whales. The vertebrae of some cetaceans
display compression damage which has been interpreted to have been
caused by a sudden and massive impact from below. This allowed for
the reconstruction of a scenario where C. megalodon
would approach a whale
from below so as to avoid being seen by its target. Once it had lined
itself up for a strike, C. megalodon would use its
powerful muscles to
propel itself to the surface at high speed and slam into the whale from
underneath. If the whale did not end up in the jaws of C.
megalodon
it
would have very likely been stunned by the impact, allowing C.
megalodon
time for a killing bite. However at least one fossil vertebra is
known to exist that shows it was subjected to this style of attack,
yet still managed to heal. This shows that in this case the lucky
animal did not just survive the attack, it also lived long enough
for the injuries to heal.
Special note* - The above sequence is intended to illustrate one possible method that C. megalodon sharks hunted prey. It is not meant to suggest that this was the only way that C. megalodon sharks hunted.
Examination
of fossils that seem to have come from C. megalodon
prey show that
C. megalodon actually targeted the bony areas like
the
ribcage. Here
C. megalodon had two things in its favour,
extremely
robust teeth that
did not break easily, and a crushing bite force that could easily
break bones which in turn caused large scale injuries to the internal
organs that they were supposed to protect. Further support for this
method comes from compression fractures of the teeth where they have
been blunted, which suggests strong impacts with a hard substance
such as bone.
When
attacking larger whales that were feasibly too big for a bite to an
area like the ribs, C. megalodon changed its
tactics. Instead of going
for the critical organs, C. megalodon attacked the
tail to try and
immobilise its prey. This is a very intelligent strategy, as even
though sharks are almost constantly swimming forward so that they can
breathe, they can only maintain extremely fast pursuit speeds for
short durations. This is because in sharks the white muscle (about
90% of the total muscle mass) which is used to provide sudden
bursts of speed gets tired very quickly, whereas a sharks red muscle
(roughly 10% of the total muscle) has less power, but an
incredible amount of endurance which is why the lesser red muscle is
used for standard cruising. By crippling a large whale, a C.
megalodon
could take its time feeding instead of over exerting itself.
Some
people have made claims that C. megalodon was
simply
too large to hunt and
could only have been a scavenger. In the face of overwhelming fossil
evidence that shows injuries, not just tooth marks, to many large
cetaceans, such a claim is not just considered unlikely but almost
impossible. While most sharks, and carnivorous animals in general,
will take the opportunity to feed from a carcass, doing so does not
make them exclusive scavengers. Also marine animals that live by just
scavenging tend to be bottom feeders that wait for dead animals to sink
to the bottom of the sea. Estimating the size of C.
megalodon
has also
brought estimates of how much food it would take to keep it going.
Amounts vary greatly but range between 600 to 1200kg of food
every day. This is a tremendous amount of food for a scavenger as
scavengers tend to be adapted to require very little energy expenditure
because they don't know when or where their next meal is coming from.
When taking all of the fossil evidence, biometric models and
knowledge about shark lifestyles and biology into account, the result
is that scavenger is the least likely method of survival for C.
megalodon.
Extinction - Why did
megalodon disappear?
C.
megalodon
disappears from the fossil record near the end of the first stage
(Gelasian) of the of the Pleistocene
1.8 million years ago. This disappearance is marked by the steady
decline in C. megalodon fossils until they
disappear
completely. While
there are a few theories as to why C. megalodon
went
extinct it seems most
likely that a sequence of changing events brought about its downfall
rather than just one thing.
The
trigger event for the extinction of C. megalodon
seems
to have been global
cooling. To start, if C. megalodon had a warm
blooded metabolism
through gigantothermy, then it would need a higher calorie intake
than an entirely cold blooded creature of similar size. The colder
the water the greater the difference, meaning that C.
megalodon
would
have needed an even greater amount of food to deal with the temperature
reduction. Additionally gigantothermy is still no substitute for a true
warm blooded metabolism and a shark in cooler waters would still have
possibly been more sluggish than it would have been in warmer waters,
something that would further impede its ability to hunt.
A
knock on effect of colder global temperatures is that large amounts of
water began to solidify into ice as evidenced by the presence of vast
ice sheets across the Northern Hemisphere. The presence of more ice
meant that the sea level dropped and the most dramatic consequence of
this was the creation of the Isthmus of Panama, something that was
also helped by new land formations being built up by ongoing volcanic
activity in this area. This essentially
created a land bridge between North and South America as well as
isolating the Pacific and Atlantic oceans from each other at this point.
The
immediate result of the creation of the Isthmus of Panama was the
closure of the Central American Seaway which seemed to have been used
as a key migration route for whales, as evidenced by the large
concentration of whale fossils. This coincides with an overall
decline in whale species with much less than half of the Pleistocene
whales surviving to the present era. Today there are only 6
genera of whales as opposed to over 20 genera during the Miocene.
The remaining whales were still migratory but seemed to have preferred
Polar Regions, presumably for the greater abundance of invertebrate
food that Baleen whales are adapted to eat. The toothed whales do not
seem to have been a viable option either as their numbers were also
dramatically reduced with the sperm whale being the only large toothed
whale to survive to today. With C. megalodon
restricted to the warmer
ocean waters it no longer had constant year round access to the food
supply that it was most adapted to kill.
The
huge size of C. megalodon undoubtedly worked
against
it during these times
as the only other prey available were smaller, faster, and even if
caught did not provide the same level of sustenance as the larger
whales did. Cannibalism has also been suggested as a possible
survival strategy for C. megalodon, but this
would
only work as long as
there were other C. megalodon to eat. If this did
indeed happen, then
all that cannibalism would do is thin out the C. megalodon
numbers even
further, which in turn would limit the numbers that would reproduce.
Linked
to this is the potential loss of nursery areas caused by changing sea
levels. In fact the very creation of the Isthmus of Panama also seems
to have removed one such Nursery area, as evidenced by large numbers
of juvenile C. megalodon teeth from this area.
Another suspected nursery
area was Maryland which was so far north the waters may have become too
cold to support C. megalodon. The loss of nursery
areas means that the
C. megalodon young would themselves have been more
susceptible to
predators, perhaps even other C. megalodon as
they
tried to survive.
The
final theory involves the rise of new predators with special references
made towards the evolution of raptorial delphinids, which today are
represented by the Orca, also known as the killer whale. As the
Numbers of C. megalodon declined the numbers of
delphinids increased.
However it is difficult to say if the rise of these new predators
played a part in the decline of C. megalodon as it
could equally be the
decline of C. megalodon that allowed the new
predators
room to thrive.
There is fossil evidence that shows predator/prey interaction between
C. megalodon and the delphinids as exhibited by C.
megalodon
tooth marks on
delphinid bones.
 |
| 1 - Basilosaurus (whale), 2 - C. megalodon - lower average estimate (shark), 3 - Livyatan melvillei - lower estimate (whale), 4 - Pliosaurus funkei, a.k.a Predator X (pliosaur), 5 - Plesiosuchus (thalattosuchian), 6 - Thalattoarchon (ichthyosaur), 7 - Dunkleosteus (arthrodire placoderm), 8 - Shastasaurus (ichthyosaur), 9 - Tylosaurus (mosasaur), 10 - Leedsichthys - upper estimate (fish)), 11 - Brygmophyseter (whale), 12 - Rhizodus (lobe finned fish). |
Last survivors?
Some
people think that C. megalodon survived the
Pleistocene era and was still
swimming the oceans as recently as the Holocene era. Their proof for
this claim comes from a partial C. megalodon tooth
that was discovered in
1872 by the crew of HMS Challenger which when tested in 1959 was
thought to be only 10,000 years old. However this test measured
the levels of manganese dioxide on the fossil, a method which is now
considered flawed due to the varying degrees of manganese dioxide that
can build up on different fossils, even from the same era. When the
tooth was submitted to later radio carbon dating techniques, the
tooth was found to have too low a nitrogen level to allow for testing.
As such the tooth has since been deemed untestable and previous
estimates of C. megalodon becoming extinct during
the early
Pleistocene remain
valid.
Classification - Is megalodon
related to the great white shark?
Perhaps
the greatest point of controversy over C. megalodon
is
if it is actually
related to the Great White Shark that we know today. Comparisons
between C. megalodon and the great white mostly
come
about from the
principal that C. megalodon was the biggest shark,
and the great white
is the biggest shark that we know of today. Also the teeth between
the two are often seen as roughly similar. Supporters of C.
megalodon
within Carcharodon point to the tooth similarity as
being the result of
both C. megalodon and the great white being
descended
from
Palaeocarcharodon
orientalis.
The
problem with comparing C. megalodon to the great
white
on the basis of
similar teeth is that the only similarities that exist are that both
sharks have teeth that are triangular and serrated. Beyond this the
teeth of the great white are more gracile, being much thinner than
those of C. megalodon. Also while C.
megalodon
is thought to have an
overall similar tooth layout to the great white shark, the third
anterior tooth (third front tooth from the centre of the upper jaw)
of C. megalodon is different in that it points
down
like the first two,
different to how it appears in the great white. C. megalodon
anterior
teeth also have a characteristic 'scar' shaped like a chevron that
lies between the crown and root of the tooth, something that is
absent in the great white.
An
alternative to placing C. megalodon within the Carcharodon
shark genus
would be to place it within the older Carcharocles
genus. The main
argument for this placement is that another large ancient shark named
Carcharocles
auriculatus is thought to actually be an ancestor
to
C. megalodon. With teeth that measured up to
almost
12 centimetres
in length Carcharocles
auriculatus was big but
roughly a third smaller
than C. megalodon, if you scale it to an 18
centimetre C. megalodon
tooth. Even so, it is quite possible that Carcharocles
auriculatus
could have grown larger, giving rise to C. megalodon
as predators in all
environments have a tendency to keep growing bigger until their
environment can no longer support further growth.
Such
a placement of C. megalodon within Carcharocles
would actually complete a
transition where sharks lost lateral cusps to their teeth. This
transition begins with the lateral tooth cusps that are clearly present
in Otodus
obliquus, the reduced tooth cusps in Carcharocles
auriculatus, to no cusps in C. megalodon.
These teeth also have
chevron shaped scars where the crown meets the root, something which
is absent from great white teeth.
Another
theory suggests that C. megalodon was ancestral to
the
great white shark
and that over time the shark simply grew smaller. The main problem
with this thinking however is that the great white shark was actually
swimming in the ocean long before C. megalodon went
extinct, with fossil
teeth of the great white shark appearing back in the mid Miocene
period 16 million years ago, over 14 million years before
C. megalodon went extinct. Supporters of the
theory
still insist that
the great white could have evolved from a smaller species of
C. megalodon. Those familiar with the sabre
toothed
cat Smilodon
may be
aware that there were three quite different species of the same genus
that not only seem to be descended from the same ancestor, but for a
time were all active together in the same time period. It is not too
much of a stretch that similar occurrences could happen in other animal
groups. Still, there appears to be no transitional link that shows
the change From C. megalodon into the great white
as
the teeth would not
just grow smaller, they would steadily change into the great white
form. If indeed related, it is more likely that the great white
shares a common immediate ancestor with C. megalodon.
In
2012 the theory that C. megalodon and Carcharodon
carcharias are not
related got a little more support with the description of a new species
of Carcharodon, Carcharodon
hubbelli,
also known as Hubbell’s white
shark. The teeth of Carcharodon hubbelli have been
interpreted by some
to be transitional in form, linking Carcharodon carcharias
with Isurus
genus which houses the mako sharks. Because most researchers do not
consider there to be a direct link between mako sharks and megatoothed
sharks like C. megalodon, this might suggest that Carcharodon
carcharias is indeed separate from C. megalodon,
and that by extension
C. megalodon should be placed within the Carcharocles
genus.
Any
similarities in the overall morphology of C. megalodon
and the great white
are most likely the result of evolution rather than genetic breeding.
This basic body shape is called fusiform, or more loosely 'torpedo
shaped', and is based upon a pointed front rising to a broad centre
before tapering off to another rearward point. This form has repeated
itself in nature countless times, and is certainly not unique to just
sharks as it is simply the most efficient form for submerged aquatic
travel. The megalodon shark species has also been
regarded to some to
belong to either the Procarcharodon or the Otodus
genus.This thinking is down to research that suggests a visible
transition from the teeth of the Otodus type genus
through to those of
the megalodon species which lived later. Again
however,
differences between researchers vary greatly as to which genus the
megalodon species belongs to.
Further reading
- Recherches sur les poissons fossiles/par Louis Agassiz - Neuchatel
:Petitpierre. p. 41. - Louis Agassiz - 1833-1843.
- Size of the Great White Shark (Carcharodon) - Science Magazine 181
(4095): 169–170 - John Randall - 1973.
- Carcharodon megalodon from the Upper Miocene of
Denmark, with
comments on elasmobranch tooth enameloid: coronoi'n - Bulletin of the
Geological Society of Denmark (Copenhagen: Geologisk Museum) 32: 1–32.
- Svend Erik Bendix-Almgreen - 1983.
- Catalogue of Cuban fossil Elasmobranchii (Paleocene to Pliocene) and
paleogeographic implications of their Lower to Middle Miocene
occurrence - Bolet�n de la Sociedad Jamaicana de Geolog�a (Cuba) 31:
7–21 - M. Iturralde-Vinent, G. Hubbel & R. Rojas - 1996.
- The Megatooth shark, Carcharodon megalodon: Rough
toothed, huge
toothed - Mundo Marino Revista Internacional de Vida (non-refereed)
(Marina) 5: 6–11. - J. C. Bruner - 1997.
- Fossil sharks from Jamaica - Bulletin of the Mizunami Fossil Museum.
pp. 211–215. - Stephen Donovan & Gunter Gavin - 2001.
- An associated specimen of Carcharodon angustidens
(Chondrichthyes,
Lamnidae) from the Late Oligocene of New Zealand, with comments on
Carcharodon interrelationships - Journal of
Vertebrate Paleontology 21
(4): 730–739. - M. D. Gottfried & R. E. Fordyce - 2001.
- 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.
- New Record of the Lamnid Shark Carcharodon megalodon
from the Middle
Miocene of Puerto Rico - Caribbean Journal of Science 39: 223–227. -
Angel M. Nieves-Rivera, Maria Ruizyantin & Michael D. Gottfried
- 2003.
- The Miocene Climatic Optimum: evidence from ectothermic vertebrates
of Central Europe - Palaeogeography, Palaeoclimatology, Palaeoecology
195 (3–4): 389–401 - M. B�hme - 2003.
- Age of Carcharocles megalodon (Lamniformes:
Otodontidae) : A review
of the stratigraphic records - The Palaeontological Society of Japan
(PSJ) (Japan) 75 (75): 7–15. - Hebe Hideo, Goto Mastatoshi &
Kaneko Naotomo - 2004.
- Giant-toothed White Sharks and Wide-toothed Mako (Lamnidae) from the
Venezuela Neogene: Their Role in the Caribbean, Shallow-water Fish
Assemblage - Caribbean Journal of Science 40 (3): 362–368. - O.
Aguilera & E. R. D. Aguilera - 2004.
- Tracing the ancestry of the Great White Shark - Journal of Vertebrate
Paleontology 26 (4): 806–814 - K. G. Nyberg, C. N. Ciampaglio &
G. A. Wray - 2006.
- Late Neogene Oceanographic Change along Florida's West Coast:
Evidence and Mechanisms - The Journal of Geology (USA: The University
of Chicago) 104 (2): 143–162. - Warren D. Allmon, Steven D. Emslie,
Douglas S. Jones & Gary S. Morgan - 2006.
- Three-dimensional computer analysis of white shark jaw mechanics: how
hard can a great white bite? - Journal of Zoology 276 (4): 336–342. -
S. Wroe, D. R. Huber, M. Lowry, C. McHenry, K. Moreno, P. Clausen, T.
L. Ferrara, E. Cunningham, M. N. Dean & A. P. Summers - 2008.
- Miocene sharks in the Kendeace and Grand Bay formations of Carriacou,
The Grenadines, Lesser Antilles - Caribbean Journal of Science. 44 (3)
pp. 279–286. - Roger Portell, Gordon Hubell, Stephen Donovan, Jeremy
Green, David Harper & Ron Pickerill - 2008.
- Giant-toothed white sharks and cetacean trophic interaction from the
Pliocene Caribbean Paraguan� Formation - Pal�ontologische Zeitschrift
(Springer Berlin) 82 (2): 204–208. - Orangel A. Augilera, Luis Garc�a *
Mario A. Cozzuol - 2008.
- Ancient Nursery Area for the Extinct Giant Shark Megalodon
from the
Miocene of Panama - PLoS ONE (Panama: PLoS.org) 5 (5): e10552 -
Catalina Pimiento, Dana J. Ehret, Bruce J. McFadden & Gordon
Hubbell - 2010.
- The Great White Shark Carcharodon carcharias
(Linne, 1758) in the
Pliocene of Portugal and its Early Distribution in Eastern Atlantic -
Revista Espa�ola de Paleontolog�a (Portugal) 25 (1): 1–6. - Miguel
Telle Antunes, Ausenda C�ceres Balbino - 2010.
- Patterns and ecosystem consequences of shark declines in the ocean -
Ecology Letters (Blackwell Publishing Ltd) 13 (8): 1055–1071. -
Francesco Ferretti, Boris Worm, Gregory L. Britten, Michael J. Heithaus
& Heike K. Lotze - 2010.
- Origin of the white shark Carcharodon
(Lamniformes: Lamnidae)
based on recalibration of the upper Neogene Pisco Formation of Peru
- Palaeontology 55(6):1139-1153 - D. J. Ehret, B.
J. MacFadden, D. S. Jones, T. J. DeVries, D. A.
Foster & R. Salas-Gismondi - 2012.
- Evolution of white and megatooth sharks, and evidence for early
predation on seals, sirenians, and whales - Natural Science (Czech
Republic) 5 (11): 1203–1218. - C. G. Diedrich - 2013.
- Sharks and Rays (Chondrichthyes, Elasmobranchii) from the Late
Miocene Gatun Formation of Panama - Journal of Paleontology 87 (5):
755–774 - Catalina Pimiento, Gerardo Gonz�lez-Barba, Dana J. Ehret,
Austin J. W. Hendy, Bruce J. MacFadden & Carlos Jaramillo -
2013.
- When Did Carcharocles megalodon Become Extinct? A
New Analysis of the
Fossil Record. - PLOS ONE. 9 (10): e111086. - C. Pimiento & C.
F. Clements - 2014.
- Body-size trends of the extinct giant shark Carcharocles
megalodon: a
deep-time perspective on marine apex predators. - Paleobiology. 41 (3):
479–490. - C. Pimiento & M. A. Balk - 2015.
- Record of Carcharocles megalodon in the Eastern
Guadalquivir Basin
(Upper Miocene, South Spain). Estudios Geol�gicos. 71 (2): e032. - M.
Reolid & J. M. Molina - 2015.
- Geographical distribution patterns of Carcharocles megalodon
over
time reveal clues about extinction mechanisms. - Journal of
Biogeography. 43 (8): 1645–1655. - C. Pimiento, B. J. MacFadden, C. F.
Clements, S. Varela, C. Jaramillo, J. Velez-Juarbe & B. R.
Silliman - 2016.
- The size of the megatooth shark, Otodus megalodon
(Lamniformes:
Otodontidae), revisited. - Historical Biology: 1–8. - Kenshu Shimada -
2019.
- The Early Pliocene extinction of the mega-toothed shark Otodus
megalodon: a view from the eastern North Pacific. - PeerJ. 7:
e6088. -
R. W. Boessenecker, D. J. Ehret, D. J. Long, M. Churchill, E. Martin
& S. J. Boessenecker - 2019.
- The transition between Carcharocles chubutensis
and Carcharocles
megalodon (Otodontidae, Chondrichthyes): lateral cusplet loss
through
time. - Journal of Vertebrate Paleontology. 38 (6): e1546732. - V. J.
Perez, S. J. Godfrey, B. W. Kent, R. E. Weems & J. R. Nance -
2019.
- Body dimensions of the extinct giant shark Otodus megalodon:
a 2D
reconstruction. - Scientific Reports. 10 (14596): 14596. - J. A.
Cooper, C. Pimiento, H. G. Ferr�n & M. J. Benton - 2020.
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