Megalodon
Overview
 
The megalodon is an extinct
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

 that lived roughly from 28 to 1.5 million years ago, during the Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...

 Era
Era
An era is a commonly used word for long period of time. When used in science, for example geology, eras denote clearly defined periods of time of arbitrary but well defined length, such as for example the Mesozoic era from 252 Ma–66 Ma, delimited by a start event and an end event. When used in...

 (late Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...

 to early Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

).

The taxonomic assignment
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 of C. megalodon has been debated for nearly a century, and is still under dispute with two major interpretations; Carcharodon megalodon (under family Lamnidae
Lamnidae
Lamnidae is a family of sharks, commonly known as mackerel sharks or white sharks. They are large, fast-swimming sharks, found in oceans worldwide....

) or Carcharocles megalodon (under family Otodontidae
Otodontidae
Otodontidae is an extinct family of sharks, belonging to the order Lamniformes....

). Consequently, the scientific name
Binomial nomenclature
Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...

 of this species has been commonly abbreviated to C.
Encyclopedia
The megalodon is an extinct
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

 that lived roughly from 28 to 1.5 million years ago, during the Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...

 Era
Era
An era is a commonly used word for long period of time. When used in science, for example geology, eras denote clearly defined periods of time of arbitrary but well defined length, such as for example the Mesozoic era from 252 Ma–66 Ma, delimited by a start event and an end event. When used in...

 (late Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...

 to early Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

).

The taxonomic assignment
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 of C. megalodon has been debated for nearly a century, and is still under dispute with two major interpretations; Carcharodon megalodon (under family Lamnidae
Lamnidae
Lamnidae is a family of sharks, commonly known as mackerel sharks or white sharks. They are large, fast-swimming sharks, found in oceans worldwide....

) or Carcharocles megalodon (under family Otodontidae
Otodontidae
Otodontidae is an extinct family of sharks, belonging to the order Lamniformes....

). Consequently, the scientific name
Binomial nomenclature
Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...

 of this species has been commonly abbreviated to C. megalodon in literature
Literature
Literature is the art of written works, and is not bound to published sources...

.

C. megalodon is regarded as one of the largest and most powerful predators in vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

 history. C. megalodon likely had a profound impact on structuring of the marine communities. Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 remains indicate that this giant shark reached a total length (TL) of more than 16 metres (52.5 ft), and also affirm that it had a cosmopolitan distribution
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...

. Scientists suggest that C. megalodon looked like a stockier version of the great white shark
Great white shark
The great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...

, Carcharodon carcharias, in life.

Glossopetrae

According to Renaissance accounts, gigantic, triangular fossil teeth often found embedded in rocky formations were once believed to be petrified tongues, or glossopetrae, of the dragon
Dragon
A dragon is a legendary creature, typically with serpentine or reptilian traits, that feature in the myths of many cultures. There are two distinct cultural traditions of dragons: the European dragon, derived from European folk traditions and ultimately related to Greek and Middle Eastern...

s and snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

s. This interpretation was corrected in 1667 by a Danish naturalist, Nicolaus Steno
Nicolas Steno
Nicolas Steno |Latinized]] to Nicolaus Steno -gen. Nicolai Stenonis-, Italian Niccolo' Stenone) was a Danish pioneer in both anatomy and geology. Already in 1659 he decided not to accept anything simply written in a book, instead resolving to do research himself. He is considered the father of...

, who recognized them as ancient shark teeth (and famously produced a depiction of a shark's head bearing such teeth). He mentioned his findings in a book, The Head of a Shark Dissected, which also contained an illustration of a C. megalodon tooth, previously considered to be a tongue stone.

Identification

A Swiss
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

 naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...

, Louis Agassiz
Louis Agassiz
Jean Louis Rodolphe Agassiz was a Swiss paleontologist, glaciologist, geologist and a prominent innovator in the study of the Earth's natural history. He grew up in Switzerland and became a professor of natural history at University of Neuchâtel...

, gave this shark its scientific name, Carcharodon megalodon, in 1835, in his research work Recherches sur les poissons fossiles (Research on fossil fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

), which he completed in 1843. The teeth of the C. megalodon are morphologically similar to the teeth of the great white shark. On the basis of this observation, Agassiz assigned the genus Carcharodon to the megalodon. While the scientific name is C. megalodon, it is often informally dubbed the megatooth shark or giant white shark or even monster shark.

Fossils

C. megalodon is represented in the fossil record primarily by teeth and vertebral centra
Vertebral column
In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...

. As with all other sharks, C. megalodons skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...

 was formed of cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

 rather than bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

; this results in mostly poorly preserved fossil specimens.

Fossil teeth

The most common fossils of
C. megalodon are its teeth. The diagnostic characters of C. megalodon teeth include: triangular shape, robust structure, large size, fine serrations, and visible v-shaped neck. The teeth of C. megalodon can measure over 180 millimetres (7.1 in) in slant height or diagonal length, and are the largest in size of any known shark species.

Fossil vertebrae

Fossil vertebrae of
C. megalodon have also been occasionally found. The most notable example is a partially preserved but associated vertebral column of a single C. megalodon specimen, which was excavated from Antwerp basin
Antwerp (province)
Antwerp is the northernmost province both of the Flemish Region, also called Flanders, and of Belgium. It borders on the Netherlands and the Belgian provinces of Limburg, Flemish Brabant and East Flanders. Its capital is Antwerp which comprises the Port of Antwerp...

, Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

 by M. Leriche in 1926. This specimen comprises 150 vertebral centra, with the largest centra being 155 mm
Millimetre
The millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length....

 in diameter
Diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...

. However, scientist
Scientist
A scientist in a broad sense is one engaging in a systematic activity to acquire knowledge. In a more restricted sense, a scientist is an individual who uses the scientific method. The person may be an expert in one or more areas of science. This article focuses on the more restricted use of the word...

s have claimed that considerably larger vertebral centra can be expected from
C. megalodon. Interestingly, a partially preserved but associated vertebral column of another C. megalodon specimen was excavated from Gram clay, Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

 by Bendix-Almgeen in 1983. This specimen comprises 20 vertebral centra, with the largest centra being around 230 mm
Millimetre
The millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length....

 in diameter.

Fossil distribution and age

The fossils of
C. megalodon have been excavated from many parts of the world
World
World is a common name for the whole of human civilization, specifically human experience, history, or the human condition in general, worldwide, i.e. anywhere on Earth....

, including Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

, Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...

, Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...

, Jamaica
Jamaica
Jamaica is an island nation of the Greater Antilles, in length, up to in width and 10,990 square kilometres in area. It is situated in the Caribbean Sea, about south of Cuba, and west of Hispaniola, the island harbouring the nation-states Haiti and the Dominican Republic...

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Malta
Malta
Malta , officially known as the Republic of Malta , is a Southern European country consisting of an archipelago situated in the centre of the Mediterranean, south of Sicily, east of Tunisia and north of Libya, with Gibraltar to the west and Alexandria to the east.Malta covers just over in...

, Grenadines
Grenadines
The Grenadines is a Caribbean island chain of over 600 islands in the Windward Islands.-Geographic boundaries:They are divided between the island nations of Saint Vincent and the Grenadines and Grenada. They lie between the islands of Saint Vincent in the north and Grenada in the south. Neither...

, and India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

.
C. megalodon teeth have also been excavated from regions far away from continental lands (e.g., the Mariana Trench
Mariana Trench
The Mariana Trench or Marianas Trench is the deepest part of the world's oceans. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about long but has a mean width of only...

 in the Pacific).

The earliest remains of
C. megalodon have been reported from late Oligocene strata
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...

, circa 28 million years old. Although fossils of
C. megalodon are predominantly absent in strata extending beyond the Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

 boundary, they have been reported from subsequent Pleistocene strata. It is believed that
C. megalodon became extinct in the Pleistocene, probably about 1.5 million years ago.

Anatomy

Among extant species, the great white shark is regarded as the best analogue to
C. megalodon. The lack of well preserved fossil skeletons of C. megalodon have forced scientists to rely on the morphology of the great white shark for the basis of its reconstruction and size estimation.

Size estimation

Due to fragmentary remains, estimating the size of
C. megalodon has been challenging. However, the scientific community acknowledges that C. megalodon was larger than the whale shark
Whale shark
The whale shark, Rhincodon typus, is a slow-moving filter feeding shark, the largest extant fish species. The largest confirmed individual had a length of and a weight of more than , but unconfirmed claims report considerably larger whale sharks...

,
Rhincodon typus. Scientists have focused their research upon two aspects of size: (1) total length (TL), and (2) body mass (BM).

Total length estimates

The first attempt to reconstruct the jaw
Jaw
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...

 of this shark was made by Professor Bashford Dean
Bashford Dean
Bashford Dean was an American zoologist, specializing in ichthyology, and at the same time an expert in medieval armor. He is the only person to have held concurrent positions at the American Museum of Natural History and the Metropolitan Museum of Art, where he was Honorary Curator of Arms and...

 in 1909. From the dimensions of this jaw reconstruction, it was hypothesized that C. megalodon could have approached 30 metres (98 ft) in total length (TL), but in light of new fossil discoveries and advances in vertebrate sciences this jaw reconstruction is now considered to be inaccurate. Major reasons cited for this inaccuracy are (1) relatively poor knowledge of C. megalodon's dentition in Dean's time, and (2) inaccurate muscle structures. Experts suggest that a rectified version of C. megalodons jaw model by Bashford Dean would be about seventy percent (70%) of its original size and would lead to a shark size consistent with modern findings. To resolve such errors, scientists, aided by new fossil discoveries of C. megalodon and improved knowledge of its closest living analogue's anatomy, introduced more quantitative methods for estimating its size based on the statistical relationships between the tooth sizes and body lengths in the great white shark. Some methods are mentioned below.
Method proposed by John E. Randall

In 1973, an ichthyologist from Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, John E. Randall, introduced a method to estimate the total length of the great white shark. The proposed method is depicted in the form of a plotted graph, which demonstrates a relationship between the enamel height (the vertical distance of the blade from the base of the enamel portion of the tooth to its tip) of the largest tooth in the upper jaw of the great white shark and its total length. Randall extrapolated this method to estimate the total length of C. megalodon as well. Randall cited two C. megalodon teeth in his work: (1) specimen number 10356 in American Museum of Natural History
American Museum of Natural History
The American Museum of Natural History , located on the Upper West Side of Manhattan in New York City, United States, is one of the largest and most celebrated museums in the world...

 and (2) specimen number 25730 in United States National Museum
National Museum of Natural History
The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. Admission is free and the museum is open 364 days a year....

, which had enamel heights of 115 mm
Millimetre
The millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length....

 and 117.5 mm
Millimetre
The millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length....

 respectively. These teeth yielded a corresponding total length of about 13 metres (43 ft). In 1991, two shark experts, Richard Ellis and John E. McCosker, pointed out a flaw in Randall's method. According to them, sharks' tooth enamel height does not necessarily increase in proportion to the animal's total length. This observation led to proposals for new, more accurate methods to determine the size of the great white shark and similar sharks.
Method proposed by Gottfried et al.

In 1996 three scientists – Michael D. Gottfried, Leonard J. V. Compagno
Leonard Compagno
Leonard Joseph Victor Compagno is an international authority on shark taxonomy and the author of many scientific papers and books on the subject, best known of which is his 1984 catalogue of shark species produced for the Food and Agriculture Organization of the United Nations.-Career:*Ph.D,...

 and S. Curtis Bowman – after thorough research and scrutiny of 73 great white shark specimens, proposed a conservative linear relationship between the maximum height of the largest upper anterior tooth (UA) and the total length (TL) in the great white shark. The proposed relationship is: total length (TL) in meters = − (0.22) + (0.096) × [UA maximum height (mm
Millimetre
The millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length....

)]. Gottfried and colleagues (1996) also extrapolated this method to estimate the total length (TL) of C. megalodon. The biggest C. megalodon tooth in the possession of this team was an upper second anterior specimen, whose maximum height was 168 millimetres (6.6 in). This tooth had been discovered by Compagno in 1993, and it yielded an estimated total length (TL) of 15.9 metres (52 ft). However, rumors of larger C. megalodon teeth persisted at that time. The maximum tooth height for this method is measured as a vertical line from the tip of the crown to the bottom of the lobes of the root, parallel to the long axis of the tooth. In layman's terms, the maximum height of the tooth is its slant height.
Method proposed by Clifford Jeremiah

In 2002, shark researcher Dr. Clifford Jeremiah proposed a method to estimate the total length (TL) of great white shark and similar sharks including C. megalodon. Shark researcher David Ward has asserted that this method is based on a sound principle that works well with most large sharks. The proposed method is: for every centimeter of root width of an upper anterior tooth, there is approximately 4.5 feet of the shark. Jeremiah pointed out that the jaw perimeter of a shark is directly proportional to its total length (TL), with the width of the roots of the largest teeth being a proxy for estimating jaw perimeter. The largest tooth in the possession of Jeremiah had a root width of about 12 centimetres (4.7 in), which yielded 15.5 metres (51 ft) total length (TL).
Method proposed by Kenshu Shimada

In 2002, paleontologist Dr. Kenshu Shimada of DePaul University
DePaul University
DePaul University is a private institution of higher education and research in Chicago, Illinois. Founded by the Vincentians in 1898, the university takes its name from the 17th century French priest Saint Vincent de Paul...

 proposed a linear relationship between tooth crown height (CH) and total length (TL) in great white sharks after conducting anatomical analysis of several specimens. In statistical terms, this relationship is expressed as: total length (TL) in cm = a + bx, where a is a constant, b is the slope of the line, and x is the crown height (CH) of tooth in mm. This proposed relationship provides the capability to predict total length (TL) on the basis of crown height (CH) of any tooth in great white shark. The crown height (CH) of the tooth is measured as maximum vertical enameloid height on the labial side for this method. Shimada pointed out that previously proposed methods were based on weaker evaluation of dental homology. Shimada pointed out that the growth rate between the crown and root is not isometric, and this factor has been taken into consideration in his proposed model. Furthermore, this proposed relationship can also be used to predict the total length (TL) of sharks that are morphologically similar to the great white shark (e.g., C. megalodon). Using this model, the upper anterior tooth (with maximum height of 168 millimetres (6.6 in)) possessed by Gottfried and colleagues (1996) corresponded to a total length (TL) of 15.1 metres (50 ft). In 2010, several shark researchers – Catalina Pimiento, Dana J. Ehret, Bruce J. MacFadden, and Gordon Hubbell — estimated the total length (TL) of C. megalodon on the basis of Shimada's method. Among the specimens found in the Gatun Formation of Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...

, specimen number 237956 yielded a total length (TL) of 16.8 metres (55 ft).
Consensus

In the 1990s, marine biologists (e.g., Patrick J. Schembri, and Staphon Papson) opined that C. megalodon may have approached a maximum of around 24 to 25 m (78.7 to 82 ft) in total length (TL). The early total length (TL) estimation of C. megalodon is perhaps not far-fetched. However, Gottfried and colleagues (1996) proposed that C. megalodon could likely approach a maximum of 20.3 metres (67 ft) in total length (TL). Currently most experts agree this giant shark reached a total length (TL) of more than 16 metres (52 ft).
Largest known specimens

Dr. Gordon Hubbell from Gainesville
Gainesville
Gainesville is the name of several places in the United States of America:*Gainesville, Alabama*Gainesville, Florida, largest municipality with this name*Gainesville, Georgia*Gainesville, Missouri*Gainesville , New York...

 in USA, possesses an upper anterior C. megalodon tooth whose maximum height is 184.15 millimetres (7.3 in). In addition, a C. megalodon jaw reconstruction contains a tooth whose maximum height is reportedly 193.675 millimetres (7.6 in). This jaw reconstruction was developed by deceased fossil hunter Vito Bertucci, who was known as "Megalodon Man".

Body mass estimates

Gottfried and colleagues (1996) also introduced a method to determine the body mass of the great white shark after studying the length–mass relationship data of 175 specimens at various growth stages and extrapolated it to estimate the body mass of C. megalodon. The proposed method is: mass in kilogram
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...

 = 3.29E−06[TL in (meters)3.174]. According to this model, a 15.9 metres (52 ft) long C. megalodon would have a body mass of about 47 metric tons (52 ST), a 17 metres (56 ft) long C. megalodon would have a body mass of about 59 metric tons (65 ST), and a 20.3 metres (67 ft) long C. megalodon would have a body mass of 103 metric tons (114 ST). Consequently, C. megalodon is regarded as the largest shark ever to have lived, and is among the largest fish known to have existed.

Dentition and jaw mechanics

A team of Japanese scientists, T. Uyeno, O. Sakamoto, and H. Sekine, discovered and excavated partial remains of a C. megalodon, with nearly complete associated set of its teeth, from Saitama
Saitama, Saitama
' is the capital and the most populous city of Saitama Prefecture in Japan, situated in the south-east of the prefecture. Its area incorporates the former cities of Urawa, Ōmiya, Yono and Iwatsuki. It is a city designated by government ordinance...

, Japan in 1989. Another nearly complete associated C. megalodon dentition was excavated from Yorktown Formation
Yorktown Formation
The Yorktown Formation is a mapped bedrock unit in the Coastal Plain of Maryland, Virginia, North Carolina and South Carolina. It is overconsolidated and highly fossiliferous.-Description:...

s of Lee Creek, North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...

 in USA and served as the basis of a jaw reconstruction of C. megalodon in the American Museum of Natural History
American Museum of Natural History
The American Museum of Natural History , located on the Upper West Side of Manhattan in New York City, United States, is one of the largest and most celebrated museums in the world...

 in NYC. These associated tooth sets solved the mystery of how many teeth would be in the jaws of the C. megalodon in each row in life. Hence, highly accurate jaw reconstructions were now possible. More associated dentitions of C. megalodon have also been found in later years. Based upon these discoveries, two scientists, S. Applegate and L. Espinosa, published an artificial dental formula
Dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...

 (representation of dentition of an animal with respect to types of teeth and their arrangement within the animal's jaw) for C. megalodon in 1996. Most accurate modern C. megalodon jaw reconstructions are based on this dental formula.

The dental formula of C. megalodon is: .

As evident from the dental formula, C. megalodon had four kinds of teeth in its jaws.
  • Anterior - A
  • Intermediate - I (In the case of C. megalodon, this tooth technically appears to be an upper anterior and is termed as "A3" because it is fairly symmetrical and does not points mesially (side of the tooth toward the midline of the jaws where left and right jaws meet), but this tooth is still designated as an intermediate tooth. However, in the case of the great white shark, the intermediate tooth does point mesially. This point has often been raised in the Carcharodon vs. Carcharocles debate regarding the megalodon and favors the case of Carcharocles proponents.)
  • Lateral - L
  • Posterior - P

C. megalodon had a very robust dentition, and it had a total of about 276 teeth in its jaws, spanning 5 rows. (See "external links" below)

Paleontologists suggest that a very large C. megalodon had jaws over 2 metres (7 ft) across.

Bite force

In 2008, a team of scientists led by Dr. Stephen Wroe conducted an experiment
Experiment
An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...

 to determine the bite force of C. megalodon; results indicate that it had one of the most powerful bites in history. At 15.9 metres (52 ft) long, C. megalodon was capable of exerting a bite force estimated at 108514 newtons (24,394.9 lbf), and at 20.3 metres (67 ft) long, C. megalodon was capable of exerting a bite force estimated at 182201 newtons (40,960.4 lbf).

C. megalodon's bite force, at maximum estimated size, is over 28 times greater than that of Dunkleosteus
Dunkleosteus
Dunkleosteus is a genus of prehistoric fish, one of the largest arthrodire placoderms ever to have lived, existing during the Late Devonian period, about 380-360 million years ago.This hunter, measuring up to and weighing , was a hypercarnivorous apex predator...

at 5.3 kilonewtons (1,191.5 lbf), over 10 times greater than that of the great white shark
Great white shark
The great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...

 at 18 kilonewtons (4,046.6 lbf), over 5 times greater than that of T. rex
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...

at 31 kilonewtons (6,969.1 lbf), and also greater than that of Predator X
Predator X
Predator X is a comic book character, in Marvel Comics' main shared universe. The character is an adversary of Marvel's mutant characters, including the X-Men.-History:...

at 150 kilonewtons (33,721.3 lbf).

In addition, Wroe and colleagues (2008) pointed out that sharks also shake sideways while feeding, amplifying the postcranial generated forces. Therefore the total forces experienced by prey are likely higher than the forces estimated through the experiment. The extraordinary bite forces in C. megalodon must be considered in the context of the great size of this fossil predator and of paleontological evidence suggesting that C. megalodon was an active predator of large whales.

Functional parameters of teeth

The exceptionally robust teeth of C. megalodon are serrated, which would have improved efficiency in slicing the flesh
Flesh
In vertebrate animals, flesh is the colloquial for biological tissue which consists of skeletal muscles and fat as opposed to bones, viscera and integuments. Flesh may be used as food, in which case it is called meat....

 of prey items. Paleontologist Dr. Bretton K. Kent from University of Maryland
University of Maryland
When the term "University of Maryland" is used without any qualification, it generally refers to the University of Maryland, College Park.University of Maryland may refer to the following:...

 suggests that these teeth are comparatively thicker for their size with much lower slenderness and bending strength ratios. They also have roots that are substantially larger relative to total tooth heights, and so have a greater mechanical advantage. Teeth with these traits are not just good cutting tools but also are well suited for grasping powerful prey and would seldom crack even when slicing through bones.

Skeletal anatomy

Aside from estimating the size of C. megalodon, Gottfried and colleagues (1996) also have tried to determine the schematics of the entire skeleton of C. megalodon.

Jaw structure

To functionally support the very large and robust dentition, the jaws of the C. megalodon would have been massive, stouter, and more strongly developed than that of the great white shark, which possesses a somewhat gracile dentition in comparison. The strongly developed jaws would have somewhat of a pig-eyed appearance.

Chondrocranium

The chondrocranium
Chondrocranium
The chondrocranium is the primitive cartilaginous skeletal structure of the fetal skull that grows to envelop the rapidly growing embryonic brain....

 of C. megalodon would have a blockier and more robust appearance than that of the great white shark, in order to functionally reflect its more massive jaws and dentition in comparison.

Fins

The fins of C. megalodon would have been most likely proportionally larger and thicker in comparison to the fins of great white sharks because relatively larger fins are a necessity for propulsion and control of movements of a larger shark.

Axial skeleton

Through thorough scrutiny of the partially preserved vertebral C. megalodon specimen from Belgium, it became apparent that C. megalodon had a higher vertebral count than found in large specimens of any known shark. Only the vertebral count in great white shark came close in quantity, symbolizing close anatomical ties between the two species.

Full skeletal reconstruction

On the basis of the characteristics mentioned above, Gottfried and colleagues (1996) eventually managed to reconstruct the entire skeleton of C. megalodon, which has been put on display in Calvert Marine Museum
Calvert Marine Museum
The Calvert Marine Museum is a maritime museum, founded in 1970, located in Solomons, Maryland. Among its exhibits are the Drum Point Light and the bugeye Wm. B. Tennison, the latter a National Historic Landmark. It also houses artifacts from the old Cedar Point Light, and maintains the Drum...

 at Solomons island, Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...

 in USA. This C. megalodon skeletal reconstruction is 11.5 metres (38 ft) long and represents a young individual. The team stresses that relative and proportional changes in the skeletal features of C. megalodon are ontogenetic in nature in comparison to that of great white shark, as they occur in great white sharks while growing larger. In addition, the fossil remains of C. megalodon confirm that it had a heavily calcified skeleton in life.

Range and habitat

Sharks, especially large species, are highly mobile organisms with a complex life history and wide distribution. Fossil records of C. megalodon indicate that it was cosmopolitan
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...

, and commonly occurred in subtropical
Subtropics
The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...

 to temperate latitudes. Prior to the formation of the Isthmus of Panama
Isthmus of Panama
The Isthmus of Panama, also historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country of Panama and the Panama Canal...

, the seas were relatively warmer. This would have made it possible for the species to live in all the ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...

s of the world.

C. megalodon had enough behavioral flexibility to inhabit wide range of marine environments (i.e. coastal shallow waters, coastal upwelling, swampy coastal lagoons, sandy littorals, and offshore deep water environments), and exhibited a transient life-style. Adult C. megalodon were not abundant in shallow water environments, and mostly lurked offshore. C. megalodon may have moved between coastal and oceanic waters, particularly in different stages in its life cycle.

Prey relationships

Sharks are generally opportunistic predators. However, scientists propose that C. megalodon was "arguably the most formidable carnivore ever to have existed." Its great size, high-speed swimming capability, and powerful jaws coupled with formidable killing apparatus, made it a super-predator
Apex predator
Apex predators are predators that have no predators of their own, residing at the top of their food chain. Zoologists define predation as the killing and consumption of another organism...

 with the capability to consume a broad spectrum of fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...

.

Fossil evidence indicates that C. megalodon preyed upon cetaceans (i.e., dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...

s, small whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...

s, (including cetotherrids
Cetotherium
Cetotherium is a genus of the extinct cetaceans from the family Cetotheriidae .-Known species:...

, squalodon
Squalodon
Squalodon is an extinct genus of whales, belonging to the family Squalodontidae. Named by Grateloup in 1840, it was originally believed to be an iguanodontid dinosaur but has since been reclassified. The name Squalodon comes from Squalus, a genus of shark...

tids, and Odobenocetops
Odobenocetops
Odobenocetops was a small whale from the Pliocene. It had two tusks, and, in some fossils, one tusk was longer than the other.-Description:...

), and large whales, (including sperm whales
Sperm whale family
Physeteroidea is a superfamily including just three living species of whale; the Sperm Whale, in the genus Physeter, and the Pygmy Sperm Whale and Dwarf Sperm Whale, in the genus Kogia...

, bowhead whale
Bowhead Whale
The bowhead whale is a baleen whale of the right whale family Balaenidae in suborder Mysticeti. A stocky dark-colored whale without a dorsal fin, it can grow to in length. This thick-bodied species can weigh to , second only to the blue whale, although the bowhead's maximum length is less than...

s, and rorquals), pinniped
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...

s, porpoises, sirenians, and giant sea turtle
Sea turtle
Sea turtles are marine reptiles that inhabit all of the world's oceans except the Arctic.-Distribution:...

s.

Marine mammals were regular prey targets for C. megalodon. Many whale bones have been found with clear signs of large bite marks (deep gashes) made by teeth that match those of C. megalodon, and various excavations have revealed C. megalodon teeth lying close to the chewed remains of whales, and sometimes in direct association with them. Fossil evidence of interactions between C. megalodon and pinnipeds also exist. In one interesting observation, a 127 millimetres (5 in) C. megalodon tooth was found lying very close to a bitten earbone of a sea lion
Sea Lion
Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...

.
C. megalodon faced a highly competitive
Interspecific competition
Interspecific competition, in ecology, is a form of competition in which individuals of different species compete for the same resource in an ecosystem...

 environment during its time of existence. However, C. megalodon, being at the top of the food chain, likely had a profound impact on the structuring of marine communities. Fossil evidence indicates a correlation between the emergence of C. megalodon and extensive diversification of cetaceans around the world. Juvenile C. megalodon preferred regions where small cetaceans were abundant, and adult C. megalodon preferred regions where large cetaceans were abundant. Such preferences may have developed shortly after they appeared in the Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...

. In addition, C. megalodon was contemporaneous with macro-predatory odontocetes (particularly raptorial sperm whales and squalodontids), which were also likely among the apex predators of that time, and provided competition. In response to competition from giant macro-predatory sharks, macro-predatory odontocetes may have evolved some defensive adaptations; some species became pack predators
Pack hunter
A pack hunter is a predator belonging to the animal kingdom, which has evolved to hunt its prey by working together with other members of its species. Normally, such animals are closely related. The most commonly known pack hunter is the Gray Wolf, the ancestor of all breeds of domesticated dogs...

, and some species attained gigantic sizes, such as Livyatan melvillei
Livyatan melvillei
Livyatan melvillei is an extinct species of physeteroid whale, which lived during the Miocene epoch, approximately 12-13 million years ago.- Discovery :...

. By the end of the Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

, raptorial sperm whales vanished from the fossil record and left an ecological void.

Like other sharks, C. megalodon also would have been piscivorous. Fossil evidence indicates that other notable species of macro-predatory sharks (e.g. great white sharks) responded to competitive pressure from C. megalodon by avoiding regions it inhabited. C. megalodon likely also had a tendency for cannibalism
Cannibalism
Cannibalism is the act or practice of humans eating the flesh of other human beings. It is also called anthropophagy...

.

Feeding strategies

Sharks often employ complex hunting strategies to engage large prey animals. Some paleontologists suggest that the hunting strategies of the great white shark may offer clues as to how C. megalodon might have hunted its unusually large prey (i.e., whales). However, fossil evidence suggests that C. megalodon employed more effective hunting strategies against large prey than those of the great white shark.

Paleontologists have conducted a survey of fossils to determine attacking patterns of C. megalodon on prey. One particular specimen — the remains of a 9 metres (30 ft) long prehistoric baleen whale (of an unknown Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 taxon) — provided the first opportunity to quantitatively analyze the attacking behavior of C. megalodon. The predator primarily focused its attack on the tough bony portions (i.e. shoulders, flippers, rib cage, and upper spine) of the prey, which great white sharks generally avoid. Dr. Bretton Kent elaborated that C. megalodon attempted to crush the bones and damage delicate organs (i.e. heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

, and lungs) harbored within the rib cage of the prey. Such an attack would have immobilized the prey, which would have died quickly due to injuries to these vital organs. These findings also clarify why the ancient shark needed more robust dentition than that of great white sharks. Furthermore, the attack patterns could differ for prey of different sizes. Fossil remains of some small cetaceans (e.g. cetotheriids) suggest that they were rammed with great force from below before being killed and eaten.

During the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

, larger and and more advanced cetaceans appeared. C. megalodon apparently further refined its hunting strategies to cope with these large whales. Numerous fossilized flipper bones (i.e., segments of the pectoral fins), and caudal vertebrae of large whales from the Pliocene have been found with bite marks that were caused by attacks of C. megalodon. This paleontological evidence suggests that C. megalodon would attempt to immobilize a large whale by ripping apart or biting off its propulsive structures before killing and feeding on it.

Nursery areas

Fossil evidence suggests that the preferred nursery sites of C. megalodon were warm water coastal environments, where potential threats were minor and food sources plentiful. Nursery sites have been identified in the Gatun Formation of Panama, the Calvert Formation of Maryland, and the Bone Valley
Bone Valley
The Bone Valley is a region of central Florida, encompassing portions of present-day Hardee, Hillsborough, Manatee, and Polk counties, in which phosphate is mined for use in the production of agricultural fertilizer...

 Formation of Florida. As is the case with most sharks, C. megalodon also gave birth to live young. The size of neonate C. megalodon teeth indicate that C. megalodon pups were around 2 to 4 m (6.6 to 13.1 ft) in total length (TL) at birth. Their dietary preferences display an ontogenetic
Ontogeny
Ontogeny is the origin and the development of an organism – for example: from the fertilized egg to mature form. It covers in essence, the study of an organism's lifespan...

 shift. Young C. megalodon commonly preyed on fish, giant sea turtles, dugongs, and small cetaceans; mature C. megalodon moved to off-shore cetacean high-use areas and consumed large cetaceans.

However, there is an exceptional case which suggests that juvenile C. megalodon may occasionally have attacked much larger balaenopterid whales. Three tooth marks apparently from a 4-7 m long Pliocene macro-predatory shark were found on a rib from an ancestral great blue or humpback whale that showed evidence of subsequent healing. Scientists suspect that this shark was a juvenile C. megalodon.

Extinction

The subject of the extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 of C. megalodon is still under investigation. Several possible causes for its decline and eventual disappearance have been proposed.

Oceanic cooling and sea level drops

The closure of Central American Seaway
Isthmus of Panama
The Isthmus of Panama, also historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country of Panama and the Panama Canal...

 fundamentally changed global ocean circulation. This event initially set the stage for glaciation in the northern hemisphere, and later on, also facilitated the cooling of the entire planet. In addition, expansion of glaciation during the Pliocene tied up huge volumes of water in the form of ice sheets, resulting in significant sea level drops. Consequently, during the late Pliocene and Pleistocene, there were ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

s, which cooled the oceans significantly. The major reason cited behind the extinction of C. megalodon is the decline in ocean temperatures at global scale during the Pliocene. This cooling trend adversely impacted C. megalodon, as it preferred warmer waters, and as a result it became extremely rare until its ultimate extinction during the Pleistocene. Fossil evidence confirms the absence of C. megalodon in regions around the world where water temperatures had significantly declined during the Pliocene. Furthermore, these oceanographic changes may have restricted many of the suitable warm water nursery sites for C. megalodon, hindering population maintenance. Nursery areas are pivotal for the survival of a species.

Decline in food supply

Cetaceans attained their greatest diversity during the Miocene, with over 20 recognized genera in comparison to only six living genera. Such diversity presented an ideal setting to support a gigantic macro-predator like C. megalodon. However, by the end-Miocene, many species of cetaceans became extinct. Furthermore, after the closure of Central American Seaway
Central American Seaway
The Central American Seaway, also called the Panamanic Seaway or Inter-American Seaway was an ancient body of water that once separated North America from South America...

, additional extinctions occurred in the marine environment, and faunal redistribution took place; the great whales abandoned the tropics
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately  N and the Tropic of Capricorn in the southern hemisphere at  S; these latitudes correspond to the axial tilt of the Earth...

. Whale migratory patterns during the Pliocene have been reconstructed from the fossil record, suggesting that most surviving species showed a trend towards polar region
Polar region
Earth's polar regions are the areas of the globe surrounding the poles also known as frigid zones. The North Pole and South Pole being the centers, these regions are dominated by the polar ice caps, resting respectively on the Arctic Ocean and the continent of Antarctica...

s. The cooling trend in oceans during the Pliocene prevented C. megalodon from gaining access to polar regions, depriving the gigantic shark from its main food source; the great whales. As a result of these developments, the food supply for C. megalodon in regions it inhabited during the Pliocene, primarily in low-to-mid latitudes, was no longer sufficient to sustain the species worldwide. C. megalodon was adapted to a specialized lifestyle, and this lifestyle was disturbed as a result of these developments. In addition, the resulting shortage of food sources in tropics during Plio-Pleistocene
Plio-Pleistocene
The term Plio-Pleistocene refers to the geological period more recent than circa 5 million years ago, incorporating both the formally defined epochs of the Pliocene and the Pleistocene...

 times may have fueled cannibalism within C. megalodon. The juvenile individuals were at increased risk from attacks by adult individuals during times of starvation.

New competition

Large raptorial delphinids (members of genus Orcinus) evolved during the Pliocene, and likely filled the ecological void left by the disappearance of raptorial sperm whales at the end of the Miocene. A minority view is that these delphinids may have outcompeted the last representatives of C. megalodon for the top predator niche. Fossil records indicate that these delphinids commonly occurred at high latitudes during the Pliocene, indicating that they could cope with the increasingly prevalent cold water temperatures. These delphinids also occurred in tropics (e.g. Orcinus sp. in South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

). Large bite marks on the fossil remains of delphinids indicate that C. megalodon preyed on them. However, Paleontologist Albert Sanders suggests that C. megalodon had become too large to sustain itself on the available food supply in the tropics. Most experts have inferred that factors such as cooling trend in oceans, and shortage of food sources, during Plio-Pleistocene
Plio-Pleistocene
The term Plio-Pleistocene refers to the geological period more recent than circa 5 million years ago, incorporating both the formally defined epochs of the Pliocene and the Pleistocene...

 times have played a significant role in downfall and demise of C. megalodon. Other apex predators seem to have gained from the extinction of this formidable species.

Taxonomy

Even after decades of research and scrutiny, controversy over the phylogeny of C. megalodon still persists. Several shark researchers (e.g. J. E. Randall, A. P. Klimley, D. G. Ainley, M. D. Gottfried, L. J. V. Compagno
Leonard Compagno
Leonard Joseph Victor Compagno is an international authority on shark taxonomy and the author of many scientific papers and books on the subject, best known of which is his 1984 catalogue of shark species produced for the Food and Agriculture Organization of the United Nations.-Career:*Ph.D,...

, S. C. Bowman, and R. W. Purdy) insist that C. megalodon is a close relative of the great white shark. However, several other shark researchers (e.g. D. S. Jordan, H. Hannibal, E. Casier, C. DeMuizon, T. J. DeVries, D. Ward, and H. Cappetta) dismiss the proposal that C. megalodon is a close relative of the great white shark, and cite convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...

 as the reason for the dental similarity. The arguments of the supporters of the Carcharocles genus for C. megalodon seem to have gained noticeable support. However, the original taxonomic assignment still has wide acceptance.

Megalodon within Carcharodon


The traditional view is that C. megalodon should be classified within the genus Carcharodon along with the great white shark. Main reasons cited for this phylogeny are; (1) an ontogenetic gradation, whereby the teeth of
C. carcharias shift from having coarse serrations as a juvenile to fine serrations as an adult, the latter resemble those of C. megalodon; (2) morphological similarity of teeth of young C. megalodon to those of C. carcharias; (3) a symmetrical second anterior tooth; (4) large intermediate tooth that is inclined mesially; and (5) upper anterior teeth that have a chevron-shaped neck area on the lingual surface. The supporters of classification as Carcharodon for C. megalodon suggest that C. megalodon and C. carcharias share a common ancestor, Palaeocarcharodon orientalis.

Megalodon within Carcharocles


Around 1923, the genus Carcharocles was proposed by two shark researchers, D. S. Jordan and H. Hannibal, to classify a shark C. auriculatus. Later on, Carcharocles proponents assigned C. megalodon to Carcharocles genus. Carcharocles proponents also suggest that the direct ancestor of the sharks belonging to the Carcharocles genus, is an ancient giant shark called Otodus obliquus
Otodus obliquus
Otodus obliquus is an extinct mackerel shark which lived during the Paleocene and Eocene epochs, approximately about 60 to 37.5 million years ago.-Known physiology:This shark is known from the fossil teeth and fossilized vertebral centra...

, which lived during the Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...

 and Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

 epochs. According to supporters of classification as Carcharocles for C. megalodon; Otodus obliquus
Otodus obliquus
Otodus obliquus is an extinct mackerel shark which lived during the Paleocene and Eocene epochs, approximately about 60 to 37.5 million years ago.-Known physiology:This shark is known from the fossil teeth and fossilized vertebral centra...

evolved in to Otodus aksuaticus, which evolved in to Carcharocles auriculatus
Carcharocles auriculatus
Carcharocles auriculatus is a species of the genus Carcharocles, closely related to the megalodon.-Size:The tooth length of C.auriculatus is relatively large - from 25 to 114 mm. Howewer, it is smaller than that of megalodon and Carcharocles angustidens; the tooth length of C. megalodon is...

, which evolved into Carcharocles angustidens, which evolved into Carcharocles chubutensis
Carcharocles chubutensis
Carcharocles chubutensis is a prehistoric megatoothed shark that lived during Oligocene, Miocene, and Pliocene epochs, approximately about 28 - 5 million years ago. This shark is considered to be a close relative of another prehistoric megatoothed shark, C. megalodon. However, as is the case with C...

, which eventually evolved into megalodon. Hence, the immediate ancestor of C. megalodon is Carcharocles chubutensis, because it serves as the missing link between Carcharocles augustidens and C. megalodon and it bridges the loss of the "lateral cusps" that characterize C. megalodon.

Megalodon as chronospecies?

Shark researcher David Ward has further elaborated on the Carcharocles evolutionary process by implying that this lineage, stretching from the Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...

 to the Pliocene, is of a single giant shark which gradually changed through time, suggesting a case of chronospecies
Chronospecies
A chronospecies describes a group of one or more species derived from a sequential development pattern which involves continual and uniform changes from an extinct ancestral form on an evolutionary scale. This sequence of alterations eventually produces a population which is physically,...

.

New evolutionary position for great white shark

Carcharocles proponents point out that the great white shark is closely related to an ancient shark Isurus hastalis, the "broad tooth mako
Isurus
Isurus is a genus of mackerel sharks in the family Lamnidae, commonly known as the mako sharks. There are two living species, the common shortfin mako shark and the rare longfin mako shark , and several extinct species known from fossils. They range in length from 9 to 15 feet, and have an...

", rather than to C. megalodon. One reason cited by paleontologist Dr. Chuck Ciampaglio is that the dental morphometrics
Morphometrics
Morphometrics refers to the quantitative analysis of form, a concept that encompasses size and shape. Morphometric analyses are commonly performed on organisms, and are useful in analyzing their fossil record, the impact of mutations on shape, developmental changes in form, covariances between...

 (variations and changes in the physical form of objects) of I. hastalis and C. carcharias are remarkably similar. Another reason cited is that C. megalodon teeth have much finer serrations than in C. carcharias teeth. Further evidence linking the great white shark more closely to ancient mako sharks, rather than to C. megalodon, has been provided in 2009 — The fossilized remains of an ancient form of the great white shark were excavated from southwestern Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

 in 1988, which are about 4 million years old. These fossilized remains demonstrate a likely shared ancestor of modern mako and great white sharks.

Existing controversy and considerations

Paleontologist Dr. Chuck Ciampaglio from Wright State University
Wright State University
Wright State University is a comprehensive public university with strong doctoral, research, and undergraduate programs, rated among the 260 Best National Universities listed in the annual "America's Best Colleges" rankings by U.S. News and World Report. Wright State is located in Fairborn, Ohio,...

 asserts that similarities between the teeth of C. megalodon and the great white shark are superficial and there are noticeable morphometric
Morphometrics
Morphometrics refers to the quantitative analysis of form, a concept that encompasses size and shape. Morphometric analyses are commonly performed on organisms, and are useful in analyzing their fossil record, the impact of mutations on shape, developmental changes in form, covariances between...

 differences between them, and that these findings are sufficient to warrant a separate genus for C. megalodon. However, some proponents of the Carcharodon genus for C. megalodon (i.e. M. D. Gottfried, and R. E. Fordyce) have provided more arguments for a close relationship between the extinct megatooth sharks and the great white shark. With respect to the recent controversy regarding fossil lamnid shark relationships, the overall morphology – particularly the internal calcification patterns – of the great white shark vertebral centra have been compared to well-preserved fossil centra from the megatooth sharks, including C. megalodon and C. angustidens. The morphological similarity apparent from these comparisons supports a close relationship of the giant fossil megatooth species to living white sharks.

With respect to the origins of the great white shark, Gottfried and Fordyce have pointed out that some great white shark fossils are about 16 million years old and predate the transitional Pliocene fossils. In addition, the Oligocene records of C. megalodon, contradict the suggestion that Carcharocles chubutensis is the immediate ancestor of C. megalodon. These records also indicate that C. megalodon actually co-existed with Carcharocles angustidens. Hence, proponents for the Carcharodon genus for C. megalodon argue that extinct megatoothed sharks should be placed within the genus Carcharodon.

Some paleontologists argue that the genus Otodus should be used for sharks within the Carcharocles lineage and the genus Carcharocles should be discarded.

At present, several proponents of the Carcharocles genus for C. megalodon (i.e. Catalina Pimiento, Dana J. Ehret, Bruce J. MacFadden, and Gordon Hubbell) accept that both species belong to the order Lamniformes, and in the absence of living members of the family Otodontidae, great white shark is the most ecologically analogous species to C. megalodon.

In fiction

Ever since the remains of C. megalodon were discovered, it has been an object of fascination. It has been portrayed in several works of fiction
Fiction
Fiction is the form of any narrative or informative work that deals, in part or in whole, with information or events that are not factual, but rather, imaginary—that is, invented by the author. Although fiction describes a major branch of literary work, it may also refer to theatrical,...

, including films and novels, and continues to hold its place among the most popular subjects for fiction involving sea monster
Sea monster
Sea monsters are sea-dwelling mythical or legendary creatures, often believed to be of immense size.Marine monsters can take many forms, including sea dragons, sea serpents, or multi-armed beasts. They can be slimy or scaly and are often pictured threatening ships or spouting jets of water...

s. Many of these works of fiction posit that at least a relict
Relict
A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....

 population of C. megalodon survived extinction and lurk in the vast depths of the ocean, and that individuals may manage to surface from the vast depths, either by human intervention or by natural means. Jim Shepard's story "Tedford and the Megalodon" is a good example of this. Such beliefs are usually inspired by the discovery of a C. megalodon tooth by members of the HMS Challenger
HMS Challenger (1858)
HMS Challenger was a steam-assisted Royal Navy Pearl-class corvette launched on 13 February 1858 at the Woolwich Dockyard. She was the flagship of the Australia Station between 1866 and 1870....

 in 1872, which some believed to be only 10,000 years old. However, this tooth has been re-examined, and findings indicate that it is untestable for age.

Some works of fiction (such as Shark Attack 3: Megalodon and Steve Alten
Steve Alten
Steven Robert "Steve" Alten is an American science fiction author. He is best known for his Meg series, a set of novels around the fictitious survival of the megalodon, a giant prehistoric shark...

's Meg
Meg: A Novel of Deep Terror
Meg: A Novel of Deep Terror is a science fiction novel by Steve Alten, and was first published in July 1997. The novel, along with its sequels, follows the under water adventures of a U.S Navy deep sea diver, Jonas Taylor.-Plot summary:...

series) incorrectly depict C. megalodon as being a species over 70 million years old, and to have been alive during the time of dinosaurs. The writers of the movie Shark Attack 3: Megalodon depicted this assumption by including an altered copy of a book by the shark researcher, Richard Ellis
Richard Ellis (biologist)
Richard Ellis is an American marine biologist, author, and illustrator. He is a research associate in the American Museum of Natural History's division of paleontology, special adviser to the American Cetacean Society, and a member of the Explorers Club. He was U.S...

, called "Great White Shark". The copy shown in the film had several pages that do not exist in the real book. The author of the real book sued the film's distributor Lions Gate Entertainment
Lions Gate Entertainment
Lions Gate Entertainment Corporation is a North American entertainment company. The company was formed in Vancouver, British Columbia in 1997, and is headquartered in Santa Monica, California...

, asking for a halt to the film's distribution along with $150,000 in damages. Steve Alten's Meg: A Novel of Deep Terror
Meg: A Novel of Deep Terror
Meg: A Novel of Deep Terror is a science fiction novel by Steve Alten, and was first published in July 1997. The novel, along with its sequels, follows the under water adventures of a U.S Navy deep sea diver, Jonas Taylor.-Plot summary:...

is probably best known for portraying this inaccuracy with its prologue and cover artworks depicting C. megalodon killing a tyrannosaur in the sea.

Mega Shark Versus Giant Octopus
Mega Shark Versus Giant Octopus
Mega Shark Versus Giant Octopus is a monster/disaster film by The Asylum, released on May 19, 2009, in the United States and on August 7, 2009, in the United Kingdom. It was directed by Ace Hannah and stars singer Debbie Gibson and actor Lorenzo Lamas...

(2009) and its sequel Mega Shark Versus Crocosaurus (2010) are parodies
Parody
A parody , in current usage, is an imitative work created to mock, comment on, or trivialise an original work, its subject, author, style, or some other target, by means of humorous, satiric or ironic imitation...

 of disaster film
Disaster film
A disaster film is a film genre that has an impending or ongoing disaster as its subject...

s with a giant shark similar to a megalodon in the title role.

See also

  • List of prehistoric cartilaginous fish
  • Prehistoric fish
    Prehistoric fish
    Prehistoric fish refers to early fish that are known only from fossil records. They are the earliest known vertebrates, and include the first and extinct fish that lived through the Cambrian to the Tertiary. The study of prehistoric fish is called paleoichthyology...

  • Largest prehistoric organisms
    Largest prehistoric organisms
    The largest prehistoric organisms include both vertebrate and invertebrate species. Many are described below, along with their typical range of size...


External links


Paleontological videos

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Adobe Flash Player
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