Bruner, John Clay. 1997. El Tiburn Megadiente Carcharodon megalodon De
dientes duros y enormes. Mundo Marino Revista Internacional de Vida Marina.
Septiembre - Octubre 1997(5):6-11.
John Clay Bruner, Dept. of Biological Sciences and Laboratory for Vertebrate Paleontology,
University of Alberta, Edmonton, Alberta, T6G 2E9 CANADA
It is a warm sunny day off the coast of what will become North
Carolina in another 15 million years. A mother right whale, Mesoteras, has
just calved and nudges her young to the surface to draw in its first
breath of air. Suddenly a large dorsal and caudal fin of a Carcharodon
megalodon breaks the surface of the water and the young calf disappears
within seconds in a swirl of red water. Swallowed whole by a 17 meter
giant "Megatooth" shark, the Mesoteras calf dies in a scene reminiscent
today of adult Great White Sharks feeding on seals off California and
The Age of the giant "Megatooth" shark
Carcharodon megalodon (Agassiz, 1843), the giant "Megatooth" shark,
ruled all the warmwater seas during the Neogene Period (Miocene [5-24 mya]
and Pliocene [1.67-5 mya]). At the beginning of its reign, C. megalodon
was unaware of the evolution of the first hominoids on land (Proconsul),
but would have witnessed the first monsoons and upwellings in the Arabian
Sea which connected the Mediterranean Sea with the Indian Ocean.
Vertebrae and Teeth and estimating size of "Megatooth"
Today, the only remains of the largest meat-eating fish to ever
live, are a few vertebrae and teeth. The teeth of the giant "Megatooth"
shark are prized by amateur fossil collectors and are known from Europe,
Africa, Australia, India, Japan, North and South America. John Maisey,
curator of vertebrate paleontology at the American Museum
of Natural History (AMNH), wrote in his 1996 book Discovering Fossil
Fishes, (p. 91) "Many other sharks, including some from the Devonian,
replaced and discarded their teeth with greater abandon. Shark tooth
production must rank as one of the most efficient organic methods of
removing phosphate from the biological environment and burying it in
sediment. There probably is more phosphate in a single 15-centimeter
Miocene fossil white shark tooth than was used during the whole life of a
meter-long Devonian shark. Fossil teeth provide dramatic testimony of
increasing phosphate consumption during the evolution of sharks." In 1982,
Maisey was hired by the Smithsonian Institution to reconstruct a more
accurate representation of the "Megatooth". Previous reconstructions had
been made of "Megatooth's" jaws but now Maisey was aided by Pete
Harmatuk's (an amateur fossil collector) find of a partial set of C.
megalodon teeth from a North Carolina phosphate quarry. Prior to this,
only individual vertebrae similar to the modern ones seen in Fig. 1 and
separate teeth (see Figs. 2-4) were known to science. The closest living
analogue, and closest living relative to the giant "Megatooth" shark is the
Great White Shark Carcharodon carcharias (Linnaeus, 1758). The Great White
Shark has been used as a model to reconstruct the giant "Megatooth". Maisey
used the partial set of "Megatooth" teeth to make a more accurate
comparison with jaws of the living Great White Shark. In 1985, the new
reconstruction went on public display. Unhappily for science fiction
writers, the "new" "Megatooth" jaws were two-thirds the size of the jaws
reconstructed by Bashford Dean before WWI at New York's AMNH. In Dean's
day, scientists still believed that the living Great White Shark reached
up to 35 to 40 feet in length. So it was not unbelievable to estimate
"Megatooth" reaching 100 to 120 feet in length when it had teeth three
times the size of a Great White Shark.
Fig. 1. Two recent shark vertebrae.
Centrum on left has been cut in half. Red arrows are the
openings for the dorsal arch base (dab) and the blue
arrows are the openings for the ventral arch base (vab).|
E. Casier (1960) questioned the monophyly of Carcharodon and split
it into three genera, using the generic name Carcharocles for "Megatooth".
Henri Cappetta (1987) followed Casier and wrote, Carcharocles is thought
to be derived from Otodus serratus, an early Eocene species, that already
shows the beginning of the serration of the cutting edges. Carcharocles
during its evolution gradually lost its lateral denticles. Gery Case
supports the use of Carcharocles. Case et al. wrote (1996, p. 107) "The
first occurrence of Carcharocles sokolowi appears in the Eocene and it was
the earliest representative of the Great White Shark. The fossil teeth of
the Great White Shark have had several names over the past 150 years,
starting with the name Carcharodon. The name Carcharodon is now relegated
to the modern White Shark. After Carcharodon these fossil teeth were
called Procarcharodon by Casier. The name Carcharocles takes precedence
over the name Procarcharodon by 37 years."
The following authors support the Carcharodon camp: Applegate and
Espinosa-Arrubarrena (1996), Gottfried, Compagno, and Bowman (1996),
Hubbell (1996), and Purdy (1996). Figure 2 is an abbreviated version of
what Applegate and Espinosa-Arrubarrena (1996) envison is the evolution of
"Megatooth". The Late Cretaceous shark Cretolamna appendiculata, through
maybe five or six intermediate species, eventually gave rise to the Early
Miocene Carcharodon subauriculatus, that may have given rise to
"Megatooth". And, there is even disagreement how many species are present
in the genus Carcharodon. Applegate and Espinosa-Arrubarrena (1996), list
nine described and undescribed species, while Purdy (1996) lists eleven.
What did "Megatooth" eat?
Although the Great White does not feed exclusively on seals it has
been shown they are an important prey item. When the population of seals
increases, so does the numbers of Great Whites (Purdy, 1996). Although it
first appeared in the Eocene, it was during the Miocene the mammalian
order Cetacea (whales) reached its highest diversity and abundance. Almost
every known family of toothed and baleen whale are known from the end of
the Miocene. Large whale vertebrae and flipper bones have been found with
large bite marks made by serrated teeth that match the teeth of C.
megalodon (Purdy, 1996). Also, identified high-use areas by marine
vertebrates during the Miocene and Pliocene often have associated fossils
of C. megalodon and whales (Purdy, 1996). From such evidence,
paleontologists have surmised a predator-prey relationship of C. megalodon
on large whales.
Death of the "Megatooth"?
By the end of its reign, C. megalodon would have witnessed the
Mediterranean becoming a tributary of the Atlantic, the closing of the
isthmus of Panama, a new genus of hominids on the African savannah called
Homo, the onset of Arctic glaciation and the returning of the Earth to a
predominantly glacial mode. The decrease in the oceans temperature during
the mid-Pliocene may have spelled the doom of C. megalodon. Casey and
Pratts (1985) report that juvenile Great White Sharks have a lower
tolerance to cooler waters and an intolerance to higher temperatures that
may limit them to nursery areas in the North Atlantic. Fossils of C.
megalodon are found only in regions that were predominantly warmwater
environments. Perhaps the reduction in ocean temperatures in the
mid-Pliocene, reduced the number of possible nursery sites on the
continental shelf for C. megalodon. Another possibility is that their
prey, the great whales, escaped to colder waters where "Megatooths" could
not follow. Recent discoveries of fossil baleen whales from the Late
Pliocene in Antarctica, demonstrate that great whales began living in
these areas at that time.
Reports of giant Great White Sharks up to 10 m long (Long, 1995,
p. 80) in recent times and perhaps the influence of Hollywood (Jaws III)
have led some scientists to suggest that "Megatooth" still lives in the
oceans somewhere. Gilbert Whitley, the late curator of
fishes of the Australian Museum, Sydney, Australia, wrote (1940, p. 125), "Large
teeth belonging to species of White Pointer have been dredged at great
depths in the oceans and indicate that enormous sharks are either still
living or only became extinct fairly recently. A man could stand upright
with ease in the jaws of such a monster which has been calculated to have
measured 80 feet in length." However, no well documented "Megatooth" fossils
have been found younger than 3 mya, but remember paleontologists once
believed that all coelacanths went extinct at the end of the Cretaceous,
65 mya, and it is still alive today!
Applegate, Shelton P., and Espinosa-Arrubarrena, Luis. 1996. Chapter 4.
The Fossil History of Carcharodon and its possible ancestor, Cretolamna: A
study in tooth identification. pp. 19-36. IN: Klimley, A. Peter, and
Ainley, David G. (editors). Great White Sharks the Biology of Carcharodon
carcharias. Academic Press. San Diego, California. 517 pp.
Cappetta, Henri. 1987. Chondrichthyes II. Mesozoic and Cenozoic
Elasmobranchii. Handbook of Paleoichthyology. Schultze, H.-P. (ed.)
Gustav Fischer Verlag, Stuutgart, Germany. Vol. 3B:1-193.
Case, G. R., Udovichenko, N. I., Nessov, L. A., Averianov, A. O. and
Borodin, P. D. 1996. A Middle Eocene selachian fauna from the White
Mountain formation of the Kizylkum Desert, Uzbekistan, C.I.S.
Palaeontographica Abt. A 242: 99-126.
Casey, J. G., and Pratt, H. L., Jr. 1985. Distribution of the white
shark, Carcharodon carcharias, in the Western North Atlantic. South.
Calif. Acad. Sci., Mem. 9:2-14.
Casier, E. 1960. Note sur la collection des Poissons Paleocènes et
Éocènes de l'Enclave de Cabinda (Congo). Annales du Musée Royal
du Congo Belge A (3). Vol. 1(2):1-47.
Gottfried, Michael D., Compagno, Leonard J. V., and Bowman, S. Curtis.
1996. Chapter 7. Size and skeletal anatomy of the Giant Megatooth shark
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G. (editors). Great White Sharks the Biology of Carcharodon carcharias.
Academic Press. San Diego, California. 517 pp.
Hubbell, Gordon. 1996. Chapter 3. Using tooth structure to determine
the evolutionary history of the White Shark. pp. 9-18. IN: Klimley, A.
Peter, and Ainley, David G. (editors). Great White Sharks The Biology of
Carcharodon carcharias. Academic Press. Sand Diego, California. 517 pp.
Long, John A. 1995. The Rise of Fishes. The John Hopkins University
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Maisey, John G. 1996. Discovering Fossil Fishes. Henry Holt and Compnay.
New York, New York. 223 pp.] This citation was removed by the editor
Purdy, Robert W. 1996. Chapter 8. Paleoecology of Fossil White Sharks.
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White Sharks the Biology of Carcharodon carcharias. Academic Press. San
Diego, California. 517 pp.
Uyeno, T., Sakamoto, O., and Sekine, H. 1989. The description of an almost
compete tooth set of Carcharodon megalodon from a Middle Miocene bed in
Saitama Prefecture, Japan. Saitama Mus. nat. Hist., Bull. Vol. 7:73-85.
Welton, Bruce J., and Farish, Roger F. 1993. The Collectors guide to
Fossil Sharks and Rays from the Cretaceous of Texas. Horton Printing Co.
Dallas, Texas. 204 pp.
Whitley, Gilbert Percy. 1940. The Fishes of Australia Part 1 The sharks,
Rays, Devil-Fish, and other primitive fishes of Australia and New Zealand.
Royal Zoological Society of New South Wales. Australian Zoological
Handbook. Sydney, Australia. 280 pp.
ERRATA (noted in original publication)
p. 6 Figure caption of life size tooth should be. C. megalodon
p. 7 Figure caption of reconstructed jaw should be. C. megalodon
p. 9 Fig. 1. Abbreviations for dorsal arch base (dab) and ventral arch
base (vab) were changed by artist to dad & vad, respectively.
Fig. 2. Color of arrows pointing to lateral denticles are BLUE
not RED and Carcharodon subauriculates is spelled wrong
p. 11 Maisey, John G. 1996 was dropped from literature cited.
Uyeno et al. change to 1989 from (1989.
Whitley, 1940 capitalize Australia both times