Extinction of megasharks

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Extinction of megasharks

• By Harley Lewis

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Main question?

• What happened to megasharks like Carcharodon
  megalodon?

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Difficulties of study

• Cartilage skeleton
• No more around
• Just teeth to go by

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Multiple theories

• Theory 1
• Temperature based growth
• Theory 2
• Diet reduction/ outcompeted
• Theory 3
• Evolved into Great White

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Theory 1 Temperature based growth

• Sharks are Ectothermic
• Lower temperatures slow growth, greater size
• Miocene plagued by ice ages

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Correlation of growth rate and temperature
Angilletta M J et al. Integr. Comp. Biol.
200444498-509
The Society for Integrative and Comparative
Biology
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Theory 2 Diet reduction / outcompeted

• Cetaceans were main foodsource of Megalodon
• Whales hit diversity peak during the Miocene
• Diversity began to decrease to smaller species

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Theory 3 Evolved to Great Whites

• Teeth and jaws look similar
• Not true!

• Shape and Roots are more like extinct makos than
  Megalodon
• Low, flat root tube
• Great White serration most likely came later

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Conclusions

• Miocene ice ages contributed to great size
• Cetacean diversity plummeted
• Megalodon did not evolve into Great Whites

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References

• Bright, M. (n.d.). Jaws the natual history of
  sharks. Retrieved from http//www.fathom.com/cours
  e/21701777/session3.html
• Bruner, John Clay. 1997. The "Megatooth" shark,
  Carcharodon megalodon "Rough toothed, huge
  toothed". Mundo Marino Revista Internacional de
  Vida Marina. September - October 1997(5)6-11.
• Uhen, Mark D., and Pyenson, Nicholas D., 2007.
  Diversity estimates, biases, and historiographic
  effects resolving cetacean diversity in the
  Tertiary. Palaeontologia Electronica Vol. 10,
  Issue 2 11A22p, 754KB http//palaeo-electronica
  .org/paleo/2007_2/00123/index.html
• Pimiento C, Ehret DJ, MacFadden BJ, Hubbell G,
  2010 Ancient Nursery Area for the Extinct Giant
  Shark Megalodon from the Miocene of Panama. PLoS
  ONE 5(5) http//www.plosone.org/article/info3Ado
  i2F10.13712Fjournal.pone.0010552
• Angilletta, M, Steury, T, Sears, M. (2010).
  Temperature, growth rate, and body size in
  ectotherms fitting pieces of a life-history
  puzzle. Integrative and Comparative Biology,
  44(6), 498-509.