By: Harley Lewis

Main question?What happened to megasharks like

Carcharodon megalodon?

Difficulties of studyCartilage skeleton

No more around

Just teeth to go by

Multiple theoriesTheory #1

Temperature based growth

Theory #2Diet reduction/

outcompeted

Theory #3Evolved into Great

White

Theory #1: Temperature based growth

Sharks are Ectothermic

Lower temperatures = slow growth, greater size

Miocene plagued by ice ages

Correlation of growth rate and temperature

Angilletta M J et al. Integr. Comp. Biol. 2004;44:498-509

The Society for Integrative and Comparative Biology

Theory #2: Diet reduction / outcompetedCetaceans were main foodsource of MegalodonWhales hit diversity peak during the MioceneDiversity began to decrease to smaller species

Theory #3: Evolved to Great WhitesTeeth and jaws look similar

Not true!

Shape and Roots are more like extinct makos than Megalodon

Low, flat root tubeGreat White serration

most likely came later

Conclusions

Miocene ice ages contributed to great size

Cetacean diversity plummeted

Megalodon did not evolve into Great Whites

References Bright, M. (n.d.). Jaws: the natual history of sharks. Retrieved from

http://www.fathom.com/course/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; 11A:22p, 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/info%3Adoi%2F10.1371%2Fjournal.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.