Extinction of megasharks By Harley Lewis Main question

Extinction of megasharks By: Harley Lewis

Main question? �What happened to megasharks like Carcharodon megalodon?

Difficulties of study �Cartilage skeleton �No more around �Just teeth to go by

Multiple theories �Theory #1 �Temperature based growth �Theory #2 �Diet reduction/ outcompeted �Theory #3 �Evolved 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 / outcompeted �Cetaceans were main foodsource of Megalodon �Whales hit diversity peak during the Miocene �Diversity began to decrease to smaller species

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

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/session 3. 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; 11 A: 22 p, 754 KB; http: //palaeoelectronica. org/paleo/2007_2/00123/index. html � Pimiento C, Ehret DJ, Mac. Fadden BJ, Hubbell G, 2010 Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama. PLo. S ONE 5(5): http: //www. plosone. org/article/info%3 Adoi%2 F 10. 1371%2 Fjournal. 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.