Megalodon Shark (Carcharocles megalodon)
after Gibbs (1848)
In 1806, William Reid of Charleston, South Carolina, sent two fossil shark teeth to Thomas Jefferson. In the accompanying letter he wrote. "Observing you attentive to Natural Philosophy as well as to other branches of science, I take occasion to present you with a fossil, which you may consider a curiosity, and not unworthy of your contemplation." Reid has collected the fossils from marine sediments near the Cooper River. As he put it, "The curious have concluded these fossils to be the teeth of some monster unknown at this day." In his reply, Jefferson thanked Reid and informed him that the teeth were forwarded to the American Philosophical Society.
The teeth Reid sent to Jefferson came from the giant shark Carcharocles megalodon (or Carcharodon megalodon, see below). The impressive triangular teeth from "Megalodon," which measure up to 6 inches (15 cm) in length, have generated intense interest among fossil collectors for two centuries. Specimens have been recovered from Miocene and Pliocene deposits worldwide, with a significant number coming from South Carolina.
after Gibbs (1848)
First described by Louis Agassiz (1), the affinity of this giant is still a matter of debate. Some authorities consider Megalodon to be a close relative —if not direct ancestor— of the great white shark (Carcharodon carcharias). They identify the shark as Carcharodon megalodon . Others consider Megalodon to be a member of a more distantly related lineage, which includes sharks belonging to the genera Otodus and Cretolamna, and identify it as Carcharocles megalodon.
As with most fossil sharks, the most frequent and informative specimens of Megalodon are its teeth (2). An early attempt at estimating Megalodon's size by extrapolating from its teeth yielded an incredible length of 80 feet (25 m). More recent estimates using considerable more refined techniques resulted in lengths ranging from 40 to 50 feet (12-15 m).
The appearance in the fossil record of this giant coincides with the appearance of large baleen whales during the Miocene and Pliocene epochs. Its disappearance is associated with the global cooling that occurred during the late Pliocene (2.6 million years ago). The great whales, Megalodon's presumed prey, are known to have inhabited polar waters at this time and some paleontologists have speculated that Megalodon was unable to follow them into the colder waters.
Web Pages:
- American Museum of Natural History's web page on Louis Agassiz:
research.amnh.org/ichthyology/neoich/collectors/agassiz.html - Fossilguy.com's web page on Megalodon:
www.fossilguy.com/topics/megshark/megshark.htm - ReefQuest's web pages on Megalodon:
www.elasmo-research.org/education/evolution/
carcharodon_vs_carcharocles.htm - SharkAttacks.com's web page on Megalodon:
www.sharkattacks.com/prehistoric.htm - U.C. Museum of Paleontology's web page on Louis Agassiz
www.ucmp.berkeley.edu/history/agassiz.html
Print Resources:
- Robert W. Gibbes. 1848. "Monograph of the fossil Squalidae of the United States". Journal of the Academy of Natural Sciences of Philadelphia. 2nd series, 1: 139-147.
- Long, J.A. 1995. The Rise of Fishes: 500 Million Years of Evolution.
Baltimore and London: John Hopkins Univ. Press.
Notes:
- Jean Louis Rodolphe Agassiz (1807-1873) was a Swiss anatomist, zoologist and geologist who published extensively on the classification of fish and invertebrates. But he is most famous for his early and energetic advocacy of massive Pleistocene (Ice Age) glaciations. In 1837 he proposed the startling idea that much of Europe was once covered by a thick sheet of ice. He found evidence for a similarly massive continental glaciation in North America after he immigrated to the United States. [go back]
- The vast majority of fossil shark species are known only from their teeth. Sharks belong to the Chondrichthys, a class of vertebrates that are characterized by a cartilaginous skeleton that almost never fossilizes. Sharks teeth, on the other hand, are extensively mineralized and readily fossilize. In fact, they're commonly the most frequent vertebrate fossils collected in marine deposits, especially those dating from and after the Cretaceous. [go back]