Fossil tooth of Carcharocles megalodon from the Atacama Desert, Chile (Miocene). Ruler is marked in centimeters.|
|Jaws of C. megalodon Reconstruction, American Museum of Natural History, New York|
The behemoth shark Carcharocles megalodon (pronounced "kar-KAR-ə-kleez MEG-ə-lə-don") is known from as early as the late Oligocene (about 28 mya), and it survived until at least as recently as 1.5 million years ago.
One of the largest predators of all time, it reached a maximum length of 20 meters, nearly 70 feet, larger even than a whale shark (Rhincodon typus) and had a nearly worldwide distribution. It's probably the biggest fish that ever lived.
At one time the gigantic, triangular teeth of this animal were thought to be the petrified tongues of dragons. One of the first scientists to recognize them as shark teeth was the Danish naturalist Nicolas Steno (Stenonis, N., 1667). In his book Recherches sur les poissons fossiles (1835-1843) Louis Agassiz gave gave this mega-fish its first scientific name, Carcharodon megalodon, which some scientists still say is the "correct" one, that is, it would belong to the same genus as the great white shark, Carcharodon carcharias. It was not until the twentieth century that megalodon was reassigned to Carcharocles, a change over which there is still disagreement.
Carcharocles megalodon had a cartilaginous skeleton and was therefore poorly preserved with exception of its teeth, but scientists generally believe that it looked a lot like a great white shark, only far larger. The largest specimens would have weighed around 100 tons. Tyrannosaurus rex, which weighed in at only about seven tons, would thus have been little more than a snack for Carcharocles megalodon.
Of course, T rex was a land animal and therefore an unlikely prey item for C. megalodon, which apparently fed on the largest types of sea animals, including the largest whales (Riordon 1999, Kallal et al. 2010). An example of direct fossil evidence of a C. megalodon attack on a whale is a fragment of whale rib recently discovered in a North Carolina strip mine, which dates to 3- to 4-million years ago during the Pliocene (Kallal et al. 2010).
Three tooth marks on the rib indicate the whale was bitten by a strong-jawed animal. The six centimeter spacing between tooth marks suggests the attacker was C. megalodon. The researchers know this particular whale survived, at least for a time, because most of the fossil fragment is covered with a type of bone known as woven bone, which forms rapidly in response to localized infection. The presence of the woven bone indicates the healing was incomplete and the whale died, the scientists estimate, between two and six weeks after the attack.
Based on the curvature of the shark's jaw, as indicated by the arc of the impressions of its teeth, the scientists believe the shark was between four and eight meters long (not big for Carcharocles).
"One certainly doesn't expect to find evidence of animal behavior preserved in the fossil record, but this fossil shows just that, a failed predation," says Stephen Godfrey, the coauthor on the Kallal paper who actually discovered the fossil. "The shark may have gone away with a mouthful, but it didn't kill the whale."
Kallal, R. J., Godfrey, S. J., Ortner, D. J. (2010-08-27). Bone Reactions on a Pliocene Cetacean Rib Indicate Short-Term Survival of Predation Event. International Journal of Osteoarchaeology, 22 (3): 253. doi:10.1002/oa.1199.
Nicolai Stenonis, Elementorum Myologiae Specimen, seu Musculi Descriptio Geometrica, cui accedunt canis carchariae dissectum caput et dissectus piscis ex canum genere... Florentiae : ex typ. sub signo Stellae, (1667) via Bibliothèque interuniversitaire de médecine (Paris).
Riordon, J. (June 1999). Hell's teeth. New Scientist, Magazine (2190): 32.
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