Carcharocles megalodon: A Study That Has Plenty of Bite
Carcharocles megalodon, also known simply as the Megalodon or “Meg,” is arguably the largest macro-predator the world has ever known. The species populated the Earth’s oceans for 18 million years from about 20 million to 2.5 million years ago.
Megalodon’s immediate ancestor, known as Carcharocles chubutensis, was another huge shark with equally impressive teeth.
And in a paper titled “The Transition Between Carcharocles Chubutensis and Carcharocles Megalodon (Otodontidae, Chrondrichthyes); Lateral Cusplet Loss Through Time,” which was recently published in the Journal of Vertebrate Paleontology, a team of paleontologists led by former Calvert Marine Museum Department of Paleontology intern Victor Perez described how the teeth of the ancestor of Megalodon (Carcharocles chubutensis) underwent its final transformation into the teeth of Carcharocles megalodon.
The very gradual transformation, which took roughly 12 million years, involved the loss of serrated lateral cusplets at the base of the cutting edge of the tooth. The results of the study are exciting because they show that some small evolutionary changes occur very gradually and may take many millions of years.
From the time of the extinction of dinosaurs 66 million years ago, the triangular teeth of the lineage of sharks that culminated in Megalodon changed in shape, evolved a serrated cutting edge, and increased significantly in size.
These massive sharks were well equipped to hunt, kill, and dismember large marine mammals such as whales and dolphins.
The loss of the serrated lateral cusplets (an ancestral feature) in these teeth is recorded in sediment preserved in the Calvert Cliffs on the western shore of the Chesapeake Bay. The sediments in and around Calvert Cliffs preserved the teeth of both species, and recorded the millions of years during which this final evolutionary transformation in the shape of the Megalodon tooth took place.
In the older sediments, most of the teeth bear lateral cusplets, but as one ascends through successively younger strata, the percentage of teeth without lateral cusplets increases until lateral cusplets all but disappear in the youngest beds.
For some reason which is not entirely resolved, in spite of its global dominance as a marine apex predator, Megalodon became extinct about three million years ago. And one or more of the following factors may have contributed to its demise: Eruption of a supernova, which cooled global temperatures; closure of the Isthmus of Panama; the extinction of groups of whales that Megalodon preyed upon, and/or competition with more modern predators like the great white shark (Carcharodon carcharias).
The research project was a collaboration between the Calvert Marine Museum, the University of Florida, the National Museum of Natural History in Washington and the University of Maryland, College Park.
To see the paper, go to http://bit.ly/JVPMegTeeth.