The sea monster terrorized the oceans from about 16 million to 2 million years ago, but it may be too big for its own good.
LOS ANGELES - Megalodon, the largest shark ever to roam the ocean, may be so large that it is vulnerable to extinction.
For some mysterious reasons, although most of the species are of the same length, many giant sea monsters last longer over a period of 14 million years, and then, they are all extinct, new research shows ..
While it is unclear why the giants are getting larger during evolutionary times, their large size may make them more vulnerable to extinction, says study co-author Catalina Pimiento, biology doctoral candidate at the University of Florida and the Smithsonian Tropical Research Institute in Panama. He presented his findings at the 73rd Annual Vertebrate Paleontology meeting. [Picture Gallery: Ancient Marine Monster]
Bigger is better?
Megalodon can grow up to 60 feet (18 meters) long and have stronger bites than Tyrannosaurus rex. Sea monsters terrorize the oceans from about 16 million to 2 million years ago. Although it may seem like a long reign, other shark species survive for 50 million years or more without significant changes in body plans, Pimiento said.
"This species is not as successful as we thought," Pimiento said. "Many sharks that lived during the Megalodon era still exist today."
A brief history of Megalodon makes Pimiento ask whether the shark's body size affects its evolutionary success.
"Body size affects almost all aspects of the biology and ecology of organisms," Pimiento told LiveScience. "If you have a very large organism like Megalodon, it can be very good or very bad."
Larger animals can eat more food and become more violent predators than their friends who whine on their cheeks. But since they eat more types of animals, they also have more competition for the animals, and their ecosystems can support lower population density as they need more resources - including space - to survive. As food supplies shrink, these giant creatures can have difficulty finding enough food, says Pimiento.
Greater over time
Pimiento went to several museums around the world and measured the tooth size of about 400 Megalodon specimens. Based on these measurements, he estimates their final body size before extinction.
He concludes that while the largest and smallest animal sizes do not change over time, there are more larger animals during the next evolutionary period.
It remains unclear why the giant is getting bigger, but Pimiento plans to look at climate data and information about other species to tease it.
"There may be something going on with the productivity and the climate that produces that pattern, or with their prey and their competitors that make the species bigger," Pimiento said.
Either way, being so big may have made them more vulnerable to extinction. Despite the dead mega sharks, their close relative - the great white shark - still terrorize the oceans today.
"The possibility of increasing body size in the megalodon lineage during geological time needs to be further tested by examining megalodon collections worldwide, but the idea is important to understand the rise and extinction of the top predator pedigrees that must have significant impact to marine ecology," said Kenshu Shimada, a paleobiologist at DePaul University in Chicago, who was not involved in the study.