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Ovleg [2016-07-05 20:55:21 +0000 UTC]

This body plan has been debunked by Bretton Kent (University of Maryland) : 

Bretton W. Kent, author of "Fossil Sharks of the Chesapeake Bay Region" believes that if Meg is more closely related to sand tiger sharks, the relationship is largely irrelevant for determining body shape. 

"I'm a functional morphologist by training and argue that the constraints on shape are so severe for an axial swimmer (i.e., that flexes the body to provide propulsion) of this size that a sand tiger style of body is physically impossible," says Kent. "Sand tigers have an acceleration body form and use drag to displace water when swimming. Displacement swimmers need to move a water mass equivalent to 3-4 times their body mass with each stroke of the tail to swim by this mechanism." 

Kent says that the problem arises at really big sizes like that of Meg. 

"This problem is based on classic biological scaling," he says. For objects of similar shape, doubling the length causes surface area (e.g., fins) to increase four times and volume (i.e., mass) to increase eight times. Consequently, a really large sand tiger would need enormous fins to offset the tremendous increase in mass. Unfortunately, these fins would also generate an enormous amount of nonproductive drag that would impede swimming. 

"The only way large axial swimmers have evolved is to switch over to a cruising body form that generates propulsion by lift rather than drag," says Kent. "Cruising fish need only displace a fraction of their body weight when swimming, relying instead on increasing the speed, rather than the mass, of the water over the tail. All of the large marine, axial swimmers (tunas, porpoises, whales, great white, mako, basking and whale sharks) use a cruising body form. As far as we know, no really large marine animal with an acceleration body shape has ever evolved. They all appear to be cruisers." 

Kent suggests that a more reasonable shape would be that of a basking or whale shark. 

"The front ends of these sharks are rather different, but the back ends (where drag is a real problem) are remarkably similar," he says. "The caudal fin is nearly lunate, the second dorsal and anal fins are tiny, and there is a caudal keel on each side of the caudal peduncle. The same pattern occurs in other large axial swimmers (e.g., bluefin tuna, billfish, whales, great whites & makos), not because they are related to each other, but because they're simply big. Again the front ends may be different, but the back ends have the same low drag shape. 

"I personally use basking sharks as the basis for my reconstruction of the Meg body shape," adds Kent. "Robustness of the body would be due to the interaction between limits on muscle-based underwater swimming speeds and the proportion of white muscle for burst swimming in the body."

In short, meg with such a body shape couldn't be functional at the size it reached.

Furthermore, the vertebra and configuration of the teeth are reminescent of lamnids so...

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ZoPteryx [2014-09-28 01:07:37 +0000 UTC]

Like you said, it's nice to see a Megalodon that doesn't just look like an overgrown Great White.  Great work!  

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