Now I might get some slack for saying this, maybe some paleo-nerd rage directed my way, but I don't think Megalodon is worthy of all the bad-azzery attributed to it. Why would I say this? Well first of all, the morphology and physique given to Megalodon is basically a scaled up great white, a conjecture we have no proof of save the similar tooth design. Instead of the homocercal tail that great whites utilize for rapid cruising and sustained acceleration augmented by endothermy, how do we not know that Megalodon had a heterocercal tail for slow cruising and ocassional short bursts of speed? What if Megalodon was not, like the great white, endothermic at all? * But I am going to venture that the greatest weakness of all for Megalodon is in fact the accolade most generously heaped upon it- it's size.
Now it does not really matter where you end up on the spectrum between the grey and red one, you still have a very large fish- probably among the largest fish that ever existed. But this brings up an interesting pattern, why do all the largest fish cluster around this 40-60 foot range? The largest predatory sharks, the largest filter feeding sharks, Leedsichthys and it's ilk of Mesozoic filter feeders- they all seem to cluster around this size but fish never truly reach blue whale size despite having a much longer tenure in the ocean to do so.
|Martill. 1986. Leedsichthys and Liopleurodon|
Megalodon succeeded because it lived at a time when their was just enough slow swimming marine mammals, abundant carcasses, and lack of competition from derived predatory pack hunting toothed whales to exist. It was limited to probably warm temperate seas and was basically good for one or two quick lunges at prey, but not extended chases like modern great whites engage in. When derived, social, and intelligent toothed whales came on the scene it was in trouble. Unable to out-swim or out-manoeuvre a couple of well placed strikes at the gills by these marine mammals and a tip into tonic immobility spelled doom for the last Megalodon just as it does today for many sharks at the hands (flippers) of killer whales. The feasts of liver ripped from Megalodon must have been a sight!!
|Killer Whale w/Mako Shark. Visser/Barcroft (c)|
I'm sure everyone remembers the hoopla surrounding that god-awful faux-documentary about a live Megalodon and all the blowback discovery channel got for it? You know when shark week, umm, jumped the shark (sorry)? Well at about the same time everyone was ranting and raving about that horrible show on Megalodon during shark week, for a critter I argue has been hyped up beyond recognition, real science about a real arch-predator of the ocean was being published that did not garner 1/100th the attention the Megalodon debacle did. And this was the revelation that a whole new species of killer whale, the type D genotype, is alive and well and swimming around the southern oceans as we speak. A whole new species of killer whale!!! No discovery channel special!! No nat-geo special!! No media hoopla!!! Hardly any fanfare to speak of for a whole new species of multi-tonne marine arch-predator!!
|Type D killer whale. Jean Pierre-Sylvestre. Nat Geo (c)|
Shame on us.
* Amendment 9/9/13. It has come to my attention that there is a paper Dermal scales of Carcharocles megalodon from the Miocene Mizunami Group, Central Japan! Author Hiroyuki Nishimoto et al 1992. Bulletin of the Mizunami Fossil Museum that purportedly shows evidence of placoid scales suggestive of high speed, fast growth and perhaps endothermy. I have not seen/or read the paper but it does exist. I don't claim to be a specialist in shark evolution, merely a fan. However I don't think this invalidates one of the premises of my article concerning gill surfaces area versus volume increase and the possible eco-physio-behavioral constraints imposed upon such large fish.