The maximum length this shark reached has been a hotbed of debate ever since paleontologists learned that they could get more accomplished by disagreeing with one another. The truth of the matter is that we will probably never know for sure exactly how long the megalodon actually extended. The most widely accepted maximum size for the megalodon is a length of approximately 55-65 feet. The reason there is no way to accurately measure the size of the megalodon is that often the only fossil evidence left behind is the teeth. Occasionally fossilized megalodon vertebrae are found, although this is extremely rare because shark vertebrae are made out of cartilage instead of bone.
Cartilage is much more easily decomposed and is therefore less likely to fossilize.
Megalodon teeth, however, can provide an excellent clue as to the massive size of the shark. Fossilized megalodon teeth are models of efficiency. These huge teeth are lined with hundreds of tiny razor-sharp serrations which served to rip hapless victims to shreds. The first shark to evolve from the Mackerel shark family was Carcharocles auriculatus. This was the first precursor to the megalodon.