Sharks belong to the superorder Selachimorpha, and have a fossil record that goes back to the Carboniferous Period. It is often said that they have gone unchanged in form for over 350 million years, but this statement couldn't be any further from the truth.
The fact is that sharks have evolved over time. One only needs to look at some of the early sharks represented in the Safari Ltd. Prehistoric Sharks Toob to see how different they are compared to modern sharks.
Of the 10 sharks in the set, four can be considered to be approximately 1/72 scale.
Cretoxyrhina, Edestus, and Sarcoprion are all thought to have been around 6.1m in length, while Helicoprion could be as long as 7.5m (although the typical specimen may have only been 3-4m long).
For Sarcoprion and Helicoprion (which I believe have been reclassified as Chimaeriformes), I used a knife to cut notches in the spiral tooth whorl of their lower jaws to make the individual teeth more pronounced.
The most famous of prehistoric sharks is Carcharocles megalodon [or Carcharodon megalodon]. Due to its presumed physical resemblance to the Great White Shark, any >8" Great White could probably be used to represent the Megalodon. Purists however may prefer the Safari Ltd. Megalodon (Wild Safari 303329).
Size estimates for this shark range from 15-30m, but I prefer the more conservative size estimate. While I would certainly be impressed by a 30m shark, I have doubts that every specimen of Megalodon was really that big. That being said, I'd say the model scales out very closely to 1/72 scale if we're talking about a 15m shark.
Luckily for us, Megalodon is now extinct... or is it?