Prehistoric Sharks

Falcatus lived in the Carboniferous period, around 325 Million Years Ago ("MYA"). It was probably piscivorous (meaning it ate fish), and lived in deeper waters, which is why it has such large eyes. The most obvious feature of this shark was its long, forward pointed spine. However, specimens of Falcatus can be found without this spine, and it does not appear to have any specific purpose.

So what could it be? Well, since it is found on only some specimens, scientists have concluded that the spine was for mating purposes, most likely as a display. This is a great example of sexual dimorphism, common among many animals today.

Edestus lived in the late Carboniferous. It was related to Helicoprion, and had strange, outward curving tooth whorls that looked like a giant pair of scissors. It probably ate soft bodied animals, and attacked using a vertical thrashing strike.

Hybodus lived throughout the mesozoic era, approximately 260 to 66 MYA. Unlike some of the previous animals, these were generalists. They had two different types of teeth: sharp teeth for grasping prey, and rounded teeth, which could crush hard shells. They most likely ate whatever they could find, and that is probably why they lived for so long. Another adaptation that helped them to survive was long spines on their dorsal fins. These were probably used for defense.

Squalicorax lived during the late Cretaceous period (approximately 105 to 65 MYA). This shark looks a lot likee a modern shark. Its teeth were definately those of a predator, and we also find its teeth in fossils of other animals, includinng turtles, Mosasaurs, and even Hadrosaurs (duck billed dinosaurs)!

And now we get to Megalodon. Megalodon lived from the early Miocene to the late Pliocene (approximately 23 to 2.6 MYA), making it the most recent of these sharks to swim the seas. it was a massive predator, reaching about sixty feet in length. It would have eaten mainly small whales, which were common in the southern oceans at the time. Scientists believe that the whales began to adapt to northern climates and migrated, but megalodon could not adapt to follow their major food source, which likely explains its extinction.

Here is my attempt to estimate Megalodon's size:

And here is my measurement, which shows I was a bit off in my estimate:

I used a 120 inch, or ten foot, tape measure, and marked off each 10 foot distance with chalk.

This is a lifesize 3D model of a megalodon tooth. I created it with Tinkercad software.

It is 18 cm long (approximately 7 inches), which is about as big as they come.

And this is a fossil megalodon tooth that my mom gave me: