The Megalodon

 This week I just wanted to do a fun post before looking at some more important topics.

So today, we are looking at the megalodon. The largest shark that ever lived. Megalodon fossils date back to the Miocene Epoch (began 23.03 million years ago) to the end of the Pliocene Epoch (2.58 million years ago).

Shifting landscapes during this period meant the megalodon swam in oceans all over the world. Except Antarctica.  

What we know about its appearance is based on hundreds of teeth and some vertebrae. The tooth shape of the megalodon is similar to modern great white sharks - triangular, serrated, and symmetrical.

But they are not identical - megalodon's teeth were obviously larger and thicker, but the serrations on the teeth occur at regular intervals and they have a bourlette. A bourlette is a darker, chevron-shaped region near the root of the tooth. 

Image from Britannica. 

This led to the belief that these two sharks are likely related, therefore the megalodon likely looked like a much larger great white shark.

The megalodon's length was calculated using "the statistical relationship between the size of megalodon's fossil teeth and the teeth and body mass of modern white sharks and other relatives." In non-scientific terms, they looked at the teeth and used that to estimate the length of the megalodon using the proportions of the great white shark as a guide. 

So how large do scientists estimate the megalodon was? The average length is believed to be 10.2 metres/33.5 feet. The largest, based on the recovered fossils, was 17.9 metres/58.7 feet.
What about weight? This varies from 30 metric tons/66,000 pounds to 65 metric tons/143,000 pounds! The females would have been larger than the males as well.

Fun fact: the megalodon was actually smaller than blue whales.

Image from Britannica. 

Juvenile teeth suggest newly birthed megalodons would have been at least 2 metres/7.2 feet.

In addition to looking like big great white sharks, the megalodon is believed to have shared the adaptation of regional endothermy. This also meant it was not exclusively cold-blooded.

So what is regional endothermy - modern great white sharks are able to generate heat by contracting their swimming muscles. This will raise the temperature of the shark to be above the temperature of the water. This adaptation allows the great white shark to swim and hunt in colder waters.

If the megalodon also had this adaptation, it would have had exclusive access to prey in these colder waters. 

Megalodon Early Life

There is a known megalodon nursey along the Panamanian coast. Juvenile teeth from various stages have been found in this area. Scientist's believe the warm water nursey meant young megalodons had access to a variety and abundance of prey. As they got older, they likely starting making short trips into deeper waters. This nursey also enabled adult megalodons to intercept predators, like hammerhead sharks, quickly.

Extinction

The megalodon went extinct for numerous reasons, but the biggest reason is believe to be the shifting food chain. The megalodon's primary food, baleen whales, were declining. Then, smaller sharks and whales, including great white sharks and killer whales, increased. Meaning the megalodon's food supply was not as plentiful, and it needed a lot of food, and they all died off.

Rafferty, John P. "Megalodon." Britannica. https://www.britannica.com/animal/megalodon/Extinction