Sharks are known as the ocean’s fiercest predators, with rows of razor sharp teeth that can rip their prey to shreds in seconds. Everyone knows what a shark is, but something lesser known about these oceanic critters is that they appear in our fossil records before trees. Sharks are a type of elasmobranch fish which are characterized by their cartilaginous skeletal systems! With over 500 species in our oceans worldwide, sharks have been around for at least 450 million years. While this is all very neat, it poses the question of just how these creatures survived for so long.
The simple answer is this: they survived because all mass extinction events occurred for differing reasons, so they were able to overcome and evolve differently each time. The longer answer is that the species survival relied heavily on the fact that sharks live everywhere, in the deepest parts of the ocean and the shallower shorelines.This ecosystem diversity allows for a larger range of food options as well, making it easier for the species to survive if they can eat anything.Â
Scientists, and even regular people out for a swim, have been able to find shark teeth dating back hundreds of thousands of years. Shark skeletons are made up of cartilage which requires very special conditions to be able to fossilize correctly, however their teeth are made up of dentin. Dentin is a material that is more dense than bone, making it a prime fossilization candidate. Plus with the ridiculous amount of teeth sharks have, there are always tons to be found!Â
With over 500 distinct species, one has to be the baby of the group and that is the hammerhead shark. Dating back only about 23 million years (oh yeah, so young) this species’ distinct head shape is actually a useful tool for them as well. It helps with the enhancement of vision and smell, and acts as an aid for electroreception, which is how they detect naturally occuring electrical fields as they swim to hunt prey! How nifty.Â
Sharks play a vital role in our oceanic ecosystems, however they are becoming endangered as more and more people kill them for food. They are seen as violent creatures, when in reality we are the ones encroaching on their territory. They have been around for so long that they deserve our respect solely for the badass fact that they survived 5 mass extinctions. Take that other species!
References:https://www.nhm.ac.uk/discover/shark-evolution-a-450-million-year-timeline.html