Sharks are sometimes referred to as living fossils because of their similarities to their ancestors that lived hundreds of millions of years ago. Looking at their fossil history, it’s clear that sharks have undergone many changes in their time on the planet. Looking at the oldest shark fossils ever found and comparing them to recent discoveries show how much these cartilaginous fish have evolved throughout their extended stay in the world’s oceans.
Before considering the oldest fossils, it’s important to understand the history of these beautiful, deadly animals.
When Did the Earliest Ancestors of Sharks First Appear?
The earliest shark ancestors may have existed upwards of 420-450 million years ago. In other words, the early ancestors of sharks lived so long ago that most animal and plant life had not yet moved to land!
Scientists have recovered scales similar to shark scales from about 450 million years ago. Yet, those creatures may not have been actual sharks or shark ancestors. These creatures had shark-like scales, but they may have been jawless fish rather than modern sharks.
As a result, some researchers have altered the timeline of ancient sharks. Scientists generally accept that the first evidence of shark scales and teeth came during the Silurian period about 420 million years ago. However, the first recognized shark ancestor was a species that lived 397-410 million years ago called Doliodus problematicus.
This creature was not particularly shark-like, but it had a cartilaginous body, shark-like teeth, and a skull and jaw structure that was similar to sharks.
Another one of the earliest shark-like cartilaginous fish that lived far in the past was cladoselache. This fish lived about 380 million years ago, and it is often called the first shark. This creature was a fast predator that lacked scales and grew about 6.6 feet long. However, some researchers have argued that this fish had more in common with chimaeras, such as ghost sharks, than true sharks.
Sharks have a long and storied history that stretches back millions of years to the oldest shark fossils ever found. Future finds could help scientists understand the evolutionary paths that sharks underwent before reaching their modern forms.
When Did Modern Sharks First Appear?
Modern sharks appeared between 100-195 million years ago. Hexanchiformes may have been the first modern phylogenetic order of sharks to appear. This order has two extant members: frilled sharks and cow sharks. However, only the latter resemble sharks as we know them today while frilled sharks have a distinct eel-like appearance.
The Somniosidae family, called sleeper sharks, evolved about 100 million years ago. They too survived the Cretaceous-ending impact. One of the most famous members of this family is the Greenland shark, the animal with the longest lifespan of any vertebrate.
Megalodon, the largest shark to ever live, appeared about 60 million years ago. Although people often imagine these sharks as being very similar to the great white shark, they’re not closely related. Speaking of great white sharks, those creatures are not quite as old, having evolved between 4-10 million years ago or possibly up to 23 million years ago.
Today, more than 500 species of sharks exist. However, scientists believe many more types of sharks used to exist prior to the middle Miocene extinction. Still, it’s interesting to consider the ancestors of modern sharks survived five different mass extinctions before arriving at their current forms.
How Old Was the Oldest Shark Fossil Ever Found?
The oldest shark fossil ever found was about 409 million years old. The fossil specimen belonged to Doliodus problematicus. Not only was this fossil important for providing some insight into how long sharks have been around, but it also helped clarify the lineage of true sharks.
The shark fossil was found in New Brunswick, Canada, in 2003. The fossil was especially interesting because it had a shark-like head and teeth. However, the creature had a mix of features from modern sharks as well as fish with bones.
This was hardly the only ancient shark fossil found, but it was the most complete. Fossils of teeth from shark ancestors date back to about 418 million years ago and scale fossils date back to around 450 million years ago. Yet, the Doliodus problematicus fossil was the earliest confirmed shark ancestor fossil, and it provided a great deal of insight into the anatomy of its family members.
What Did the Oldest Shark Fossil Teach Us?
The oldest shark fossil ever found was incredibly useful to scientists. The fossil proved that Doliodus problematicus was an acanthodian and a chondrichthyan with some shark-like features and others that belonged to other fish.
Modern tests using X-ray imaging helped scientists confirm that sharks evolved from acanthodians. That information alone helps recontextualize the search for the lineage of these creatures.
The lessons that scientists gleaned from studying the fossil specimen were very important because fish-to-fish transitions are difficult to study from an evolutionary standpoint.
What’s the Oldest Shark to Ever Live?
The oldest shark to ever live was between 272-512 years old. The creature was a Greenland shark, a sleeper shark whose family evolved about 100 million years ago. They have a very low metabolism and can live over a mile or deeper in the ocean.
These deep-diving sharks are the longest-living vertebrates, but their lifespan is hard to estimate. Scientists learned that they could estimate the shark’s age based on its growth rate. They also recently discovered they could use carbon-dating on proteins in sharks’ bodies.
Based on that data, the shark was born before the U.S. became a country and possibly before King Henry VIII was crowned the King of England.
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