Fact 2 of 10
2. Sharks are older than trees
The oldest relatives of sharks were already swimming in the seas around 450 million years ago. The first trees only appeared about 385 million years ago. In other words, sharks existed before there were forests.
How the age of a fossil shark is determined
A shark's skeleton is made of cartilage, a material that almost never becomes fossilized. That is why what remains of ancient sharks is mainly teeth and small scales. The oldest scales attributed to shark relatives are about 450 million years old, and the oldest teeth, about 400 million.
On the plant side, the first true trees, with wooden trunks, emerged about 385 million years ago. Before that, vegetation on dry land was low and simple, with nothing resembling a tall forest.
Scientists add a caveat: the answer depends on what is meant by a shark. Modern sharks, from the families that exist today, are much more recent. But the shark lineage, counting its oldest relatives, does indeed predate trees, and it has survived several mass extinctions since then.
Today there are more than 500 shark species, from the whale shark, the largest fish in the world, at over 12 meters, to species that fit in the palm of a hand. Most pose no danger to people, and many are threatened by overfishing.
Você sabia? Os tubarões trocam de dente a vida inteira. Os dentes ficam em fileiras, e quando um cai, o de trás ocupa o lugar. É por isso que dentes de tubarão estão entre os fósseis mais comuns do mundo.
