Sharks, escualos or selachimorfos (from the Greek σελαχος selachosshark and μορφή morpheform), are marine animals belonging to the superorder of the chondrichthyans. chondrichthyans are all cartilaginous fish, that is, their skeleton is made up of cartilage, a type of connective tissue. In other words, the sharks they have no bones.

To give you an idea of ​​what cartilage is, you can find it in human ears. Although there are several types of cartilage and it can be much harder than the one we have in our ears, it is never as hard as the bone tissue that forms the bones. Having cartilage and not bones offers several advantages to sharks; for example, it allows them to move faster through water, get through tight spots, or allow some injuries to heal faster. Cartilage does not fossilize so no shark skeleton fossils foundalthough of his teeth.

To reinforce the cartilaginous structure of their skeleton and increase stability, sharks have extra calcium deposits in their skulls, jaws, and spines. It is not very well known why the skeleton of sharks is not made of bone, but it is believed that it is due to the absence of certain genes in their DNA.

More curiosities about sharks

  • The whale shark (Rhincodon typus) can live up to 100 years, feeds only on plankton and can reach up to 18 meters in length (it is the biggest fish; remember that the whale, the largest marine animal, is not a fish, it is a mammal).
  • Some shark tooth fossils have been dated to be more than 400 million years old, which would make sharks were older than dinosaurs. The oldest known shark rest is 100 million years old.
  • 375 species of sharks have been discovered (currently 368 exist) but only about 30 attacks on humans have been described.
  • Sharks can go up to 6 weeks without eating.