Sharks appeared approximately 450 million years ago. span>
Today, the fossil record of sharks is three times as long as that of dinosaurs, going back to times a hundred times older than that of man.
This means that your family tree encompasses more than 450 million years of evolution. Sharks swam in the waters of prehistoric oceans long before the first vertebrate animals crawled on land, before insects took flight, even before many plants had effectively colonized the continents.
This fossil record of sharks is fragmentary for the most part, that normally the only thing found is the teeth, which sometimes have large quantities.
There have been cases in which parts of the internal skeleton and even complete specimens have been discovered.
Shark teeth are tough, tough objects that easily fossilize. span>One of the oldest and most primitive sharks isCladoselache, i> about 400 million years old, found in Paleozoic strata of Ohio, Kentucky and Tennessee (USA). This shark was not very big, only half a meter long and had stiff fins.
All the fossils found between 300 and 150 million years old, belonged to two groups, one, the xenacanths, which were confined to freshwater environments, spread throughout the world and had a quite remarkable longevity. And the second, the hybodonts, which predominated in the oceans and fresh waters during the time of the dinosaurs.
Today, there are fossils of current sharks, such as the Mako shark and nearby species.
At the beginning of the evolution of the Jaquetones, at least two lines of this appear, one, presents teeth with a relatively rough side serration, which probably is where the current Jaquetones come from, and the other has a much more serration.
Another of the ancestors of today’s sharks is the giganticCarcharodon megalodon,whose teeth were over eighteen centimeters in height and whose total length may have exceeded twelve meters./ span>
Its predecessors include:
- heHelicoprion, with its spiral-shaped teeth
- heEchinochimarea, which had the so-called wings of today’s flying fish
- heOrthacanthus, or river shark span>
- heBelantsea, fish-like
- hePaleocarcharias, predecessor of today’s hammerhead sharks
- heCladoselache, an ancestor similar to today’s sharks
- heIniopteryx, with an abyssal fish appearance and flying fish fins
- heHybodus, shark that fed on animals much larger than the
- hePaleospinax, one of the first sharks to have a structure like today’s sharks
- heStethacanthus, with an anvil-shaped structure on its back
- heProtospinax, modern predecessor of stripes
- thePseudorhina, ancestor of angel sharks/ span>
- he Ischyodus, ancestor of cat and nurse sharks
- heScapanorhynchus, extinct relative of the current goblin shark span>
- heEdestus, with scissors-shaped teeth
- heCretoxyrhina, relative of Hybodus
- heLanma, ancestor of the bull shark
- heCobelodus, with a tiny head compared to the body. span>