What are placodermy?

Placederms are an extinct class of armored fish, the first known animals of any type that develop real jaws. Placederms evolved from the fish Agnathan (Jawless) during the Silurian period, about 425 million years ago. It is about the same time as the first earthly animals as Millipedes, it is known to dare on the ground.

Placederms (Class Placedermi) diversified in the Central-Silurian or maybe earlier, the first pioneer in the evolution of vertebrates, which would immediately continue during the Devonian period, which represented so much diversification of fish, which was called the "age of fish". Unfortunately, no complete placoderm fossils are known - the species has been described from the fragments of their armor body, which are preserved when the body of the fish disintegrates after death.

The characteristic feature of the placema is a layer of segmented armor over the head and chest. Depending on the species, the rest of the body has been modified or naked. Instead of actual Placodermy teeth, they dumped their food with sharpeningthe bone points that protrude from the head. This method of feeding is a clear evolutionary intermediate between fish without jaws and highly adapted gears of modern fish groups.

Placederms ranged from several inches to a huge 6 m (20 ft) dunklosteus Teleleri , which lived for about 360 - 415 million years and weighed a ton. Dunkleosteus is considered the first superterist of vertebrates and probably took over some segments of the evolutionary alcove previously killed only by large predatile invertebrates, such as sea scorpion. These animals showed the ability of members of the phylum Chordat (vertebrates) to occupy the apex niche Predator, which would continue to dominate the rest of history. dunkleosteus It is assumed that the strength of the bite Similar had the strongest bitters in history, such as Tyrannosaurus rex modern crocodiles.

Placederma was also the first animals to iIt did not unify the fertilization of eggs, which led to the first live birth in evolutionary history. They died in the late Devonian extinction, which also erased virtually all fish without jaws and many other species.