Agnatha

The jawless fishes ( Agnatha ) were formerly as an original group of vertebrates that is completely extinct except for the lampreys and hagfish the. As an indication was that they have no jaws, but unlike the acrania possessed a skull.

It was assumed that the heyday of the jawless have located several hundred species during the Cambrian period in which they have evolved and spread. The extinct groups were summarized as Ostracodermi. It was believed that many species at that time as a substitute for a real pine either freely seated in the mouth teeth or tooth-like outgrowths at the then frequent head tank ( Ostracodermi ) developed. Your time had ended with the appearance of the first fish with jaws, which had developed in these animals from the front gill arches.

In modern taxonomy taxon of jawless is no longer used because it is paraphyletic. The absence of pines is only an original feature. According to modern research, the state of Inger ( hagfish ) are the sister group of all vertebrates, to which they themselves are no longer counted (they have no hard parts to the notochord, the precursor of vortices would be ). The only extant agnathans class that cyclostomes ( cyclostomes ), however, is the sister group of the gnathostomes ( gnathostomata ), and both together are the only extant representatives of vertebrates. Cyclo - and Gnathostomen together form the taxon Myopterygia because skeletal muscles win with them on fin rays approach, which is not the case with the hagfish.