Tuesday, November 28, 2017

Placoderms with osteichthyan like jaw bones

Placoderms gave rise to all modern fishes. The discovery of a fossil and a specimen by the name Entelognathus fills the gap between placoderms and all modern fishes. This revolutionizes the way ichthyologists perceive the common ancestors of modern fishes. Entelognathus had the first complex mouth which had gulars, which are common in modern fishes.
                                          This discovery puts acanthodians to the condrichthian stem group, basically saying that ancient spiny sharks are related to modern cartilaginous fishes. The fossil was taken from china and was analyzed for what miniscule DNA remained.
                                          Because evolution is ultimately reflected in the genetic sequences, the DNA of Entelognathus was compared to that of a modern condrichtyan, it was then found based off of the remaining genes of Entelognathus that it has similar base pair pattern and structure to that of a spiny shark and also that of a modern day bony fish. Because of the ability to investigate this from a genetic aspect it very quickly makes scientists rethink everything they know about evolution of fishes and this combines with a morphological and anatomical analysis is what shocks many scientists. The idea that there is a new member in the lineage it arises many new ideas and theory’s regarding the evolution past this new point and how anatomically things came to be.
                                          The skull roof pattern of a basic acantodiian compared to that of entelognathus suggests homology across the gnathostome crown group node, therefore this evidence in conjunction with the genetic evidence of close relation is the final proof that ties Entelognathus to modern fishes. The genetic importance of this study is that because of genetics it is possible that we can rethink about the way that evolution works and come to conclusions about Darwinian Theory.

                                          This to me is very important because this same technique can be applied to any phylum to trace it back to a common ancestor and revolutionize the way that evolution from a common ancestor to modern day is perceived. All in all due to paleontology and geneticists Chinese and American scientists were able to connect the dots between spiny sharks and modern fishes which revolutionized marine biology.

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