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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