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The last group of the diapsids that we need to
recognize were the flying reptiles.
Now, I want to hasten, these were not dinosaurs, these were flying reptiles.
And they, again, were radiating off of the main line that was going towards
dinosaurs, but they are not dinosaurs, they branched off and
radiated in a slightly different direction.
So the flying reptiles, the flying diapsids, we call them pterosaurs,and
the pterosaurs were the first vertebrates to be able to access the air environment.
So, what were they composed of, what made them different?
Well, as you've seen some of these diagrams and some of the reconstructed
sketches of the pterosaurs, the pterosaurs did something that was just remarkable.
They had a limb that had finger projections off them,
and they had five fingers that came off.
But one of the fingers ended up growing meters in length, so
the little finger on both hands,
on the pterosaur, grew to be longer than the entire body of the pterosaur.
So, as you can see in the diagram you can see the fingers coming off and
then that last little finger it extends out and
makes a very long spine that runs out and away from the hand.
Now, what the pterosaurs did was through evolutionary selection they
ended up stretching a skin membrane between the little finger and the body.
So that skin membrane, the wing if you will, it was attached across the entire
length the little finger and then attached across the entire length of the body,
so it was a very different flying apparatus from a modern day bird.
So I want to make it clear the birds evolved from the dinosaurs and
the pterosaurs were flying reptiles that emerged prior to and were not dinosaurs.
So the pterosaurs had a unique strategy for flight, and
another thing about the pterosaurs is that they ended up developing, and
we think this has to do with aerodynamics as well as the need to make their
skeletons as light as possible, because flight takes a lot of energy Is that their
heads became very well oriented and the bones within the head became hollow.
And so as you can see from some of the reconstructions in these diagrams is
the pterosaurs ended up with an extremely well what we call ornamented skull.
The skull had many shapes and projections, became elongated and
in some places flattened.
And there was a great radiation in the diversity of the different types of
species of these pterosaurs.
So the pterodactyls were very good at accessing the air environment and
they diversified greatly in that process.
Now, unfortunately, the pterosaurs were one of the diopside lineages that
went extinct at the cretaceous tertiary meteor impact event at 65.5 million.
So that meteor event took out the dinosaurs, took out the pterosaurs,
took out the plesiosaurs, took out the ichthyosaurs.
Only one small lineage of dinosaurs survived across the cretaceous
tertiary boundary and that went extinct very rapidly right afterwards.
So virtually every one of the great lineages of the diopses went
extinct except for the crocodiles, and except for a few,
small representatives of some of the other reptiles that made it through.
And, of course, the enapses also survived,
the lineage of the reptile that had no hole in the skull behind the eye socket.