6.3. Pterosaurs: The ONLY Flying Reptiles

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Emergence of Life

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University of Illinois at Urbana-Champaign

Emergence of Life

58 個評分

How did life emerge on Earth? How have life and Earth co-evolved through geological time? Is life elsewhere in the universe? Take a look through the 4-billion-year history of life on Earth through the lens of the modern Tree of Life! This course will evaluate the entire history of life on Earth within the context of our cutting-edge understanding of the Tree of Life. This includes the pioneering work of Professor Carl Woese on the University of Illinois Urbana-Champaign campus which revolutionized our understanding with a new "Tree of Life." Other themes include: -Reconnaissance of ancient primordial life before the first cell evolved -The entire ~4-billion-year development of single- and multi-celled life through the lens of the Tree of Life -The influence of Earth system processes (meteor impacts, volcanoes, ice sheets) on shaping and structuring the Tree of Life This synthesis emphasizes the universality of the emergence of life as a prelude for the search for extraterrestrial life.

從本節課中

Week 6 - Mesozoic Reign of the Dinosaurs and the Development of Flight

This week, you'll learn more about the Permian-Triassic extinction event, which caused more than 80% of life to go extinct. This opened vast swaths of ecological opportunity for radiation and diversification of life during the Mesozoic. You'll learn about symbiosis, which was widely utilized during this period, as well as the fascinating lineage of diapsid reptiles that rose to replace the synapsid predators of the late Paleozoic. We'll also discuss the rise of the dinosaurs, as well as the catastrophic meteor impact that drove the dinosaurs to extinction.

6.1. Symbiosis as a Strategy of Survival5:40

6.2. Rise of the Diapsids13:53

6.3. Pterosaurs: The ONLY Flying Reptiles4:37

6.4. Dinosaur Phylogeny: Hips Don't Lie7:06

6.5. Evolution of Flight: Life Invades the Sky6:09

6.6. Wild Wings: Fit to Fly10:46

6.7. Cretaceous Warming on a Reorganized Earth8:11

6.8. T. rex, and the Crater of Doom11:48

與講師見面

Bruce W. Fouke, Ph.D.
Director of the Roy J. Carver Biotechnology Center
Department of Geology, Department of Microbiology, and Institute for Genomic Biology

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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.

So the meteor impacts visiting the Earth, they were somewhat fickle,

they destroyed and caused extinction in a lot of different organisms, but

some of theme eked through each of these events.

And then as the events happened, then the ones that made it through were the ones

that had the chance to radiate and diversify and fill the new empty ecosystem

that had been made empty by the catastrophe of the meteor impact.

So this is the history of the Mesozoic age of the diapsids reptiles.

And this set the stage for

the manifestation of diapsids to then rule the planet and

make the Cretaceous truly the age of the dinosaurs.

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