The following chart shows the
main branches of the dinosaur family tree.
During this time the synapsids or "mammal-like reptiles" were the
dominate terrestrial species. Some authorities maintain that
they accounted for 95% of all land animals. They were all but wiped
out by the Permian Mass Extinction. A few small survived and
they evolved into modern day mammals.
The principal of "Radiant Adaptive" maintains that a species will
evolve into different forms in order to take advantage of ecological
niches. This was the case following the Permian Mass Extinction.
With the synapsids no longer competing for food, some reptiles evolved
into a new form - the archosaurs. This clad quickly diversified
resulting in the flying pterosaurs, giant marine reptiles,
crocodiles and the first dinosaurs.
Jurassic & Triassic Periods
These were the periods in which the dinosaurs ruled the Earth.
The first birds appeared during this time.
This ended in another mass extinction, one that destroyed all
the archosaurs, except the birds. In accordance with adaptive
radiation, many of the ecological niches were filled by the mammals
that rapidly evolved into many different forms. The birds
underwent a massive adaptive radiation. There are now over
10,000 documented species.