Head says he hasn't found fossil records that show why the creature eventually went extinct.
The big deal
The evolution of such a large reptile shows what a huge effect a slight warming bump can have, Head said. With the ice caps gone, Earth's climate became warm and muggy, and forest covered the planet.
There was plenty of greenery for the chubby lizard to munch through.
As man-made climate change progresses, existing reptiles will spread out into new territory, Head predicts.
So can we see another spurt of such giant lizards?
For them to evolve to the size of the Bearded King Morrison, they would require global temperatures to slowly rise a few degrees -- and then remain stable for a very long time.
Today's climate is warming so rapidly that "we'll basically block off their ability to respond to the temperature increase," Head said.
Instead of evolution, he said, we'll see extinction.
Or, as Morrison sang, "This is the end, my only friend."