A TIMELINE FOR THE PLANET click for Home Page
There was something of a clearout at the end of the Palaeocene, caused by global warming. It was nothing approaching a mass extinction, on land at least. But the oceans suffered much more. The entire ocean warmed dramatically, changing its chemistry and causing underwater mayhem. As a result, some 40% of the deep ocean micro-organisms died out.
However by the end of the transition recognisably modern animals were beginning to appear.
The clearout had to do with tectonic changes, as
The collision produced flood basalts, volcanism and methane outpourings, and hence the global warming.
Back to the animals
Even the land climate became pretty hot however, and
crocodiles were to be seen swimming off northern
The mammals that survived the clearout were pretty primitive. Short thick limbs, clumsy feet and hands, and simple teeth capable only of tearing. But they quickly evolved modern capabilities, like long thin legs, grasping hands and teeth that could chew. They were the direct ancestors of horses, camels, sheep, cows and of course humans.
The collision also allowed animals to migrate to new pastures and possibly out-compete those already there.
Many modern mammals appeared early, including modern rodents, the earliest known horse and modern primates.
In fact the clearout began shortly before the end of the Palaeocene. It resulted in animals becoming very small, the better to cope with the heat. Small animals can lose heat much faster than large animals can.
This is the first horse, Hyracoterium, or Eohippus,
“the Dawn Horse”. It first appeared early in the Eocene in the forests of
Most of the animals seemed to start off as herbivores. And they didn’t stay small for long. By shortly after the beginning of the Eocene (around 55 million years ago) some had grown to 2 metres tall, weighing as much as 5 tons.
The carnivores that came through remained small for a lot longer.
This rhino is Uintatherium. It was around during the late Eocene, in
I’ve read that grass didn’t appear until about 8 million years ago, so these animals must have dined off leaves and other coarse material.
Soon after came animals that were into digging, climbing, running and even flying. Yes, bats had finally appeared.
(I’m indebted to an article by Elisabeth Nadine in Cuss’s ‘Science Notes’ for parts of this.)
© C B Pease, Oct 07