As the contents continued to drift catastrophically toward throe current configuration, many of the animals we know and eat today were evolving into their modern forms. Id like to start identifying where in particular these actually evolved, based on where the oldest fossils have been found. There’s no way of telling where the first sponge formed, or where the first millipedes came onto land, because those things don’t leave a strong fossil record, but also because the tectonic plates from those eras are partially sub ducted under other, modern plates. Now that we are in the Eocene, I can begin to describe where things “came” form, at least according to the fossil record.
In this period, the first elephants evolved in Egypt (0.43 bya). Cats (Lions, Tigers, Leopards) (0.042 bya) diverged from carnivores in Africa, and then (Wolves, Coyotes, Foxes) evolved in North America (0.034 bya). Even though North America was detaching from Eurasia at this time, they were connected when Carnivores evolved from Miacids, and there was enough connection for Canines to make their way to Asian and later Africa. Africa was not yet connected to Asia, actually. Proto-Camels, the ancestor of Llamas, Alpacas, Vicunas and Camels, evolved in the area of Colorado and Nevada 0.035 bya. The horse continued its well documented evolution in the Midwest of the United States as of 0.037 bya. The peak in horse diversity was 0.034 bya all while isolated North America was moving away from Europe and towards South America.
It was around this time that some mammals began returning to the seas, something they had not done since the amphibian exodus over 300 million years earlier. Maybe the fishing was too good, but the ancestors to whales, dolphins and porpoises began the move back to the ocean 0.048 bya in Pakistan. The other major class of aquatic mammal, the dugongs and manatees, moved back to the rivers and oceans at about the same time (0.049 bya), starting from the Caribbean. By 0.34 bya, Sirenians and cetaceans (0.045 bya) had achieved their modern form.
A hard to find fossil was soft bodied & fragile winged butterflies and moths*, first found from 0.04 bya. I can’t find the source on where that fossil was found, or if it is considered to the “cradle” of the Lepidopterans.
The Bering Strait land bridge made its fist alternate connection to Asia by 0.03 bya, enabling dogs, among others to migrate to Asia. Antarctica iced over 0.04 bya, and has remained covered in glaciers ever since. South America was still populated by marsupials at this time, like Australia today, isolated in the middle of the Atlantic and Pacific oceans.
At the same time Antarctica was icing over, early primates like the Lemur were diverging from the tailed monkeys in Asia (0.04 bya). Monkeys dispersed over the whole of Asia, and were ready to disperse to Europe when it joined with Asia 0.03 bya and Africa 0.02 bya. Most impressively, some monkeys made it to the Americas across the Bering Strait and even the Atlantic Ocean, one starving pregnant female at a time**. Old world and new world monkeys diverged as early as 0.04 bya, mixing with, but not supplanting the South American marsupials.
The end of this period, the “Eocene-Oligocene” extinction event (0.034 bya) may have been cause by another meteorite strike, this time leaving a crater on the east coast of the US that we recognize as the arc of the Chesapeake Bay.
Now about 127/128 through the history of life.
*if I recall, what distinguishes a Butterfly from a Moth is its clubbed antennae. I’m pretty sure that didn’t fossilize
** These “waif dispersers remain a mystery, and I’d like to read more about them when I get the time thos summer