65-50Mya Paleocene

Following the great KT extinction event, the great winners were the mammals. Without the dominant dinosaurs, and thus with the size and night constraint lifted, they started becoming larger and filling all niches. Other proliferating survivors were frogs, lizards, etc.

In Laurasia, the condylarth-like mammals diversified:

Mesonychids
dominant carnivores
(*Pachyaena*)

hooved runners

digging omnivores

Oxygen level reached 23%. Europe was now separate from N America.

Primates
insectivores

Leptictids

Other mammals survived the extinction, but they were outcompeted by the rodents.

Grasses
developed from the lily family; their flowers changed to wind-pollinated, independent of insects.

Vipers, cobras, mambas, ..., with venomous fangs to catch rodents

At first the marine crocs found new niches, including land, but they became extinct as the land and sea life recovered.

Ants became extremely successful because of their symbiosis with fungi, spreading out even to arid places.

Similarly, the deep-sea ray-finned fishes survived the extinction and radiated out to fill in the niches left open, especially the perch-like fish with their prominent dorsal fins:

Cod family in the arctic (haddock, whiting,...)

Angelfish, pilotfish, moonfish
perches, snappers,
many living among corals

pufferfish, triggerfish
anglerfish, monkfish

Sunfish (1ton)

The only surviving dinosaurs were the (mostly flightless) ornithine birds, with three main lines.

Ratites
large running birds:
ostrich in India
rhea in S America
emu, cassowary in Australia
moa, kiwi, in N Zealand
elephant bird in Madagascar

Fowl
pheasant, chicken,
quail, grouse, turkey

Geese (e.g. swans), migratory
Ducks

The most successful of these early fowl radiated out:

50-25Mya Eocene and Oligocene

When India made first contact with Asia, the perissodactyls diversified:

The artiodactyls diversified even more:

agile forest herbivores, able to ferment, ruminate, then digest leaves.

*Pakicetus*
ambush carnivores in swamps (Asia)

Protocetus

Whales
in Tethys sea
at first giving birth on land
but eventually permanently at sea

The African mammals grew in size:

The South American mammals grew in isolation:

Notoungulates

The Australian (+New Guinea) marsupials also diversified in isolation:

Koala
able to eat toxic Eucalyptus leaves.

But reptiles such as crocodiles and monitor lizards were the top predators in Australia's arid climate.

As the sea level fell, New Zealand formed, with practically no fauna.

The birds continued to diversify:

gannets, frigatebirds ...
including *Pelagornis*
with 5m wingspan

The mesonychids fluorished, but in the end, the creodonts replaced them and the flightless carnivore birds in Laurasia. They lived in Africa, some as big as bears hunting arsinoitheres.

*Andrewsarchus*
largest carnivorous entelodont mammal

Rodents diversified and spread, replacing the multituberculates.

Squirrels
(+chipmunks, prairie dogs);
dormice

rock rats and mole rats, porcupines of Africa

Similarly looking mammals are unrelated:

With time, mammals evolved to their largest sizes.

25-5Mya Miocene

condors
in Americas; *Argentavis* largest bird ever, with 6m wingspan

parrots
perching seed-eaters
'intelligent' - as they grew in size, they became 'brainy'

wrens, crows, thrushes, sparrows, swallows, larks,...
spread worldwide

The leaf eating monkeys diversified, especially in Africa; many like to sit.

apes: larger, fruit-eating, tail-less, arm-swinging and hanging from branches.

Some monkeys crossed over from Africa to S America (35Mya) on rafts of uprooted trees, where they diversified:
titi, uakari, saki, howlers, spider monkeys, capuchins, tamarins, marmosets

In the same event, some rodents crossed from Africa to S America and diversified into guinea pigs, chinchillas, capybaras (up to 1ton).

Grass savannas replaced forest as the climate started to become drier. Herbivores evolved into new grazers.

In Asia

In N America, the horse and the llama evolved.

The miacids evolved into felids and canids, displacing the creodonts. The cunning canids diversified, first in Asia, replacing the creodonts.

Seals, sea-lions, walrus in Arctic
(decimate penguins in Antarctic)
safe from predators
in Antarctica

skunks, otters, badgers, weasels,
eating rodents and birds in grassland

Felids
nocturnal tree climbers,
stalk+sprint hunters
of rodents, birds

Hyaenas
dog-like snatchers
and scavengers
in Asia

The whales split 25Mya into two main lineages:

Dolphins
porpoises, and their larger versions, sperm whales, orcas, beluga + narwhal, ...;
able to echolocate with their head-dome.

Baleen whales grew large, able to migrate far and deep to filter-feeding on fish, squid, or shrimp; as the Arctic cooled, and krill grew in abundance, they became very large (similarly whale shark).

In S. America, the ant-eaters and litopterns diversified.

Late Miocene

10-4Mya The climate became much drier and colder (av. temp. 15°C), as the Himalayan erosion removed CO₂ from the atmosphere. The advanced grasses discovered a novel C4 synthesis pathway, more efficient at capturing CO₂, so were able to survive a dry season; they proliferated, forming savannas.

In N. America, the marsupials, taeniodonts, pantodonts, dinocerates and titanotheres did not survive the change in habitat; only a few species remained. Similarly their predators, the creodonts were replaced by new canids and felids.

New herbivores, such as the horses, rhinos, llamas, antelopes, oreodonts, and hippos, had to have specialized digestive systems, with symbiotic cellulose-digesting bacteria, to deal with the nutrient-poor grasses.

Cactus, in arid parts of Americas, evolved from the carnation family; they radiated out about 5Mya.

In Africa, the elephant and monkeys evolved on the partial savannas.

Baboons and mangabeys evolved from macaques.

18 – 16Mya Africa joined Eurasia, allowing many animals to cross over and adapt from Eurasia to Africa:

Gazelles

...or the other way round:

*Gomphotheres* and *Mastodons* in America

*Orangutan*,
*Gigantopithecus* - 200-ton, gorilla-like

... but 7Mya, the Mediterranean filled up and isolated Africa. The African elephants and apes diverged from their Asian counterparts.

social omnivores

5Mya Ice Ages — Pleistocene

Around 5Mya, the climate worldwide became cooler as the Antarctic, then N. America and Europe/Siberia, accumulated ice; several species adapted, some by growing larger.

Foxes, jackals, wolves
(replaced hyaenas in Asia)

Mammoths
on Asian savannas,
from African elephant
(today it survives as the Indian elephant).

Goats, ibex, sheep
evolved on mountains from antelopes.

4Mya N. America joined Eurasia, as sea-levels fell: many animals passed from America to Eurasia...

or vice versa, from Eurasia to America:

Similarly the waters around Australia were sufficiently low that bats, birds and rodents were able to pass from Asia.

3Mya N. America joined S. America: various animals diffused from either continent, tapirs, llamas, cougars, leopards became jaguars, peccaries; but in the end, the large S. American animals (giant ground sloth, glyptodon, terror birds) became extinct.

The Ice Age, and interglacials, proved too much for many animals: sabre-toothed cats, most elephants (deinotheres, gomphotheres, mammoths, and mastodons), mid-range whales, several fresh-water fish; but they provided opportunities for others e.g., big cats, pigs, rats and mice, the gigantic whales (180-ton blue whale, largest animal ever).