IV. Cenozoic (65 - 0 mya). The major groups of mammals had evolved in the Jurassic and Cretaceous

IV. Cenozoic (65 - 0 mya)

The major groups of mammals had evolved in the Jurassic and Cretaceous.

The extinction of the dinosaurs opened many niches, but the mammals were hammered by extinctions, too.

The extinction of the dinosaurs opened many niches, but the mammals were hammered by extinctions, too. Small mammals, however, quickly radiate into most ecological niches except large predators.

In the absence of dinosaurs, the birds radiated:

Diatryma (Gastornis) in NA/Asia

seed eater?

Phorusrhacids in SA: Top Predators

Largest one yet, found in Argentina in Oct. 2006, probably stood over 10 feet tall.

Chiappe and Bertelli. 2006. Nature 443:929.

2.3 ft

condor

MAMMALIAN RADIATIONS:

The nature of these radiations varied on the different, separated continents

The earliest marsupials evolved in North America, but the were practically wiped out there at the K-T. They didn't recover in NA, but weathered the K-T (and ultimately dominated the fauna) in the southern supercontinent of SA, Antarctica, and Australia, eventually radiating into all ecological niches.

late Cretaceous Alphodon, a Didelphiformian (common marsupial group)

The earliest Cenozoic marsupials are in SA (Paleocene), but by the Eocene they are present in Antarctica and Australia. They begin as insectivores...

Argyrolagus (SA)

then radiate as large herbivores (in Australia, primarily)...

Diprotodon

and finally radiate as top predators.

Thylacoleo

Marsupial "Lion"

(Australia)

'cat-like'

Thylacosmilus (SA and Australia)

Borhyaena (SA)

'Dog-like'

Thylacine (Australia)

In the isolation of Australia, they radiated to fill all mammalian niches:

Insectivore

Fossorial

“teddy bear” niche 45 species of terrestrial

herbivores (Wallabies and Kangaroos

Nectarivore

Honey Possum

IV. Cenozoic (65 - 0 mya)In the isolation of Australia, they radiated to fill all mammalian

niches:

Arboreal Glider Arboreal Herbivore/Frugivore

brush-tailed Possum

niches:

'cat-like'

Predator

Quolls (several species)

niches:

'dog-like'

Predator

niches:

Omnivore/Scavenger

Tasmanian Devil

In SA, in addition to the marsupials, there were placental mammals - but only radiating as large herbivores:

Toxodon

and a notable mammalian clade, the Xenarthans - Sloths, Armadillos, Anteaters - were diverse and abundant in SA faunas:

Megatherium

Glyptodon

Xenarthans – a very primitive mammalian clade

and an Africarabian fauna evolved in isolation on Africa/Arabia - the modern group called that Afrotheria:

Aardvarks

Tenrecs

Hyraxes

Elephants

Elephant Shrews

Golden Moles

Is the Afrotheria polyphyletic?(1995)

Kriegs JO, Churakov G, Kiefmann M, Jordan U, Brosius J, et al. (2006) Retroposed elements as archives for the evolutionary history of placental mammals. PLoS Biol4(4): e91.

A more recent genetic analysis says no… (2006)

Curiously, this places the Pangolins (Pholidota) with Carnivores.

- Paleocene (65-55 mya)

The multituberculates dominated the "rodent niche" in northern continents. Ptilodus

The first large herbivores were Pantodonts... including Titanoides and Coryphodon. There are few direct adaptations to an herbivorous lifestyle

Ptilodus

The next clade of mammals were the Condylarths – omnivorous ancestral to the modern ungulates (Artiodactyls and Perissiodactlys).

Phenocodus

- Eocene (54-38 mya)

Many modern groups evolve in the northern continents:

Artiodactyls and Perrissiodactyls replace condylarths

proto- horses (Hyracotherium), tapirs, rhinoceroses, and camels, and bats, primates (Purgatorius), and whales (Basilosaurus) evolve.

Mesonychid (a condylarth)

Ambulocetus

Pakicetus

Basilosaurus

Icaronycterus index

First Primates - Plesiadapids

(Paleocene)

Purgatorius

Many modern groups evolve in the northern continents:

creodonts replaced large birds as major predators

- Oligocene (38-24 mya)

a cooling period, creating savannahs - grazers and browsers radiate

Mesohippus

Calicotherium

grasses evolve

a cooling period, creating savannahs - grazers and browsers radiate

Arsinotherium

a cooling period, creating savannahs - browsers radiate

Indricotherium (Baluchitherium)

Titanotheres

- Miocene (24 - 5 mya) – “NEOGENE”

- Miocene (24-5 mya)

Extensification of grassland habitats

Radiation of grazer fauna: camelids, horse ancestors, cervids, rhinos

- Miocene (24 - 5 mya)

True Dog and Cat Carnivores replace creodonts

- Pliocene (5 - 2 mya)

Sloths, Armadillos, Porcupines, Opposum

Deer, horses, monkeys, cats and dogs, rodents

Great American Interfaunal Exchange

- Pleistocene (2 mya - 10K)

American Mastodon Mammut americanum

Complete Mitochondrial Genome and Phylogeny of Pleistocene Mammoth Mammuthus primigeniusEvgeny I. Rogaev, et al. 2006. PLoS.

- Pleistocene (2 mya - 10K) - Periodic Ice Ages

391.06 (2010)

379.1 (2005)

Last Maximum ~ 18,000 ybp

Extinction of the Pleistocene Megafuana

- Human overhunting and keystone effects

- Climate change

- diseases brought by humans and their dogs.

IV. Cenozoic (65 - 0 mya). The major groups of mammals had evolved in the Jurassic and Cretaceous

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