The Pliocene (5,3-1,8 MY)- transition towards the Ice Age -

Jarðsaga 2

Ólafur Ingólfsson

Háskóla Íslands

Definition of the PliocenePliocene (very recent), was defined frommarine sediments in Italy which contain essentially modern fossil fauna

In Pliocene, continentalconfiguration becomes modern

Pliocene tectonics

A very important tectonic event was when S America reap-proached North America for the first time since theCretaceous period, almost 100 million years earlier. The Panamanian Isthmus emerged due to tectonics and fluctu-ating sea levels.

Pliocene Ocean Currents

Warm shallow ocean currents weaved between the Plio-cene continents. Cooler shallow currents were restrictedto the N Atlantic, and the Antarctic. Deeper, cooler currents flowed from the Antarctic into the Atlantic.

Pliocene SST

Differences from modern values values for two selected months in °C.

http://www.giss.nasa.gov/research/paleo/pliocene/page3.html

Pliocene and modern vegetationglobal albedo distribution

Pliocene vegetationThe climatecooled and driedas the Worldmoved from theMiocene into thePliocene. Theclimate became sharply seasonal, similar to the modern day. However, more dramatic changes were afoot...

Still warm at highlatitudes in early

Pliocene

A peat deposit on Ellesmere Island, Nunavut, Canada, allows a unique glimpse of the Early Pliocene terrestrial biota north of theArctic Circle. The peat accumulated in a beaver pond surroundedby boreal larch forest near regional tree line in coastal hills close to the Arctic Ocean. The ecological affinities of the plant and beetle remains contained in the peat indicate that winter temperatures on Ellesmere Island were nearly 15 °C higher and summer temperatures 10 °C higher than they are today.

Pliocene life in the Oceans

The Pliocene Oceans were modern in that all major groupsof marine mammals, fish, invertebrates, plankton andcorals were in place, and even on the species level, 50-90% of presently living marine species were already there.

Miocene-Pliocenedevelopment of

whalesThe Miocene-Pliocene warmseas teemed with life. Thewhales evolved and mostpresent groups were already in place in Pliocene. Below: Por-poise (“höfrungar”) evolution.

Pliocene marinetop predators

Toothed whales and seals, together with sharks, have remained top predators in the Oceans since Miocene times.

http://www.cnn.com/EARTH/9804/30/orca.whale.attack/orca.whale.attack.32.4.9.mov

Megalodon and the Great White• Carcharocles megalodon was a giantshark similar to, but much largerthan, the modern great white sharkCarcharodon carcharias. The maxi-mum size reached by Megalodon was probably 15-20 m; at least three times the size of the great white.

Megalodon becameextinct at the end of the Pliocene, about 1,6 MY ago...

The Great Barrier Reef- a bridge back in time -

The Great Barrier Reefpartly steems back to theMiocene, 25 MY ago. Itsrelatively stable environ-ments have been the breed-ing grounds through time for thousands of species of animals and plants...

Stretching > 2000 km and covering >25,000 km2 the Great BarrierReef is the world’s largest coral reef and probably the richest. More than 1500 species of fish, 4000 species of molluscs, 400 species of sponge and 300 species of hard corals live here.

South America: Birdcontinent...

S America has more species than any other continentalregion, and over a third of all the world's species. Thisbird fauna, as well as being extremely rich, is highlydistinctive, with 22 endemic families. Evidence from DNA sequences makes it almost certain that a very large part of the S American bird fauna is authochthonous - that is, it originated and diversified in place.

More on bird evolution...

By late Tertiary, the avifauna was basically modern, with many presently living species present. Thespread of grasslands favoured birds in open habi-tats, especially the song-birds (söngfuglar, spörfuglar)

Great diversity of song-birds

• Songbirds have developed rich and complex songs for mating and territorial displays. • They sing to court and they sing to fight, conservingtheir energy for important tasks like eating and mating. • Songbirds, as their name implies, sing complex andelegant melodies. All birds sing songs, but songbirds REALLY sing. Instead of fighting, an energy-intensive action, they sing to defend territories, attract the opposite sex and to sound alarms. • Birds, like humans, have distinct accents developed from where they grew up. Singing is learned from tutor.

Pliocene Australia

Australia was close to its present global position. Thecontinental plate carrying Australia had collided with the South East Asian plate.

Australia's climate was warm and wet but soon began todry again. Australia's forests were dominated by gum andwattle trees (“gúmmí- og tágafléttutré”). A dazzling mixture of wildflowers blossomed in the open spaces.

Pliocene animals of Australia

The extinct BluffDowns Python isthe largest snakeever to have lived - 10 m long with a 0.3 m girth.

Agile Wallaby (Macropusagilis) is the most com-mon kangaroo of tropical Australia.

The Saltwater Crocodileis the world's largestliving reptile. 9 m long and weighs >900 kg!

Many animals such as Agile Wallabies and SaltwaterCrocodiles made their appearance for the first time. Most of the older marsupials animals also remained. In some animal groups, giant species evolved for example, the largest snake that ever lived, a 10 m long python.

A Pliocene-Pleistocene giant lizzard

The name Megalania prisca means the “ancient giant but-cher”, and this may certainly have been a fitting descrip-tion for this large meat eater. Megalania belonged to thefamily that includes the monitor lizards, the largest of which today is the Komodo Dragon found in Indonesia. It was 4-5 m long, scavanger and killer. Rumour has it that it still exists in remote areas in Indonesia...

Island-hopping causes new immigrant species

The Australian Water Rator Beaver Rat is aquaticand occurs whereversuitable habitat is pro-vided by rivers, swamps, marshes, backwaters, or estuaries

New groups of animals were arriving from South EastAsia via island chains. Among these were Australia's first rats and mice. These did not threaten the ruling marsupials.

Pliocene Eurasia 1

• The mixture of animals we know today in Eurasia took shape in the Pliocene.

• The rodents were as successful as ever, and in Asia, elephants and stegodonts were successful. Hyraxes (“hnubbar”) also moved across from Africa.

• Horses suffered a slight decline in diversity, but tapirsand rhinos, continued to survive throughout Eurasia.

Rock Hyrax – an “elephant rodent”

Elephantevolution

The family Elephantidaeis the root from whichthe mammoth, Asianelephant, and Africanelephant came from. Interestingly, the Asian elephant is more closely related to the extinct mammoth than to the African elephant.

Deinotherium, only distantly related to elephants proper, these animals are distinguished by its downturned tusks. Appearing during the Miocene, they grew progressively larger, and grew as big as the biggest elephant. They flourished in Africa, Europe, and parts of Asia, but became extinct in early Pleistocene.

http://www.copyrightexpired.com/earlyimage/prehistoriclifeafterkt/dinotherium01.html

Pliocene Eurasia 2

Smilodon, the famous sabre-toothedcat, is well known because of theenormous numbers of skeletons of the North America species Smilodonfatalis, beautifully preserved in the tar pits of La Brea in California. The South America species, Smilodon populator, was even larger.

• Cows and antelopes were successful throughoutEurasia. The camels, which developed in N America, crossed into Asia. Hyaenas and the first sabre-toothed cats developed in Eurasia.

Pliocene drying-out of theMediterranean area

During Pliocene, the Mediterranean area driedout and the forests retreated, whereas N Africa was still largely warm and humid, with extensive forests bordering the East African savannas.

The Mediterranean Sea dries out!

The Mediterranean Sea (2,510,000 km2) became isolatedduring the Miocene, and about 6-5 MY ago the seafloor consisted of several basins of variable size and topo-graphy, with depths ranging from 200-1600 m. Highly saline waters of greatly varying depth probably covered the bottom and deposited salts. The Gibraltar Sill is at waterdepth of 320 m.

Pliocene AfricaThe late Pliocene Vertebrate site of Ahl al Oughlam

Geological map of the Casablanca area with dunes (yellow) along the main plio-pleistocene shores.

Late Pliocene (~2.6 MY) Casablanca

The Ahl al Oughlam site is extremely rich in fossils. Theyinclude fish, sharks, dolphins, toothed whales, amphibians(frogs), reptiles (crocodiles, turtles, snakes, lizzards), primates (baboons, no hominoids), hyaenas, leopard, bats, cheetas, wild cats, foxes, otters, bears, walruses, rodents (rats and mice), shrews, hares, rabbits, elephants, camels, horses, giraffes, antelopes, gazellas...

Casablanca horseHipparion is a primitive three-toed Equid, still havinglateral toes no longer present in Equus. It persists untilabout 0.5 My. in Africa. Ahl al Oughlam has yielded one of the best pliocene fossils of this group. The lateral toes show that this species had almost reached an Equus stage of evolution.

During late Pliocene(2.6 MY), certainEquus speciescrossed from N America to the Old World. Some entered Africa and diversified into the modern zebras.

Pliohippus Equus

The Pliohippus lived during thePliocene period and was the firstof the mammals on the horseevolution chain to have only one toe. He is believed to be a direct ancestor to the Equus.

An unexpected find: walrus!The walrus is probably the mostunexpected inhabitant of Ahl al Oughlam. Because of hunting, they are now restricted to theArctic, but in prehistoric and historical times they reached as far south as Belgium. Ahl al Oughlam remains by far their southernmost record, and the only one in Africa.

The walrus find raises interestingquestions as to natural habitats of animals versus the effects of hunting...

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