Eocene-Oligocene 2 - paradise lostoi/Historical Geology pdf/Fyrirlestur 6... · Eocene-Oligocene 2 - paradise lost - Jarðsaga 2 - Saga Lífs og Jarðar - Ólafur Ingólfsson ...

Eocene-Oligocene 2- paradise lost -

Jarðsaga 2- Saga Lífs og Jarðar -

Ólafur Ingólfsson

Háskóli Íslands

Changing environments through Oligocene

Tropical areas, such as jungles and rainforests, were replaced by more temperate savannahs andgrasslands. This change in biomass forced dram-atic changes in the distribution of Oligoceneflora and fauna. Typically, forest dwellers de-clined as forested habitat became less abundant, and in their place, hoofed animals flourished due to the growing number of temperate grasslands. Major mammal groups that perished included mesonychids (ancestors of whales and hippos) and creodonts (carnivorous mammals).

But... grasses come to rule the world

Grasses, a product of the cooler, drier Oligoceneclimate, become one of the most important groups of organisms on the planet. They feed herds of grazingmammals, shelter smaller animals and birds, andstabilize soil, which in turn reduces erosion. They arehigh-fiber, low-protein plants and must be eaten in largequantities to provide adequate nutrition. Because they contain tiny silica fragments, though, they are tough to chew and wear down animal teeth. Grasses are adapted to recover quickly after their tips are grazed. Grasses rely on wind for pollination rather than insects or birds, and are thus not as dependant on other organisms as are some other flowering plants...

The three great biomes of the WorldGrasslands are foundon either side of twodesert belts thatcircle the earth. About 30% of the earth's land is in the grasslands.

In a natural state, forests would cover ca. 40% of earth’s land

Deserts (including Antarctica) cover about 30% of earth’s land surface

Mesohippus

Mesohippus was a small animal, only 60 cm shoulder height

The "middle horse“, Mesohippus, is intermediate betweenthe eohippus-like horses of the Eocene, and more"modern" horses. Fossils are found at many Oligocene sites in N America. Mesohippus lived about 37-32 MY ago.

Learn more about the horse evolution...

http://www.flmnh.ufl.edu/natsci/vertpaleo/fhc/StratMap1.htm

Large (and many) herbivores meanlots of food for vicious carnivores

The Hyaenodon, 41-25 MY, a creodont, were top pre-dators of Eocene andOligocene in Laurasia. A number of species, ranging in size from 30 cm to 1.4 m at the shoulder. Hyaenodon gigas was largest.

Hyaenodon were very successfulpredators. Their skulls show thatthey had a very acute sense of smell. The smaller species would probably have hunted in packs, whilst the largest, the size of small rhinos, would probably have hunted alone.

Who were the creodonts?Hyaenodon horridus

Creodonts are an extinct group of carnivorous mammalsthat were long thought to be the ancestors of modernCarnivora. This is no longer thought to be the case. Creodonts were the dominant group of carnivorous mammals in the early Tertiary and were quite diverse. The Creodonts 44 teeth did not have the characteristic teeth of a mammal seen today.

When did the true carnivores take over?

In Eocene, the Carnivora were a group of weasel-like foresthunters. There were two types that eventually gave rise to the two branches of today. The “dog branch” was based in N America. The “cat branch” developed mainly in Europe.

True carnivores on the move in Oligocene...

It was a carnivore, and ate small rodents and rabbits. Its closest living relatives are bears and dogs. The bear dog was 30 cm at the shoulder. Fossils are commonly found in Eurasia and North America.

...one of them was theBear-dog (Amphicyonid, "in between dog" ), which lived 40-9 MY ago.

Large omnivores were not out of place

Entelodont (“perfecttoothed”), 45-25 MY ago. Omnivorous animal - Mostly scavenging carcasses

Closest living relative: Pigs and other cloven-hoofed animals

Their huge skulls were verypowerful and designed to crushbones. They were scavengers and probably ate anything that they came across.

In Africa: Moeritherium 36-33 MY

"Moeris beast" named after the Lake Moeris wherethe first fossils were found. Herbivore - browsingsea-grass and other waterside vegetation. Closest living relative: Elephants. Size: 0.7m at the shoulder

Elephants developBy 36 MY ago there were alreadyseveral members of the elephantfamily - some of them resembled tomodern elephants. Moeritherium adopted a hippo-like lifestyle, and didn’t have trunk or tusks.

A scene from the Oligo-cene, 30 MY ago. Here a Paleomastodon and proto-hippos enjoy a wallow at the river's edge

Oligocene Mastodont

Creodontswere the toppredators in

AfricaArsinoitherium, the largebeast in this picture, hasbeen brought to bay by a pack of creodonts. Ars-inoitherium looked like a rhino but was more close-ly related to elephants.

Giant Ground Sloths in S America

South America developed its own megafauna in Eocene-Oligocene, which was largely dominated by huge GroundSloths and Armadillos. The last of the Great Ground Sloths did not become extinct until about 10.000 years ago

Absence of large mammalian predatorsin Eocene-Oligocene S America

Huge terror birds were among the top predators.

Andalgalornis

Huge, flightless birdsin general, andcarnivorous terrorbirds in particular, evolve primarily in the absence of other fast and vicious predators.

Andalgalornis

Standing up to 3 metres tall, with a powerful hooked beak, Andalgalornis was truly a “Terror-bird”. These large, flightless birds roamed theSouth American grasslandsbetween 62-2 MY ago. They had strong, powerful legs and could probably run at speeds of up to 60 km/hour, chasing down the mammals which were their prey.

Phorusrhacos 27 MY-15 ka ago

Carnivorous - Small mammals and carcasses. Size: 2.5m tall

Phorusrhacos belonged to the Terror Birds. The earliestknown Terror bird, Aenigmavis, only the size of a modernchicken, was found in the 49 MY old Messel deposits of Germany. In South America Aenigmavis’ descendants became huge and were the continents top predator for millions of years until the cats arrived from N America.

S American carnivorous marsupialsTodays marsupials are generally not carnivorous (althoughthe Tasmanian Devil and the Marsupial Mole of Australia are noteable axceptions).

Thylacosmilus evolved intohunters from primitivemarsupial insectivores thatbecame isolated in S America. Isolation allowed marsupialevolution to fill unexploited niches left open after the demise of the dinosaurs. The result was many diverse, geo-graphically distinct creatures that existed nowhere else

Tasmanian Tiger

When the last known Tasmanian tiger died in a zoo in 1936, it was the end of the line for an entire family of marsupialswhich had lived in Australia for millions of years. It lookedlike a large, long dog, with stripes, a heavy stiff tail and a big head. Its name, Thylacinus cynocephalus, means pouched dog with a wolf's head (Pokahundur með úlfshöfuð) . Fully grown it measured about 1.8 m from nose to tail tip, stood about 58 cm high at the shoulder and weighed up to 30 kg.

What about the primates?Well, they kept to the trees, out of harms way on theground. They were very much restricted to the warm tropical and subtropical forests

Godinotia lived in Europe(found in the Messel shales) 49 MY ago. This was a omni-vorous creature – ate insects and fruit. It was about 30 cm long, + a long tail

Latin name: Godinotia neglecta,named after the primate resear-cher Marc Godinot

Apidium (“small bull”) 36-34 MY ago

Apidium fossils have beenfound in the Fayum deposits of Egypt. Body 25-30 cm long, not including the tail

Apidium was a primate, adapted to life in the tropical for-ests of North Africa at the time. It was adapted for leap-ing from branch to branch. The males were much bigger, and had large canine teeth to fight over groups of females, so they were probably social like most monkeys today.

Primate Evolution

Although they originated in the Northern Hemisphere, therodents and primates colonised the Southern continents. There they have lived alongside the Afrotheres and Xenar-thrans. The primates (humans) have also invaded the mar-supial stronghold, Australia - bringing with them their rodent relatives.

The problem of New World primatesThe earliest South American primates are known fromOligocene. A site in Bolivia dates the arrival of primatesin South America to ca 30 MY BP. Given the fact thatSouth America was an island for much of the Cenozoic, colliding with North America not until the middlePliocene, it is not entirely clear how these speciesarrived on the continent and where they came from. It is unknown, for example, whether the primates rafted to the island from North America or Africa. Primate species traveling from either continent would have had to cross major bodies of water. The S American species resemble African primates more than they do the N American ones, which leads many to believe in an African origin for the New World primates.

Maybe the NewWorld primateswere there since mid-Cretaceous?

Many primates were(and are) very small, and the fossil record is biased towards larger animals...

An excellent review of primate evolution at: http://highered.mcgraw-hill.com/sites/dl/free/0072500506/1/26527_ch05.pdf

Eocene-Oligocene Oceans

The increase in heavyoxygen isotopes at the Eocene-Oligoceneboundary reflectstwo things: increaseof water locked out of circulation in the Antarctic ice sheet and the greater availability of cold deep water.

ODP results...Intense researh efforts directedtowards knowing more about theEocene-Oligocene boundary, to understand what happened...

Marine mass extinctionNearly 34 MY ago, shellfish the world overperished in the largest mass extinction sincethe one that claimed the dinosaurs. Along theU.S. Gulf Coast, for example, almost 90% of the mollusks were wiped out--to be replacedlater by new species. The cause of this fatal event, however, has remained somewhat of a mystery. The results of a study published in Nature in 2000 suggest that climate change -colder winters along the Gulf Coast - resulted in the mass extinction at the Eocene/Oligocene boundary.

Studies of fish otoliths – kvarnir, jafnvægiskorn

• Otoliths are found in the earof all teleost (bony) fish. Theyaid in hearing and balance in thefish. Otoliths are made up of crystalline aragonite and a pro-tein matrix. They grow concen-trically from inside to outside, much like the rings of a tree. Light and dark bands on the otolith represent periods of high and low growth, either on yearly, monthly or daily cycles.

Otolites register the environment• Otoliths are composed of around 90% calcium carbonate(CaCO3), mostly in the form of aragonite. The other 10% of the otolith is minor and trace elements within the aragonitic matrix that are derived from the water sur-rounding the fish. These impurities reflect the water chemistry, as well as the fish's metabolism. • Otoliths are of particular use to scientists because theyare metabolically inert, meaning that there is no re-adsorption and once any material is added to the otolith, it remains there un-altered. The concentric nature of the otolith also provides a chronological life history of the fish, from the fish's embryonic stages at the center to its death in the outside ring.

Cause of marine extinctionNot only marine bivalves underwent mass extinc-tion at the Eocene-Oligocene boundary: 70% of foraminifer species in the sea went extinct.

It is speculated thatradical changes inoceanic circulation ingeneral and in bottomwater circulation in particular had some-thing to do with this extinction episode.

The Oligoceneextinction: a minor one seen in the bigger frame of things

Genera: ættkvíslir;

Families: ættir

Insects florish with flowering plants

There is very good paleontological material reflectinginsect develoment through the Tertiary – mainly becauseof preservation in amber. Most groups of modern insects had arrived on the scene in paleogene times.

Not onlypleasantinsects...

A number of bloodsuckinginsects first appaer inOligocene times, such asAnoplura (sucking lice), Glossinidae (Tsetse flies) and Hippoboscidae (louse flies)

The Oligocene bird watcher

By Oligocene most of the bird orders (ættbálkar) that we recognize today had appeared. TheOligocene birdwatcher could have seen closerelatives of today's fowls, doves, parrots, penguins, crows, owls, falcons, eagles, hawks, petrells, nightjars and songbirds...

Classification of birds

The Class (flokkur) Aves is currentlydivided up into 23 orders (ættbálkar), 142 families (ættir), 2,057 genera (ættkvíslir) and 9,702 species (tegundir) of birds.

http://www.earthlife.net/birds/classification.html

Snakes...Modern snakes start showingup in numbers in theOligocene. The vast majorityof snake fossils are from N America and W Europe, andwe have a very limited ideaof what went on in the evo-lution of snakes. There was a rapid evolution of species from 22-5 MY ago. Venomous snakes appeared in the fossil record for the first time during Oligocene, possibly as late as 25 mya.

There are 18 families, 464 genera, >2,700 species of living snakes.

Other reptilesTurtles and crocodilescontinued to be successful, despite the changingenvironments. The crocodilehabitats diminished, but the crocs could cope with that. Turtles radiated and developed, occupying more diverse habitats, even dry grasslandsFossil Turtle dung specimens. EXCEL-LENT for study, display, or as a wonderful gift to that special person who thought "they had everything"!

Oligocene - the judgement of geological history

By standards of Earths history, the Oligoceneis relatively uneventful, both geologically andbiologically. Following the rapid cooling thatends the Eocene, the climate remains coolerand more seasonal. Plants adapted to dry and cool climates, including herbaceous plants (jurtkenndar plöntur) and grasses, begin to diversify. Most terrestrial animal groups presently living were established already by the end of Oligocene

How did it end...?Well, not with a mass extinction. The Oligocene-Miocene boundary ischaracterized by bioticchanges that signal brief rapid warming and dimini-shing ice in Antarctica for some time around 23 MY. Oligocene, Miocene, Pliocene, Pleistocene established on basis of marine strata and fossils in France and Italy (Charles Lyell 1833).

References used for this lectureStanley: Earth System History. Arnold, LondonFortey: Life. A Natural History of the First Four Billion Years on Earth. Vintage, New York.

http://www.sci.tamucc.edu/tmmsn/extinct/archaeocetes.html

http://www.cetaceen.de/images/zeichnungen/EvolutionWale.png

http://www1.thdo.bbc.co.uk/beasts/factfiles/index_all.shtml

http://www.palaeos.com/Vertebrates/Units/520Cetartiodactyla/520.120.html#Georgiacetus

http://www.sciencenews.org/20010922/fob1.asp

http://www.kokogiak.com/megafauna/strange.asp

http://www.ucmp.berkeley.edu/mammal/eutheria/creodonta.html

http://www.flmnh.ufl.edu/natsci/vertpaleo/fhc/mesoh1.htm

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

http://www.ucmp.berkeley.edu/tertiary/oli/olilife.html

http://www.clas.ufl.edu/users/emartin/GLY3074S03/lecturenotes/cenozoicclimate.htm

http://www.palaeoentomolog.ru/Publ/PALJ153.pdf

http://www.nature-source.com/turtles.htm

http://www.earthlife.net/birds/classification.html

http://mbgnet.mobot.org/sets/grasslnd/world.htm

http://www.nearctica.com/nathist/reptile/list.htm

http://sorcerer.ucsd.edu/tauxe/pdfs/shackleton00.pdf