Eocene-Oligocene 2 - paradise lost

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 and
grasslands. This change in biomass forced dramatic changes in the distribution of Oligocene
flora and fauna. Typically, forest dwellers declined 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 Oligocene
climate, become one of the most important groups of
organisms on the planet. They feed herds of grazing
mammals, shelter smaller animals and birds, and
stabilize soil, which in turn reduces erosion. They are
high-fiber, low-protein plants and must be eaten in large
quantities 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 World
Grasslands are found
on either side of two
desert belts that
circle 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 between
the 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 mean
lots of food for vicious carnivores
The Hyaenodon, 41-25 MY,
a creodont, were top predators of Eocene and
Oligocene 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 successful
predators. Their skulls show that
they 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 mammals
that were long thought to be the ancestors of modern
Carnivora. 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 forest
hunters. 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...
...one of them was the
Bear-dog (Amphicyonid,
"in between dog" ), which
lived 40-9 MY ago.
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.
Large omnivores were not out of place
Their huge skulls were very
powerful and designed to crush
bones. They were scavengers and
probably ate anything that they
came across.
Entelodont (“perfect
toothed”), 45-25 MY
ago. Omnivorous animal
- Mostly scavenging
carcasses
Closest living relative:
Pigs and other clovenhoofed animals
In Africa: Moeritherium 36-33 MY
"Moeris beast" named after the Lake Moeris where
the first fossils were found. Herbivore - browsing
sea-grass and other waterside vegetation. Closest
living relative: Elephants. Size: 0.7m at the shoulder
Elephants develop
By 36 MY ago there were already
several members of the elephant
family - some of them resembled to
modern elephants. Moeritherium
adopted a hippo-like lifestyle, and
didn’t have trunk or tusks.
A scene from the Oligocene, 30 MY ago. Here a
Paleomastodon and protohippos enjoy a wallow at
the river's edge
Oligocene Mastodont
Creodonts
were the top
predators in
Africa
Arsinoitherium, the large
beast in this picture, has
been brought to bay by a
pack of creodonts. Arsinoitherium looked like a
rhino but was more closely related to elephants.
Giant Ground Sloths in S America
South America developed its own megafauna in EoceneOligocene, which was largely dominated by huge Ground
Sloths and Armadillos. The last of the Great Ground Sloths
did not become extinct until about 10.000 years ago
Absence of large mammalian predators
in Eocene-Oligocene S America
Huge terror birds were among the top predators.
Huge, flightless birds
in general, and
carnivorous terror
birds in particular,
evolve primarily in the
absence of other fast
and vicious predators.
Andalgalornis
Andalgalornis
Standing up to 3 metres tall,
with a powerful hooked beak,
Andalgalornis was truly a
“Terror-bird”. These large,
flightless birds roamed the
South American grasslands
between 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 earliest
known Terror bird, Aenigmavis, only the size of a modern
chicken, 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 marsupials
Todays marsupials are generally not carnivorous (although
the Tasmanian Devil and the Marsupial Mole of Australia
are noteable axceptions).
Thylacosmilus evolved into
hunters from primitive
marsupial insectivores that
became isolated in S America.
Isolation allowed marsupial
evolution to fill unexploited
niches left open after the
demise of the dinosaurs. The
result was many diverse, geographically 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 marsupials
which had lived in Australia for millions of years. It looked
like 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 the
ground. 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 omnivorous creature – ate insects
and fruit. It was about 30
cm long, + a long tail
Latin name: Godinotia neglecta,
named after the primate researcher Marc Godinot
Apidium (“small bull”) 36-34 MY ago
Apidium fossils have been
found 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 leaping 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, the
rodents and primates colonised the Southern continents.
There they have lived alongside the Afrotheres and Xenarthrans. The primates (humans) have also invaded the marsupial stronghold, Australia - bringing with them their
rodent relatives.
The problem of New World primates
The earliest South American primates are known from
Oligocene. A site in Bolivia dates the arrival of primates
in South America to ca 30 MY BP. Given the fact that
South America was an island for much of the Cenozoic,
colliding with North America not until the middle
Pliocene, it is not entirely clear how these species
arrived 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 New
World primates
were 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 heavy
oxygen isotopes at
the Eocene-Oligocene
boundary reflects
two things: increase
of water locked out
of circulation in the
Antarctic ice sheet
and the greater
availability of cold
deep water.
ODP results...
Intense researh efforts directed
towards knowing more about the
Eocene-Oligocene boundary, to
understand what happened...
Marine mass extinction
Nearly 34 MY ago, shellfish the world over
perished in the largest mass extinction since
the one that claimed the dinosaurs. Along the
U.S. Gulf Coast, for example, almost 90% of
the mollusks were wiped out--to be replaced
later 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 ear
of all teleost (bony) fish. They
aid in hearing and balance in the
fish. Otoliths are made up of
crystalline aragonite and a protein matrix. They grow concentrically 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 surrounding the fish. These impurities reflect the water
chemistry, as well as the fish's metabolism.
• Otoliths are of particular use to scientists because they
are metabolically inert, meaning that there is no readsorption 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 extinction
Not only marine bivalves underwent mass extinction at the Eocene-Oligocene boundary: 70% of
foraminifer species in the sea went extinct.
It is speculated that
radical changes in
oceanic circulation in
general and in bottom
water circulation in
particular had something to do with this
extinction episode.
The Oligocene
extinction: 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 reflecting
insect develoment through the Tertiary – mainly because
of preservation in amber. Most groups of modern insects
had arrived on the scene in paleogene times.
Not only
pleasant
insects...
A number of bloodsucking
insects first appaer in
Oligocene times, such as
Anoplura (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. The
Oligocene birdwatcher could have seen close
relatives of today's fowls, doves, parrots,
penguins, crows, owls, falcons, eagles, hawks,
petrells, nightjars and songbirds...
Classification of birds
The Class (flokkur)
Aves is currently
divided 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...
There are 18 families, 464 genera,
>2,700 species of living snakes.
Modern snakes start showing
up in numbers in the
Oligocene. The vast majority
of snake fossils are from N
America and W Europe, and
we have a very limited idea
of what went on in the evolution 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.
Other reptiles
Turtles and crocodiles
continued to be successful,
despite the changing
environments. The crocodile
habitats diminished, but the
crocs could cope with that.
Turtles radiated and
developed, occupying more
diverse habitats, even dry
grasslands
Fossil Turtle dung specimens. EXCELLENT 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 Oligocene
is relatively uneventful, both geologically and
biologically. Following the rapid cooling that
ends the Eocene, the climate remains cooler
and 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 OligoceneMiocene boundary is
characterized by biotic
changes that signal brief
rapid warming and diminishing 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 lecture
Stanley: Earth System History. Arnold, London
Fortey: 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