Miocene Development of Life

Miocene Development
of Life
Jarðsaga 2
- Saga Lífs og Lands -
Ólafur Ingólfsson
The high-point of the age of
mammals
The Miocene or "less recent" is so called because it
contains fewer modern animals than the following
Pliocene. The Miocene lasted for 18 MY, ~23-5 MY ago.
This was a huge time of transition, the end of the old
prehistoric world and the birth of the more recent sort
of world. It was also the high point of the age of
mammals
Open vegetation systems expand
• The overall pattern of biological change for the
Miocene is one of expanding open vegetation
systems (such as deserts, tundra, and
grasslands) at the expense of diminishing closed
vegetation (such as forests).
• This led to a rediversification of temperate
ecosystems and many morphological changes in
animals. Mammals and birds in particular
developed new forms, whether as fast-running
herbivores, large predatory mammals and birds,
or small quick birds and rodents.
Two major ecosystems evolve
Two major ecosystems first appeared during the
Miocene: kelp forests and grasslands. The expansion of
grasslands is correlated to a drying of continental
interiors and a global cooling. Later in the Miocene a
distinct cooling of the climate resulted in the further
reduction of both tropical and conifer forests, and the
flourishing of grasslands and savanna in their stead.
Modern Grasslands
Over one quarter of the Earth's surface is covered by
grasslands. Grasslands are found on every continent
except Antarctica, and they make up most of Africa and
Asia. There are several types of grassland and each one
has its own name. Prairies, plains and savannas are all
grasslands.
Where do grasslands form?
Grasslands develop where there isn't enough rain for
forests but too much rain for deserts. Grasslands are
filled with - you guessed it - grass. There are many types
of grass, though. Fields of wheat are considered
grasslands, even though they are often cultivated by
people. Grass is special because it grows underneath the
ground. During cold/dry periods the grass can stay
dormant until it warms up. Consequently, the development
of grasslands also signifies increased seasonality...
The
Kelp
Forest
Ecosystem
The Kelp Forest Ecosystem
The Kelp Forests are very different from other
habitats. It is made of seaweed called giant kelp
(Macrocystis pyrifera). Giant kelp grows in cool coastal
waters where sunlight can go down to a rocky sea floor.
Kelp needs sunlight and a hard surface to grow on. Kelp
consists of at least three parts: the holdfast, stipe, and
blade. Giant kelp is one of the world's fastest growing
organisms. It can grow as much as 100 m in a single year.
When the tops reach the surface, they keep on growing
to form a floating mat. The kelp forest provides shelter
and protection for many animals.
The giant kelp is not a
plant, it is a brown algae
Present distribution
In North America, kelp forests
range from Alaska to California,
where they are confined to cool,
upwelling water areas. Macrocystis
pyrifera is also found on the west
coast of South America, south
Africa, and southern Australia.
They prefer water temperatures
between 5-20°C.
Mammals and Land Bridges
• The great diversification of land
mammals during the Miocene is due in
large part to the formation of land
bridges. These routes, which emerge as
sea levels drop and inland seas dry out,
connect continents previously separated
by water. They provide access to new
habitats and enable migrating animals to
greatly extend their geographic ranges.
Mammals and Land Bridges
• Routes between Africa, Eurasia, and North
America are the primary migratory paths.
• The once-great Tethys Ocean no longer
divides Africa and Eurasia. Elephants and apes
are among the mammals that venture out of
Africa and settle in parts of Eurasia, while
rabbits, pigs, saber-toothed cats, and modern
rhinos move in the opposite direction.
• To the north, a dry corridor, the Bering land
bridge, connects what are now Siberia and
Alaska. Eventually, both elephants and rhinos
make their way to North America, perhaps
crossing paths with horses on their way to
Eurasia.
A landmark study on land bridges
Mammals and Land Bridges by George Gaylord Simpson
(1940). Journal of the Washington Academy of Sciences
30 (1940): 137-163.
(http://clk.about.com/?zi=1/XJ&sdn=geology&zu=http%3A%2F%2Fwww.wku.edu%2F%7Esmithch%2Fbiogeog%2FSIM
P940B.htm)
Some aspects of land bridges
Beringia Land Bridge – bridging two worlds
During Miocene and
Pliocene the Beringia
Land Bridge was
available for mainly
tectonic reasons.
During Pleistocene
the growth of ice
sheets periodically
opened the route...
Low Miocene global sea levels helped
bridging continents...
Land bridge over
“Iceland”...
The Tertiary biota of Iceland
is closely related to the
modern Eastern Deciduous
Forests of N America. Flora
and fauna used the dynamic
land bridge between North
America and Europe via
Greenland-”Iceland” as a
migration route during the
Paleogene. This land bridge
emerged due to hotspot
activity on the Mid Atlantic
ridge in connection with the
opening of the N Atlantic.
Mammals and the Miocene World
North
America
ADAPTIVE
RADIATIONS
OF MORE
EVOLVED
PLACENTAL
MAMMALS
South
America
Eurasia
Continued isolation
of early monotremes
and marsupials
Africa
Extinctions of mammals
Antarctica
About 20 million years ago, during the Miocene
Mammals in the Miocene
Maps showing
distribution of
important fossil
sites for Miocene
mammals
• Mammal forms were essentially modern; almost half of modern placental
mammal families were present.
• Higher primates, including monkeys
and apes were present across southern
Europe and Asia.
• The new grassy plains had a dramatic
effect on mammals. Those that
adapted to eating grass did well.
• Many spread across the continents
when Africa, Eurasia and North
America joined.
• Only Australia and South America
were isolated continents and unique
grazers evolved there.
Hypothetical cladogram for mammals
North American mammals 1
1.
2.
3.
4.
5.
• North America was a centre of
diversity for hoofed mammals. They
were followed by carnivorous cats and
dogs, hunting on the open plains.
Moropus (a relative of
horses and camels);
Promerycochoerus (“dog-
pig”)
Menoceras (pig-sized
rhino)
Oxydactylus (early camel)
Daphaenodon (“bear-
dog”)
6. Stenomylus (early camel)
7. Dinohyus (“terrible pig”,
an omnivore)
8. Merychyus (early
ungulate, herbivore)
9. Palaeocastor (“ancient
beaver”)
10. Parahippus (early horse)
11. Syndyoceras (ungulate)
North American mammals 2
Merychippus represents
20 MY
10 MY
a milestone in the
evolution of horses. It
had a long face, and its
long legs allowed it to
escape from predators
and migrate long
distances to feed. It was
the first known grazing
horse and the ancestor
of all later horse
lineages. Lived in North
America from 17 - 11
million years ago.
Frábær heimasíða um Miocen fánu N Ameríku=
http://www.npwrc.usgs.gov/resource/1998/agate/visit.htm
North American mammals 3
Beavers do more to shape their landscape than any other mammal except
for human beings, and their ancestors
were building dams 10 MY years ago.
The Miocene beavers were >2m long.
The beaver is a clever engineer, but its brain is
embarrassingly small . . . and they don't see
well. Nevertheless, there is abundant evidence
that much of their building technique appears
to be learned through their long childhood.
• The primates suffered with the demise of the forests.
The prosimians (lemur group) that had lived in North
America disappeared. Rodents were the only survivors of
the rodent and primate group.
North American mammals 4
Gomphothers, Miocene (12-8 MY ago).
They differ from elephants primarily in
the form of the chewing surfaces of
their molar teeth. Fossils show that
there were many different types of
gomphotheres.
• The first afrotheres, the mastodons and the gomphotheres first appeared in North America. The Afrotherian sea cows and almost all the modern groups of whales
were present, as well as the early seals and walruses.
North American mammals 5
The skeleton is from a fossil sea cow (Dusisiren jordani) that lived in
the Pacific Ocean 10-12 MY ago. Sea cows are herbivorous aquatic
mammals. Like cetaceans (whales, dolphins) sea cows lack hind limbs
and are thus restricted to life in the water. Dusisiren was common in
the shallow coastal waters of late Miocene California. The climate
was slightly warmer than today, and there were many more bays and
inland seas over California. The sea cow fed on algae and sea
grasses, pulling up the vegetation with the horny pads in the front
of its mouth. It did not have front teeth.
North American
mammals 6
A giant camel skeleton
(Late Miocene in age).
Gigantocamelus weighted
over a ton, twice as much
as today's camels.
Skeleton discovered in
1936
Giraffe-like
camel
Deer, antelope, camel (even toed), and horses (odd toed)
covered the continent in huge numbers and specialised
in grazing.
North American mammals 7
Pseudaelurus is a prehistoric cat that lived in Europe and North
America approximately 20-10 million years ago. It is regarded to
be an ancestor of today's domestic and big cats
Cats from Eurasia joined the carnivorous running bears,
bear dogs, dogs and mustelids hunting the herbivores on
the plains.
North American
mammals 8
By Miocene times, about 20 MY
ago, the two superfamilies of
carnivores (canines and felines)
were distinct. Tomarctus was an
early-mid Miocene relative of the
dogs (Canis) and foxes (Vulpes)
Tomarctus (lower) and
Pseudocynodictis (upper).
P was an ancestor of T
and an early member of
the Canidae family, 25 MY
ago.
Dog evolution in North America
The Dog linage began in late Eocene, 37 MY ago
in North America in predators that had distinctive pairs of shearing teeth and ran down prey.
The canid radiation begins in late Miocene, with
the small fox Leptocyon, ancestor of the Canis
and Vulpes. It began in the southwest United
States, the birthplace of modern dogs.
More about N American dogs
8 MY ago a powerful canid
called Epicyon attacks a horned
herbivore. Epicyon were the
size of large wolves
The Eucyon, a fox-size canid, developed about 9 MY ago. It spread
to Eurasia 7-6 MY ago and gave rise
to most modern canids, including
wolves, coyotes, and jackals.
From wolf to
woof
All family dogs are
senso strictu
domesticated wolfs
Seals first
occurred during
the Miocene
Kingdom (ríki): Animalia - dýraríki
Phylum (fylking): Chordata - seildýr
Class (flokkur): Mammalia - spendýr
Order (ættbálkur): Carnivora - rándýr
Family (ætt): Pinnipedia - seldýr
Most scientists believe seals and sea lions may have
evolved from the same ancestor because their genes are
fairly similar. Using fossils and comparative morphology,
scientists believe that both seals and sea lions, under the
family name Pinnipeds, originated from an otterlike
carnivore found in the North Atlantic during the Miocene.
...and bears first appeared in Miocene
time
http://www.angellis.net/Web/DFGmam/Cephalogale.htm
The origins of the bears can be traced back to the raccoonsized, dog-like Cephalogale from the middle Oligocene and early
Miocene (20-30 MY ago) of Europe. Cephalogale gave rise to a
lineage of early bears, the genus Ursavus. This genus radiated in
Asia and ultimately gave rise to the first true bears (genus
Ursus) in Europe, 5 MY ago. Extinct bear genera includes
Arctodus, Agriarctos, Agriotherium, Plionarctos and Indarctos.
Bears and seals share an ancestor
Bears are members of the Order
Carnivora, Sub-Order Caniformia,
and Family Ursidae. Other
members of the Caniformia
include wolves and other dog-like
mammals (Family Canidae),
weasels, skunks, and badgers
(Family Mustelidae), raccoons
(Family Procyonidae), and
walruses (Family Odobenidae),
seals (Family Phocidae), and sea
lions (Family Otariidae). Although
bears are often described as
having evolved from a dog-like
ancestor, their closest living
relatives are the pinnipeds
(walruses, seals, and sea lions).
South American Miocene mammal
development
Adrift on its own, South America’s strange mixture of marsupials, hoofed animals and ‘native’
xenarthra (armadillos, sloths and anteaters)
were adapting in their own way to the spreading
grasslands. South America was the only continent
on the planet with representatives from all major
mammalian groups.
Marsupial carnivores decline – “killer
birds” hold their position
Thylacinus sp. This group
of marsupial carnivores
was represented in the
Miocene South American
fauna
Giant
carnivorous
ground bird
(Phorusrhacus),
1.5 m tall. These
creatures were
wholly
indigenous to
South America
The marsupial carnivores began to decline and only the
smaller animals remained by the end of the Miocene.
Rodents and primates were both
successful
Cow-sized guinea pigs (“marsvín”),
weighing up to 700 kg, grazed the
riverbanks of South America about five
million years ago, confirms a newly
found skeleton. This biggest-ever
rodent, Phoberomys patersoni, shared
its home with two-metre turtles, tenmetre crocodiles (sebecosuchids) and
three-metre carnivorous birds.
Charles Darwin wrote extensively on South American mammals in his
book “The Voyage of the Beagle”. The book is available on the net:
http://www.literature.org/authors/darwin-charles/the-voyage-ofthe-beagle/
The isolated hoofed animals
(litopterns and ‘notoungulates)
formed herds living on the plains
Archaeohyrax
Left: Reconstruction of
the head of Mesotherium. Right: lateral view
of the skull of Eutypo-
therium superans.
Toxodon sp
Native xenarthrans adapted
The two-tonne, South
American glyptodont –
relative of armadillos –
became extinct 10,000
years ago. About the
size of a Volkswagen
beetle, glyptodonts had
protective armour that
weighed up to 400 kg.
The ‘native’ xenarthrans adapted to the plains
and huge grazing glyptodonts roamed
alongside giant ground sloths and smaller
armadillos. Anteaters lived in the trees.
Miocene Australia
Big flightless birds develop in the absence of
numerous mammalian carnivores. Dromornis
stirtoni was one of the biggest bird that ever
lived. It weighed over 500 kilos, and stood
nearly 3 metres tall. It had a huge beak and jaw
capable of great force. Although they looked
like giant emus, the Dromornis stirtoni are more
closely related to geese. They are part of a
family of giant birds called Dromornithidae that
lived from 15 million years ago until less than
30,000 years ago.
Isolated from other continents, Australia developed its
own unique marsupial fauna during the Tertiary. The
drying out of Australia in Miocene sped the evolution of
animals that live in open and dry habitats...
Huge marsupial herbivores
Alkwertatherium webbi was a large marsupial almost the
size of a rhinoceros. It weighed about 400 kg and was
about 1 m tall and 2.5 m long. The Alkwertatherium webbi
had a long snout with a mouth like a scoop. This was
probably used for finding food under the ground such as
tubers, or semi aquatic plants along a river's edge.
Alkwertatherium survived through almost all the Miocene
period, or from 24 - 5 million years ago.
Kolopsis – a large
Miocene herbivore
Kolopsis torus was a bull-like
marsupial that stood nearly 1 m
high and was about 2 m long. It
is related to our modern day
koalas. Kolopsis was a herbivore
and ate leaves, stems and small
plants. Kolopsis probably lived in
large herds. Kolopsis lived
during the Miocene period, in a
habitat of forests and
grasslands and a small
permanent water supply.
Another large herbivore
The Plaisiodon centralis was a
very big marsupial with a long
narrow head. Its closest
living relatives are wombats
and koalas. Plaisodons
weighed between 500 - 700
kg and were about 1.5 m tall
and 3 m long. The Plaisiodon
was very similar to the
Kolopsis torus. Both of these
animals ate leaves and coarse
foliage and probably lived in
herds. The female Plaisiodons
were much smaller than the
males.
Enter the
kangaroos...
Hadronomas puckridgei was a
big marsupial that looked like a
kangaroo. It is probably an
ancestor of the short-faced
kangaroo, and stood about 2 m
tall. Hadronomas weighed about
60 kg and had very big feet. It
also had small eyes facing
outward that gave it a wide field
of vision.
Hadronomas was a browser and ate
leaves and grasses that it chewed with
its little nibbling teeth. Hadronomas
lived together with herds of large
marsupials and large birds but with
very few predators.
And there were predators...
Baru darrowi was a large
crocodile. It reached 4 - 5 m in
length and had powerful jaws
and long curved teeth that it
used to catch marsupials and
other mammals or birds. Baru
was the largest crocodile to live
during late Miocene times
around 8 MY ago
These crocodiles were among
the few Australian predators. It
was adapted to periodic
draughts, and spent a lot of time
out of the water.
Web page on Miocene Australia: http://amol.org.au/discovernet/alcoota/
Other predators included...
Powerful Thylacine (Thylacinus
potens) lived 8 MY ago (late Miocene).
It was 1.5 m long. Several kinds of
thylacine have lived in Australia
during the past 25 million years; the
Powerful Thylacine was the largest of
them all. It was also the largest meateating marsupial of its time. The
death of the last known Thylacine in
Hobart Zoo, in 1936, marked the end
of thylacines for all time.
Huge Pythons (>8 m long) and
giant lizzards also prayed on
animals at waterholes. Both
evolved to become top
predators in Pliocene and
Pleistocene times.
Brief summary of Miocene
24 MY ago: Short-term warming and drying.
20 MY ago: Great mountain building. The Cascades, the Andes and
the Himalayas. These massive Mts disrupt weather patterns and alter
rainfall distribution.
20 MY ago: Kelp forests. Support evolving marine life, such as sea
otters, as well as established groups of fishes and invertebrates.
20 MY ago: Inland seas dry out. The shifting continents, changing
climate patterns, and formation of a polar ice cap cause sea levels to
drop and inland seas to shrink. Land routes open between continents.
18 MY ago: Grazing horses. Grazing horses quickly spread from
North America to Europe and Asia, and from there to Africa, where
some species become today's zebras.
16 MY ago: Orangutan line separates from African ape/hominid line
Antarctica's deep freeze, the spread of grasslands, and perhaps
even the effects of mountain building probably contribute to the
extinction of several browsing mammal species. Animals adapted for
cooler conditions and coarse, grassy vegetation fare well.
References used when preparing 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.ivry.cnrs.fr/deh/gommery/gommery.htm
http://amol.org.au/discovernet/alcoota/thylacinus.asp
Sánchez-Villagra, M. R., Aguilera, O. & Horovitz, I. The anatomy of the world's largest extinct rodent.
Science, 301, 1708 - 1710, (2003).
http://www.kerwoodwolf.com/EVOLUTION.htm
http://www-museum.unl.edu/research/vertpaleo/ashfall.html
http://www.idir.net/%7Ewolf2dog/wayne2.htm
http://www.nebraskastudies.org/
http://www.santacruzpl.org/history/spanish/seacow.shtml
http://www.flmnh.ufl.edu/tusks/index.htm
http://allelephants.com/allinfo/evol.php#gomp
http://www.biology.ucsc.edu/classes/bio161/KFE%20algae%20photos/Macrocystis.html
http://www.mbari.org/~conn/botany/browns/james/default.htm
http://www.oceanlight.com/html/kelp.html
http://www.calstatela.edu/faculty/eviau/edit557/oceans/norma/oklpfst.htm
http://www.palaeos.com/Cenozoic/Miocene/Miocene.htm
http://www-museum.unl.edu/research/vertpaleo/ashfall.html
http://www.glasgowzoo.co.uk/articles/carnivores/conferencebears2.php
http://www.windows.ucar.edu/tour/link=/earth/grassland_eco.html
http://www.shore.ctc.edu/access/geology100/life6.html#anchor1057826