Transcript Powerpoint Presentation: Evolution of the Horse

THE
EVOLUTION
OF THE
HORSE
(Equus)
Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS
The odd-toed ungulates
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Horses belong to the
Perissodactyla, the
odd-toed ungulates
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This group includes
horses, rhinos and
tapirs today
© 2008 Paul Billiet ODWS
White Rhinoceros (Ceratotherium simum) © KHW
Equus
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The genus Equus includes horses, zebra and
asses
The last remaining branch of a diverse group of
equids
Similar to the status of Homo sapiens, the last
remaining species of a once diverse group of
Hominids
The evolution of the horse is much better
documented than ours
The fossil record is very complete
© 2008 Paul Billiet ODWS
Trends in the evolution of the horses
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Increased size
Reduced number of toes and longer legs
A stiffer back
Merychippus
20Ma
© 2008 Paul Billiet ODWS
Equus
Teeth for grazing
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Larger teeth and a
larger skull to hold
them
© 2008 Paul Billiet ODWS
Teeth for grazing
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Teeth with bands of
hard (enamel) and soft
(dentine) material on
the crown
Open tooth roots
permitting continuous
growth
© 2008 Paul Billiet ODWS
Trends in the evolution of the horses
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The trends correspond to changes in the climate
and vegetation of the Earth over the past 55 million
years,
combined with the arms race between predators
and prey.
From…….. rich rainforest which covered most of
the Earth in which the horses ancestors
browsed on leaves and hid from predators.
To ……. open savannah grassland where the
modern horses grazed grass and had to run
from predators.
© 2008 Paul Billiet ODWS
From ladders to bushes
Equus
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The view of evolution
in Darwin’s day was
that of Gradualism
One species slowly
transforming into
another
Pliohippus
Merychippus
Mesohippus
Orohippus
Hyracotherium
(aka Eohippus)
© 2008 Paul Billiet ODWS
From ladders to bushes
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The modern fossil record reveals a different
picture
Periods of radiation where species diversify
and fill different niches
Species giving rise to new species whilst
they still thrive
Species do not “turn into” new species
and completely disappear
The result is a more bushy appearance of
the pathway of evolution not a linear ladder
An irregular rate of evolution
© 2008 Paul Billiet ODWS
© 2008 Paul Billiet ODWS