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THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse ( Equus ferus przewalski ) © WWF-Canon / Hartmut JUNG

THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

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Page 1: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Page 2: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

The odd-toed ungulates

Horses belong to the Perissodactyla, the odd-toed ungulates

This group includes horses, rhinos and tapirs today White Rhinoceros (Ceratotherium simum) © KHW

© 2008 Paul Billiet ODWS

Page 3: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

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

Equus

© 2008 Paul Billiet ODWS

Page 4: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Evolution of the Horse

Did not occur in a straight line

Many horse like animals branched off

Now one genus is the only surviving branch of a once large evolutionary bush Equus

Page 5: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS
Page 6: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

© 2008 Paul Billiet ODWS

Page 7: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Evolution of the Horse

What is the earliest known ancestor of the horse? Eohippus

a.k.a. Hyracotherium or dawn horse

~ the size of a fox (8 -18” at shoulder)

Four functional toes on each front foot

Three toes on hind feet

Page 8: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Eohippus Structure of teeth suggest

Browser

Earliest remains found in North America

Thought to have lived ~54 million years ago

Remains also found in Europe dating 50 million years old

Page 9: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Eohippus Alert ears,

doglike, furry coat, swishing tail

Long face w/ 44 teeth Unlike today’s horse

36 -42

Both front and back toes replaced by tiny hooves

Page 10: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS
Page 11: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Evolution of the Horse

Mesohippus Lived ~ 35 million years ago

Earth’s temperature and climate had changed

Forest thinned and grass became more prevalent

Mesohippus appeared

Page 12: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Mesohippus A.k.a. “Middle Horse”

Larger than Eohippus 24” at shoulder

Teeth had further evolved but 44 remained intact

Only had three toes on front Was better suited to outrun predators

Lateral supporting toes decreased in size Middle toe strengthened

Page 13: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Mesohippus Toes now ended

in little hooves Still had a pad

behind them

Became extinct in Europe and North America~ 7 million years ago

Page 14: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Merychippus

Lived ~ 20 million years ago

Completely new type of horse

Evolved in North America

Adapted to hard grasses of plains

Beginning of grazing horse of today

Page 15: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Merychippus

Stood ~35”

Increasingly gregarious

Developed complicated grinding teeth similar to present day horses

Lateral toes diminished No longer touched the ground

Main toe thickened and hardened

Page 16: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS
Page 17: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Pliohippus

Developed ~5 million yrs ago

Branch of horses crossed into Asia

Quickly multiplied

Spread to Europe

North America Horse developed into the final

model

Page 18: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Pliohippus

First true monodactyl One-toed animal

Used speed to flee from predators

Further evolution of teeth and limbs

Spread into South America, Asia, Europe, and

Africa

Page 19: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS
Page 20: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Equus caballus ~2 million years ago

Modern day horse

Became extinct in N. America ~8,000 yrs ago

Was not to return until Spanish arrived in 1400’s

Page 21: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

How Evolution Works Common evolutionary trends are

Not seen in all horse lines

On the whole, horses Progressively larger Some then grew smaller

Many evolved Complex facial pits

Page 22: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Trends in the evolution of the horses

Increased size Reduced number of toes and longer legs A stiffer back

EquusMerychippus

20Ma© 2008 Paul Billiet ODWS

Page 23: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Trends in the evolution of the horses

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

Page 24: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Teeth for grazing

Larger teeth and a larger skull to hold them

© 2008 Paul Billiet ODWS

Page 25: THE EVOLUTION OF THE HORSE (Equus) Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS

Teeth for grazing

Teeth with bands of hard (enamel) and soft (dentine) material on the crown

Open tooth roots permitting continuous growth

© 2008 Paul Billiet ODWS