1. THE EVOLUTION OF THE HORSE (Equus)
Przewalski's horse (Equus ferus przewalski) © WWF-Canon / Hartmut JUNGIUS
© 2016 Paul Billiet ODWS

2. 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
© 2016 Paul Billiet ODWS

3. Equus 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
© 2016 Paul Billiet ODWS

4. Trends in the evolution of the horses
Increased size
Reduced number of toes and longer legs
A stiffer back
Merychippus
20Ma
Equus
© 2016 Paul Billiet ODWS

5. Teeth for grazing Larger teeth and a larger skull to hold them
© 2016 Paul Billiet ODWS

6. Teeth for grazing
Teeth with bands of hard (enamel) and soft (dentine) material on the crown
Open tooth roots permitting continuous growth
© 2016 Paul Billiet ODWS

7. 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.
© 2016 Paul Billiet ODWS

8. From ladders to bushes
Equus
Pliohippus
Merychippus
Mesohippus
Hyracotherium
(aka Eohippus)
Orohippus
The view of evolution in Darwin’s day was that of Gradualism
One species slowly transforming into another
© 2016 Paul Billiet ODWS

9. From ladders to bushes
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
© 2016 Paul Billiet ODWS

10. © 2016 Paul Billiet ODWS