37 Questions
Which digit was enlarged and developed in the horse during its evolution?
Third digit (median)
What structural change in the horse's limbs aided in faster running?
Lengthening of limbs and perfection of hoof
Which bone reduction in the hind limb contributed to the horse's evolutionary adaptation?
Reduction of the fibula and strengthening of the tibia
What significant locomotion change occurred in horse evolution?
From digitigrade to unguligrade
Which skull trait developed to support a larger brain in horses?
Increase in size and complexity of the brain
To which order do horses belong?
Perissodactyla
Which genus includes horses, zebras, and asses?
Equus
During which epoch did the very first horse evolve?
Eocene
Which category of the scientific classification does 'Chordata' refer to for horses?
Phylum
Which animals are included in the order Perissodactyla along with horses?
Rhinos and tapirs
Which of the following horse ancestors existed 60 million years ago?
Hyracotherium
Which horse ancestor was slightly larger than Eohippus and had 3 toes?
Mesohippus
Which horse ancestor had a single toe that developed into a hoof and could run faster?
Merychippus
What is the earliest known ancestor of the horse?
Hyracotherium
Which horse ancestor lived on grasslands approximately 5 million years ago?
Pliohippus
During which geological epoch did Mesohippus live?
Oligocene
Which horse ancestor is characterized by having four toes well spread for walking on soft ground?
Hyracotherium
How many toes did the front feet of Eohippus have?
Four
Which feature is common in the modern horse Equus?
Single hoof
Which of the following ancestors of the horse is known for having lived between 23 and 2 million years ago and was well adapted to grasslands?
Hipparion
Which characteristic is true of Mesohippus?
Had six grinding cheek teeth with a premolar in front
What was the main function of the toes of Eohippus?
To keep the feet off the ground and bear the animal's weight
Which ancestor of the horse still survives today in a wild form similar to Equus but with distinct features?
Przewalski horse
Which statement is true about the dentition of Eohippus?
They had low-crowned and low-cusped teeth for soft vegetation
What evolutionary change is evident in Mesohippus compared to Eohippus?
Elongation of face, snout, and neck
Approximately how tall was Eohippus?
14 inches
Which evolutionary stage of the horse had longer legs and neck compared to other species?
Eohippus
Which horse species lived during the Miocene Epoch about 30 million years ago?
Merychippus
What feature made Pliohippus's teeth better suited for eating grass?
Teeth became better fitted for eating grass
Which evolutionary stage of the horse was an effective grazer and runner?
Merychippus
Which stage of the horse evolution had three toes on each foot where the middle toe was long and useful?
Merychippus
During which epoch did Pliohippus live?
Pliocene
Which prehistoric horse is considered directly linked to the genus Equus?
Pliohippus
In what regions have fossils of Pliohippus been found?
Great Plains of the US and Canada
What significant change occurred in the horse's body modification during its evolution?
Increased in size and height
Which characteristic distinguishes Equus from its predecessor Pliohippus?
Does not have a dished face
What are some uses of the modern-day horse, Equus, that continue from 3000 years ago?
Travel
Study Notes
Early Evolution of Horses
- Eohippus (50 million years ago): small, 4-toed, lived in forests, about the size of a cat or a dog, with an arched back and snout-like nose
- Eohippus had a dentition adapted to feed on soft vegetation, with 4 toes on the front feet and 5 toes on the hind feet, with the 1st and 5th toes not touching the ground
- Hyracotherium (60 million years ago): the ancestor of the horse, with a similar size and characteristics to Eohippus
Evolutionary Stages
- Mesohippus (35 million years ago): slightly larger than Eohippus, with 3 toes, and a stronger middle toe
- Merychippus (10 million years ago): larger, with a single toe, and a hoof, lived on grasslands
- Pliohippus (5 million years ago): single-toed or hooved, with strong leg ligaments for increased speed and power, and a dished face
- Equus (present): the modern horse, evolved from Pliohippus, with a single hoof, long legs, and a fast runner
Key Characteristics
- Increase in size and height over time, from rabbit-like to 6-feet grassland animal
- Lengthening of limbs and perfection of hoof for fast running in grasslands
- Enlargement and development of the 3rd digit (median) and reduction of the lateral digits
- Reduction of the ulna (fore) and fibula (hind) and strengthening of radius and tibia
- Change from digitigrade to unguligrade locomotion for fast running
Body Modifications
- Increase in size and height, from rabbit-like to 6-feet grassland animal
- Development of the hooves and leg ligaments for increased speed and power
Evolution
- Evolution means change, a dynamic process full of twists, transitions, and dead ends (extinctions)
- Result of genetic adaptation to environmental changes
- Horses belong to the order Perissodactyla, the odd-toed ungulates, which includes horses, rhinos, and tapirs today
Scientific Classification of Horse
- Kingdom: Animalia
- Phylum: Chordata
- Class: Mammalia
- Order: Perissodactyla
- Genus: Equus, which includes horses, zebras, and asses
This quiz covers the early evolution of the horse, from Eohippus to Equus, including the stages of development and the characteristics of each horse ancestor.
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