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Equine biology > evolution > Flashcards

evolution Flashcards

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1
Q

roles of equids in society

A

food source, spiritual symbols, warfare, hunting, work, transport, sport, companions

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2
Q

horse taxonomy: class

A

mammalia

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3
Q

family

A

equidae

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4
Q

genus

A

equus

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5
Q

domestic breeds are

A

Equus caballus

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6
Q

equus asinus

A

african wild ass

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7
Q

equss burchelli

A

east african zebra

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8
Q

equus grevyl

A

grevy’s zebra of east africa

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9
Q

equus zebra

A

south african zebra

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10
Q

equus kiang

A

asian ass

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11
Q

equus hemionus

A

middle eastern/asian ass

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12
Q

equus przewalski

A

last truly wild horse

-from Mongolia

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13
Q

last common ancestor of domestic and przewalski

A
  1. 5 million years ago

- no genomic evidence of prze mixing with domestic, so they retain their genetic diversity

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14
Q

accurate picture of horse evolution

A
  • not a straight line
  • different traits evolved at different rates; not always evolving together and occasionally reversed
  • development was not always gradual either
  • ancestors did co-exist
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15
Q

adaptations: digits

A

from 4 to 1 central digit, adapted for running on hard ground, receiving impact of their heavier bodies, and for kicking predators

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16
Q

adaptations: long, crowned, hard teeth

A

-adapted for grazing on fibrous/tougher vegetation found on open, dry plains

17
Q

adaptations: fossae

A

a depression or hollow point of skull, allowing for greater jaw muscle strength

18
Q

adaptations: brain

A

larger cerebral hemispheres

19
Q

hyracotherium (“eohippus”)

A
  • 54-34 mya
  • north american small forest animal
  • looked like “a dog”
  • ate fruit and soft foliage
  • 4 digints in front, 3 on back (1-2 vestigal digits)
20
Q

epihippus

A
  • 47 mya
  • teeth change to allow for tougher food intake
  • some premolars more like molars for grinding
21
Q

mesohippus and miohippus

A
  • medium sized browsers/grazers
  • late eocene, oligocene: climate of NA gets drier, grasses evolving and forests shrinking
  • larger, taller, less doglike, longer faces, 3 digits, horse brain develops
  • 6 grinding teeth
22
Q

Plains horses: grinders

A

-crests on teeth enlarged and connected together in series of ridges for grinding
-hypsodont teeth: teeth keep growing and must be worn down through use
cement layer on teeth made them harder

23
Q

plains horses: runners

A
  • increase body size, leg length
  • 1 digit in some
  • muscles and legs specialized for forward and back strides
  • standing on tips of digits with springy ligaments on central phalanx
24
Q

parahippus and merychippus

A

17 mya

  • 3 digits
  • radius and ulna FUSED so leg rotation is eliminated
  • fibula greatly reduced
  • eyes moved further back to accomodate large tooth roots
  • larger brain
25
Q

merychippene radiation

A

miocene

  • 19 new grazing horse species in three major groups:
    1. hipparions
    2. protohippines
    3. merychippines (3 and 1 digits horses)
26
Q

1 digit horses

A

-late miocene, pliocene, and pleistocene

pliahippus, hipparion, and dinohippus

27
Q

pilohippus

A

similar to modern horse

28
Q

hipparion:

A

3 digits, grazers and browsers, spread from new to old world

29
Q

dinohippus

A

common in NA, probably gave rise to modern Equus

  • 1 digit with side ligament to prevent twisting
  • long nose
  • high crowns, straight grazing teeth with crests lined with cement
30
Q

old equus

A

common ancestor 4.5 mya

  • 12 species, coexisting with hipparions, protohippines, and astohippus
  • pony sized, 1 digit
31
Q

Splint bones

A
  • metacarpals 2 and 4 are usually vestigial “splint bones” around large central 3rd digit
  • rarely, modern equus can be born with small but fully formed side toes
32
Q

spread of equus

A
  • major glaciations of late piocene (2.6 mya) allows species to cross to
  • africa, creating zebras
  • asia, mideast, and N Africa as desert-adapted onagers and asses
  • asia, mideast, and europe as the true horse E. Caballus
  • south america
  • other species died out, with Equus surviving
33
Q

extinction 10,000 years ago

A

removed equus from Americas

-no definitive reason, could have been due to changes in environment, disease, or overhunting by humans

34
Q

other existing relatives:

A

rhinoceroses and tapirs

Equine biology (16 decks)

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