PERISSODACTYLA Mammalogy EEOB 625 3 March 2004

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PERISSODACTYLAMammalogy EEOB 625 -3 March
2004

• The Origin Adaptive Radiation of Ungulates
• Order Condylartha dominant "Ungulates of the
  Paleocene
• Ancestral to Perissodactyla, Artiodactyla,
• Subungulates and
  Cetacea
• Coevolution of Ungulates with
• Food Woody plants, forbs, and grasses
• Predators Arms race of size speed

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Coevolutionary Factors in the Adaptive Radiation
of Ungulates

• Climate Change in the early Cenozoic
• Progressive cooling drying of continents
• Loss of forests expansion of prairies
• Grasses Origin (Oligocene) and radiation
• Anti-grazing defenses of grasses
• - growth from the base, near the roots
• - silica in the cell wall increases the
• cost of mastication

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Adaptations for Cellulose Digestion

• Plant anatomy Cell wall, cell membrane, and
  cytoplasm with protein carbohydrates
• Dental adaptations for mastication of cell walls
  and lignified plant structures
• 1) the hypsodont (high crowned) molar,
• ever growing or rootless in some
  species
• 2) Selenodont occlusal surface a rasping,
  
• grinding surface, highly resistant to
  wear
• Digestive Adaptations Cecum rumen

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Evolution of the hypsodont molar
hypsodont
bunodont selenodont
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Ungulate Adaptations for Locomotion

• Selection for mass, mobility, speed
• Determinants of speed
• length of stride rate of striding
• Adaptations for long stride
• - lengthening of metacarpals metatarsals
• - free swing of the scapula
• - flexible vertebral column

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Ungulate Adaptations for Locomotion

• Determinants of running speed
• length of stride rate of striding
• Adaptations for high stride rate
• - reduction of mass of distal limb elements
• - cannon bone springing ligament
• - short lever arms for high gear muscles
• - summing velocities of many limb segments

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Power vs Speed of Movement
Cheetah
Badger
Lever arm ratios (R) m joint to insertion l
joint to ground
m
10 cm
m
6 cm
Badger R 0.4
l
15 cm
l
50 cm
Cheetah R 0.2
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Cannon bone Springing ligament
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PERISSODACTYLA A clade defined by the
mesaxony,

• Mesaxonic? Weight-bearing axis through digit 3
• Early descendants of Condylartha
• Eocene radiation, decline in late Oligocene
• Evolution of the horse in N. America
• A classic phylogeny, but what is wrong with
  this picture?
• Trends and misconceptions regarding equid
  evolution Compare Text Figs.

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Mesaxonic For meso i.e., middle
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PERISSODACTYLA Systematics

• Mesaxonic ?
• Early descendants of Condylartha
• Eocene radiation, decline in late Oligocene
• Evolution of the horse in N. America
• Three Extant families
• Equidae, Tapiridae Rhinocerotidae

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J.Z. Young
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Fig. 19.2, Feldhamer
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Fig 19.4,Feldhamer