1. PERISSODACTYLA Mammalogy – 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

2. 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

3. 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

4. Evolution of the hypsodont molar
bunodont selenodont

5. 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

7. 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

8. 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

10. Cannon bone & Springing ligament

11. 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.

12. Mesaxonic
For “meso”
i.e., middle

13. 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

14. J.Z. Young

15. Fig. 19.2, Feldhamer

16. Fig 19.4,Feldhamer