Zusammenfassung der Ressource
17 - Perissodactyla
Anmerkungen:
- large, hoofed, terrestrial herbivores
- walk around on tips of toes
- hard, KERATINIZED hooves
- limbs move in single plane because of pulley-like ASTRAGALUS in ankle
- cursorial locomotion
- usually HYPSODONT dentition
- morphology and life histories typically suited for open habitats
- efficient feeding and outrunning predators
- ungulate distribution limited by forage
- morphology of forage the result of pressures of ungulates over evolutionary time
- ungulates = the most IMPORTANT group of mammals to humans for commerce and economics
- domestication, sport hunting, ecotourism
- perissodactyls today much LESS diverse than artiodactyls
- a switch from 50 mya, when they far outnumbered smaller, less diverse artiodactyles
- MONOPHYLETIC group
- 3 families, 6 genera, 16 species
- horses, asses, zebras, tapirs, rhinos
- formerly much more DIVERSE
- oldest identifiable perissodactyl fossils from late Paleocene (55 mya)
- characteristics
Anmerkungen:
- adapted to UNGULIGRADE (hoofs) CURSORIAL locomotion
- clavicle ABSENT
- group defined by FOOT structure
- odd-toed ungulates
- only ONE functional digit on each foot, weight borne on middle digit - the LARGEST
- tapirs with 4 digits on front, 3 on hind, 3 on each in rhinos, 3rd digit the only one on HORSES
- cannot bend hindlimbs enough to get up hindfeet first when laying on ground
- elongate skull with long ROSTRUM
- large molars and premolars, typically HYPSODONT and LOPHODONT for grazing lifestyle
- diastema between incisors and cheekteeth
- no true HORNS or ANTLERS
- rhino "horn" lacks bony core and keratinized sheath; a dermal mass of agglutinised, keratinized fibers (fused hairs)
- evolutionary/fossil
history
Anmerkungen:
- arose in late PALEOCENE in Asia
- Rhinos evolved in Eurasia and North America in early Eocene
- largest known land mammal = PARACERATHERIUM (5 meters tall, 11,000 kg)
- tapirs evolved in North America in EOCENE
- dominant browsers of Eocene
- began to decline in Miocene (climatic changes, competition with artiodactyls)
- horses evolved in North America in early EOCENE
- cursorial
locomotion
adaptations
Anmerkungen:
- integrated LOCOMOTOR and RESPIRATORY functions
- synchronize breathing with stride cycles
- tracheal valving shunts air from side to side between lungs
- slim, elongate legs
- muscles positioned near body
- tendons DISTALLY
- long legs
- metacarpals and metatarsals elongate
- LOSS or REDUCTION of clavicle
- FLEXION and EXTENSION of spine
- increase number of moveable joints in limb
- only hoof-bearing TIPS of digits contact ground
- ASTRAGALUS rests on distal tarsal bones
- tarsals modified by loss or fusion of elements
- weight transferred to central digits
- SPRINGING ligament in feet
- NUCHAL ligament supports weight of head
- feeding specializations
Anmerkungen:
- herbivorous
- simple stomach, but large CECUM for microorganism-facilitated breakdown of cellulose
- molariform cheek teeth with large complex occlusal surfaces
- food retained shorter period than for ruminant artiodactyls
- less efficient and must consume LARGER amounts than ruminants
- economics
&
conservation
Anmerkungen:
- horses domesticated ~4,500 years ago in Central Asia
- second only to CATTLE in importance to human development or cultural and economic systems
- travel, exploration, warfare, agriculture
- domestic horses doing VERY WELL (introductions)
- other perissodactyls in trouble (human interference, poaching rhino horns, habitat destruction)
- African ass and quagga recently extinct
- Onager, Przewalski's horse, Grevy's and mountain zebra endangered
- mountain tapir endangered
- all rhinos endangered or vulnerable
- families
- Equidae
Anmerkungen:
- most species are HIGHLY social
- form herds and/or clans
- polygynous mating system
- social hierarchy - led by DOMINANT stallion
- HAREMS formed in some species
- bachelor species
- complex behavior and vocal communication
- fission-fusion social system common
- Tapiridae
Anmerkungen:
- Stocky build (weigh up to 320 kilograms)
- short, flexible (proboscis)
- limbs short and stout
- 4 toes on front, 3 toes on hind feet
- brachyodont cheek teeth
- nasal bones of skull RETRACTED - above orbits
- Rhinocerotidae
Anmerkungen:
- large, heavy-bodied, short-legged
- graviportal limbs
- weigh up to 2,800 kg
- 3 or 4 toes on front foot, 3 toes on hind foot
- nasal bones THICKENED and enlarged
- supported horn of dermal material
- use of horns in traditional Eastern "medicine" and more recently sprinkled in alcoholic cocktails
- $75,000 per kg (twice the value of gold)
- 90% decrease in number of wild rhinos today compared to 1970
- critically threatened - 35 Javan rhinos, ~100 Sumatran, and <5,000 black rhinos
- near threatened - ~20,000 white rhinos
- vulnerable - as few as 600 greater one-horned rhinos in 1976, increased since then