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2604771
17 - Perissodactyla
Descripción
(Final Exam) Mammalogy Mapa Mental sobre 17 - Perissodactyla, creado por nicolepridemore el 27/04/2015.
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mammalogy
final exam
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nicolepridemore
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nicolepridemore
hace alrededor de 9 años
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Resumen del Recurso
17 - Perissodactyla
Nota:
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
Nota:
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
Nota:
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
Nota:
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
Nota:
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
Nota:
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
Nota:
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
Nota:
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
Nota:
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
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