Lec 13 Flashcards
Ungulata/Euungulata
unguis = distal most phalanx; covered with keratin sheath
Mammals with hooves
Reduced number of toes
Lengthened foot - Calcaneum doesn’t articulate with the fibula
-Calcaneum is point of attachment for achille’s tendon
Deep groove in astragalus
In both perissodactyla (odd-toed) and artiodactyla (even-toed) astragalus contacts fibula, NOT calcaneum
Differently shaped astragalus
Perissodactyla: Bottom surface flat; single pulley
Artiodactyla: Bottom surface pulley-shaped; double pulley; proximal and distal “saddle”
Order Perissodactyla
Sister to artiodactyla
The “odd-toed ungulates)
Monophyletic group
Mesaxonic condition: Weight of foot just on third digit
-Axis of symmetry of foot: 3rd, or middle, digit
Elongate rostrum with molariform teeth (essentially homodont teeth)
Simple stomach, but large caecum
-Caecum is first part of large intestine that forms line sac; caecum modified fermentation chamber
Perissodactyl Evolution
Arose in late paleocene in Asia (60-56Mya)
-Fossil first found in this time frame
Diversified and spread to Europe and North America by early Eocene
The dominant browsers of the Eocene
Began to decline in Miocene (23-5Mya)
- Climatic changes (dry to ice sheets rising)
- Possibly due to competition from artiodactyls
- Domination of artiodactyls
Family level evoltuion
- Tapiridae evolved in North America in Eocene
- Rhinocerotidae evolved in Eurasia and North America in early Eocene
- -Paraceratherium: largest known land mammal (5m tall; 11,000kg)
- –Historically largest land mammal
- Equidae evolved in North America in early Eocene
Cursorial Specialization
Expanding grasslands favored running adpatations (cursorial = adapted for running)
- Escape predators
- Long migrations to new food sources
Integrated locomotor and respiratory functions
-Synchronize breathing with stride cycles
Slim elongate legs
Running spped determined by:
- Stride length
- Stride rate
Cursorial Specialization: Increase Stride LENGTH
Ways to increase SPEED
Absence of clavicle = scapula free-floating
Shows sternum articulating with humerus
Forelimb moves freely far anterior
1) increase length of limbs
- Metacarpals/metatarsals
- Digits elongate
2) Loss or reduction of clavicle
- Clavicle bridge-like support; prevents from moving forelimb too far in any direction
3) Flexion and extension of spinal column
- Adds 10km/hr to speed of cheetah
Cursorial Specialization: Increase Stride RATE
1) Increase the number of moveable joints
- More joints moving in the same direction = more vectors = faster speed
- 4 joints due to digitigrade/unguligrade posture
- Produces longer leg without increasing limb mass and adds joint that participates in limb swing
2) Only distal-most digits contact the ground
3) Muscles positioned close to body
4) Tendons positioned distally
Ankle joint
- Astragulus rests on distal tarsal bones
- Tarsals modified by loss or fusion of elements
- Weight transferred to central digits
- -Mesaxonis = weight on 3rd digit
- -Paraxonic - weight on 3rd and 4th digits (3 and 4 fused)
Nuchal ligament supports weight of head
Springing ligament in feet
Perissodactyla have ___________ foot symmetry
Mesaxonic
Axis of symmetry is trhough 3rd/middle digit
Artiodactyla have ___________ foot symmetry
Paraxonic
Axis of symmetry is between 3rd and 4th digits
Cannon bone and Springing ligament
Springing ligament: Connects anterior part of hoof with midline of metatarsal
When foot comes up off ground, it’s like releasing band and energy is released
Tendon
Muscle to bone
Ligament
Bone to bone
Feeding Specialization
herbivorous diet
Molariform cheek teeth with large complex occlusal surfaces for efficient grinding
Plant material difficult to digest
- Plants have defensive secondary compounds
- Cellulose in plant cell walls (mammals can’t digest)
Necessary to digest cellulose by means other than enzymatic action
-Co-opted microbes in order to process cellulose; need cellulase to digest cellulose, animals don’t produce this but microbes do
Microbial fermentation necessary
- Slow process
- Requires a fermentation chamber
Perissodactyla use ___________ fermentation
HINDGUT FERMENTATION
-Caecum = expanded colon
Foregut Fermentation
Found in Artiodacyls
Rumination: Complex multichambered stomach
Cellulose digesting microorganisms
1st chamber = rumen-fermentation
2nd chamber = reticulum - forms softened cud
Absoprtion of nutrients in rumen and reticulum
Regurgitation = further breakdown by saliva
Moves through last 2 chambers then intestines
Slow - process less food in a long amount of time
Gain nutrients from digested microorganisms
thorough breakdown
Requires less food
Optimal when there is limited high quality forage
