L4 Mills - Form and Function in Placentals 2 - locomotion Flashcards
What are antlers?
Outgrowths of frontal bone from the skull
Describe the structure of antlers
Vascularised core with a velvet cover on. Mature antlers - loss of velvet which reveals bone core, vascular part no longer functional
What kind of horns do sheep and goats have?
no lobes
bone and keratin
What kind of horns do rhinos have?
entirely keratin
not paired - midline of nose
What kind of horns do giraffes have?
Ossicones
- no true horn
- instead they have an ossified cartilaginous growth that is covered in skin
What are the 3 primary roles that horns evolved?
- sexual display
- jousting in males
- social recognition
What is the hypothesis of why horns evolved?
The development of horns is correlated with the change from Miocene forest to grassland, which caused a decline in food quality therefore animals want to protect their territory
What kind of animals have:
a) Plantigrade feet
b) Digitigrade feet
c) Unguligrade feet
a) beavers, bears, rodents, shrews
b) dogs, rabbits, foxes
c) pigs, horses, zebras
What is the structure of each:
a) Plantigrade feet
b) Digitigrade feet
c) Unguligrade feet
a) Plantigrade: all of feet bones on the ground, with flexion at the wrist/ankle
b) Digitigrade feet: metatarsals/carpels suspended, this creates another extension element in the limb - spring/more power/ acceleration
c) Unguligrade feet: walk on their terminal phalanges and hooves support their weight. Extremities move via tendons, heavy proximal and little distal musculature
What does it mean when an ungulate is Perissodactyla?
odd-toed ungulates
- tapirs (3), rhinos (3), horses (1)
What does it mean when an ungulate is Artiodactyla?
Even toes ungulates
- hippopotamus, pigs, cervidae, bovidae
What is meant when an animal is Graviportal? which animal is one?
Elephants have massive column like limb bones, to resist crushing under their great body weird - creates an even pressure
Larger herbivorous dinosaurs e.g. Diplodocus
What are the 2 hypothesises for why cursorial herbivores evolved
H1: an evolutionary arms race between predators and prey
- pursuit carnivore mammals only appear in Pliocene (5mya), long after long-legged ungulates do
H2: low productivity of grasslands replaced highly productive woodlands, requiring wider ranging to obtain food
- Cursorial ungulates appear at these times on each separate landmass:
Oligocene (30mya) in S.America
Early Miocene (20mya) in N.America
Late Miocene (10mya) Eurasia
Which hypothesis is circumstantial evidence in support of?
H2 rather than H1
What are fossorial adaptions?
burrowing animals with very special limbs:
- short massive limbs
- specialised claws and teeth (Hypselodont)
- mole, gopher, mole rat
