Appendicular Skeleton Flashcards
Pelvic girdle attachment in osteichthyes
Suspended
Describe limb movement in jumping
Hindlimbs extend rapidly to launch into air, forelimbs extend to cushion landing
Type of joint between pelvic girdle & hind limbs of tetrapods
Ball and socket (allows wide range of motion)
Effect of sprawled posture on girdles
Forces go up and in (medial), so large ventral girdle bones
Girdle composition in chondrichthyes
Cartilage
Pelvic girdle attachment in chondrichthyes
Suspended
Changes from sarcopterygiian to tetrapod girdles
- Became stronger, more completely ossified
- Thin fin rays -> thick digits
- Pectoral girdle detached from skull
- Pelvic girdle fused to sacral vertebrae
Advantages of terrestrial tetrapods having forward-pointing digits
Increased tractive (pulling) and propulsive (pushing) forces
Components of terrestrial limb locomotion during walking/running
Propulsion: contact ground, push/pull body forwards
Recovery: don’t contact ground, bring limb back to propulsive position
Pectoral girdle composition in teleostomi
Dermal & replacement bone
Which pelvic girdle bone in tetrapods fuses to the sacral vertebrae?
Ilium
Use of sarcopterygiian fins
Highly maneuverable -> propulsion, pivoting, supporting some weight
2 types of terrestrial tetrapod limb posture
Sprawled (to sides) - many amphibians & sauropsids
Erect (limbs beneath body)
What is included in the appendicular skeleton?
Paired appendages & supporting girdles
Describe pelvic girdle of birds & reasoning
3 bones fuse into innominate bone; provides stability in flight & strength to withstand forces of landing
Pectoral girdle attachment in chondrichthyes
Suspended in body wall muscle
Advantages of erect limb posture
Recovery stroke is efficient pendulum-swing (cursorial movement) -> sagittal plane movement only
Describe fin support in jawed fish
Proximal: Sturdy elements
Distal: Fin rays
Bones of pelvic girdle in tetrapods
Ilium, ischium, pubis
Pelvic girdle composition in teleostomi
Replacement bone
Why would tetrapods have sturdier, more ossified girdles than sarcopterygiians?
Better to support weight and locomotion
Effect of erect limb posture on girdles
Forces directed upwards, so strong dorsal pectoral girdle (scapula) vs small ventral girdle (clavicles)
Advantages of sprawled limb posture
Retain lateral undulation -> good for swimming
Function of paired fins in sharks & why
Provide stability (against pitch, roll, yaw) b/c stiff & inflexible Adjust angle for steering
Advantages of thick digits of tetrapods over sarcopterygiian thin fin rays
better grip, better weight support, sturdier
Describe pectoral girdle attachment in tetrapods & reasoning
Axial skeleton suspended like a sling by muscles; acts as shock absorber so landing/impact doesn’t transmit forces to skull & brain
Why are distal regions of jawed fish fins supported by fin rays?
Allow control over surface area of fin hitting water
Benefits of detaching pectoral girdle from cranium in sarcopterygii -> tetrapods
Head moves independently
Pectoral girdle at better angle (digits can point forwards instead of splaying outwards)
Brain not jarred on each step
Disadvantages of sprawled limb posture
Recovery stroke requires slow, expensive over-arm swing (dorsal/ventral movement as well as anterior/posterior)
What’s special about male sharks’ pelvic girdles?
Have long claspers to transfer sperm for internal fertilization
Function of pelvic & pectoral girdles
Brace, support paired appendages & provide attachment sites for the muscles controlling them
Describe pectoral girdle structure in tetrapods compared to osteichthyans
Smaller dermal bone components (clavicles)
Larger replacment bones (scapulas, procoracoid, coracoid)
Function of actinopterygiian fins & why they can do this
Steer, balance, propel
-flexible & mobile -> can execute precise maneuvers, but doesn’t provide speed
Pectoral girdle attachment in osteichthyes
Fused to vertebral column & sometimes also to skull
Benefits of fusing pelvic girdle to sacral vertebrae in tetrapods
More efficient transfer of energy from hindlimb propulsion to vertebral column via girdle
Describe adaptation of pectoral girdle in birds
Clavicles fuse into furculum; acts as spring to make flight & breathing more efficient
