VIII. APPENDICULAR SKELETON
A. Definition –Appendages and supporting girdles
B. PECTORAL GIRDLE
1. Function
2. Replacement bones
a. Coracoid
b. Epicoracoid
c. Scapula
d. Suprascapula
3. Membrane bones
a. Clavicle
b. Cleithrum
c. Supracleithrum
d. Postcleithrum
e. Posttemporal
f. Interclavicle
g. Episternum [tetrapods]
4. Glenoid fossa of scapula
5. Trends
6. PLACODERMS
7. CARTILAGINOUS FISH
a. Completely cartilage
b. Dermal elements absent
c. Coracoid, scapula, suprascapula (scapulacoracoid)
d. Not connected to axial skeleton –Fused at midline
8. BONY FISH
a. Membrane bones
1. Clavicle – not most holeosts & teleosts –Interclavicle in a few
2. Cleithrum, supracleithrum, postcleithrum
3. Posttemporal – anchors to skull
b. Replacement bones –Ossifies & unites in most teleosts
1. Coracoid
2. Scapula
9. AMPHIBIANS
a. Membrane bones
1. Reduced
2. Lose posttemporal
3. Early amphibians gain interclavicle as an internal brace
b. Replacement bones
1. Coracoid
2. Scapula & Suprascapula
c. Urodeles [necturus] – no membrane bones, no clavicle
d. Anurans – no interclavicle, have clavicle, usually lack cleithrum
10. REPTILES
a. Stem reptiles & Synapsids
1. Many membrane bones present
2. Most replacement bones present
3. New posterior coracoid
b. Modern Reptiles have scapula, coracoid, sometimes a clavicle, sometimes an interclavicle
c. Crocodiles
-Clavicle decreased or absent
d. Turtles
-Acromion process, clavicle (inter) fused with shell
e. Snakes
-No girdle
f. Lizards
-Clavicle, (Only group of reptiles with significant clavicle) Interclavicle
11. BIRDS
a. Furcula (2 clavicles + interclavicle)
b. Scapula –Bladelike; parallel to spine
c. Coracoid (anterior or procoracoid) –Articulates with sternum
12. MAMMALS
a. Monotremes –Similar to stem reptiles
b. Clavicle –In most
c. Scapula
1. Coracoid process –(Posterior coracoid)
2. Spine
3. Acromion process –Ventral, articulates with clavicle; Not unique
B. PELVIC GIRDLE
1. Function
2. Ilium, Pubis, Ischium – Tetrapods
3. Innominate or Coxal bone when three bones are fused into one
4. Acetabulum, Symphysis, Pelvic cavity
5. Replacement bone
6. FISH
a. Pelvic plate –Often very anterior
b. Pelvic symphysis
7. AMPHIBIANS
a. Pubis
-Cartilage pelvic plate
b. Ilium
-long and slanted in frog
c. Ischium
8. REPTILE
-Sacroiliac joint – Stronger & broader for muscle attachment and stability
9. BIRDS
-Synsacrum – No Symphysis, very wide ilium, braced against vertebrae
10. MAMMALS
Unique epipubic bone spans from the pubis to ventral body wall to support pouch in marsupials
C. FINS
1. Function –Steering, rolling, braking, stabilizers, forward & vertical movement
2. Structure
a. Skin
b. Fin Rays –In dermis
1. Lepidotrichia– Bony dermal scales; segmented
2. Ceratotrichia– “Horn hairs”‘; cartilaginous unsegmented rays
c. Skeletal base-Cartilaginous or bony
1. Pterygiophores– “Bearing fins”
a. Basals
b. Radials
3. Paired fins
a. Agnathans
b. Placoderms & Acanthodians –Experimented with fins
c. Chondrichthyes
-Fin fold fins – Very broad base
d. Bony fish
1. Actinopterygii
-Ray finned – Very flexible, thinner base
2. Sarcopterygii –Fleshy muscular base
a. Dipnoi – lobe fins
b. Crossopterygii
-Lobe fins – Fringe fins, radial pterygiophores on only one side of fin axis
-Ancestor of limbs
e. Origins –From Acanthodians, from fleshy folds?
4. Dorsal and Anal Fins = Median Fins
a. Function –Rolling, defense, display
b.Location
c. Dorsals may artic. with vert. column
d. Variations
5. Caudal fins
a. Heterocercal –Sharks with larger dorsal lobe
b. Hypocercal– Ichthyosaurs with larger ventral lobe
c. Diphycercal– Cyclostomes & Dipnoans with equal lobes
d. Homocercal
1. Teleosts
2. Neural & Hemal arch for support
3. Bony sheath for notochord {=urostyle}
D. LIMBS
1. Origin
a. Crawl –Crawling in swampy areas, bottom dwellers, escaping predators to the shore
b. Crossopterygians vs labyrinthodonts
2. Function and Trends
a. Locomotion
1. Axial for fish
2. Appendicular for tetrapods
b. Support
1. Limbs under body
2. Elevate body
c. Functional diversification distally
d. Decreased # bones
3. Structure
a. Propodium
1. Upper arm [humerus]
2. Thigh [femur]
b. Epipodium
1. Forearm [radius & ulna]
2. Leg/shank [tibia & fibula]
c. Mesopodium
1. Wrist [carpals]
2. Ankle [tarsals]
d. Metapodium
1. Palm [metacarpals]
2. Instep [metatarsals]
e. Phalanges– Digits
f. Manus –Forefoot; mesopodium, metapodium, phalanges
g. Pes –Hindfoot; mesopodium, metapodium, phalanges
h. Epiphysis and Diaphysis –Ends and Shaft of long bone
4. AMPHIBIANS
a. Cartilage epiphyses
b. Cartilage carpals/tarsals
c. Marrow cavity
d. # digits
5. REPTILES
a. Epiphysis
b. Pisiform –New mesopodial bone
c. Phalanges 2,3,4,5,3; 2,3,4,5,4
6. BIRDS
a. Epiphysis
b. Digit #2 –Longest in wing of 3 digits
c. Phalanges 2,3,4,5,0
7. MAMMALS
a. Epiphyses –Bony
b. Pisiform
c. Phalanges 2,3,3,3,3
d. Prominent Olecranon Process –Mammal characteristic on Ulna
8. Development and Growth
a. Length
b. Diameter