Origin of Paired Appendages

1
Origin of Paired Appendages

• Gill Arch Hypothesis
• Fin Spine Hypothesis
• Fin Fold Hypothesis

2
Basic Anatomy of the Tetrapod Limb
Proximal
Middle
Distal
3
Origin of the tetrapod limb Crossopterygian
4
Pectoral Girdle of Bony Fish
Site of articulation
Dermal bones Clavicle Cleithrum Supracleithrum Po
sttemporal
Endochondral bones Scapula Coracoid plate
5
Pectoral girdle of early Amphibians
Dermal components -loss of supracleithrum -loss
of post-temporal -loss of connection to
skull Clavicle, cleithrum retained New
interclavicle
Endoskeletal Retained/expanded
New element
6
Pectoral girdle of some Reptiles and the
Prototherians
Dermal components -loss of cleithrum -clavicle
retained -interclavicle retained
Endoskeletal -Coracoid appears in rear of
coracoid plate -scapula persists
7
Stem reptile
Pelycosaur
Mammal
8
The Human Clavicles                              
                                            
Menu
The human collar bone arches from the scapula
to the sternum
9
Evolution of the Pectoral Girdle
10
Pelvic girdle of tetrapods
Dermal components NONE!
Endoskeletal Pubis Ischium Ilium
Anchored to vertebral column
(socket)
Anterior
Posterior
11
Reptilian spraddle-legged position
Mammalian stance
12
Limbs functional adaptations
bird
crossop
amphibian
human
bat
dog
whale
13
Modifications of forelimbs for flight
4th digit of hand
4
1
2
Forearm and hand
(digits 2-5 elongated)
3
4
5
1
Forearm and hand
(1-3 metacarpals and Phalanges elongated)
2
3
14
Pelvic girdle can be reduced/lost
Whale skeleton
Sea cow (manatee) skeleton