Cranial Topic 8: Appendicular Skeleton Divisions of the ... · Topic 8: Appendicular Skeleton What...
Transcript of Cranial Topic 8: Appendicular Skeleton Divisions of the ... · Topic 8: Appendicular Skeleton What...
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Topic 8: Appendicular Skeleton
� What makes up the appendicular skeleton?
� What is the pattern of serial homology of the limbs?
� Tetrapod front limb morphology
� Tetrapod hind limb morphology
� How do the limbs develop?
� What patterns of evolution have limbs undergone?
� Transition from water to land
� What are some specializations of the limbs?
Divisions of the Skeleton:
Liem et al. Fig. 8-15, 8-18; Dean 1895
� Cranial
� Postcranial
� Axial
� Appendicular
What are the components of
the appendicular skeleton?
Appendicular Components
� _____________� Multiple elements
� In body proper
� _____________� Single long bone
� _____________� Two long bones
� _____________� Many bones
� How have these bones developed?
Modified from Liem et al. Fig. 9-7
Appendicular Components
� Girdle� Variable elements (see later)
� Stylopodium� Humerus
� Femur
� Zeugopodium� Radius & Ulna
� Tibia & Fibula
� Autopodium� Carpals, Metacarpals & Phalanges
� Tarsals, Metatarsals & Phalanges
Liem et al. Fig. 9-10, 9-11
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Limb Development
� Starts with formation of ______________
� What germ layers are involved?
© P Martin; ncbi.nlm.nih.gov
Limb Development
© E Uthman; BioDes; cmrb.eu
� Early formation of ___________ ________________ (AER)
� Zone of cell proliferation
� Zone of differentiation
� Proximal structures develop first
� Zone of _______________ (ZPA)
� Expresses Sonic Hedgehog to define digit polarity
Limb Development
� Fibroblast Growth Factor (FGF)
� Induces AER formation
� Proliferation of Mesoderm
� Formation of digits
� Bone Morphogenetic Protein (BMP)
� Involved in apoptosis
� Noggin gene
� Blocks apoptosis
© BioDes
Limb Development
� Limb element identity
� _____________ expression patterns
� Slight differences between front and hind limbs
Hall, Fig. 7-4
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Limb Development
� Solid line indicates limb axis
� Gene expression data inform us about homology
� Are tetrapod digits homologous to radials or are they neomorphs?
Liem et al. Focus 9-1
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� Front limb differentiation
� Addition of elements
� Increased _____________
of elements
� Evolution of ___________
Liem et al. Fig. 9-5, 9-6, 9-8
Front Limb & Pectoral
Girdle Evolution
Liem et al. Fig. 9-5, 9-9, 9-11
Front Limb & Pectoral
Girdle Evolution
Mammal
� ______________
� Cleithrum, supracleithrum,
interclavicle lost
� Clavicle remains
� ______________
� Scapula and coracoidincrease in size
� Coracoid lost in mammals
� What has happened in terms of what
elements are
involved?
Front Limb & Pectoral Girdle Evolution
Basal Amphibian
Benton 1997 pg 183; Benton Fig 4-2a; Pough et al 2004 Fig 2-2
Panderichthys
Bony Fish
� Separation of front limb &
girdle from the head skeleton
� Why?
Hind Limb Evolution
Liem et al. Fig. 9-4, 9-6, 9-10; Hall 4-3
� Very similar to front limb evolution� Evolution of autopodium
� Evolution of digits
� Increased robustnesss
Pelvic Girdle Evolution
� How does this differ
developmentally from the pectoral girdle?
� Bones are conserved in
position
� _________
� _________
� _________
Liem et al. Fig. 9-4, 9-9, 9-11
Mammal
Pelvic Girdle Evolution
Benton 1997 Fig 3.22; Pough et al 2004 Fig 2-2a
Acanthostega
Protopterus
(African lungfish)
� Transition in articulation of pelvic girdle
� Fishes: ______________
� Tetrapods: solidly articulated with vertebral column
� Why?
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Evolution of Limbs
Transition from water to land
What are the
functional reasons for
each change?
Terrestrial
Obligate Aquatic
What morphological
changes are involved
in this evolutionary
transition?
Evolution of Limbs
What are the
functional reasons for
each change?
What morphological
changes are involved
in this evolutionary
transition?
� �
So, how does the function of front & hind limbs differ?
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Specialization of the Limbs
� Limbs to Fins
� Shortening of stylopodium & zeugopodium
� __________________
� Fusion of digits (not phalanges)
Storrs, 1993
Specialization of the Limbs - Wings
� Digits 1-3 reduced
� Phalanges in digit 4 elongated
� Metacarpal 4 elongated
Liem et al. Fig. 9-12
________ _____ ____
� Loss of digits 1 & 5
� Digits 2-4 reduced
� Carpometacarpus
� Elongation of radius & ulna
� Phalanges & metacarpals in digits
2-5 elongated
� Digit 1 reduced
� Radius elongated
� Ulna reduced
Limb Specializations
� Limb posture and cursoriality
� ______________
� ______________
� ______________
� Fusion of tibia & fibula
� Elongation and fusion of metatarsals
� Fusion of phalanges
& loss of digits
� How does this
improve speed?
� What species have each posture?
© UMMZ
Limb Specializations
� A dog at full gallop with long strides
Liem et al. Fig. 9-14
Limb Specializations
� Human skeletal
adaptations for endurance running
� Narrow waist
� Large vertebral centra
� Relatively short _______
� Large _______________
� Long _______________
� Spring-like ___________
� Short ______________
� Relatively ___________
After Lieberman et al. 2009