Axial Skeleton Skull

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Axial Skeleton - Skull

• Neurocranium
• Dermatocranium
• Splanchnocranium

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Dermatocranium

• Phylogeny membrane bone which evolved from
  dermal armor
• Roofing bones
• Along side and above brain

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Roofing Bones

• Nasal
• Frontal
• Parietal
• Orbital
• Lacrimal
• Jugal Infraorbital Zygomatic
• Squamosal

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• Look at the Skull Lower Jaw components page.
  Examine the roofing bones.

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Upper jaw

• Premaxilla
• Maxilla

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Lower Jaw

• Dentary - largest
• Splenial small, dorsomedial
• Surangular - lateral
• Angular medial, becomes typanic bulla
• Coronoid medial
• Prearticular medial caudal becomes anterior
  malleus in mammals

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Key Points

• Look at upper and lower jaw dermatocranium bones
  on Skull Lower Jaw Components page
• Give an example of homology.
• What trend do you see in lower jaw evolution?

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Primary Palate Bones

• Roof of oropharyngeal cavity in fish, amphibians
• Roof of nasal cavity in amniotes

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Primary Palate

• Vomer
• Palatine
• Pterygoid

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Primary Palate

• Examine Skull Lower Jaw Components page

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Dermatocranium

• Operculum

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Key Point

• Describe dermatocranium bones in the shark

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Axial Skeleton - Skull

• Neurocranium
• Dermatocranium
• Splanchnocranium Visceral skeleton

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Splanchnocranium

• Supports allows movement of jaws, gill, tongue
• Associated with hearing
• Ancient in evolution
• Replacement bone

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Splanchnocranium

• Typically 6 gill slits between
• Visceral arches
• A typical visceral arch that is gill in function
  has five segments
• Pharyngobranchial
• Epibranchial
• Ceratobranchial
• Hypobranchial
• Basibranchial

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Splanchnocranium

• Mandibular arch Visceral Arch I
• Palatoquadrate
• Mandibular Meckels Cartilage

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Splanchnocranium

• Hyoid arch Visceral arch II
• Hyomandibula
• Ceratohyal
• Basihyal

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Interrelationships

• The neurocranium, dermatocranium and
  splanchnocranium eventually becomes intimately
  associated to form one single, firm skull

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Key Point Describe the origin of jaws from this
picture
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Key Point

• The three main components of the cranium are