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Axial Skeleton - Skull. Neurocranium Dermatocranium Splanchnocranium. Dermatocranium. Phylogeny – membrane bone which evolved from dermal armor Roofing bones Along side and above brain. Roofing Bones. Nasal Frontal Parietal Orbital Lacrimal Jugal = Infraorbital = Zygomatic Squamosal.
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Axial Skeleton - Skull • Neurocranium • Dermatocranium • Splanchnocranium
Dermatocranium • Phylogeny – membrane bone which evolved from dermal armor • Roofing bones • Along side and above brain
Roofing Bones • Nasal • Frontal • Parietal • Orbital • Lacrimal • Jugal = Infraorbital = Zygomatic • Squamosal
Look at the Skull & Lower Jaw components page. Examine the roofing bones.
Upper jaw • Premaxilla • Maxilla
Lower Jaw • Dentary - largest • Splenial – small, dorsomedial • Surangular - lateral • Angular – medial, becomes typanic bulla • Coronoid – medial • Prearticular – medial & caudal – becomes anterior malleus in mammals
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?
Primary Palate Bones • Roof of oropharyngeal cavity in fish, amphibians • Roof of nasal cavity in amniotes
Primary Palate • Vomer • Palatine • Pterygoid
Primary Palate • Examine Skull & Lower Jaw Components page
Dermatocranium • Operculum
Key Point • Describe dermatocranium bones in the shark…
Axial Skeleton - Skull • Neurocranium • Dermatocranium • Splanchnocranium – Visceral skeleton
Splanchnocranium • Supports & allows movement of jaws, gill, tongue • Associated with hearing • Ancient in evolution • Replacement bone
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
Splanchnocranium • Mandibular arch = Visceral Arch I • Palatoquadrate • Mandibular = Meckel’s Cartilage
Splanchnocranium • Hyoid arch = Visceral arch II • Hyomandibula • Ceratohyal • Basihyal
Interrelationships • The neurocranium, dermatocranium and splanchnocranium eventually becomes intimately associated to form one single, firm skull
Key Point • The three main components of the cranium are: