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 Squamosal Lacrimal Jugal = Infraorbital = Zygomatic Squamosal

Look at the Skull & Lower Jaw components page 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 Describe the origin of jaws from this picture

Key Point The three main components of the cranium are: