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Key Points. Name the three parts of the cranium Synonym for dermal bone? What does this mean in terms of development? Synonym for replacement bone? What does this mean in terms of develoment?. Skull - Agnatha. Chondrocranium protects brain & sensory structures
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Key Points • Name the three parts of the cranium • Synonym for dermal bone? • What does this mean in terms of development? • Synonym for replacement bone? • What does this mean in terms of develoment?
Skull - Agnatha • Chondrocranium protects brain & sensory structures • Visceral skeleton – continuous basket with branchial function • Dermatocranium – none to dermal armor, depending on group
Skull - Placoderms • Chondrocranium • Splanchnocranium • JAWS • Autostylic suspension • Dermatocranium – dermal armor
Skull - Chondrichthyes • Chondrocranium • Calcification • 2 occipital condyles, foramen magnum • Otic and nasal capsules fused to neurcranium • No dermatocranium
Skull - Chondrichthyes • Splanchnocranium • Mandibular arch is the Palatoquadrate and Mandibular (Meckel’s) cartilage • Hyoid arch is the hyomandibula, ceratohyal, basihyal
Skull - Chondrichthyes • Jaw Suspension • Amphistylic, palatoquadrate is partly suspended by neurocranium and partly by hyomandibula
Skull - Chondrichthyes • Jaw suspension • Hyostylic – palatoquadrate attaches to the hyomandibula which, in turn, hangs from the otic capsule
Skull - Chondrichthyes • Jaw suspension • Autostylic in Chimeras
Skull Chondrichthyes • See Visceral arches & derivatives page
Skull – bony fish • Neurocranium • Cartilaginous in some • Ossifies via the four ossification centers in others
Skull – bony fish • Dermatocranium • Complete • Joins to pectoral girdle • Maxilla and Premaxilla support teeth • Numerous bones, overlying neurocranium • Moveable bony operculum
Skull – bony fish • Splanchnocranium • Bony replacement • Quadrate replaces palatoquadrate • Articular replaces Mandibular cartilage
Skull – bony fish • Splanchnocranium • Arch II is not branchial in function • Hyomandibula + others • Five branchial arches • Hyostylic suspension (ray-finned fish) • Amphistylic suspension (Crossopterygians) • Autostylic suspension (Dipnoans)
Key PointsSkull-bony fish • See Visceral Arches & Derivatives page • What do you see as a key change?
Skull - Amphibians • Neurocranium & Dermatocranium • Neurocranium flat • 2 occipital condyles • Not jointed to pectoral girdle
Skull - Amphibians • Splanchnocranium • Larval stages have fish-like gills • Quadrate is upper jaw with autostylic suspension • Articular is lower jaw
Skull - Amphibians • Hyomandibula is no longer needed since the jaw has an autostylic suspension • It is freed up and becomes a rudimentary stapes called the columella
Skull - Amphibian • Splanchnocranium • The rest of Arch II plus arches III and IV are no longer needed and become the Hyoid apparatus for tongue support
Skull - Amphibian • Splanchnocranium • Visceral arch V is no longer needed and becomes the new larynx • Visceral Arch VI and VII are absent
Key Points • Look at Visceral Arches and Derivatives Page. • Name three important evolutionary events with the amphibians.
Skull - Reptiles • Neurocranium • Fewer bones • One occipital condyle • Well ossified
Skull - Reptile • Dermatocranium • Many bones, fewer than bony fish • Temporal region accounts for reptile classification
Temporal Region - Reptiles • Temporal Fossas or Fenestrae • Separated by arches • Infratemporal arch – below ventral fossa • Zygomatic arch = Infratemporal arch • Supratemporal arch – below dorsal fossa
Anapsid • No arch
Synapsid • Infratemporal arch only • Ventral fossa only
Diapsid • Both arches (infratemporal & supratemporal) present • Lizards, crocodiles • May have some modifications in some