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Key Points

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

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  1. 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?

  2. Skull - Agnatha • Chondrocranium protects brain & sensory structures • Visceral skeleton – continuous basket with branchial function • Dermatocranium – none to dermal armor, depending on group

  3. Skull - Placoderms

  4. Skull - Placoderms • Chondrocranium • Splanchnocranium • JAWS • Autostylic suspension • Dermatocranium – dermal armor

  5. Skull - Chondrichthyes • Chondrocranium • Calcification • 2 occipital condyles, foramen magnum • Otic and nasal capsules fused to neurcranium • No dermatocranium

  6. Skull - Chondrichthyes • Splanchnocranium • Mandibular arch is the Palatoquadrate and Mandibular (Meckel’s) cartilage • Hyoid arch is the hyomandibula, ceratohyal, basihyal

  7. Skull - Chondrichthyes • Jaw Suspension • Amphistylic, palatoquadrate is partly suspended by neurocranium and partly by hyomandibula

  8. Skull - Chondrichthyes • Jaw suspension • Hyostylic – palatoquadrate attaches to the hyomandibula which, in turn, hangs from the otic capsule

  9. Skull - Chondrichthyes • Jaw suspension • Autostylic in Chimeras

  10. Skull Chondrichthyes • See Visceral arches & derivatives page

  11. Skull – bony fish • Neurocranium • Cartilaginous in some • Ossifies via the four ossification centers in others

  12. Skull – bony fish • Dermatocranium • Complete • Joins to pectoral girdle • Maxilla and Premaxilla support teeth • Numerous bones, overlying neurocranium • Moveable bony operculum

  13. Skull – bony fish • Splanchnocranium • Bony replacement • Quadrate replaces palatoquadrate • Articular replaces Mandibular cartilage

  14. 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)

  15. Key PointsSkull-bony fish • See Visceral Arches & Derivatives page • What do you see as a key change?

  16. Skull - Amphibians • Neurocranium & Dermatocranium • Neurocranium flat • 2 occipital condyles • Not jointed to pectoral girdle

  17. Skull - Amphibians • Splanchnocranium • Larval stages have fish-like gills • Quadrate is upper jaw with autostylic suspension • Articular is lower jaw

  18. 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

  19. 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

  20. Skull - Amphibian • Splanchnocranium • Visceral arch V is no longer needed and becomes the new larynx • Visceral Arch VI and VII are absent

  21. Key Points • Look at Visceral Arches and Derivatives Page. • Name three important evolutionary events with the amphibians.

  22. Skull - Reptiles • Neurocranium • Fewer bones • One occipital condyle • Well ossified

  23. Skull - Reptile • Dermatocranium • Many bones, fewer than bony fish • Temporal region accounts for reptile classification

  24. Temporal Region - Reptiles • Temporal Fossas or Fenestrae • Separated by arches • Infratemporal arch – below ventral fossa • Zygomatic arch = Infratemporal arch • Supratemporal arch – below dorsal fossa

  25. Anapsid • No arch

  26. Synapsid • Infratemporal arch only • Ventral fossa only

  27. Diapsid • Both arches (infratemporal & supratemporal) present • Lizards, crocodiles • May have some modifications in some

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