Key Points

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

5. Skull - Placoderms

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

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

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

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

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

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

18. Skull Chondrichthyes • See Visceral arches & derivatives page

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

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

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

25. 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)

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

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

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

32. 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

34. 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

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

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

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

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

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

46. Anapsid • No arch

48. Synapsid • Infratemporal arch only • Ventral fossa only

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