1. Skull and Visceral Skeleton
Neurocranium
Dermatocranium
Splanchnocranium:
Palatoquadrate cartilage and replacement bone
Meckel’s cartilage and replacement bone
Skeleton of the branchial arches

3. Neurocranium Primary braincase protects brain
arises as cartilage, which...
is replaced by bone
similar development in all vertebrates

4. Formation
Paired prechordal (neural crest) and parachordal (lat. plate mesoderm) cartilage. Also cartilage around olfactory, otic and, sometimes, optic capsules

5. Parachordal cartilage unites to form basal plate and joins otic capsules
Prechordal cartilage unites to form ethmoid plate and joins olfactory (and optic) capsules

6. Further development involves:
formation of walls
a cartilaginous tectum (lower vertebrates)
fenestra and foramina for passage of blood vessels

7. Cartilaginous Neurocrania in Adult Vertebrates
Cyclostomes: individual components more or less independent throughout life
Cartilaginous fish: union of components to enclose brain forming the chondrocranium
Lower bony fish: cartilaginous neurocranium persists; overlain with dermal bone (chondrosteans and holosteans)

9. Ossification Centers in Neurocranium
Occipital: 4 areas around the foramen magnum
Sphenoid: under midbrain and pituitary - forms sphenoid
Ethmoid: ethmoid plate and olfactory capsules. Tends to remain cartilaginous in adults as cribiform plate.
Otic: several bones form (prootics, opisthotic, epiotics form petrosal). Petrosal fuses with squamosal to form the temporal bone

10. Dermatocranium Membrane bones of the skull which may have originated in bony dermal armor of the ostracoderms
In modern vertebrates, formation from subdermal mesenchyme of neural crest and lateral plate mesoderm rather than dermal mesenchyme
Basic structural elements: roofing bones of the neurocranium, marginal bones of upper jaw, bones of primary palate and opercular bones

11. Roofing bones: nasal (N), frontal (F), parietals (P) and dermooccipitals (DO)

12. Orbit of eye: lacrimal (lac), prefrontal (PF), postfrontal (PoF), postorbital (PO) and jugal.

13. Posterior angle of skull: intertemporal (IT), supratemporal (ST), tabular (Tab), squamosal (Sq) and quadrojugal (Qj)

14. Marginal bones of upper jaw: premaxillae (Pre) and maxilla

15. Primary palatal bones: volmer (1), palatines (2), ectopterygoid (3), pterygoid (4) and parasphenoid (5)