cranium

Question 1

Splanchnocranium

Answer 1

Primarily neural crest derived and endochondrally ossifying or cartilaginous

Gill arches and their derivatives

Makes up the hyomandibula, quadrate and articular in bony fish

In mammals, these 3 bones became inner-ear bones

Question 2

Chondrocranium

Answer 2

brain boat

cranial neural crest derived, except occipitals which are mesodermally derived (sclerotomes, homolgous to vertebrae)

Made up of sphenoids, occipitals, otic capsules, and ethmoids (nasal capsules)

endochondrally ossifying

Brain boat and back of head and nose bones and eye sockets

Question 3

Dermatocranium

Answer 3

top of skull and facial bones

dermally ossifying (derived from dermal exoskeletal armor in early vertebrates)

NC & mesodermally derived dermally ossifying elements

Dermal roof, palate, bones encasing the lower jaw.

Question 4

Occipitals

Answer 4

back of the head and connection with vertebrae, paraxial mesoderm and endochondrally ossifying, derived from vertebrae
collectively referred to as occipital arch

Question 5

Occipital condyles

Answer 5

bump(s) on occipital bones that connects the skull to the neck
Mammals and amphibians have two occipital condyles → puts less stress on the spinal cord and reduces the movement at this joint
most tetrapods have 1
paraxial mesoderm (part of occipitals)

Question 6

Sphenoids

Answer 6

Eye capsules
neural crest derived

Question 7

Ethmoids

Answer 7

bones associated with nose capsule
turbinates - spiral
frequently cartilaginous
cribriform plate - Mesh framework where olfactory nerves pass through skull to brain
Turbinates: thin scroll-like bones in the nasal cavity covered with a highly vascularized epithelium
Ethmoturbinates/ olfactory turbinates: associated with increasing surface area for olfaction - very deep in the skull - associated with very good sense of smell (think dogs)
Respiratory turbinates - more front of the cavity, for increasing surface area so air is moistened and warmed before entering the body –> endothermy - keeping inner body temperature warm

Question 8

Otics

Answer 8

associated with ear capsule

Question 9

Splanchnocranium evolution

Answer 9

jawless fish: gill arches
gnathostomes: hyomandibula, quadrate, articular made for a hyostylic flexible jaw for suction
tetrapods - autostylic - upper jaw fused to chondrocranium, hyomandibula free to assume other function → hyomandibula becomes columella or stapes
Mammals: inner ear bone