Skull

• composite structure with three distinct parts:
• - splanchnocranium
• - chondrocranium
• - dermatocranium

most ancient portion, which arose to protect and support pharyngeal arches in protochordates

found underneath the brain; underlies and supports the brain; can be made up of cartilage or bone

in more advanced vertebrates; forms the outer covering of brain

means brain case; ossified strcture (usually, not in chondrichthyes); it’s the covering (top, sides, and bottom—the splancho, chondro, and dermato..) plus the associated sensory capsules

beneath and supports the brain

In most vertebrates (bony fish onward), the chondrocranium is primarily an embryonic structure; and, as an embryonic structure, it serves as a scaffolding for the developing brain and also as a support for the sensory capsules

- As it forms and then starts evolving (disappearing), the brain uses it to develop

Portions that remain become partly/ entirely ossified

In chondrichthyes, the chondrocranim expands and envelopes the brain to become the protective walls and roof

• it is the skeleton of the pharyngeal arches
• - the number of skeletal structures and arches varies depending on the organism

• fish: gives rise to skeleton of the jaws and pharygeal arches
• tetrapods: modified greatly for new structures

they support the mouth

The first is the mandibular: it is the largest and most anterior of the series of arches and is composed of palatoquadrate (dorsal) and Merkel's cartilage (ventral)

The second is the hyoid arch: Its most prominent element is the hyomandibular cartilage 

A number of arches (3 onward) are given in roman numerals

• Bony fish: the palatoquadrate (caudal ends) becomes the quadrate bone
• The remainder become the palatine and pterygoid bone
• Merkel's cartilage becomes the articulate bone in fish

It essentially becomes three bones

There are a lot of modifications because the gills don't remain in tetrapods

• 1st arch: pterygoquardrate--> quadrate
• In mamals, the quadrate becomes the incus of the middle ear 
• Merkel's:
• - reptile: becomes ensheathed by dermal bones (remains but is coered)

- Birds and mammals: there are few or no remnants in the adult

• 2nd arch: hyoid arch with hyomandibular cartilage
• - in sharks, it is retained and found between the quadrate and the otiocapsule (capsule of the ear)
• Sharks are not tetrapods

In tetrapods, it ossifies to become the stapes or columellar (ear bone)

• Arches III-V give rise to hyoid apparatus, which is located high in neck region; doesn't articulate with anything
• function: anchor the tongue adn serves as attachment for muscles of the larynx nd muscles that aid in swallowing

• sharks: comes from mandibular cartialge (some from first arch)
• bony fish: the mandibular cartialge is reinforced by a series of dermal bones
• tetrapods: it arises from one of the most anterior of the gill arches

consists of bones that form the roof and contribute to the lateral walls of the skull

also forms boens of the upper jaw, bones of the palate, and the operculor bone

there is a tendency for a loss or fusion of bony elements--> skull is reduced and simplified in terms of number of bones

the dermatocranium becomes the predominant structure of the brain case and teh lower jaw, consisting of many series of dermal bones

it does not exist in adult cartilaginous fish

• facial
• orbital
• temporal
• vault
• palatal

• presence or lack thereof of bones in the temporal bones
• - anapsid: no holes  (turtles)
• - synapsid: one hole (mammals)
• - diapsid: two holes (crocodiles and lizards)

upper and lower temporal openings; above and below the post-orbital squamosal bone

defined as the movement of one or more cranial bones independent of others

faciliate acquisition of food; they can take in prey that are much larger than their mouth or head region if they can move

• intercranial joints
• teleosts, lizards, snakes, and birds
• crocodiles, frogs, salamanders, and mammals