Skulls - Components, jaws

Question 1

Function of branchial arches III-VII in most fish

Answer 1

Support gills

Question 2

Who has modified hyostyly?

Answer 2

Actinopterygii

Question 3

What does the splanchnocranium form?

Answer 3

7 branchial arches & their derivatives (jaws, middle ear bones)

Question 4

What feeding method do actinopterygiians use?

Answer 4

Suction feeding

Question 5

Embryonic origin of splanchnocranium

Answer 5

Neural crest cells (-> cartilage, ossifies in most teleostomi)

Question 6

Describe branchial arches III-VII

Answer 6

Made of 5 pieces (usually)

Question 7

Precise functions of dermatocranium

Answer 7

• Cover chondrocranium & brain (dorsal, ventral)
• Cover & protect gills (opercular bone)
• Cover parts of jaw splanchnocranium

Question 8

Describe modified hyostyly

Answer 8

Quadrate: Articulation point of upper jaw, not fused to chondrocranium
Articular: Articulation point lower jaw
Hyomandibula & symplectic bone: suspend jaws from chondrocranium
-> Many joints = highly kinetic (suction feeding)

Question 9

Describe paleostyly

Answer 9

All branchial arches used to support gills; no jaws

Question 10

Lower jaw bone in teleostomi

Answer 10

Dentary (encases Meckel’s cartilage except for ossified back portion; part of dermatocranium)

Question 11

General function of dermatocranium

Answer 11

Form hard, protective structures

Question 12

Function of branchial arches III-VII in amniotes

Answer 12

Form cartilage around trachea & larynx

Question 13

Who has a dermatocranium?

Answer 13

Teleostomi (Osteichthyes, Tetrapods, not Agnathans, Chondrichthyes b/c no bone)

Question 14

Who has paleostyly?

Answer 14

Agnathans

Question 15

Adaptations of actinopterygiian skull to feed by biting prey

Answer 15

2° loss of cranial kinesis by bone fusion to provide strength

Question 16

Upper jaw bones of teleostomi

Answer 16

Premaxilla, maxilla (dermatocranium)

Question 17

Embryonic origin: chondrocranium

Answer 17

Neural crest cells, mesodermal mesenchyme

Question 18

Describe Autostyly

Answer 18

Palatoquadrate: Upper jaw, fused to chondrocranium
Meckel’s cartilage: lower jaw
Hyoid arch: gill support

Question 19

Embryonic origin & final tissue type: Dermatocranium

Answer 19

Mesenchyme from dermatome epimere mesoderm -> Dermal bone

Question 20

Who has hyostyly?

Answer 20

Most sharks

Question 21

Describe metautostyly

Answer 21

Quadrate (upper) and articular (lower) form jaw joint; quadrate fused or articulates w/ chondrocranium; II -> columella in middle ear (not for jaw suspension)

Question 22

Who has craniostyly?

Answer 22

mammals

Question 23

Describe adaptations of actinopterygiian skull for suction feeding

Answer 23

1. Maxilla connected loosely to chondrocranium & lower jaw (rotates forward as jaw opens)
2. Premaxilla connected loosely to maxilla (can be projected forwards faster)
3. Chondrocranium rotates at spinal connection (rises as lower jaw drops)
4. Hyoid apparatus: struts in buccal cavity floor, pulled perpendicular to push out lateral walls as mouth opens
   => Creates suction

Question 24

How does hyostyly affect feeding?

Answer 24

Allows jaws to swing forwards to open wider & for teeth to contact prey at same time (good for grabbing slippery prey)

Question 25

Regions of brain protected by chondrocranium

Answer 25

All vertebrates: ventral, lateral, posterior | Agnathans & chondrichthyans: dorsal (-> forms entire braincase)

Question 26

Chondrocranium tissue type

Answer 26

Cartilage: initially, all; remains in agnathans, chondrichthyes Bone (replacement): teleostomi

Question 27

Who has metautostyly?

Answer 27

Amphibians, sauropsids

Question 28

Who has autostyly?

Answer 28

Holocephali (ratfish), dipnoi (lungfish)

Question 29

Describe hyostyly

Answer 29

Palatoquadrate: Upper jaw, not fused to chondrocranium Meckel's cartilage: lower jaw Hyomandibula: Forms swinging bridge attaching jaw to chondrocranium -Spiracle: reduced pharyngeal slit between mandibular & hyoid arches

Question 30

Describe amphistyly

Answer 30

Palatoquadrate: upper jaw, held to chondrocranium by ligament Meckel's cartilage: lower jaw Hyomandibula: stabilizes back of palatoquadrate, also gill support

Question 31

3 components of the skull

Answer 31

Chondrocranium, splanchnocranium, dermatocranium

Question 32

Describe craniostyly

Answer 32

``` Entire upper jaw fused to chondrocranium Dentary (lower) articulates with squamosal (upper) Jaws entirely dermatocranium I & II in middle ear Quadrate -> Incus Articular -> Malleus Hyomandibula -> Stapes ```

Question 33

Who has amphistyly?

Answer 33

6-gilled sharks