The Skull And Appendicular Skeleton

Question 1

what is the splanchnocranium?

Answer 1

bones etc of the throat and lower mouth
arose to support pharyngeal slits in protochordates

Question 2

what is the chondrocranium?

Answer 2

cartilage of the skull
supports the brain

Question 3

what is the dermatocranium?

Answer 3

cells that form the dermis
‘outer casing’ and dermal bones of skull

Question 4

what is dermal bone formation?

Answer 4

‘intramembranous’ ie from mesenchyme via osteoclasts etc
osteoblast deposition superficially
eg: jaw, gills, scapula, most flat bones

Question 5

what is endochondral bone formation?

Answer 5

cartilage (chondrocranium) replaced by bone
eg: most of the postcranial internal skeleton

Question 6

what is the function of the splanchnocranium in vertebrates?

Answer 6

supports gills via branchial arches
attachment points for respiratory muscles

Question 7

what is the function of the splanchnocranium in gnathostomes?

Answer 7

contributes to formation of jaws and hyoid apparatus
supports mouth and functional gills (interposed with pharyngeal slits)

Question 8

give examples of bones of the splanchnocranium

Answer 8

hyomandibula, meckel’s cartilage, brancial arches

Question 9

give examples of the bones of the chondrocranium

Answer 9

sensory capsules, occipitals, ethmoid

Question 10

give examples of the bones of the dermatocranium

Answer 10

orbital, pre/maxilla, nasal, quadrate, jugal, temporal…

Question 11

what are the major bones that are found around the fenestrae of skulls?

Answer 11

quadratojugal
jugal
squamosal
parietal
postorbital

Question 12

what is different about the bones associated with the jaws of birds?

Answer 12

they are greatly reduced

Question 13

what are some common trends with synapsid skulls?

Answer 13

heterodont teeth
many bone fusions/losses
temporal-dentary jaw joint

Question 14

what bones make up the pectoral girdle?

Answer 14

scapula
(cleithrum)
coracoid
clavicle

Question 15

what bones make up the forelimb?

Answer 15

humerus
radius
ulna
carpals
metacarpals
phalanges

Question 16

what bones make up the pelvic girdle?

Answer 16

ilium
pubis
ischium

Question 17

what bones make up the hindlimb?

Answer 17

femur
(patella)
tibia
fibula
tarsals
metatarsals
phalanges

Question 18

what are some trends seen in tetrapod evolution?

Answer 18

• reduction/ simplification of the pectoral girdle (reduction of coracoids/ clavicles)
• changes in digit numbers
• development of sesamoid bones (tendon anchoring bones)

Question 19

what are some trends seen during the evolution of the pectoral girdle?

Answer 19

• loss of cliethrum/ gill parts (= head mobility)
• high variations in clavicle
• reduction/ loss of the interclavicle
  domination of the scapula

Question 20

what are some trends seen during the evolution of the pelvic girdle?

Answer 20

• divergence and enlargement of the three bones
• caudal rotation of the pubis
• opening of the hip socket
  -overall is more conservative than pectoral girdle

Question 21

what are some adaptations of the mammalian design?

Answer 21

• enlarged pectoral girdle
• erect posture (parasaggital gait)
• dorsoventricular flexibility in vertebrae

Question 22

describe continuum in the context of autopodial posture?

Answer 22

the straightening of the distal joints (like the posture of ungiligrades)

Question 23

what are some tradeoffs with the different types of autopodial postures?

Answer 23

plantigrades = stable base, shorter stride length
unguligrade = less stable base, longer stride length. lighter distal limb = easy to swing = faster locomotion

Question 24

what are some limb adaptations which can increase speed and efficiency?

Answer 24

• upright posture/ longer distal limbs
• larger proximal muscles, longer distal tendons
• larger levels ie of the carpals/tarsals
• vertebral dorso-ventral flexibility