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Compatative anatomy
Appendicular skeleton
Question | Answer |
---|---|
anterior | pectoral girdle supporting pectoral fin or limb |
posterior | pelvic girdle supporting pelvic fin or limb |
ostracoderms | no paired appendages.pectoral "spikes","lobes","folds"(keep orientation in h2o).non mobile.no skeleton associated with them. |
what are the 2 theories for the origin of paired fins | gill arch theory(not really) says that gills got modified but there is no evidence.fin fold theory says that flabs of tissue get bone associated with them. |
placoderms | first paired appendages.skeleton associated with them therefore true appendages."prints" of muscle therfore mobile(places for muscle attachment).bony or cartilage fin rays. |
fin skeleton(bony fish) | basal pterygiophores(proximal).radial ptergiophored.fin rays(distal)-ceratotrichia in shark.lepidotrichia in bony fish."trichia"-thread |
fish girdles | pelvicsmall- and not attached to vert.pectoral is large and attached to head.dermal components form directly as bone are the clavicle,cleithrum,supracleithrum,post-temporal.replacement bones(from cartilage precursors)are the coracoid,scapula,suprascapula |
sarcopterygii | basals and radials line up into the fin and homologies with tetrapod limbs are clear.muscles are no longer in bony wall.muscles extend down into the fin. |
tetrapod pelvic girdle | 3 bones,fused(innominate bone) invlude ilium,ischium,pubis.trend toward firmer attachment to vert column via sacrum. |
tetrapod pectoral girdle | dermal bone less important(lighter).replacement bone(endochondral) more important.connection of pectoral girdle to skull is broken leads to cervical vert. |
trend | early appendicular skeleton is dermal.increase in subdermal elements;loss of dermal bone.ex humans only have one dermal bone in appendicular skeleton(clavicle) |
fish appendages | uniform because they only swim.varied number of bone in limb. |
tetrapod appendages | varied function.uniform structure(same bones). |
fish to amphibians | tiktaalik to labyrinodont.fins to limbs.amphibians have weak limbs,splayed to side.lateral swimming movements. |
reptiles | stronger limbs and girdles.most have splayed stance.some have legs under body(rotate elbow to increase stride)-synapsid,thecodonts,dinosaurs |
birds and mammals | specialization birds(fly,swim,run),fast running,reduction of digits,bears are plantigrade. |
tetrapod trends | reduction in number of limb elements(frogs fused radioulna,tibiofibular;birds tibiotarsus,loss of digits in deer,horse,rhino).disproportionate lengthening of limb elements(bat fingers,horse foot). |
sub axial flexion | limbs held more under the body then splayed to the side |
alteration of foot does what? | lengthens limb |
plantigrade | heal,wrist touch ground.primitive:humans and bears. |
digitigrade | walk with heal and wrist above ground:cat and dog |
unguligrade | walk on toe tips.can be even or odd toed.horse(1) deer(2). |
perissodactyl | horse and rhino.odd # |
artiodactyl | deer.even # |
evolution of flight | to help escape predators,to help catch prey,move efficiently,free hind legs for use as weapons,to gain access to new food sources or an unoccupied niche.**3 separate lineages |