chapter 17 (sarcopterygians) Flashcards
what is a sarcopterygian?
lobe-finned fishes. COSMOID SCALES. 2 dorsals (unlike actinoperygian fishes)
cosmoid scales
layer of cosmine, thin hard layer of enamel, inner layer of spongy vascular bone, deep layer of lamellar bone. also, dentine
do lungfishes have cosmoid scales?
no.
how does the lobed fins connect to more primitive fishes?
similar to the branching arrangement still embedded in the fins of paddlefishes, sturgeons and sharks.
2 primary groups of sarcopterygian fishes
crossopterygians :coelacanths
dipnoi :the lungfishes
when did coelacanths first appear in history?
the Devonian period, “age of fishes”
other than lobed fins, what are the two combinations of characteristics for coelacanths?
large TRI LOBED TAIL (diphycercal tail)
an INTRACRANIAL JOINT (skull bens backwards!)
who found the first coelacanth in ‘38?
Margaret Latimer
who tried to steal the fame for the first discovered coelacanth?
JLB Smith
which dude is a major player in coelacanth research?
Hans Fricke
what are further characteristics found in LATIMERIA?
lungs (fat-filled sac)
bone much reduced
spiral valve
osmoregulation (retention of urea) THINK SHARKS
uniqure characteristics of the coelacanth
rostral organ (snout): electrosensory system intracranial joint: head swing upwards
early dipnoi:
bony skeletons, heterocercal or diphycercal tail, heavy armor of thick cosmoid scales
late dipnoi:
dramatic reduction in bones, loss of the outer layer of scales, reduction in skull bones, loss of distinct fins, including tail.
modern lungfish are characterized by:
air breathing lungs cartilaginous skeleton internal nostrils plate like teeth spiral valve intestine
what can be said of fw preference and distribution in lungfishes?
evidence of continental break up since they’re fw. (africa and s. america distribution)
why is Sir Richard Owen famous?
declared the lungfish a fish instead of an amphibian
Edward Cope:
crossopterygians must be the sister group of tetrapods
3 reasons why coelacanths have perhaps labyrinthodont linkage:
paired fins more like tetrapod than lungfish
bones of crossopterygians, particularily cranial, like labyrinthodonts
crossopts have specialized tooth structure like labs.
rosen said three points on that lungfish gave rise to tetrapods
- internal nostrils
- tetrapod like limbs
- tetrapod like locomotion
