Appendicular Skeleton Flashcards
what is the point of fins
Fins allow fish to continue on intended line of travel
what do pectoral fins do
increase maneuverability, especially within
vegetation. Can help initiate rising or sinking (sharks).
Gill-arch Theory of the Origin of Pectoral Fins
(Gegenbaur 1870s)
Suggested that the
pectoral girdle arose
from the gill arch &
the primitive
archipterygial fin
arose from the gill ray
Initially based on
anatomy of sharks &
then upon discovery of
Australian lung fish
(1872)
what was the problem with Gill-arch Theory of the Origin of Pectoral Fins
(Gegenbaur 1870s)
How to explain pelvic
fins found distally, the
presence of dermal bone
in the pectoral girdle, the
embryology of the
pectoral girdles and gill
arches
Fin folds in Early Cambrian Agnathan:
Haikouichthys
Fin fold = thickening
of ectoderm
Fin folds in Early Cambrian Agnathan:
Myllokunmingia
Fin fold = thickening
of ectoderm
Ventrolateral fin fold was probably paired
E Jarvisk fin fold theory
scales are the origin of dermal fin rays, fin ray is of dermal origin
F Balfour, J thatcher fin fold theory evidence
examples of pectoral girdles with fin endoskeleton, paired pelvic fins present
haikouichthys, placodermi, ostracoderms
E. Jarvisk–
____ bone in
pectoral girdle
originated in the
___
dermal, skull
Genes involved in Fin/Limb Development - Tbx gene
expressed along body
Genes involved in Fin/Limb Development - Engrailed-1
role in
dorsal/ventral patterning, restricted
to ventral compartment of embryo
Genes involved in Fin/Limb Development - Duplication of Tbx gene
within
ventral zone, Tbx4 and Tbx5
determine identity of paired
appendages
Genes involved in Fin/Limb Development - Acquisition of Shh
promotes
growth away from the body
who has the shh gene
absent in sharks, present in
tetrapods, promotes growth away from the body
Hoxc8, Hoxc6
they are present in areas where there are no limbs, all along python, trunk of chick
Fin rays are called ___ in bony
fishes and ___ in elasmobranchs
lepidotrichia, ceratotrichia
pterygiophores derive from what
mesodermal
dermal fin rays initially form at interface between ____, as do dermal scales, but sink into the ____
dermis and epidermis, dermis
Basals and Radials = name + what are they made of
pterygiophores (cartilage or endochondral bone)
what is lepidotrichai made of
Cartilage or dermal bone rods
whoa has archipterygial fin
Living sarcopterygians
who has metapterygial fins
Rhipidistians, and a few
other bony fish
Primitive structure of pectoral girdle:
Endochrondral bones
* Scapula and coracoid
–Dermal bones (from skull)
* Postemporal, supracleithrum, cleithrum,
clavicle
trend of pectoral girdle over time
Trend over time:
–Loss of some dermal bones: posttemporal,
supracleithrum, and cleithrum
be able to label
Pectoral girdle of Amia–
connected to skull,
partly endochondral, but mostly dermal
Rays of the pectoral fins articulate with a series of ___ bones
which in turn articulate with the ___ and ___
radial, scapula, coracoid
Rays - These bones are attached to the ___ -a large bone firmly
united with body musculature and that is joined to the skull via the
___
cleithrum, supracleithrum
Trend in Pectoral Girdle – loss of some dermal bones (___) – and gain in ___ bone
posttemporal,
supracleithrum, and cleithrum,
endochondral
Australian Lungfish. PG
Dermal pectoral girdle =
cleithrum, clavical, and
postcleithrum. Endo-
skeletal pectoral girdle =
scapulocoracoid.
Pelvic girdle is a single bar.
coelacanth pG
Coelacanth. Dermal
pectoral girdle lacks
interclavicle.
Pelvic girdle is a single bar.
In sharks, fusion of
____ gave
rise to ___
and ___ bars
– fusion of separate
basal girdle elements
across the midline
pterygiophores, scapulocoracoid, pubioschiac
Examples of modified pectoral
fins in actinopterygians
flying fish
Evolutionary Trends of Pelvic Girdle:
Pelvic girdle consists of all
endochondral bones:
–ilium, ischium, and pubic
* Mainly changes in shape and
function
Bothriolepis, a placoderm from the Late Devonian PG
Pelvic girdle is
exclusively
endoskeletal -
never joined by
dermal bone
Fused pelvic bones of birds = the
innominate bone
Pelvic girdle is reduced
in animals that become
___ secondarily
marine
Where can you find pelvic fins in Actinopterygians
Pectoral fin of primitive fish:
basals and radials
Pectoral fin of rhipidistian fish:
humerus, radius, and ulna
plus radials/radialia
Pelvic fin of primitive fish:
basals and radials
Pelvic fin of rhipidistian fish:
femur, tibia, and fibula
plus radials/radialia
Eusthenopteron, Pandericthys, and Tiktaalik are an
example of
Rhipidistians
Tiktaalik– NOTE SHOULDER GIRDLE! Looks very
amphibian-like
Rhipidistian Fish PG and Pectoral girdle
Pelvic girdle not
attached to
vertebral column
Pectoral girdle
attached to skull
Rhipidistian pectoral girdle and fin compared to forelimb
of an early tetrapod (a labyrinthodont)
R; Girdle
attached
to skull
ET: girdle not attache - loss of supracleithrum and postcleithrum, has digits
Acanthostega, Icthyostega, and
Seymouria are an example of
labyrinthodonts
labyrinthodonts
*NOTE Pectoral (not attached to skull) and pelvic girdles (attached to vertebral column).
*Note: Lack of
supracleithrum
and postcleithrum
Embryological and Hox
gene studies support the
view that tetrapod limbs
are built upon the ___ curved around
to produce the ___
along its ___ margin
fish-fin
major axis, digits, posterior
the pandas thumb
elongated wrist bone
More robust limbs and
girdles in primitive
tetrapods, reflecting an
____
increased use of limbs for
terrestrial locomotion
With sprawled limbs, propulsive forces
are transferred more
vertically
