Post on 31-Mar-2015
Appendicular Skeleton
Appendages and supporting girdles
Pectoral Girdle
Function
Pectoral Girdle – Replacement bones
Coracoid(Epicoracoid)ScapulaSuprascapula
Pectoral Girdle – Membrane bones
ClavicleCleithrumSupracleithrumPostcleithrumPosttemporalInterclavicle(Episternum in tetrapods)
Pectoral Girdle
Glenoid fossa on scapula for limb attachment
Key Point
What trend do you see as you look at the overview of pectoral girdles?
Pectoral Girdle - Placoderms
First to have a pectoral girdle
Pectoral Girdle - Chondrichthyes
CartilageNo dermal elementsCoracoid, scapula, suprascapula
(scapulacoracoid)Not connect to axial skeleton, but fused at
midline
Pectoral Girdle – Bony fish
Membrane bonesClavicle, some have interclavicleCleithrum – largestSupracleithrum, postcleithrumPosttemporal – anchors to skull
Pectoral girdle – bony fish
Replacement bones CoracoidScapula
Pectoral Girdle - amphibians
Membrane bonesReducedLose posttemporalEarly amphibians gained an interclavicle as
a brace
Pectoral Girdle - amphibians
Replacement bonesCoracoidScapula and suprascapula
Pectoral Girdle - amphibians
Urodeles have no membrane bones, including clavicle
Anurans have clavicle, no interclavicle and usually no cleithrum
Pectoral girdle - Reptiles
Stem reptiles & synapsidsMany membrane bones presentMost replacement bones presentNew posterior coracoid present
Pectoral girdle - Reptiles
Modern reptiles have scapula, coracoid, sometimes clavicle, sometimes interclavicle
Crocodiles have reduced clavicleTurtles have interclavicle fused with shellSnakes have no girdleLizards have a significant clavicle and
interclavicle
Pectoral Girdle - birds
Furcula (2 clavicles plus interclavicle)Scapula – bladelikeCoracoid (anterior or pro-) which articulates
with sternum
Pectoral Girdle - mammals
Monotremes similar to stem reptilesClavicle in mostScapula
– Coracoid process from posterior coracoid– Spine is new– Acromion process articulates with clavicle (not
new)
Pelvic Girdle
Stability, encloses pelvic cavity organsIn tetrapods, it has three parts called the
ilium, pubis and ischiumWhen these three bones fuse into one, the
fused bone is the innominate or coxal boneAcetabulum is the socket for the thighSymphysis in all but birdsReplacement bone
Pelvic Girdle - Fish
Pelvic plate or symphysis
Pelvic Girdle - amphibians
PubisIlium (long & slanted in frog)Ischium
Pelvic Girdle - Reptile
Sacroiliac joint is stronger and broader for more muscle attachment and stability
Pelvic Girdle - birds
Synsacrum – Ilium is braced against fused vertebrae
No symphysis WHY??
Pelvic girdle - mammals
Epipubic bone in marsupials is unique for pouch support
FINS
Steering, rolling, braking, stabilizers, forward & vertical movement
Fin structure
Skin epidermis coveringFin rays in dermis
– Lepidotrichia (scale-hair) bony dermal scales, segmented
– Ceratotrichia (horn-hair) cartilaginous unsegmented rays
Fin Structure
Skeletal base (cartilage or bone) for supportPterygiophores (bearing fin)Basals are proximalRadials are distal
Paired Fins
Absent in agnathansSome in placoderms & acanthodiansChondrichthyes
– Fin Fold Fins – very broad based
Paired Fins
Bony fishActinopterygii has ray fins, very flexible
with thin baseSacrcopterygii has fleshy muscular base
– Dipnoi has lobe fins– Crossopterygii has lobe fins that are called
fringe fins & have pterygiophores on one side of fin axis
Osteichthyes skeletonOsteichthyes skeleton
Pelvic finPectoral fin
Caudal fin
Dorsal fins
Anal fin
Origins of fins
From acanthodian spines?From fleshy folds?From gills?
Median fins – Dorsal and Anal fins
Dorsal and Anal Fins
Function for rolling, defense, displayLocation – rests on vertebral columnVariations among groups
Caudal fins
HeterocercalHypocercalDiphycercalHomocercal
– Teleosts– Neural and Hemal arch for support– Bony sheath for notochord
Pelvic finPectoral fin
Caudal fin
Dorsal fins
Anal fin
Fish tailsHeterocercal
HomocercalDiphycercal