Appendicular Skeleton Appendages and supporting girdles

Pectoral Girdle Function

Pectoral Girdle – Replacement bones Coracoid (Epicoracoid) Scapula Suprascapula

Pectoral Girdle – Membrane bones Clavicle Cleithrum Supracleithrum Postcleithrum Posttemporal Interclavicle (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 Cartilage No dermal elements Coracoid, scapula, suprascapula (scapulacoracoid) Not connect to axial skeleton, but fused at midline

Pectoral Girdle – Bony fish Membrane bones Clavicle, some have interclavicle Cleithrum – largest Supracleithrum, postcleithrum Posttemporal – anchors to skull

Pectoral girdle – bony fish Replacement bones Coracoid Scapula

Pectoral Girdle - amphibians Membrane bones Reduced Lose posttemporal Early amphibians gained an interclavicle as a brace

Pectoral Girdle - amphibians Replacement bones Coracoid Scapula 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 & synapsids Many membrane bones present Most replacement bones present New posterior coracoid present

Pectoral girdle - Reptiles Modern reptiles have scapula, coracoid, sometimes clavicle, sometimes interclavicle Crocodiles have reduced clavicle Turtles have interclavicle fused with shell Snakes have no girdle Lizards have a significant clavicle and interclavicle

Pectoral Girdle - birds Furcula (2 clavicles plus interclavicle) Scapula – bladelike Coracoid (anterior or pro-) which articulates with sternum

Pectoral Girdle - mammals Monotremes similar to stem reptiles Clavicle in most Scapula Coracoid process from posterior coracoid Spine is new Acromion process articulates with clavicle (not new)

Pelvic Girdle Stability, encloses pelvic cavity organs In tetrapods, it has three parts called the ilium, pubis and ischium When these three bones fuse into one, the fused bone is the innominate or coxal bone Acetabulum is the socket for the thigh Symphysis in all but birds Replacement bone

Pelvic Girdle - Fish Pelvic plate or symphysis

Pelvic Girdle - amphibians Pubis Ilium (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 covering Fin rays in dermis Lepidotrichia (scale-hair) bony dermal scales, segmented Ceratotrichia (horn-hair) cartilaginous unsegmented rays

Fin Structure Skeletal base (cartilage or bone) for support Pterygiophores (bearing fin) Basals are proximal Radials are distal

Paired Fins Absent in agnathans Some in placoderms & acanthodians Chondrichthyes Fin Fold Fins – very broad based

Paired Fins Bony fish Actinopterygii has ray fins, very flexible with thin base Sacrcopterygii 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 skeleton Dorsal fins Caudal fin Pectoral fin Anal fin Pelvic 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, display Location – rests on vertebral column Variations among groups

Caudal fins Heterocercal Hypocercal Diphycercal Homocercal Teleosts Neural and Hemal arch for support Bony sheath for notochord

Dorsal fins Caudal fin Pectoral fin Anal fin Pelvic fin

Fish tails Heterocercal Diphycercal Homocercal