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Appendicular Skeleton

Appendicular Skeleton. Includes all of the following: limbs or fins pectoral girdle pelvic girdle. Pectoral Girdles. Primative Condition: 3 pairs of endochondral replacement bones (coracoid, scapula and suprascapular)

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Appendicular Skeleton

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  1. Appendicular Skeleton Includes all of the following: • limbs or fins • pectoral girdle • pelvic girdle

  2. Pectoral Girdles Primative Condition: • 3 pairs of endochondral replacement bones (coracoid, scapula and suprascapular) • 4 pairs of dermal investing bones (clavicle, cleithrum, supracleithrum, posttemporal)

  3. Modern Teleosts • cleithrum becomes major bone of pg • clavicle is lost • scapula and coracoid become smaller and/or • fuse to form a coracoscapula

  4. Early Tetrapods • similar to bony fish with… • loss of the posttemporal and… • gain of an interclavicle Modern Tetrapods • supracleithrum and cleithrum are reduced then lost… • interclavicle and clavicle (dermal) and • coracoid and scapula (endochondral) remain.

  5. What happens to the remaining bones??? • Interclavicle: absent in amphibians, persists in reptiles, birds and lower mammals. • Clavicle: absent in amphibians (except frogs) and some reptiles. Present in birds and mammals. • Coracoids: replace clavicle in lower tetrapods. absent in mammals except for coracoid process. • Scapula: present in all tetrapods. Forms the glenoid fossa which allows articulation with humerus.

  6. Pelvic Girdles • Ischiopubic plates in fish • Plates in amphibians ossify to form pubis and ischium. • Additional ossification center forms the ilium • These bones ankylose to form innominate bone

  7. Acetabulum forms at junction of these 3 bones, • Tetrapod ilium articulates with transverse processes of sacral vertebrae forming sacroiliac joint. • Pubic symphysis in all vertebrates except birds • Obturator foramen between ischium and pubic bones transmits obturator nerve and associated blood vessels

  8. Fins and Limbs

  9. Fins • serve as steering, stabilizing and inclination devices • composed of two integumental surfaces reinforced by dermal fin rays resting on a base of cartilage • dermal elements are lepidotrichia (bony fish) or ceratotrichia (cartilaginous fish) • actinotrichia are distal elements in both groups • pterygiophores form the skeletal base

  10. Paired fins brace against a girdle.3 Categories: • Lobed fins - fleshy proximal region, distal membranous component reinforced by fin rays - Dipnoans • Fin fold fins - broad base - cartilaginous fish • Ray fins - reduction of basal elements with increased flexibiity - bony fish (actinopterygians)

  11. Median finsAct as keels to prevent rolling • Several median fins may be present including median dorsal fin and midventral anal fin. • Anal fins may be modified as gonopodia (claspers)

  12. Caudal finsClassified by direction of terminal notochord • Heterocercal - notochord turns upward - modern sharks. • Diphycercal - little bending of notochord - Dipnoans. • Homocercal - notochord turns dorsally - bony fish.

  13. Tetrapod LimbsVarious modifications for locomotion 5 basic skeletal elements in all limbs: • propodium - proximal element - humerus/femur • epipodium - forelimb elements - radius/ulna or tibia/fibula • mesopodium - carpal/tarsal bones • metapodium - metacarpals/metatarsals • phalanges - digital bones of fingers and toes

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