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Appendicular Skeleto
Comparative Vertebrate Anatomy
| Question | Answer |
|---|---|
| Fins | -Help stabilize and maneuver the body when in motion -Fin girdles stabilize the fins and serve as muscle attachment points |
| Pterygiophores | Basals (articulate with girdle) and radials (articulate with basals) |
| Fin Rays | Articulate with radials Likely modified scales |
| Ceratotrichia | Slender filaments of keratin like protein Type of fin ray Ex:// Elasmobranchs |
| Lepidotrichia | Series of tiny cartilaginous or bony elements Type of fin ray Ex:// Osteichthyans |
| Gill-Arch Hypothesis | Paired fins are modified gill arches. Specifically, the girdle arose from the gill arch and the pterygiophores arose from gill rays. Issues: -Pelvic fins are distally placed from the gill arches -Pectoral girdle has components made of dermal bone |
| Fin-fold hypothesis | Paired fins are derived from ventrolateral folds in the body wall. Girdles were later formed by fusion of basals on each side and across the midline |
| Archipterygical fin | Symmetric midline axis -Radials project anteriorly (preaxial) and posteriorly (postaxial) -Likely derived and present in sarcopterygians |
| Metapterygial fin | Asymmetric axis -Radials project anteriorly -Likely ancestral and present in most gnathostome fish |
| Chiridium | Weight-bearing muscular appendage with well-defined joints bearing digits |
| Stylopodium | Upper arm/thigh |
| Zeugopodium | Forearm/shank (crus) |
| Autopodium | Manus (wrist-palm-fingers)/Pes (ankle-sole-toes) |
| Pectoral girdle trends | -Endochondral and intramembranous development -Attached to skull in fish but detached from skull in tetrapods -Positioned in a muscular sling in tetrapods |
| Pelvic girdle trends | -Endochondral development -Not attached to other skeletal structures in fish but attached to vertebral column in tetrapods -Fused to the vertebral column via the sacrum in tetrapods |
| Shark Pectoral girdle | Scapulocoracoid bar (u-shaped structure) (bottom of u faces ventrally) 1.) Coracoid bar (most ventral 2.) Scapular cartilage- project dorsally from coracoid bar Glenoid surface- articulates with basals 3.) Suprascapular cartilage |
| Osteichthyans Pectoral girdle | - Most of it derived from dermal armor -Scapulocoracoid articulates with the pectoral fin -Posttemporal articulates with the posterior skull - Clavicles articulate in the ventral midline |
| Tetrapods pectoral girdle | 1.) Pectoral girdle becomes detached from the skull 2.) Dermal elements tend to be lost while endochondral elements become more prominent 3.) Clavicle becomes braced to sternum 4.) Scapulocoracoid becomes scapula and procoracoid (anterior coracoid) |
| Pecotral girdle elements in different vertebrates | Fish: scapulocoracoid Tetrapods (ancestral): scapula and procoracoid Amniotes (ancestral): scapula and procoracoid and coracoid Non-mammals and monotremes: scapula and procoracoid and coracoid Therian mammals: scapula and coracoid |
| Fish pelvic girdle | Puboischiadic bars -Meet in the midline at a pubic symphysis and have no attachment to the vertebral column -In derived fish these have moved anteriorly to lie ventral to the pectoral girdle |
| Tetrapod pelvic girdle | Composed of 3 bones joined at the acetabulum Ilium (dorsal)- Articulates with sacrum at sacroiliac joint Ischium (caudal-ventral) Pubis (cranial-ventral)- forms pubic symphysis at midline |
| Os coxa (innominate bone) | Fusion of ilium, ischium and pubis |
| Pelvis | sacrum and pelvic girdle |
| Epipubic bones | -Found in all non-eutharian mammals -Thought to have evolved to assist locomotion by supporting some thigh flexors |
| Locomotion in fish vs tetrapods | - In fish, locomotion occurs via lateral movements and tail propulsion -In tetrapods, limbs are responsible for locomotion |
| Evolution of tetrapod locomotion | 1.) limbs and girdles become larger and strengthened 2.) Digit orientation changes from lateral to anterior as a result of limb position changes and stylopodium torsion |
| Preaxial (radius and tibia) limb position | Lateral limb position: preaxial elements are anterior Vertical limb position: preaxial elements are medial |
| Postaxial (ulna and fibula) limb position | Lateral limb position: postaxial elements are posterior Vertical limb position: postaxial elements are lateral |
| Embryonic development Pterygiophores, tetrapod libs, endochondral part of pectoral girdle and pelvic girdle | somatic mesoderm |
| Embryonic development of fin rays and the intramembranous part of the pectoral girlde | Somites |
Created by:
trinann04
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