comparative anatomy notes for exam 3

comparative anatomy notes for exam 3 - Appendicular...

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Appendicular Skeleton I. Basic Components a. Fins i. Thin, membranous processes internally supported by dermal fin rays ii. Elasmobranches-ceratotrichia (dermal and cartilaginous) iii. Bony Fish- bony lepidotrichia (dermal and bony) iv. Proximal part of the fin supported by two pterygiophores 1. basals-large and next to body 2. radials-thinner and connect basals to the rays v. basal pterygiophores articulate with the internal girdles. b. Limbs i. Limbs of tetrapods also have 3 regions: ii. Autopodium 1. distal portion 2. contains multiple elements 3. manus-on the forelimb- hand 4. pes-on the rear limb-foot iii. Zeugopodium 1. middle region 2. consists of 2 bones, the tibia and fibula or the radius and ulna iv. Stylopodium 1. proximal region 2. single element-humerus or femur II. Origin of Paired Fins a. Gill Arch Theory i. Paired fins and girdles arose from the gill arches ii. Accounts for the evolution of the girdle itself but no the other elements 1. pelvic girdle is displaced too far 2. presence of dermal and not endochondral bone 3. different embryology (implied by endochondral vs. dermal) b. Fin-fold theory i. Arose from a continuous paired set of ventral-lateral folds in the body wall ii. Folds were then stiffened by a transverse series of endoskeletal pterygiophores. iii. Composed of the basals and radials iv. Girdle evolution 1. basals extended toward the midline 2. fused to each other to form the girdles 3. increased the stability of the fins v. support 1. early fossil fish contain hints of a lateral fold 2. some fossil fish have paired rows of spines in the pelvic girdle 3. the paired fins of sharks develop from a continuous thickening of the body’s lateral wall III. Phylogeny a. Fishes
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i. Agnathans generally lacked paired fins ii. Chondrichthyes 1. paired fins are stabilizers and provide anterior lift 2. basal portions of the girdles are fused to provide rigidity 3. girdles are endochondral iii. Actinopterygians 1. girdles are mostly dermal with some endochondral elements 2. hydrofoils are not needed because the air bladder is common 3. fins are used for slow swimming, turning, hovering, and maneuvering 4. well developed girdle with multiple elements iv. Sarcopterygians 1. mostly dermal shoulder girdle (there are some endochondral just not very much) 2. Eusthenopteron a. Late Devonian b. Had limb bones homologous to the tetrapods 3. good fossil record of the change b. Tetrapods i. Amphibians quickly displayed adaptations to terrestrial life 1. pectoral girdle lost its attachment to the skull 2. enabled the animal to turn its head without turning its body 3. reduced the jarring of the head during locomotion ii. Ichthyostega – early amphibian 1. pubis, ischium, and ileum were fused 2. the ileum was fused to the sacral vertebrae 3. fin rays became the digits iii. Pectoral girdle 1. composed of both endochondral and dermal elements 2. not attached to the skull 3. the number of girdle bones tends to decline across classes iv. Pelvic Girdle 1. composed of 3 endochondral bones: ileum, ischium, and pubis 2.
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This note was uploaded on 04/09/2011 for the course CHEM 4461 taught by Professor Max during the Spring '08 term at Lamar University.

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comparative anatomy notes for exam 3 - Appendicular...

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