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L06_Teleosts_11COLOR - TELEOSTS AT LAST ! Trends in the...

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TELEOSTS AT LAST !
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Structure Chondrostean Neopterygian/Teleost New Function Jaws Rigid, biting Flexible, protrusible Gape and Suck Maxilla Main bone w/ teeth Serves as lever Gape and Suck Premaxilla Small w/ teeth Main tooth bearing Gape and Suck Branchiostegals One ray, rigid cavity 2-23 rays w/ interopercle bone 2 pump respiration Scales Ganoid, heavy Cycloid or ctenoid Maneuverability Swimbladder Lung/ physostomous Physoclistous Neutral buoyancy, hearing, sound production Tail Heterocercal Homocercal Propulsion Pectoral fins Ventral to mid Mid to dorsal Steering, locomotion Pelvic fins Abdominal Thoracic Brakes, steering Rays Many, stiff Fewer, flexible Maneuverability Spines None In A, D, and P2s Protection Trends in the Class Actinopterygii (pgs 192-197, text)
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Teleost evolution: • Late Triassic, 200 MYBP – First appeared • Late Jurassic 150 MYBP – Explosive radiation • Mid Cretaceous, 100 MYBP – Six major orders • Late Cretaceous, 70 MYBP – All modern-day families (515) • Early Cenozoic, 50 MYBP – Most modern-day genera (4,400) • Modern times – All modern-day species (>28,000) Early teleost ancestor (order Pholidophoriformes)
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5 major trends in Teleosts ! Reduction in bony elements - fewer vertebrae - fewer bones in skull - fin ray reduction in C, P1, P2 ! Dorsal fin function and position changes ! P1s and P2s change body position ! Caudal fin and swimbladder modifications ! Improvements in feeding apparatus
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Evolution of paired fin location in teleosts A C Primitive Derived
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Characters of Teleosts 1) operculum has 4 bones 2) homocercal tail, partly supported by uroneurals, hypurals, and epurals 3) cycloid/ctenoid scales 4) vertebrae are ossified, but lightweight 5) swimbladder is hydrostatic organ (i.e. provides buoyancy) 6) maxilla and premaxilla are moveable, premaxilla is principal bone of upper jaw 7) fins are highly maneuverable with rays and spines 8) body shape variety is extensive
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Teleosts radiated due to improvements in: 1. Swimming abilities = maneuverability 2. Feeding mechanisms (upper jaw mobility) New trophic possibilities = unexploited niches vs. • Replacement of heavy armor with flexible scales • Develop hydrostatic organ from lungs (swim bladder) • Develop homocercal tail, expand functions of paired fins Heterocercal tail Homocercal tail
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Caudal fin reinforced by hypurals, uroneurals, and epurals
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Evolution of protrusible jaws Chondrostean " Neopterygian/Teleost
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The elements involved in jaw protrusion include the premaxilla , maxilla , and mandible (lower jaw), ligamentous connections of these bones to the skull and to each other, and several jaw muscles. The entire jaw moves forward and slightly up or down. Feeding is initiated as the cranium is lifted and the lower jaw is depressed.
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This note was uploaded on 01/10/2012 for the course EEMB 106 taught by Professor Staff during the Spring '08 term at UCSB.

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L06_Teleosts_11COLOR - TELEOSTS AT LAST ! Trends in the...

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