L03-04_ChondrichthyesHO11

L03-04_ChondrichthyesHO11 - EEMB 106 Lectures 3 & 4...

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EEMB 106 – Lectures 3 & 4 – Chondrichthyes 1 EEMB 106 Chondrichthyes SuperClass Gnathostomata - Jawed fishes Class Placodermi (plate-skinned) extinct Class Acanthodii (spiny sharks) extinct Class Chondrichthyes Class Sarcopterygii Class Actinopterygii Class Chondrichthys, Cartilaginous fishes SubC. Elasmobranchii, sharklike SubC. Holocephali, chimaeras Outline for lecture: A. Evolution of elasmobranchs B. Elasmobranch basic characteristics C. Elasmobranch basic adaptive patterns A. Evolution of Elasmobranchs Class Chondrichthyes Subclass Elasmobranchii SuperO: Cladoselachimorpa - extinct SuperO: Euselachii Order Hybodontiformes - extinct 13 Orders of modern elasmobranchs Elasmobranchs 1) arose in early Devonian (400 mya) 2) modern forms in place by early Cretaceous (144 mya) 3) three major radiations: a) SuperO: Cladoselachimorpha SuperO: Euselachii i) Hybodonts ii) modern elasmobranchs 1st elasmobranch radiation: SuperO. Cladoselachid sharks (example Cladoselache ) Cladodont = branched tooth: all had a three-cusped tooth 1. Terminal mouth 2. Fins broad based and stiff, long radial elements 3. No anal fin 4. Caudal fin is homocercal 5. Body supported by notochord only 6. Often spines in front of dorsal, pectoral, pelvics
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EEMB 106 – Lectures 3 & 4 – Chondrichthyes 2 2nd elasmobranch radiation: SuperO. Euselachii: Hybodonts early Mesozoic 250 (mya) Hybodont=humpback tooth 1. Terminal mouth 2. Fins flexible and mobile 3. Anal fin 4. Caudal fin heterocercal 3rd elasmobranch radiation: coming of the modern sharks Mid-Mesozoic (200 mya) 1. Jaws: ventral mouth with protrusible upper jaw 2. Dentition: tooth replacement system 3. Fins: ceratotrichia supporting the fin 4. Vertebra: calcified vertebrae instead of notochord
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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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L03-04_ChondrichthyesHO11 - EEMB 106 Lectures 3 & 4...

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