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Chordates Zoology Donald Winslow 4 April 2008 Following Hickman et al. 2008, Ch 23 pp 497-506, 508-510, 512 (protochordates & early vertebrates) Ch 24 515-540 (fishes); Ch 25 544-559 (amphibians) Ch 26 563-582 (reptiles); Ch 27 586-610 (birds); Ch 28 613-640 (mammals)
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Characteristics of chordates Notocord, often endoskeleton Dorsal hollow nerve cords Often predators Pharyngeal gill slits, often become gills Paired appendages—fins, limbs, wings Postanal tail Segmented myotomes
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Phylum Chordata Subphylum Urochordata—tunicates Subphylum Cephalochordata—lancelets Subphylum Vertebrata (Craniata) –The fishes (paraphyletic) –Class Amphibia (paraphyletic) –Class Reptilia (paraphyletic) –Class Aves (monophyletic) –Class Mammalia (monophyletic)
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Quasi-cladistic classification Chordata –Urochordata –Euchordata Cephalochordata Craniata –Myxini (hagfishes) –Petromyzontida (lampreys) –Gnathostomata (jawed fishes & tetrapods) »Chondrichthyes (cartilaginous fishes) »Teleostomi (bony fishes & tetrapods)
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The Teleostomi Osteichthyes (bony fishes) –Class Actinopterygii (ray-finned fishes) –Class Sarcopterygii (lobe-finned fishes) Tetrapoda (terrestrial four-legged beasts) –Class Amphibia –Amniota Class Reptilia & Class Aves (birds) Class Mammalia
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The Fishes Pisces, ichthyology Superclass Agnatha (jawless fishes) –Slender, eel-like, median fins –Cartilaginous skeleton, persistent notochord –No vertebrae –External fertilization, separate sexes Superclass Gnathostomata –Jawed fishes & tetrapods
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Superclass Agnatha Class Myxini (hagfishes) –Feed on dead & dying animals, knots Class Petromyzontida (lampreys) –Ectoparasites –Larvae (ammocoetes) resemble Amphioxus
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Gnathostomes Class Chondrichthyes (cartilaginous fishes) –Subclass Elasmobranchii (sharks & rays) –Subclass Holocephali (chimaeras) Osteichthyes (bony fishes) –Class Actinopterygii (ray-finned fishes) Chondrosteans (sturgeon, paddlefish, bichir) Neopterygians (bowfins, gars, teleosts) –Class Sarcopterygii (lobe-finned fishes) Lungfishes & coelacanth
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Spotted Gar
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