ChordatesZoology
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)
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
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)
Quasi-cladistic classification
• Chordata– Urochordata– Euchordata
• Cephalochordata• Craniata
– Myxini (hagfishes)– Petromyzontida (lampreys)– Gnathostomata (jawed fishes & tetrapods)
» Chondrichthyes (cartilaginous fishes)» Teleostomi (bony fishes & tetrapods)
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
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
Superclass Agnatha
• Class Myxini (hagfishes)– Feed on dead & dying animals, knots
• Class Petromyzontida (lampreys)– Ectoparasites– Larvae (ammocoetes) resemble Amphioxus
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
Spotted Gar
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