Chordates Zoology Donald Winslow 4 April 2008 Following Hickman et al. 2008, Ch 23 pp , , 512 (protochordates & early vertebrates)‏ Ch (fishes); Ch (amphibians)‏ Ch (reptiles); Ch (birds); Ch (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