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