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Vertebrate Characteristics . Kingdom Animalia; Phylum Chordata; Subphylum Vertebrata. Chordata Characteristics. Dorsal hollow nerve cord Notochord (“back cord”) Pharyngeal gill slits/arches +/- postanal tail. Subphylum Vertebrata. 500 million years ago; Ordovician Period
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Vertebrate Characteristics Kingdom Animalia; Phylum Chordata; Subphylum Vertebrata
Chordata Characteristics • Dorsal hollow nerve cord • Notochord (“back cord”) • Pharyngeal gill slits/arches • +/- postanal tail
Subphylum Vertebrata • 500 million years ago; Ordovician Period • About 50,000 species known
Geologic PeriodsPALEOZOIC ERA • Cambrian Period 600 mya • appearance of all major invertebrate phyla • Ordovician Period 500 • appearance of vertebrates (ostracoderms) • Silurian Period 440 • archaic fishes
-Devonian Period 410 • age of fishes; first amphibians • -Carboniferous Period 360 • amphibians dominant; first reptiles • -Permian Period 290 • primitive reptiles, decline of early amphibians
MESOZOIC ERA (age of reptiles; 185 million yrs. duration) -Triassic Period 245 first dinosaurs, turtles, mammals -Jurassic Period 210 reptiles dominant; first birds; arc. mammals -Cretaceous Period 145 extinction large reptiles
CENOZOIC ERA • (age of mammals; 65 million yrs. duration)
Key Points • From the Geologic Periods page, name 3 of the most important dates & events
Origins of Vertebrates • Prochordate, such as Amphioxus • Compare to Ammocoete larvae
Amphioxus Larval agnathan - Ammocoetes
SUPERCLASS AGNATHA • Ostracoderms
SUPERCLASS AGNATHA • Cyclostomes
SUPERCLASS GNATHOSTOMATA • Class Acanthodii
Class Chondrichthyes • Cartilaginous fish
Bony Fish • Osteichthyes • Greatest number of species of vertebrates
Class Actinopterygii • Ray-finned fish • Operculum • Bony skeleton • Terminal mouth • Swim bladder in most
“perfect” bone • 95% of all fish • Modern cycloid or ctenoid scales
Class Sarcopterygii • Fleshy finned fish
Class Amphibia • Both life • Fewest numbers of species • Terrestrial life changes • More oxygen in atmosphere than water • Air less dense than water for body support • More temperature fluctuations
Class AmphibiaSubclass Labyrinthodontia • OLDEST TETRAPOD, about 350 mya • Crossopterygian features such as dermal scales, ray-fin tail, skull and sensory structures fish-like • GAVE RISE TO REPTILES