34-35_Ward_Chordata+Outline

34-35_Ward_Chordata+Outline - BIS2C W2011 Chordata What are...

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Lectures 34-35 (9, 11 March 2011) 1 Chordata What are chordates? Sea squirts, lancelets, jawless fishes, jawed fishes, and tetrapods (amphibians, reptiles, mammals). Deuterostomes with… 1. Notochord 2. Dorsal hollow nerve cord 3. Postanal tail 4. Pharyngeal slits First three characters are synapomorphies for Chordata. Cephalochordates lancelets (or “amphioxus”) small burrowing filter feeders chordate features present in adults segmented body muscles Urochordates sea squirts (tunicates, ascidians) and relatives bag-like with large perforated pharynx for filter-feeding sea squirt larvae have chordate features (also adults of larvaceans) Vertebrata 1. Enlarged brain 2. Cranial skeleton (braincase) 3. Vertebral column (jointed, supporting dorsal structure) of bone or cartilage Hagfishes (Myxini) scavengers on dead or dying animals no bone, no jaws tongue with rasping teeth produce copious amounts of slime Lampreys (Petromyzontida)
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34-35_Ward_Chordata+Outline - BIS2C W2011 Chordata What are...

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