outline22 - Outline22 4/23/03

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  Outline 22 4/23/03   Phylum Chordata  - Have notochord  (dorsal rod of cartilage), dorsal      nerve tube, + gill slits at some stage; advanced deuterostomes      along with echinoderms , and hemichordates  (with extinct      graptolites); biggest living chordate groups are tunicates        (urochordates with ~3,000 sp.) and vertebrates , including      aquatic fish groups (~25,000 sp.) and terrestrial vertebrates      (4 groups with ~26,000 sp.)   Subphylum Vertebrata  - Have vertebrae and armored braincase.      Fossil record from Late Cambrian (poss. M. Camb.?) - Recent      Origin  - 3 proposed ancestors, nearest relatives, or "sister      groups".           1. Carpoid echinoderms † - similar body form but with calcite                plates, convergent on bottom-living way-of-life, M. Camb.-               Penn.           2. Hemichordate
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outline22 - Outline22 4/23/03

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