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GRAPTOLITES and HEMICHORDATES

GRAPTOLITES and HEMICHORDATES. HEMICHORDATES tubular structure in place of notochord dorsal nerve chord ventral blood vessel pharynx w multiple openings Today include “acorn worms” (F) And Pterobranchs (A,B). Graptolites - Cambrian? Ordovician-Carb

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GRAPTOLITES and HEMICHORDATES

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  1. GRAPTOLITES and HEMICHORDATES

  2. HEMICHORDATES • tubular structure in place of notochord • dorsal nerve chord • ventral blood vessel • pharynx w multiple openings • Today include “acorn worms” (F) • And Pterobranchs (A,B)

  3. Graptolites - Cambrian? Ordovician-Carb Preserved remains resemble pterobranch stolon – classed as hemichordates

  4. Pterobranch Cephalodiscus graptoloides – discovered 1993 Best living analog for graptolites

  5. Important biostratigraphic index fossils for Ord-Sil Common in deep water mudstones, probably planktonic forms. Declined in Devonian – probably due to predation Planktonic forms extinct in Devonian Most often preserved as carbon films and impressions, rarely 3-D

  6. Dendrograptus Cyrtograptus Dictyonema Didymograptus Tetragraptus Monograptus

  7. CEPHALOCHORDATES Evolution of Chordates UROCHORDATES HEMICHORDATES

  8. TUNICATES

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