Hemichordates

Hemichordates - index fossils for Ord-Sil Common in deep...

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GRAPTOLITES and HEMICHORDATES
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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)
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Graptolites - Cambrian? Ordovician-Carb Preserved remains resemble pterobranch stolon – classed as hemichordates
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Pterobranch Cephalodiscus graptoloides – discovered 1993 Best living analog for graptolites
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Important biostratigraphic
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Unformatted text preview: 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 Dictyonema Didymograptus Cyrtograptus Tetragraptus Dendrograptus Monograptus Evolution of Chordates HEMICHORDATES UROCHORDATES CEPHALOCHORDATES TUNICATES...
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This note was uploaded on 10/23/2011 for the course GLY 1000 taught by Professor Parker during the Spring '11 term at FSU.

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Hemichordates - index fossils for Ord-Sil Common in deep...

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