A varied but small group, probably related to the Chordata, but without a notochord.
class ENTEROPNEUSTA (Present)
Worm-like animals with no external skeleton.
class PTEROBRANCHIA (Ordovician to Present)
Fixed colonial organisms. Skeleton of protein. Lophophore attached by a stalk to an internal protein tube (the stolon).
class GRAPTOLITHINA (Cambrian to Carboniferous) Colonial marine animals with a skeleton of protein.
order Dendroidea (Cambrian to Carboniferous)
Graptolites with a protein stolon, include benthic and pelagic forms.
order Graptolidea (Ordovician to Lower Devonian)
Graptolites with no preserved stolon; probably all pelagic.
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