Graptolites Flashcards
What is their phylum, class and order
Hemichordata
Graptolithinia
Graptoloidea
Are they extinct or extant
Extinct
What kind of organism were they
Colonial
What kind of skeleton did they lay down
Scleroprotein Skeleton
What lived in the thecae and what did they do
Zooids
Built up the thecae
How did zooids live
The first Zooid secreted a tube called the sicula which often had a long tapering point. Thecae were stacked vertically on top of each other and on top of the sicula. The thecae overlap and makeup the stipes
How did they feed
They were a filter feeder
What is their mode of life
Lived in the water column
Probably pelagic
Attached on a floating object via the Nema
What are they similar to and what does this tell us
Pterobranchs
Structure of Rhabdosome makes us believe they were filter feeders
filter feed through the emerging zooids capturing the food
What is their geological timeline
Early Ordovician to Early Devonian
What makes them a great zone fossil
When they died they sank and were preserved in deep water, low oxygen, low-energy muds (as a death assemblage)
What are their four trends of their evolution
Change in number of stipes
Changes in the attitude of the stipes
Changes in the shape of the thecae
Changes in the arrangement of the thecae on the stipe
What changes occurred in the number of stipes
It went from 4 to 2 to 1
What changes occurred in the attitude of the stipes
Pendant to Horizontal to Scandant
What changes occurred in the shape of the thecae
Went from simple thecae to hooked/curved thecae and wide separation along the stipe called isolate
