Graptolites
- Created by: rosie.may7
- Created on: 02-05-16 17:59
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- Graptolites
- Morphology
- Nema
- Thin tube extension of the sicula. Possibly used to attach to a floating object
- Stipe
- Branch of Rhabdosome
- Sicula
- Conical tube secreted by the first member of the colony
- Virgella
- Spine at the end of the sicula
- Theca
- Individual cup in which one zooid lived
- Aperture of the Sicula
- Where the fist zooid protruded through the skeleton
- Rhabdosome
- The whole Graptolite skeleton
- Nema
- Mode of life
- Mostly planktonic, attached to a floatation device via the Nema
- Importance
- Used in biostratigraphy as a some fossil
- Close similarity with modern day pterobranchs
- First appeared in the ordovician
- Hemichordata, Graptodoidea
- Evolution
- Number of stipes reduces over time. Many in the ordovician to one in the silurian
- attitude of the steps changes from pendant to horizontal to reclined to scandent from ordovician to silurian
- Shape of the thecae change from simple tube shape to more elaborate shapes
- from early uniserial thecae to biserial in the ordovician
- Morphology
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