Major Subgroups


Order Graptoloidea (Subphylum Stomochordata, Class Graptolithina)

  • Existed from the Lower Ordovician to Lower Devonian.
  • Rhabdosomes originally had up to eight stipes, in later forms this number was reduced to two or even one.
  • Thecae occur on one or both sides of the stipe and show a high morphological diversity.
  • There are three suborders: 1) Anisograptidae (Lower Ordovician), 2) Dichograptina (Ordovician) and 3) Virgellina (Ordovician-Devonian).
 

 

Order Dendroidea (Subphylum Stomochordata, Class Graptolithina)

Chart showing the evolution of graptolite form. Specimens within the Order Graptoloidea, are characterized by rhabdosomes with relatively few stipes. Thecae are normally situated on one or both sides of the stipe. Specimens representative of the Order Dendroidea, are characterized by rhabdosomes with numerous stipes. Thecae are numerous and can be of two types: autothecae or bithecae (large, single theca, ot small, numerous thecae).

 

 

 

Chart reproduced with permission of ENK Clarkson


Author: LShychoski
Last updated: Date

 


Websites produced by students on the MSc Palaeobiology programme in the Department of Earth Sciences at the University of Bristol for academic year 2005-6